Reversibly Reconfigurable Colloidal Plasmonic Nanomaterials

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Perspective

Reversibly Reconfigurable Colloidal Plasmonic Nanomaterials Zhaoxia Qian, and David S Ginger J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b00711 • Publication Date (Web): 16 Mar 2017 Downloaded from http://pubs.acs.org on March 16, 2017

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Journal of the American Chemical Society

Reversibly Reconfigurable Colloidal Plasmonic Nanomaterials Zhaoxia Qian, David S. Ginger* *Department of Chemistry, University of Washington, Seattle, WA, 98105, USA

ABSTRACT: With their unique ability to concentrate and scatter light, plasmonic nanomaterials have been the focus of tremendous syntheses and characterization efforts in the past two decades. Recently, the topic of reversibly-reconfigurable plasmonic nanomaterials has become an intensive research area offering the opportunity to reconfigure the optical, mechanical, electronic and catalytic properties of materials with promising applications in fields ranging from biosensors, to nanorobotics and energy. This perspective discusses the state of the art in the fabrication and application of reversibly reconfigurable colloidal plasmonic nanomaterials based on the actuation of interparticle couplings and explores some promising directions for future research ranging from direction control, 2D materials, and the incorporation of feedback mechanisms for designing robust responses.

1. INTRODUCTION Plasmonic nanoparticles have been used for millennia (Figure 1) to realize optical properties that would be otherwise difficult to achieve. From the Lycurgus cup in the 4th-century, to the colloidal gold nanoparticle (AuNP) solutions of Michael Faraday, to modern nanotechnology 1 ACS Paragon Plus Environment


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(Figure 1), there has been an evolution of the sophistication with which chemists and materials scientists are able to tailor the properties of plasmonic nanomaterials. At the most basic level, control over the size, shape, and chemical composition of plasmonic NPs through new syntheses and growth methods has afforded an impressive degree of tunability over the optical and chemical properties of the resulting materials. This progress has opened up exciting opportunities for using plasmonic NPs in various applications including spectroscopy,1,2 catalysis,3,4 sensing,5-7 solar energy harvesting8-12 and biomedicine.13 We classify the next level of sophistication as the utilization of collective effects through the fabrication of plasmonic NP assemblies with increased structural complexity that exhibit new collective properties absent in their individual counterparts. For example, local hot spots created at the gap between adjacent NPs separated by several nanometers exhibit significantly enhanced electromagnetic field intensities, and can offer enhancement factors of 109~1011 for surface enhanced Raman scattering, in some cases even allowing single-molecule detection.14-17 Nonlinear optical phenomena such as second-harmonic generation or third-harmonic generation are also greatly enhanced by NP assemblies.18,19 Moreover, the high local density of states created in NP assemblies make them interesting for use in energy conversion applications including light trapping in solar photovoltaics and photocatalysis.10,20 Other novel collective physical properties offered by NP assemblies include ultrahigh sensitivity provided by Fano resonances21-24, high Q factors in photonic crystals25 and optical magnetism in metamaterials26,27, to name a few. These examples highlight how, over the last decade, scientists have demonstrated increasingly impressive examples of tailored collective properties by engineering the assembly of size- and shape- controlled NPs. Because these collective properties are exquisitely sensitive to the distance and directionality of the coupling between the constituent particles, we propose here that the next

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revolution in plasmonic materials is poised to occur in the area of reconfigurable materials: where the engineered collective properties of plasmonic materials are reconfigured dynamically in response to external stimuli in a reversible manner. Already, a number of researchers have been making impressive progress towards these goals: some selected examples include DNA-based reversible AuNP assembly,28,29 photonic crystals composed of AuNPs and temperature responsive polymers30 and thermosensitive AuNPs 31,32 (Figure 1). We believe the widespread availability of building blocks that exhibit desirable physical properties and materials that change configurations in response to external stimuli would represent a transformative materials advance with applications spanning nanomedicine, renewable energy, biology, and even information technology. While research in this area involves many disciplines, we highlight here emerging examples of such reconfigurable plasmonic nanomaterials that are fabricated by methods of colloidal chemistry and respond to stimuli with dynamic structure changes. We organize our discussion of recent developments together by stimulus type, focusing on materials that respond to input signals that may be chemical, thermal, or --- most importantly from our point of view --- optical in nature. With the goal of accelerating the transition of this field from adolescence to maturity, we also offer our opinions on some key challenges and opportunities we feel face the field, such as the ability to engineer feedback mechanisms into reconfigurable assemblies of plasmonic NPs so that they can respond to external stimuli in a robust and reversible fashion.



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Figure 1. Selected highlights in the development of plasmonic nanoparticles and their applications. (A) Lycurgus cup, ca. ~ 400 C.E. Reproduced from ref 33 with permission from The British Museum. (B) A colloidal solution of aqueous Au nanoparticles (AuNPs) made by Michael Faraday in the 1850s. Reproduced with permission from the Royal Institution of Great Britain (© Paul Wilkinson). (C) TEM image of spherical AuNPs. (D) AuNP superlattice engineered with DNA. Reproduced with permission from ref 29. Copyright 2011 The American Association for the Advancement of Science. (E) AuNP crystals assembled using thermoresponsive polymer. Reproduced with permission from ref 30. Copyright 2011 John Wiley & Sons, Inc. (F) Thermoresponsive AuNP clusters exhibiting different colors and transparency at 35oC and 25oC. Reproduced from ref 31 with permission from American Chemical Society. (G) Solar water evaporation using SiO2@Au nanoshells. Reproduced from ref 34 with permission from. American Chemical Society. (H) Schematic showing plasmonic NP assemblies used in surface enhanced Raman spectroscopy. (I) Schematic showing targeted molecule delivery using reconfigurable plasmonic nanomaterials. (J) Schematic showing smart windows made of reconfigurable plasmonic nanomaterials change color and transparency reversibly under external stimuli. 4 ACS Paragon Plus Environment

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2. RECENT DEVELOPMENTS IN REVERSIBLY RECONFIGURABLE PLASMONIC NANOMATERIALS Reversibly reconfigurable plasmonic nanomaterials based on changes in interparticle coupling are usually built by combining two components: (1) plasmonic nanoparticles, and (2) some kind of stimuli-responsive molecules. These components can be tethered together either by covalent bonds, or by weaker interactions such as electrostatic attraction, allowing for enormous diversity in the possible pairings of particle types and stimulus-responsive triggers that are possible. Figure 2 summarizes some of the more widely-employed stimuli-responsive molecules: target-responsive biomolecules

such

as

DNA,35

thermally

responsive

hydrogels

such

as

poly(N-

isopropylacrylamide) (PNIPAM),36 and molecular photoswitches such as azobenzene.37 Responding to external stimuli such as chemicals, heat or light, the responsive components adopt different conformations or geometries in order to minimize the energy of the system as the interactions between constituents are altered, switching from one state to the other, as shown in Figure 2A. As a result of this change, the assembly state of the plasmonic NPs is altered, resulting in change in the electromagnetic coupling strength between the plasmonic NPs. Upon removal of existing stimuli or the introduction of other stimuli, the system may relax back to the initial state (Figure 2A). The transition of the stimuli-responsive components between different states is interesting as it involves many fundamental scientific challenges including energy transfer,20 molecular dynamics38,39 and molecular mechanics40 at the nanoscale. We summarize some representative examples of reversibly reconfigurable plasmonic nanomaterials fabricated by colloidal chemistry methods based on structural changes and their applications below, with the goal of highlighting emerging trends. We focus here on materials that respond to changes in the



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chemical environment, local temperature, and optical illumination as broad, but not exclusive taxonomies, and we direct the interested reader to other articles for discussions of some of the other myriad possibilities for reconfiguring responsive nanomaterials, such as elasticity41, pressure42,43 or magnetic field.44,45

Figure 2. Examples of some families of commonly used stimulus-responsive molecules. (A) Cartoon energy diagram showing how the responsive systems switch reversibly between two different energy states. (B) Biomolecules, such as double-stranded DNA which can reversibly dissociate into two single-stranded DNA upon heating above its melting transition temperature Tm or decreasing the ionic strength to below a critical value [ion] m. (C) Thermally responsive hydrogels, of which poly(N-isopropylacrylamide) (PNIPAM) is just one example, undergo reversible lower critical solution temperature (LCST) phase transitions from a swollen hydrated state to a shrunken dehydrated state, resulting in significant volume decrease. (D) Photoswitches, for example azobenzene, undergo reversible structural changes: azobenzene switches to cis form


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under ultraviolet (UV) light illumination and back to trans form under visible (Vis) light illumination.

2.1 Chemical Inputs DNA is arguably one of the most important molecules in nanotechnology at present,13,46,47 and has been widely used for developing technologies ranging from Mirkin-type NPs (spherical nucleic acids),48 to plasmon rulers,49 plasmon-induced fluorescence quenching50 and enhancement,2 templated three-dimensional assembly of nanomaterials51 and chiral responsive materials.52-54 In 1996, Mirkin et al.28 pioneered the use of thiolated DNA as a molecular linker to assemble individual AuNPs into clusters with nanometer separation distances. The separation distances between the linked AuNPs can be controlled by regulating the length and conformation of the linker DNA, allowing for precise control of the interparticle distances on the nanometer scale. Plasmon rulers, as an example, are usually made of a pair of AuNPs linked by DNA, and exhibit scattering spectra that can be adjusted by changing the linker DNA length.49 Compared to the individual nanoparticles, the optical properties of the plasmonic rulers are much more sensitive to chemical changes in the environment due to the plasmonic coupling of the AuNP pairs. Indeed, plasmon rulers have been used to demonstrate enhanced detection sensitivity of AuNP-DNA conjugates even down to the single-molecular level.49,55,56 Importantly, by careful design of the DNA structure, the length of the DNA can be increased or decreased reversibly, allowing dual signal detection. One way to modulate the DNA length is to use an aptamer that can bind or unbind to the target molecules reversibly. For example, Lee et al.57 reported a plasmon ruler composed of two AuNPs linked by a single aptamer with a thiol group on one end and a biotin group on the other end. Binding to a matrix metalloproteinase (MMP3) induced a conformation change of the



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aptamer which brought the two AuNPs closer to each other, resulting in ~ 10 nm red shift in the peak wavelength of the scattering spectra (Figure 3A). Given that the binding and unbinding of MMP3 to the aptamer is fully reversible, the scattering spectra red shifted and blue shifted alternatively upon flushing the plasmon ruler with buffer with and without MMP3 (Figure 3B). Since each plasmon ruler comprised only one aptamer (Figure 3), actuation could be achieved by binding of only a single target molecule.57

Figure 3. (A) Plasmon ruler composed of an aptamer-AuNP dimer with one AuNP immobilized on the glass surface using biotin-avidin chemistry. The distance between the two AuNPs changes reversibly upon addition or removal of a matrix metalloproteinase (MMP3), which serves as a target molecule. (B) Reversible shift of the peak wavelength of the plasmon resonance of the aptamer-Au plasmon ruler when alternately flushed with buffer with or without 9 nM MMP3. The alternating red shift and blue shift of the peak wavelength indicates that MMP3 binds to the aptamer-Au plasmon ruler reversibly. Reproduced from ref 57 with permission from American Chemical Society.


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An alternative way to reversibly control the length of the DNA linker is to control its rigidity by adding a filler or stripper sequence to switch its conformation between compressible single stranded DNA (ssDNA) and rigid double-stranded DNA (dsDNA) with a spacing of ~0.34 nm per base pair. Along these lines, Maye et al.58 reported the assembly of AuNPs into superlattices and dimer clusters using DNA linkers, demonstrating that by adding filler or stripper DNA, the interparticle distance could be controlled effectively at the nanometer scale. Zhou et al.59 recently reported a gold nanorod that could walk on a DNA origami template. The gold nanorod was functionalized with ssDNA and initially anchored onto a DNA origami structure whose surface was decorated with precisely designed ssDNA and dsDNA. By subsequently adding blocking strands and removal strands, two toehold-mediated strand-displacement reactions occuring simultaneously on the DNA origami could induce movement of the gold nanorod towards the position where the new dsDNA formed. Furthermore, by monitoring the circular dichroism signal of the gold nanorods, they confirmed that the walking direction of the gold nanorods was reversible. Not only can this strategy achieve structural modulation of AuNP assemblies, but it also results in reversible switching of the optical properties and mechanical properties of the AuNP-DNA complex. As another example, Shim et al.60 fabricated free-standing AuNP films with DNA linkers using a layer-by-layer deposition method and demonstrated that they could change the shapes of these films, achieving movements over distances of hundreds of microns (Figure 4). The film comprised an active and a passive layer with the former containing an ssDNA segment whose length could be increased or decreased by adding the appropriate DNA sequences (Figure 4A). Upon adding stripper (Figure 4B, i, iii) or filler (Figure 4B, ii, iv) DNA, the active layer



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contracted (Figure 4B, i, iii) or expanded (Figure 4B, ii, iv) respectively, inducing mechanical tension in the film, causing it either to roll up into a tubular geometry, or to flatten out. The tubular film could be switched back reversibly to a flat film by expansion (Figure 4B, i, iii) or contraction (Figure 4B, ii, iv) upon adding filler (Figure 4B, i, iii) or stripper (Figure 4B, ii, iv) DNA. In addition to DNA, other chemical stimuli such as pH, electrolyte and solvent also provide facile routes to tune the interactions between colloidal particles, and thus reversibly control the dynamics of responsive plasmonic nanomaterials.61-64 For example, Tian et al.65 functionalized AuNPs with pH-responsive ligands including glycyrrhetinic acid (GA) segments that can switch reversibly from assembled AuNPs in normal tissue at pH = 7.4 to a disassembled state in tumor tissue extracellularly at pH = 6.8. Gold nanorods can also be reversibly assembled side-by-side and end-to-end via adjusting the solution pH.66 While such chemical inputs are natural for many chemical and biochemical applications, the use of chemical signals can result in increased solution volumes and decreased solute concentrations, and often require fluid or reagent handling, which can limit the number of achievable cycles or environments in which such materials can be applied.

Figure 4. Free-standing AuNP films fabricated using AuNPs functionalized with DNA reversibly coil along two different directions upon adding filler and stripper DNA sequences. (A) Schematic 10 ACS Paragon Plus Environment

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of the AuNP-DNA film composed of an active layer (green) and a passive layer (red). (B) Schematics (i, ii) and series of microscope images (iii, iv) for the programmed actuation of AuNPDNA films. The flat film was actuated by adding stripper DNA (i, iii) or filler DNA (ii, iv) to form tubular structures where the passive (i, iii) or active (ii, iv) domains acted as an outer layer by contraction or expansion of the active layer, respectively. The scale bar is 200 µm and applies to all images in (B).

2.2 Temperature A key component of temperature-responsive plasmonic assemblies is a material with a physical property such as solubility or phase that exhibits a nonlinear relationship with temperature. Effects ranging from temperature-dependent zeta potentials32 to temperature responsive polymers67 can be used for this purpose. One of the most well-investigated temperatureresponsive materials is poly (N-isopropylacrylamide) (PNIPAM),68,69 which undergoes a reversible lower critical solution temperature (LCST) phase transition from a swollen hydrated state to a shrunken dehydrated state around 32oC (depending on its crosslinking density and composition).36,70 This LCST transition results in as much as a 90% decrease in volume of the PNIPAM and can therefore be used to change the assembly states of the NPs tethered to it.36,71,72 One of the earliest approaches utilized AuNPs that were surface functionalized with un-crosslinked PNIPAM : solutions of these particles change their transmission with temperature as the interparticle distances can be tuned by temperature-induced thickness change of the PNIPAM layer, resulting in change in the optical properties of NPs such as transmission31 or color.30 Another strategy is to tether plasmonic NPs to presynthesized PNIPAM microspheres. The interparticle distance between plasmonic NPs is then determined by the size of the PNIPAM



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template, which can be reversibly tuned by increasing or decreasing temperature.72,73 As an example, Lim et al.74 assembled spherical AuNPs on PNIPAM spheres and showed that the hybrids exhibited a wide range of colors from red to purple to dark blue with varying temperatures. Besides PNIPAM, other temperature-responsive hydrogels67,75 or peptides76,77 which exhibit similar solubility or phase change with temperature, can also induce reversible change of reconfigurable plasmonic nanomaterials. For example, Lemieux et al.77 functionalized AuNPs with elastin-like peptides and the hybrid showed LCST transition within a large range of temperature tunable by varying the pH of the solution. Liquid crystals, which have properties between those of convectional liquids and solid crystals and whose phase changes with temperature in the form of molecular ordering, have also emerged as materials for dynamically modulating the distances between plasmonic NPs in nonaqueous solution.81,82 Typically, plasmonic NPs are surface functionalized with a liquid-crystalline compound,83 and their assembly states are varied as the liquid-crystalline compound reorganize with changing temperatures to achieve thermodynamic stable state.80,81 For example, Lewandowski et al. 78 has successfully functionalized silver NPs with a promesogenic ligand and observed that silver NPs changed from isotropic structures to long-range-ordered lamellar phase (Figure 5A) as the solution temperature decreased from 120oC to 30oC. This structural change resulted in 20 nm red shift in extinction peak that could be reversibly cycled.78 Similar temperatureinduced structural change has also been observed on AuNPs.80 Temperature-dependent molecular interactions such as hydrogen bonding present another strategy to effectively modulate the interparticle distances and assembly states of plasmonic NPs. One representative example is AuNPs surface functionalized with complementary DNA sequences, which disassemble when the hydrogen bonds between the complementary DNA base


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pairs break above the melting temperature Tm and reassemble when the hydrogen bonds form below Tm.28,29 Surface-capping ligands terminated with complementary hydrogen-motifs are also good candidates for controlling interparticle distances via a similar working principle. Zhang et al.84 recently fabricated what they termed “nanocomposite tectons” (NCTs) composed of AuNPs grafted with polystyrene chains that terminate with diaminopyridine and thymine. These NCTs assemble into ordered structures at low temperatures when the hydrogen bonds form and disassemble at high temperatures when the hydrogen bonds broke, exhibiting dynamic structural changes between 20oC and 55oC (Figure 5B-C).84 These types of ligands with terminal hydrogen motifs can enable different synthetic approaches, providing functional diversity, and opportunities of scale-up for plasmonic nanomaterials that complement those available with DNA linkers.

Figure 5. Temperature-responsive plasmonic nanomaterials composed of AuNPs and liquidcrystalline molecules (A) and ligand-terminated polystyrene (B, C). (A) Small-angle X-ray diffraction patterns for annealed silver NPs functionalized with a promesogenic ligand at 120oC and 30oC (left) and the corresponding TEM image (right). Reproduced from ref 78 with permission from Macmillan Publisher’s Limited. (B) Schematic showing nanocomposite tectons (NCT) composed of AuNPs surface-functionalized with polystyrene terminated with complementary 13 ACS Paragon Plus Environment


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hydrogen-bonding motifs assembling into ordered structures via temperature-modulated supramolecular binding. (C) Cycling of normalized extinction intensity at 520 nm for a mixture of complementary NCTs between 20oC (lower data points) and 55°C (upper data points). Inserted are images of corresponding solutions. Reproduced from ref 84 with permission from American Chemical Society.

2.3 Light Light can be used to modulate the response of plasmonic nanomaterials by effects as varied as configuration changes of light-sensitive molecules incorporated in the plasmonic nanomaterials, or by photothermal heating effects. Compared to other stimuli, light has several advantages including fast response, avoidance of additional chemical reagents, and the potential for nondestructive cycling. In addition to photochemical actuation of classic molecular photoswitches such as azobenzene,37 photothermal actuation is possible because plasmonic NPs can effectively concentrate and absorb light with at frequencies close to their LSPR, effectively converting light to heat.85 Compared to conventional temperature changes achieved by heating or cooling the entire solution, such photothermal heating has the advantage of heating only the local NP environment instead of heating up the bulk solution -- which can be more energy efficient and, potentially, faster. At equilibrium, the temperature inside of an illuminated plasmonic NP is effectively uniform (Figure 6A) due to the large thermal conductivity of the NP compared to its surrounding environment such as liquid and glass.85 The surrounding temperature rise around a single isolated gold nanosphere falls off in inverse proportion to the distance from the center of the sphere (Figure 6A, right).85 A small, isolated, gold nanosphere with a diameter of 20 nm in water will increase its temperature by approximately 5oC upon illumination at 530 nm with a constant 1 mW/µm2 light


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intensity.85 On the other hand, plasmonic NP solutions can be heated effectively via collective photothermal effects at relatively low laser powers.86,87 For example, the temperature of a 1 mL colloidal solution of AuNPs with a broad range of diameters from 5 to 50 nm and approximately 0.2 mM gold atom concentration has been reported to increase about ~6 oC after 20 min of illumination with a 532 nm CW laser at a power of ~ 228 mW and an illumination area of about 2 mm in diameter.88 Such temperature increases in either the local surrounding of the plasmonic NPs or the bulk NP solution can induce phase or solubility changes of molecules tethered to the NPs, and therefore tune the interactions between the NPs and alter their assembly state (Figure 6A). Demonstrating this concept, Ding et al.89 recently reported photothermally actuated nanotransducers made of AuNPs coated with PNIPAM. These particles assembled into AuNP clusters upon illumination with a 532 nm laser and disassembled upon removal of laser with a power of 5W (Figure 6B). As a result, the peak wavelength of the extinction spectrum of the AuNPs coated with PNIPAM shifted reversibly between ~ 525 nm and ~ 645 nm and their color switched between red and dark blue (Figure 6C). Notably, the polymer shell on the AuNP surface was reported to collapse millions of times faster than the free polymer,89 possibly due to the large forces introduced by the van der Waals attraction between the AuNPs, though the mechanism bears further study. PNIPAM is ubiquitous, but certainly not unique: similar results have also been achieved with AuNPs surface-functionalized with temperature responsive peptides. For example, Slocik et al.90 achieved the reversible photothermally controlled dissociation and assembly of a hybrid composed of AuNPs and thermal-responsive coiled-coil peptides.



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Figure 6. Plasmonic nanomaterials responsive to light via photothermal heating of AuNPs. (A) Schematic showing the temperature profile of a spherical AuNP upon light irradiation. The AuNP is functionalized with PNIPAM which crashes when its temperature rises above its LCST. (B) Actuating nanotransducers (ANTs) made of AuNPs surface-functionalized with PNIPAM assemble and disassemble stimulated by irradiation using a 532 nm 5W laser. The color of the colloidal solution changes reversibly between red and dark blue upon adding or removal of the laser. (C) Extinction spectra of colloidal solution of AuNPs, AuNTs, AuNTs upon heating and cooling. Inset is the extinction peak wavelength (λpk) change as the AuNTs cycled with illumination laser on and off. Image (B) and (C) reproduced with permission from ref 89.

Light-sensitive molecules offer another effective route to modulate the response of plasmonic nanomaterials. As one of the most commonly used photoswitches,91 azobenene is a photoswitchable molecule that undergoes a reversible conformation change from the planar trans to the folded cis isomer under ~330 nm ultraviolet (UV) light radiation and switches back to the trans conformation under visible light radiation (Figure 7A).92 This conformation change imposes 16 ACS Paragon Plus Environment

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mechanical strains to the system and induces structural change of components that require strict geometric confinement. Attaching azobenzene to a DNA backbone makes it possible to photoregulate the formation and dissociation of duplex DNA (Figure 7A).92 Duplex DNA forms when the azobenzene molecule is in its planar trans-form and dissociates when azobenzene switches to its folded cis-form under UV light. Upon visible light illumination, azobenzene goes back to the trans-form and the duplex DNA forms again. This reversible conformation change of duplex DNA allows remote control of the distances and coupling between plasmonic NPs tethered using DNA linkers. Yan et al.93,94 reported one of the first examples of light-controlled reversible aggregation and dissociation of DNA-functionalized AuNPs by incorporating azobenzene into the backbone of the DNA linker (Figure 7B). Azobenzene-functionalized DNA also makes it possible to precisely control of the orientation of plasmonic NPs in delicately designed structures. For example, Kuzyk et al.95 anchored two gold nanorods on DNA origami at a less than 90o angle and tethered their ends using a dsDNA with azobenzene modification (Figure 7C). Upon UV illumination, the linker DNA dehybridized due to the configuration change of azobenzene from trans to cis, relieving the mechanical strain and thus the angle between the two gold nanorods increased to a maximum of 90o (Figure 7C). This orientation change between the two crossing gold nanorods is reversible and can be transduced into circular dichroism changes in the visible wavelength range.95 Moreover, the conformation change of azobenzene moieties in capping ligands of plasmonic NPs under light illumination can change the molecular interactions between the NPs and thus alter their assembly states. For example, Zhao et al.96 observed self-assembly of AuNPs functionalized with ligands terminated with azobenzene upon exposure to UV light, partially due to the attractive dipole-dipole interactions between cis-azobenzene moieties on different NPs.



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Figure 7. Plasmonic nanomaterials functionalized with azobenzene-modified DNA respond to ultraviolet (UV) and visible (VIS) light reversibly. (A) Schematic of the photo-regulation of the hybridization of azobenzene-modified DNA. Reproduced with permission from ref 92. Copyright 2007 Nature Publishing Group. (B) Reversible assembly and disassembly of AuNPs functionalized with azobenzene-modified DNA with blue and UV light illumination. (C) (Top) Schematic of a 3D plasmonic nanosystem made of two gold nanorods anchored on two linked DNA origami templates whose crossing angle was regulated by UV/VIS light illumination; (Bottom) TEM images of the DNA origami templates after VIS (left) and UV (right) light illumination. The mode of the crossing angle is ~ 50o (left) and ~ 90o (right), respectively. Reproduced with permission from ref 95. Copyright 2016 Nature Publishing Group.

Beyond the standard categories of chemical changes, temperature and light, multifunctional plasmonic nanomaterials that respond simultaneously to multiple external stimuli such as temperature, pH and light are also successfully fabricated. For example, Shi et al.97 fabricated poly(n-isopropylacrylamide-co-methacrylic acid)−AuNP hybrid microgels by in-situ reduction of a Au precursor in the polymer matrix. The hybrid exhibited a well-defined size and optical properties that changed in response to temperature, pH, and optical illumination due to the


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temperature responsiveness of PNIPAM, the pH responsiveness of poly-methacrylic acid and photothermal heating of AuNPs, respectively.97

3. CURRENT AND FUTURE APPLICATIONS Advances in nanomaterials synthesis and self-assembly have not only made it possible to control the assembly geometry and movement of plasmonic NPs with nanometer precision, but also opened new doors for various applications including LSPR sensing,98 energy transformation,60 modulated bioactivity99 and controlled drug delivery.100 Compared to their non-reconfigurable cousins, reconfigurable plasmonic nanomaterials offer several advantages. For instance, in LSPR sensing, while retaining the ability to perform a wide variety of functions such as chemical and biochemical sensing,49,57,101 pH sensing,102,103 temperature sensing104,105 and photosensing,56,93,98 reconfigurable plasmonic nanomaterials offer the prospect of improved specificity and selectivity as one can use the stimulus-response function to verify, for instance, that the capture molecules have not been denatured, or that a ligand is properly bound to its functional acceptor rather than simply binding to the NPs in a non-specific fashion. Given that selectivity is often the limiting factor in real-world sensing of unpurified samples, we anticipate that researchers will continue to devise clever strategies to utilize reconfigurable materials to achieve better selectivity.98,101,106 Furthermore, reconfigurability could be used to improve signal-to-noise ratio in samples with large background fluorescence or scattering signals,107 and is thus attractive for applications as diverse as remote sensing and deep-tissue imaging. The nanoscale structural changes of reconfigurable plasmonic nanomaterials induced by external stimuli also offer a pathway to transform chemical, thermal, light and electrical energy



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into mechanical work at the nano- and microscale. We have already discussed how plasmonic NPs are efficient nanoscale heating sources to convert light energy to thermal energy due to their ability to concentrate light and absorption cross section much higher than that of their physical cross sections.85 This thermal energy can be sequestered by the reconfigurable components and used to induce structural changes when transformed into mechanical energy, as shown in Figure 6. Similarly, the structural change induced by chemical changes or electric fields make it possible to transform chemical energy and electrical energy to mechanical energy.44,60 Often borrowing lessons from biology, these different forms of energy can be transformed to mechanical energy to induce directional movements such as walking and rotation. Liu et al.59,95,108 demonstrated manipulation of the relative translational or rotational movement of two gold nanorods on DNA origami templates via adding filler or striper DNA or introducing light-sensitive azobenzene photoswitches in the DNA backbone. In addition to nanoscale directional movement, macroscale manipulation can also been realized, as evidenced by the muscle-like structures fabricated using free-standing AuNPs films assembled using DNA linkers (Figure 4).60 The structural changes of reconfigurable plasmonic nanomaterials exposed to stimuli also provide possible routes to modulate bioactivity and chemical reactivity. Due to their high surface area, tunable surface functionality and biocompatiblity, plasmonic NPs, especially AuNPs, are widely used to conjugate with biomolecules to enable their targeted delivery.109,110 A key challenge in this strategy is to dynamically modulate the structure and activity of these conjugates to ensure adjustable functionality in different in-vivo or in-vitro environments.111 For instance, Tan and coworkers have demonstrated the ability to reversibly control the affinity of DNA aptamers for their targets by using molecular photoswitches to regulate the aptamer structure.112,113 In addition to studying how the aptamer binds to its substrate, we imagine such approaches could be used to


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control the binding affinity of a ligand to expand the working dynamic range of a sensor platform beyond that imposed by a traditionally fixed dissociation constant.

Beyond molecular

photoswitches, the temperature-dependent conformation changes of PNIPAM make it useful as shading material to adjust the exposed proportion of the surface conjugated biomolecules and their bioactivities. Using such an approach, Mirkin et al.99 tethered both PNIPAM and DNA onto AuNP surfaces and demonstrated that the particles can be reversibly switched from hiding, to exposing, the DNA by switching the PNIPAM below and above the LCST, respectively. Tethering a biotin to the end of the DNA, they showed that the AuNP-DNA-PNIPAM conjugates had much higher affinity for streptavidin above the PNIPAM LCST.99 Similarly, Mastrotto et al.114 attached both thiolated folic acid and PNIPAM to the surface of AuNPs and found that these conjugates displayed temperature-controlled tumor cell targeting. Similar temperature-modulated bioactivity has also been observed on PNIPAM-modified AuNP-protein conjugates.115 Combining these types of approaches with photothermal or photochemical actuation of the polymer shell would seem an attractive approach for future researchers. On the other hand, the confined space in NP assemblies can serve as nanoreactors to modulate the chemical reactions inside. For example, Zhao et al.96 demonstrated that the molecules trapped inside of the gaps between assembled AuNPs exhibited faster reaction kinetics and stereo-selectivity than those in bulk solution. We envision that future work on controlling the size and shape of these nanoreactors based on dynamic control of the structure of reconfigurable plasmonic nanomaterials will open promising routes to modulate catalytic activities or thermodynamics of enantioselective reactions. Furthermore, reversibly reconfigurable plasmonic nanomaterials have been widely used in controlled drug delivery based on their structural changes at targeted sites.116 A general strategy is to photothermally heat plasmonic NPs and induce release of biomolecules loaded on the NP



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surfaces at a targeted site using near-infrared (NIR) illumination.117,118 As an example, Kang et al.119 coated Au-Ag nanorods with DNA cross-linked polymeric shells hybridized with targeting aptamers and found that NIR illumination induced fast release of the aptamer as a result of local temperature increase originated from the photothermal heating of the nanorod. Interestingly, recent theory work by Masiello and co-workers has indicated that coupled metal nanostructures possessing multimodal plasmon resonances may be selectively heated at different spatial locations by photoexcitation with different wavelengths.120 We propose that in the future it should therefore be possible to engineer nanostructures with complex multimodal plasmon resonances: in principle, if these nanostructures were chemically functionalized in an anisotropic fashion, then it would be possible to selectively release different chemical payloads, or selectively disassemble, through the choice of excitation wavelength (which would dictate where the local photothermal heating was localized).

4. CONCLUSIONS AND OUTLOOK In this Perspective, we have summarized recent developments in the fabrication of reversibly reconfigurable plasmonic nanomaterials. The overall design principle is to tether plasmonic nanomaterials with stimuli-responsive components that can reversibly switch between two or more different steady states under various stimuli such as chemical input, temperature and light. Given their reconfigurable structures, these plasmonic nanomaterials exhibit highly tunable optical, thermal and mechanical properties in response to external stimuli. Therefore, these plasmonic nanomaterials are being widely explored for use in applications such as LSPR sensing, energy transformation and modulated bioactivity and drug delivery. Despite the significant progress in fabricating reconfigurable plasmonic nanomaterials and developing their applications as 22 ACS Paragon Plus Environment

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summarized above, this field is still in a phase of rapid growth and discovery, and we end our perspective here by discussing some of the scientific challenges to be conquered while proposing some additional areas for future work beyond those described in Section 3. In all of the examples we have described so far, the input stimuli result in an organizational and physiochemical change in the properties of the reconfigurable plasmonic nanomaterials. However, these changes usually provide feedback signals that are too small -- if they are present at all -- to regulate the response of the reconfigurable materials. Thus, a straightforward question is, can we incorporate a feedback mechanism into such materials so that their responses to the stimuli become self-regulated? The collective optical properties of plasmonic materials provide many routes through which one might imagine designing such feedback. For instance, to expand on the theme of optically reconfigurable plasmonic nanomaterials, such structures could be designed with positive (or negative) feedback by bringing the plasmon resonance into, or out of, resonance with the excitation source. For example, if the LSPR is designed to shift away from the excitation wavelength, the absorption of the plasmonic components will weaken with increasing photoexcitation thus causing the light absorption (and hence local photothermal heating rate, or molecular photoswitching rate) to drop. In this fashion, one could design photothermally responsive structures that “self-regulate” to an equilibrium local temperature over a wider range of input powers.121 Another possible route to realize such feedback loops might be to integrate plasmonic nanostructures that are responsive to stimuli pairs such as light and temperature, or light and chemical inputs, so that the physical or chemical changes in response of one stimulus cancels out or facilitate the changes induced by the other stimuli, forcing the system into a quasi-steady or steady state without external interference. One pioneering example is the plasmon-enhanced thermophoresis of AuNPs presented by Lin et al.121 They demonstrated that laser irradiation of Au



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nanoislands on a substrate resulted in temperature gradient of the surrounding environment due to photothermal heating; Au nanotriangles in the solution responded to the temperature gradient and migrated from the hot region to the cool region to form assemblies which could disassemble upon removal of the laser.121 Another challenge is to better introduce directionality into a linear or rotational structural change of the reconfigurable plasmonic nanomaterials under stimuli. Recent developments in structural DNA and protein nanotechnology have made it possible to design DNA and protein scaffolds with a variety of one, two or three dimensional geometries.122-126 Importantly, the structural diversity and complexity of these DNA and protein scaffolds make it possible to introduce directional responses into these reconfigurable plasmonic nanomaterials,59,95 which can be transduced to produce observable directional movement and detectable signals that are normally buried inside of isotropic responses.95,108 We envision that future efforts in integrating linear59 or rotary movement127 reported in molecular machines into plasmonic nanomaterials will lead to enhanced functionalities such as triggered transportation of nanoscale targets, or as components of addressable nanomachines. A rich library of plasmonic NPs and stimulus-responsive building blocks can also be used to fabricate reconfigurable plasmonic nanomaterials with novel properties and functionalities. Currently, gold nanospheres and nanorods are the most commonly used plasmonic NPs that are assembled into reconfigurable plasmonic nanomaterials because of their mature syntheses, chemical stability, robust surface chemistry and tunable optical properties in the visible-NIR region. A much wider collection of plasmonic NPs of varying chemical compositions from aluminum128 to silver and gold, varying shapes from spheres and rods to plates and stars can be used to fabricate reconfigurable plasmonic nanomaterials to realize tunable optical properties in 24 ACS Paragon Plus Environment

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the UV, visible, NIR and mid-NIR region.129,130 On the other hand, incorporating novel materials is another route to add functionalities to the reconfigurable plasmonic nanomaterials. As one example, we consider the example of non-linear optical responses mentioned in the introduction.131 Because of their dramatic concentrations of local fields and their exquisite sensitivity to interparticle couplings, one can imagine plasmonic composites exhibiting non-linear optical properties whose enhancement factors or spectral responses can be reprogrammed in response to an external signal – even an optical trigger. As another possibility, we note that recent years have seen rapid development and application of two-dimensional (2D) materials due to their interesting physicochemical properties including high surface area, high carrier mobility and density.132,133 However, while 2D materials have high extinction per volume, they are so thin they often do not effectively harvest incident light. The synergy between 2D materials and plasmonic NPs that can effectively harvest light can be harnessed to realize many interesting properties such as tunable optical properties of both 2D materials and plasmonic nanomaterials, enhanced PL and SERS signals and application in sensing and spectroscopy.134,135 Finally, we note that scaled-up syntheses of reconfigurable plasmonic nanomaterials will be critical for large-scale applications such as temperature responsive smart windows; therefore, significant efforts are needed to delicately control the parameters for largescale reactions that scale size, shape, and composition control of plasmonic nanomaterials beyond the small-batch reactions carried out in academic laboratories. In this regard, the very recent work to reproduce DNA-like assembly motifs, but using synthetic polymers,84 represents a promising first step. Even at the small scale, however, such reconfigurable materials are poised to transform diagnostic and sensing applications.



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Although this Perspective is focused on a subset of reconfigurable plasmonic nanomaterials synthesized by colloidal chemistry methods, these design strategies can be extended to nanostructures fabricated by lithography, and to categories of stimuli beyond those we have considered here. Given the wide interest in the fabrication and application of reconfigurable nanomaterials,75,136-139 we are confident that a large collection of reversibly reconfigurable plasmonic nanostructures with interesting physical properties will emerge and become indispensable as building blocks for enabling applications in areas as diverse as sensing, imaging, energy harvesting, biomaterials, and optoelectronics.

AUTHOR INFORMATION Corresponding Author *Email: [email protected] (D.S.G.)

Notes The authors declare no competing financial interests. ACKNOWLEDGEMENT D.S.G acknowledges that this perspective is based in part on work supported by AFOSR FA955014-1-0250. D.S.G also acknowledges additional support from the University of Washington Kwiram Endowment, and Washington Research Foundation. Z.Q acknowledges the Washington Research Foundation Innovation Fellowships in Clean Energy offered by the Clean Energy Institute at the University of Washington.


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REFERENCES (1) Sharma, B.; Frontiera, R. R.; Henry, A.-I.; Ringe, E.; Van Duyne, R. P. Mater. Today 2012, 15, 16. (2) Chen, Y.; Munechika, K.; Ginger, D. S. Nano Lett. 2007, 7, 690. (3) Linic, S.; Aslam, U.; Boerigter, C.; Morabito, M. Nat. Mater. 2015, 14, 567. (4) Deraedt, C.; Astruc, D. Acc. Chem. Res. 2014, 47, 494. (5) Sepúlveda, B.; Angelomé, P. C.; Lechuga, L. M.; Liz-Marzán, L. M. Nano Today 2009, 4, 244. (6) Willets, K.A.; Van Duyne, R. P. Annu. Rev. Phys. Chem. 2007, 58, 267. (7) Du, J.; Jiang, L.; Shao, Q.; Liu, X.; Marks, R. S.; Ma, J.; Chen, X. Small 2013, 9, 1467. (8) Stratakis, E.; Kymakis, E. Mater. Today 2013, 16, 133. (9) Kulkarni, A. P.; Noone, K. M.; Munechika, K.; Guyer, S. R.; Ginger, D. S. Nano Lett. 2010, 10, 1501. (10) Karatay, D. U.; Salvador, M.; Yao, K.; Jen, A. K. Y.; Ginger, D. S. Appl. Phys. Lett. 2014, 105, 033304. (11) Yao, K.; Salvador, M.; Chueh, C.-C.; Xin, X.-K.; Xu, Y.-X.; deQuilettes, D. W.; Hu, T.; Chen, Y.; Ginger, D. S.; Jen, A. K. Y. Adv. Energy Mater. 2014, 4, 1400206. (12) Stavytska-Barba, M.; Salvador, M.; Kulkarni, A.; Ginger, D. S.; Kelley, A. M. J. Phys. Chem. C 2011, 115, 20788. (13) Rosi, N. L.; Mirkin, C. A. Chem. Rev. 2005, 105, 1547. (14) Xu, H.; Bjerneld, E. J.; Käll, M.; Börjesson, L. Phys. Rev. Lett. 1999, 83, 4357. (15) Nie, S.; Emory, S. R. Science 1997, 275, 1102. (16) Le Ru, E. C.; Etchegoin, P. G.; Meyer, M. J. Chem. Phys 2006, 125, 204701. (17) Le Ru, E. C.; Etchegoin, P. G. Annu. Rev. Phys. Chem. 2012, 63, 65. (18) Gwo, S.; Wang, C.-Y.; Chen, H.-Y.; Lin, M.-H.; Sun, L.; Li, X.; Chen, W.-L.; Chang, Y.-M.; Ahn, H. ACS Photonics 2016, 3, 1371. (19) Kauranen, M.; Zayats, A. V. Nat. Photon. 2012, 6, 737. (20) Boriskina, S. V.; Ghasemi, H.; Chen, G. Mater. Today 2013, 16, 375. (21) Hao, F.; Sonnefraud, Y.; Dorpe, P. V.; Maier, S. A.; Halas, N. J.; Nordlander, P. Nano Lett. 2008, 8, 3983. (22) King, N. S.; Liu, L.; Yang, X.; Cerjan, B.; Everitt, H. O.; Nordlander, P.; Halas, N. J. ACS Nano 2015, 9, 10628. (23) Verellen, N.; Van Dorpe, P.; Huang, C.; Lodewijks, K.; Vandenbosch, G. A. E.; Lagae, L.; Moshchalkov, V. V. Nano Lett. 2011, 11, 391. (24) Lassiter, J. B.; Sobhani, H.; Fan, J. A.; Kundu, J.; Capasso, F.; Nordlander, P.; Halas, N. J. Nano Lett. 2010, 10, 3184. (25) Park, D. J.; Zhang, C.; Ku, J. C.; Zhou, Y.; Schatz, G. C.; Mirkin, C. A. Proc. Natl. Acad. Sci. U.S.A. 2015, 112, 977. (26) Qian, Z.; Hastings, S. P.; Li, C.; Edward, B.; McGinn, C. K.; Engheta, N.; Fakhraai, Z.; Park, S.-J. ACS Nano 2015, 9, 1263. (27) Sheikholeslami, S. N.; Alaeian, H.; Koh, A. L.; Dionne, J. A. Nano Lett. 2013, 13, 4137. (28) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. Nature 1996, 382, 607. 27 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 40

(29) Macfarlane, R. J.; Lee, B.; Jones, M. R.; Harris, N.; Schatz, G. C.; Mirkin, C. A. Science 2011, 334, 204. (30) Karg, M.; Hellweg, T.; Mulvaney, P. Adv. Funct. Mater. 2011, 21, 4668. (31) Zhu, M.-Q.; Wang, L.-Q.; Exarhos, G. J.; Li, A. D. Q. J. Am. Chem. Soc. 2004, 126, 2656. (32) Liu, Y.; Han, X.; He, L.; Yin, Y. Angew. Chem. Int. Ed. 2012, 51, 6373. (33) Museum:, T. B.; The British Museum: http://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?objectI d=61219&partId=1, 2017; Vol. 2017. (34) Neumann, O.; Urban, A. S.; Day, J.; Lal, S.; Nordlander, P.; Halas, N. J. ACS Nano 2013, 7, 42. (35) Li, D.; Song, S.; Fan, C. Acc. Chem. Res. 2010, 43, 631. (36) Schild, H. G. Prog. Polym. Sci. 1992, 17, 163. (37) Russew, M.-M.; Hecht, S. Adv. Mater. 2010, 22, 3348. (38) Choi, J.; Chung, H.; Yun, J.-H.; Cho, M. ACS Appl. Mater. Interfaces 2016, 8, 24008. (39) Kingsland, A.; Samai, S.; Yan, Y.; Ginger, D. S.; Maibaum, L. J. Phys. Chem. Lett. 2016, 7, 3027. (40) Duchstein, P.; Neiss, C.; Görling, A.; Zahn, D. J. Mol. Model. 2012, 18, 2479. (41) Tsutsui, Y.; Fudouzi, H.; Hayakawa, T.; Nogami, M. Materials Science and Engineering 2011, 18, 082008. (42) Fu, L.; Liu, Y.; Wang, W.; Wang, M.; Bai, Y.; Chronister, E. L.; Zhen, L.; Yin, Y. Nanoscale 2015, 7, 14483. (43) Han, X.; Liu, Y.; Yin, Y. Nano Lett. 2014, 14, 2466. (44) Kim, K.; Xu, X.; Guo, J.; Fan, D. L. Nat. Commun. 2014, 5, 3632. (45) Wang, M.; Gao, C.; He, L.; Lu, Q.; Zhang, J.; Tang, C.; Zorba, S.; Yin, Y. J. Am. Chem. Soc. 2013, 135, 15302. (46) Pinheiro, A. V.; Han, D.; Shih, W. M.; Yan, H. Nat Nano 2011, 6, 763. (47) Seeman, N. C. Annu. Rev. Biochem 2010, 79, 65. (48) Cutler, J. I.; Auyeung, E.; Mirkin, C. A. J. Am. Chem. Soc. 2012, 134, 1376. (49) Sonnichsen, C.; Reinhard, B. M.; Liphardt, J.; Alivisatos, A. P. Nat Biotech 2005, 23, 741. (50) Dubertret, B.; Calame, M.; Libchaber, A. J. Nat Biotech 2001, 19, 365. (51) Aldaye, F. A.; Palmer, A. L.; Sleiman, H. F. Science 2008, 321, 1795. (52) Yan, W.; Xu, L.; Xu, C.; Ma, W.; Kuang, H.; Wang, L.; Kotov, N. A. J. Am. Chem. Soc. 2012, 134, 15114. (53) Mastroianni, A. J.; Claridge, S. A.; Alivisatos, A. P. J. Am. Chem. Soc. 2009, 131, 8455. (54) Shen, X.; Asenjo-Garcia, A.; Liu, Q.; Jiang, Q.; García de Abajo, F. J.; Liu, N.; Ding, B. Nano Lett. 2013, 13, 2128. (55) Jain, P. K.; Huang, W.; El-Sayed, M. A. Nano Lett. 2007, 7, 2080. (56) Chen, J. I. L.; Chen, Y.; Ginger, D. S. J. Am. Chem. Soc. 2010, 132, 9600. (57) Lee, S. E.; Chen, Q.; Bhat, R.; Petkiewicz, S.; Smith, J. M.; Ferry, V. E.; Correia, A. L.; Alivisatos, A. P.; Bissell, M. J. Nano Lett. 2015, 15, 4564. (58) Maye, M. M.; Kumara, M. T.; Nykypanchuk, D.; Sherman, W. B.; Gang, O. Nat. Nano 2010, 5, 116. 28 ACS Paragon Plus Environment

Page 29 of 40

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(59) Zhou, C.; Duan, X.; Liu, N. Nat. Commun. 2015, 6, 8102. (60) Shim, T. S.; Estephan, Z. G.; Qian, Z.; Prosser, J. H.; Lee, S. Y.; Chenoweth, D. M.; Lee, D.; Park, S.-J.; Crocker, J. C. Nat. Nanotechnol. 2017, 12, 41. (61) Nie, Z.; Fava, D.; Kumacheva, E.; Zou, S.; Walker, G. C.; Rubinstein, M. Nat Mater. 2007, 6, 609. (62) Liu, K.; Zhao, N.; Kumacheva, E. Chem. Soc. Rev. 2011, 40, 656. (63) Gong, J.; Li, G.; Tang, Z. Nano Today 2012, 7, 564. (64) Taladriz-Blanco, P.; Buurma, N. J.; Rodriguez-Lorenzo, L.; Perez-Juste, J.; LizMarzan, L. M.; Herves, P. J. Mater. Chem. 2011, 21, 16880. (65) Tian, Z.; Yang, C.; Wang, W.; Yuan, Z. ACS Appl. Mater. Interfaces 2014, 6, 17865. (66) Sun, Z.; Ni, W.; Yang, Z.; Kou, X.; Li, L.; Wang, J. Small 2008, 4, 1287. (67) Roy, D.; Brooks, W. L. A.; Sumerlin, B. S. Chem. Soc. Rev. 2013, 42, 7214. (68) Nguyen, M.; Felidj, N.; Mangeney, C. Chem. Mater. 2016, 28, 3564. (69) Karg, M.; Hellweg, T. Curr. Opin. Colloid Interface Sci. 2009, 14, 438. (70) Heskins, M.; Guillet, J. E. J. Macromol. Sci: Part A - Chem. 1968, 2, 1441. (71) Shimizu, H.; Wada, R.; Okabe, M. Polym. J 2009, 41, 771. (72) Qian, Z.; Guye, K. N.; Masiello, D. J.; Ginger, D. S. J.Phys.Chem. B 2017, 121, 1092. (73) Karg, M.; Pastoriza-Santos, I.; Pérez-Juste, J.; Hellweg, T.; Liz-Marzán, L. M. Small 2007, 3, 1222. (74) Lim, S.; Song, J. E.; La, J. A.; Cho, E. C. Chem. Mater. 2014, 26, 3272. (75) Stuart, M. A. C.; Huck, W. T. S.; Genzer, J.; Muller, M.; Ober, C.; Stamm, M.; Sukhorukov, G. B.; Szleifer, I.; Tsukruk, V. V.; Urban, M.; Winnik, F.; Zauscher, S.; Luzinov, I.; Minko, S. Nat. Mater. 2010, 9, 101. (76) Lowik, D. W. P. M.; Leunissen, E. H. P.; van den Heuvel, M.; Hansen, M. B.; van Hest, J. C. M. Chem. Soc. Rev. 2010, 39, 3394. (77) Lemieux, V.; Adams, P. H. H. M.; van Hest, J. C. M. Chem. Commun. 2010, 46, 3071. (78) Lewandowski, W.; Fruhnert, M.; Mieczkowski, J.; Rockstuhl, C.; Górecka, E. Nat. Commun. 2015, 6, 6590. (79) Zep, A.; Wojcik, M. M.; Lewandowski, W.; Sitkowska, K.; Prominski, A.; Mieczkowski, J.; Pociecha, D.; Gorecka, E. Angew. Chem. Int. Ed. 2014, 53, 13725. (80) Wojcik, M. M.; Gora, M.; Mieczkowski, J.; Romiszewski, J.; Gorecka, E.; Pociecha, D. Soft Matter 2011, 7, 10561. (81) Bisoyi, H. K.; Kumar, S. Chem. Soc. Rev. 2011, 40, 306. (82) Choudhary, A.; Singh, G.; Biradar, A. M. Nanoscale 2014, 6, 7743. (83) Kanayama, N.; Tsutsumi, O.; Kanazawa, A.; Ikeda, T. Chem. Commun. 2001, 2640. (84) Zhang, J.; Santos, P. J.; Gabrys, P. A.; Lee, S.; Liu, C.; Macfarlane, R. J. J. Am. Chem. Soc. 2016, 138, 16228. (85) Baffou, G.; Quidant, R. Laser Photon. Rev. 2013, 7, 171. (86) Richardson, H. H.; Carlson, M. T.; Tandler, P. J.; Hernandez, P.; Govorov, A. O. Nano Lett. 2009, 9, 1139. (87) Baffou, G.; Quidant, R.; Girard, C. Phys. Rev. B 2010, 82, 165424. (88) Jiang, K.; Smith, D. A.; Pinchuk, A. J. Phys. Chem. C 2013, 117, 27073. 29 ACS Paragon Plus Environment


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(89) Ding, T.; Valev, V. K.; Salmon, A. R.; Forman, C. J.; Smoukov, S. K.; Scherman, O. A.; Frenkel, D.; Baumberg, J. J. Proc. Natl. Acad. Sci. U.S.A. 2016, 113, 5503. (90) Slocik, J. M.; Tam, F.; Halas, N. J.; Naik, R. R. Nano Lett. 2007, 7, 1054. (91) Browne, W. R.; Feringa, B. L. Annu. Rev. Phys. Chem. 2009, 60, 407. (92) Asanuma, H.; Liang, X.; Nishioka, H.; Matsunaga, D.; Liu, M.; Komiyama, M. Nat. Protoc. 2007, 2, 203. (93) Yan, Y.; Chen, J. I. L.; Ginger, D. S. Nano Lett. 2012, 12, 2530. (94) Yan, Y.; Wang, X.; Chen, J. I. L.; Ginger, D. S. J. Am. Chem. Soc. 2013, 135, 8382. (95) Kuzyk, A.; Yang, Y.; Duan, X.; Stoll, S.; Govorov, A. O.; Sugiyama, H.; Endo, M.; Liu, N. Nat. Commun. 2016, 7, 10591. (96) Zhao, H.; Sen, S.; UdayabhaskararaoT; Sawczyk, M.; Kučanda, K.; Manna, D.; Kundu, P. K.; Lee, J.-W.; Král, P.; Klajn, R. Nat. Nanotech. 2016, 11, 82. (97) Shi, S.; Wang, Q.; Wang, T.; Ren, S.; Gao, Y.; Wang, N. J.Phys.Chem. B 2014, 118, 7177. (98) Joshi, G. K.; Blodgett, K. N.; Muhoberac, B. B.; Johnson, M. A.; Smith, K. A.; Sardar, R. Nano Lett. 2014, 14, 532. (99) Zhang, K.; Zhu, X.; Jia, F.; Auyeung, E.; Mirkin, C. A. J. Am. Chem. Soc. 2013, 135, 14102. (100) Yavuz, M. S.; Cheng, Y.; Chen, J.; Cobley, C. M.; Zhang, Q.; Rycenga, M.; Xie, J.; Kim, C.; Song, K. H.; Schwartz, A. G.; Wang, L. V.; Xia, Y. Nat. Mater. 2009, 8, 935. (101) Yan, Y.; Samai, S.; Bischoff, K. L.; Zhang, J.; Ginger, D. S. ACS Sensors 2016, 1, 566. (102) Wang, C.; Du, Y.; Wu, Q.; Xuan, S.; Zhou, J.; Song, J.; Shao, F.; Duan, H. Chem. Commun. 2013, 49, 5739. (103) Zhao, Y.; Cao, L.; Ouyang, J.; Wang, M.; Wang, K.; Xia, X.-H. Anal. Chem. 2013, 85, 1053. (104) Liu, X.-Y.; Cheng, F.; Liu, Y.; Li, W.-G.; Chen, Y.; Pan, H.; Liu, H.-J. J. Mater. Chem. 2010, 20, 278. (105) Tagliazucchi, M.; Blaber, M. G.; Schatz, G. C.; Weiss, E. A.; Szleifer, I. ACS Nano 2012, 6, 8397. (106) Anker, J. N.; Hall, W. P.; Lyandres, O.; Shah, N. C.; Zhao, J.; Van Duyne, R. P. Nat. Mater. 2008, 7, 442. (107) Hsiang, J.-C.; Jablonski, A. E.; Dickson, R. M. Acc. Chem. Res. 2014, 47, 1545. (108) Urban, M. J.; Zhou, C.; Duan, X.; Liu, N. Nano Lett. 2015, 15, 8392. (109) Arvizo, R.; Bhattacharya, R.; Mukherjee, P. Expert Opin. Drug Deliv 2010, 7, 753. (110) Doane, T.; Burda, C. Adv. Drug Deliv. Rev. 2013, 65, 607. (111) Xie, J.; Lee, S.; Chen, X. Adv. Drug Deliv. Rev. 2010, 62, 1064. (112) Kim, Y.; Phillips, J. A.; Liu, H.; Kang, H.; Tan, W. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 6489. (113) Phillips, J. A.; Liu, H.; O’Donoghue, M. B.; Xiong, X.; Wang, R.; You, M.; Sefah, K.; Tan, W. Bioconjugate Chem. 2011, 22, 282. (114) Mastrotto, F.; Caliceti, P.; Amendola, V.; Bersani, S.; Magnusson, J. P.; Meneghetti, M.; Mantovani, G.; Alexander, C.; Salmaso, S. Chem. Commun. 2011, 47, 9846.


Page 31 of 40

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(115) Liu, F.; Cui, Y.; Wang, L.; Wang, H.; Yuan, Y.; Pan, J.; Chen, H.; Yuan, L. ACS Appl. Mater. Interfaces 2015, 7, 11547. (116) Mura, S.; Nicolas, J.; Couvreur, P. Nat. Mater. 2013, 12, 991. (117) Hribar, K. C.; Lee, M. H.; Lee, D.; Burdick, J. A. ACS Nano 2011, 5, 2948. (118) Xiao, Z.; Ji, C.; Shi, J.; Pridgen, E. M.; Frieder, J.; Wu, J.; Farokhzad, O. C. Angew. Chem. Int. Ed. 2012, 51, 11853. (119) Kang, H.; Trondoli, A. C.; Zhu, G.; Chen, Y.; Chang, Y.-J.; Liu, H.; Huang, Y.F.; Zhang, X.; Tan, W. ACS Nano 2011, 5, 5094. (120) Baldwin, C. L.; Bigelow, N. W.; Masiello, D. J. J. Phys. Chem. Lett. 2014, 5, 1347. (121) Lin, L.; Peng, X.; Wang, M.; Scarabelli, L.; Mao, Z.; Liz-Marzán, L. M.; Becker, M. F.; Zheng, Y. ACS Nano 2016, 10, 9659. (122) Zhang, F.; Nangreave, J.; Liu, Y.; Yan, H. J. Am. Chem. Soc. 2014, 136, 11198. (123) Lu, C.-H.; Cecconello, A.; Willner, I. J. Am. Chem. Soc. 2016, 138, 5172. (124) Torring, T.; Voigt, N. V.; Nangreave, J.; Yan, H.; Gothelf, K. V. Chem. Soc. Rev. 2011, 40, 5636. (125) Huang, P.-S.; Boyken, S. E.; Baker, D. Nature 2016, 537, 320. (126) Khoury, G. A.; Smadbeck, J.; Kieslich, C. A.; Floudas, C. A. Trends Biotechnol. 2014, 32, 99. (127) Browne, W. R.; Feringa, B. L. Nat. Nano. 2006, 1, 25. (128) McClain, M. J.; Schlather, A. E.; Ringe, E.; King, N. S.; Liu, L.; Manjavacas, A.; Knight, M. W.; Kumar, I.; Whitmire, K. H.; Everitt, H. O.; Nordlander, P.; Halas, N. J. Nano Lett. 2015, 15, 2751. (129) Lu, X. R., Matthew; Skrabalak, Sara E.; Wiley, Benjamin; Xia, Younan Annu. Rev. Phys. Chem. 2009, 60, 167. (130) Romo-Herrera, J. M.; Alvarez-Puebla, R. A.; Liz-Marzan, L. M. Nanoscale 2011, 3, 1304. (131) Stellacci, F.; Bauer, C. A.; Meyer-Friedrichsen, T.; Wenseleers, W.; Marder, S. R.; Perry, J. W. J. Am. Chem. Soc. 2003, 125, 328. (132) Castro Neto, A. H.; Guinea, F.; Peres, N. M. R.; Novoselov, K. S.; Geim, A. K. Rev. Mod. Phys. 2009, 81, 109. (133) Wang, Q. H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J. N.; Strano, M. S. Nat Nano 2012, 7, 699. (134) Li, X.; Zhu, J.; Wei, B. Chem. Soc. Rev. 2016, 45, 3145. (135) Yin, P. T.; Kim, T.-H.; Choi, J.-W.; Lee, K.-B. Phys. Chem. Chem. Phys. 2013, 15, 12785. (136) Wang, M.; Yin, Y. J. Am. Chem. Soc. 2016, 138, 6315. (137) Ge, J.; Yin, Y. Angew. Chem. Int. Ed. 2011, 50, 1492. (138) Blum, A. P.; Kammeyer, J. K.; Rush, A. M.; Callmann, C. E.; Hahn, M. E.; Gianneschi, N. C. J. Am. Chem. Soc. 2015, 137, 2140. (139) Lu, Y.; Sun, W.; Gu, Z. J. Control. Release 2014, 194, 1.



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Table of Content


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Figure 1 201x134mm (300 x 300 DPI)

ACS Paragon Plus Environment


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Figure 2 147x79mm (300 x 300 DPI)


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Figure 3 147x178mm (300 x 300 DPI)



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Figure 4 187x131mm (300 x 300 DPI)


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Figure 5 203x91mm (150 x 150 DPI)



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Figure 6 245x161mm (300 x 300 DPI)


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Figure 7 199x57mm (300 x 300 DPI)



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Table of Contents Figure 82x35mm (300 x 300 DPI)


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Reversibly Reconfigurable Colloidal Plasmonic Nanomaterials

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