Plasmon Controlled Shaping of Metal Nanoparticle Aggregates by

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Plasmon Controlled Shaping of Metal Nanoparticle Aggregates by Femtosecond Laser Induced Melting Daniele Catone, Alessandra Ciavardini, Lorenzo Di Mario, Alessandra Paladini, Francesco Toschi, Antonella Cartoni, Ilaria Fratoddi, Iole Venditti, Alessandro Alabastri, Remo Proietti Zaccaria, and Patrick O'Keeffe J. Phys. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.jpclett.8b02117 • Publication Date (Web): 14 Aug 2018 Downloaded from http://pubs.acs.org on August 16, 2018

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The Journal of Physical Chemistry Letters

Plasmon Controlled Shaping of Metal Nanoparticle Aggregates by Femtosecond

†

Laser Induced Melting.

D. Catone,‡ A. Ciavardinia,‡ L. Di Mario,‡ A. Paladini,‡ F. Toschi,‡ A. Cartoni,¶ ‡ I. ,

Fratoddi,¶ I. Venditti,§ A. Alabastri,k R. Proietti Zaccaria,⊥ # and P. O'Keee∗ ‡ ,

,

‡Istituto di Struttura della Materia-CNR (ISM-CNR), Division of Ultrafast Processes in Materials (FLASHit), Italy.

¶Department of Chemistry, Università "Sapienza", 5 Piazzale Aldo Moro, Rome, Italy. §Department of Sciences, Roma Tre University, Via della Vasca Navale 79, Rome, Italy. kDepartment of Physics and Astronomy MS 61 and Laboratory for Nanophotonics, Smalley-Curl Institute, Rice University, Houston, Texas 77005, United States.

⊥Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy. #Cixi Institute of Biomedical Engineering, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.

E-mail: patrick.okee[email protected] Phone: +39 (0)6 90672248. Fax: +39 (0)6 90672235 a Present address: Elettra-Sincrotrone Trieste S.c.p.A., in Area di Ricerca, Strada statale 14, km 163.5,34149 Basovizza (Trieste), Italy

†

August 10, 2018

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Abstract In this work we show how to control the morphology of femtosecond laser melted gold nanosphere aggregates. A careful choice of both laser uence and wavelength makes it possible to selectively excite dierent aggregate substructures to produce larger spherical nanoparticles, nanorods and nanoprisms or necklace-like 1D nanostructures in which the nanoparticles are interlinked by bridges. Finite integral technique calculations have been performed on the near-eld concentration of light in the nanostructures which conrm the wavelength dependence of the light concentration and suggest that the resulting localized high intensities lead to non-thermal melting. We show that by tuning the wavelength of the melting light it is possible to choose the spatial extension of the ensembles of NPs heated thus allowing us to exhibit control over the morphology of the nanostructures formed by the melting process. By a proper combination of this method with self assembly of chemically synthesized nanoparticles, one can envisage the development of an innovative high-throughput high-resolution nanofabrication technique.

Graphical TOC Entry

Keywords Thermoplasmonics, Nanomelting, Nanofabrication

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The interaction of visible light with noble metal nanoparticles and nanostructures has been the subject of intensive study in recent decades. 1,2 Much of this interest has been stimulated, in particular, by the presence of the localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) in the visible range due to a resonance between the oscillating dipole created by displaced electrons in the NPs and the light eld impinging on the NPs. The photon connement induced by the LSPR strongly enhances all radiative and non-radiative processes in the vicinity of the surface of the particles. AuNPs have found applications in a wide range of areas 3 and for this reason here we concentrate on the study of the melting of AuNP aggregates although the concepts outlined are also applicable to other metals. One of the most attractive features of these structures is the possibility to deposit heat in a controlled manner at the nanoscale level, 4,5 which is exploited in elds such as photothermal therapy 610 and photocatalysis. 11 Furthermore, the light irradiation of NPs can be exploited to control their morphology either by guiding wet synthesis paths, 12,13 direct reshaping of the nanoparticles by melting 1420 or nanowelding. 2125 For example, Au nanorods have been reshaped with light in order to achieve an aspect ratio dispersity as low a 2%. 20 Furthermore, light induced nanowelding has been used to weld Au/Ag nanoparticles in aggregates 22,26 and Ag nanowires 25 to each other. Recently, some notable renements of this technique have been made in which light has been used to "thread" strings of NPs together 27 as well as to weld gold nanorods tip-to-tip in a controlled manner, 18 in some cases achieving sub-nanometer resolution on the nal morphology of the welded NPs. In spite of the extensive research in this area the precise mechanisms of the aforementioned processes are not fully understood. This is due to the complex interplay of a large number of factors such as the temporal length of the melting light pulse, the eect of hot spots due to the nanoantenna eect in metal nanostructures, dierent regimes where absorption or near eld eects dominate, thermal vs. non-thermal melting, 28,29 local vs. isotropic melting, 28,29 plasma generation 29 and non-linear eects. 3032 Achieving a full understanding of these factors together with accurately controlled self-assembly of nanopar3



ticles will lead to a nanofabrication technique with unprecedented spatial resolution and processing speed by combining the advantages of top-down and bottom-up techniques. 33

Figure 1: Schematic of the experimental setup employed for inducing the melting process and spectroscopic diagnostics of the AuNP aggregate solutions. The melting beam induces the melting of the AuNP aggregates, the pump beam excites the melted aggregates and the probe beam is delivered to the sample with a variable delay time providing an in-situ monitor of the eect of the melting laser. The trasmitted probe beam is dispersed and analyzed in the spectrometer providing the bidimensional TA spectrum of the sample (see text for details). In this work, we propose the use of tunable femtosecond laser radiation to induce the melting of nanoparticle aggregates into nanostructures with controlled size and shape, by tuning the wavelength of the melting radiation to coincide with plasmonic and/or interband excitation of the NPs. In particular, self-assembled aggregates formed by 10 nm spherical AuNPs stabilized by Isothiocyanate Rhodamine B (RITC) in water solution have been subjected to melting. The resulting nanostructures have been observed by scanning electron 4


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microscopy (SEM) and characterized by static and transient absorbance (TA) spectroscopy.

In a previous publication, 34 we characterized the structure and the spectroscopic behavior of the investigated aggregates, and demonstrated how their plasmonic response could be controlled by varying the quantity of RITC molecules on the surface of the AuNPs. The comparison between a model calculation and the experimental static absorbance data revealed that the measurements were best reproduced by a model involving chains of 10 nm diameter spherical gold nanoparticles of various lengths separated by 1 nm with the interparticle region described by the dielectric constant of water. These results agree with previous studies which showed that the plasmonic response of chains of NPs consists of a transverse plasmon resonance and a broad spatially extended longitudinal plasmon resonance due to delocalization of the plasmon resonance over a number of particles. 35,36 In the case of the transverse plasmon resonance the polarization of the light is perpendicular to the principal axis of the chain of NPs while for the longitudinal resonance this polarization lies along the axis. In general, interacting plasmon resonances in closely spaced chains of metal NPs can be qualitatively understood by the plasmon hybridization concept 37 in which the plasmons of a chain of NPs can be expressed as a linear combination of the plasmons of the individual NPs. This model predicts that the longitudinal (or extended) plasmon resonance exhibits small red shifts for short chains and larger red shifts for longer chains 3537 which is consistent with our observations. The transverse plasmonic resonance is much less dependent on the number of particles in the chain. 3537 Here, we have used the plasmonic response of the nanoparticle aggregates as a tool to induce selective melting of aggregates with dierent spatial extents. The eects of the laser uence and wavelength of the melting beam on the nanostructures have been explored using a 3 beam set-up (see Figure 1): namely a melting, a pump and a probe beam. The melting beam is used to irradiate the sample and to induce melting of the AuNPs aggregates. Afterwards, this melting beam is blocked and the pump and probe beams are focused on the 5



same spot to record the TA spectrum of the melted sample. This procedure makes it possible to locally characterize the eect of the melting laser before diusion disperses the melted structures. This step is useful during the optimization stage when the melting laser power is being tuned. The temporal delay between the low power pump (400 nm, 50 µJ/cm2 ) and the white light probe (350-800 nm) is set to a single value (1 ps) so that the transient spectra can be acquired in a few seconds. This in-situ spectroscopic diagnostic procedure allowed us to set the laser uence of the melting beam so as to induce the desired change of the transient spectral response of the aggregates within seconds. In this way it was possible to avoid low power levels where the nanoparticles are able to dissipate all of the heat of the melting laser without morphological changes and high powers where the plasmonic response (particularly the extended plasmon) is completely depleted due, for example, to explosive heating of the solvent around the NPs (nanocavitation) and/or precipitation of the nanostructures. 2 The three wavelengths chosen for the melting laser were 400 nm, 570 nm and 620 nm. The 400 nm and 620 nm correspond to mainly interband and longitudinal plasmon resonance excitations, respectively. The 570 nm, on the other hand, corresponds to the shoulder in the static spectrum of the non-irradiated solution (see Figure 2 (a)) and is mainly due to transverse plasmon resonance but sits on a background of both interband and longitudinal plasmon absorption. The power densities chosen for these melting wavelengths were 7.0 x 1010 W/cm2 , 2.5 x 1010 W/cm2 and 2.5 x 1010 W/cm2 , for 400 nm, 570 nm and 620 nm, respectively. These power densities were achieved by focusing a 50 fs (FWHM) laser to a 500 µm diameter circular spot on the sample. In order to produce a macroscopic quantity of melted aggregates for further analysis the cuvette containing the solution was rastered over the laser spot until the entire solution (100

µl) had been irradiated for the same amount of time (5 - 10 sec). The repetition rate of 500 Hz and the irradiation time means that each spot received 2500 - 5000 pulses. These solutions were then characterized by static absorbance measured by the transmission in a standard UV/Vis spectrometer and by the transient absorbance measured as the variation in 6


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Figure 2: (a) Static and (b) transient absorbances of non-irradiated sample and samples irradiated at 400, 570 and 620 nm acquired at a pump-probe delay of 1 ps. The inset in panel (b) shows a photograph of the rastered solutions showing the macroscopic eects of the melting. transmission following the low-power photoexcitation of the solutions at 400 nm. The result was a change in both the static (see Figure 2 (a)) and transient spectra (see Figure 2 (b)) of the entire solutions due to the morphological changes brought on by the irradiation (see inset of Figure 2 (b) for a photograph of the irradiated samples). The spectroscopic evidence shows the progressive depletion of the extended plasmon resonance on going from 620 to 570 nm with a shift of the resonance to the blue occurring for irradiation with 400 nm. These eects are even clearer in the transient absorbance spectra due to the narrower plasmonic features (see Figure 2 (b)). Our interpretation of these observations is that the plasmonic heating (570 and 620 nm) leads to a preferential melting of specic structures within the aggregates while the interband heating at 400 nm heats all of the aggregate. The 570 nm light is mainly absorbed by small structures (dimers and trimers) while the 620 nm light is mainly absorbed by long (≥ 4 NPs) chain-like structures. 34 The 400 nm melting exhibits

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dierent spectroscopic markers with respect to the plasmonically heated samples showing a change in the shape of the plasmonic resonance and a strong shift of the resonance to higher energy. This can be interpreted as being due to destruction of the aggregates and formation of isolated particles. Single spherical AuNPs in water exhibit a plasmon resonance at 520 nm (for 5 - 40 nm diameter particles) 38 and the appearance of new peaks at 523 nm in the static spectrum and 527 nm in the transient spectra following irradiation at 400 nm are consistent with the formation of such particles.

Figure 3: Size distributions of spherical particles (histogram) and log-normal t (solid line) of the non-irradiated sample (a), and samples irradiated at 400 nm (b), 570 nm (c) and 620 nm (d), with values of the mean xc = 9.6, 11.5, 10.2 and 9.3, respectively. Measurements are extracted from a series of SEM images. We have analysed the size distribution of the spherical particles contained in the melted samples by performing SEM measurements. To perform the SEM measurements the AuRITC aggregates in water are sonicated in order to assure good dispersion, deposited by 8


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casting on a monocrystalline silicon wafer and dried. The samples prepared in this way were investigated using a Field Emission SEM Zeiss Auriga 405. The size distribution of the non-irradiated and the 400 nm irradiated samples are shown in Figures 3 (a) and (b), respectively. A log-normal t of each size distribution is also reported, using the formula

y = y0 +

√ A e 2πwx

−(ln xx )2 c 2w2

, with y0 , xc , w and A corresponding to oset, mean, standard

deviation and area, respectively. Comparison of the two size distributions clearly shows that the melting has led to the formation of larger spherical NPs with diameters up to 30 nm accompanied by a shift of the mean of the log-normal t of the size distribution from xc = 9.6 to xc = 11.5 nm). The appearance of these larger particles which were not present in the non-irradiated sample (Figure 4 (a)) can be observed in the SEM image shown in Figure 4 (b). In contrast, melting at 570 and 620 nm do not result in signicant changes in the size distributions of the spherial particles (see Figures 3 (c) and (d)) with respect to the non irradiated sample. However, careful examination of the SEM images revealed the appearance of some new particle shapes which were not present in the original samples. A number of triangular and rod shaped particles appear in the 570 nm irradiated sample (see Figures 4 (c)) while necklace like structures appear in the 620 nm irradiated samples (see Figures 4 (d)). The overall number of these morphologically modied particles is relatively low as only a small subset of the aggregates undergo melting. The heating at 620 nm involves almost exclusively plasmonic heating and according to the model outlined above mainly chains of particles with more than 4 NPs are excited. 34 In this case the melting is strongly self-limiting because the nanoparticle structure changes shape in the initial pulses of the melting laser. This change of shape (linking of NP chains into longer structures) is known to provoke a dramatic shift of the longitudinal plasmon resonance to the red as observed in the threading of NPs by Herrmann et al. 27 and in the welding of nanorods by Ahijado et al. 10 Thus after the rst few melting laser pulses the melted structure no longer absorbs light. The melting at 570 nm is slightly dierent as it arises from the overlap of interband, transverse and longitudinal plasmon resonances. The illustrations in panel (c) of Figure 4 9



Figure 4: SEM images of (a) non-irradiated AuNP aggregates and aggregates irradiated with (b) 400 nm, (c) 570 nm (d) 620 nm laser light. Illustrations of the proposed mechanism of how the melting takes place following irradiation at 400 nm, 570 nm and at 620 nm are shown as insets in the corresponding panels. Colored ovals on the SEM images highlight particular shapes formed in the melting. White bars of length 100 nm are shown on each of the SEM images. show the suggested processes that take place to produce the nanorods and nanotriangles and involve the fusion of dimers and trimers. These particles are not simply due to the formation of bridges between particles but rather to the complete melting of particles and formation of new shapes. This may be due to the combined eects of heating through the interband and plasmonic resonances which means that the melting is not completely self-limiting as the interband absorption is independent of morphology and thus continues to be absorpbed by the melted structure.

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As previously mentioned the laser uence of the melting beam was set to between 2.5 x 1010 W/cm2 and 7.0 x 1010 W/cm2 in order to avoid two extreme conditions. The rst of these is the case of complete dissipation of heat by gold NPs at low pump uences. For non-aggregated spherical NPs of diameter 10 nm at laser uences < 1010 W/cm2 (500

µJ/cm2 for a 50 fs laser) the particles are capable of dissipating all of the heat generated by the absorbed light via the following sequence of events: absorption of light (during laser pulse), electron thermalization via electron-electron scattering (up to several hundreds of femtoseconds), electron-phonon scattering allowing exchange of energy between the electrons and the lattice (< 10 ps) and, nally, phonon-phonon scattering (hundreds of ps) in which the NP dissipates the energy absorbed as heat to the enviroment. 38 Therefore the lattice temperature of the NPs returns to room temperature on the scale of hundred of picoseconds by phonon-phonon coupling between the Au lattice and the environment (capping molecules and water). Considering the fact that the time between laser pulses is 1 ms, the above timescales imply that the melting must take place with a single laser pulse as there is no possibility for the NPs to store heat from one laser shot to the next. The second extreme takes place under high uences (> 1012 W/cm2 ) when one observes nanocavitation and explosive boiling of the water surrounding the NPs. 39 Between these extremes it is possible to encounter intermediate cases where part or all of the NP melts, e.g. Petrova et al. 40 observed reshaping of nanorods with intensities in the range 1.0 x 109 - 2.6 x 1010 W/cm2 . The laser uences used here are almost identical to those used by Petrova et al. 40 Boulais et

al. 28 suggested the existence of two regimes in the laser irradiation of nanorods in water: i) an absorption regime in which the NPs strongly absorb radiation and ii) a near eld regime in which the energy transfer from the light eld is dominated by the action of the hot spots (created by the nanoantenna eect) in ionizing and heating the resulting nanoplasma in the surrounding water. Furthermore, they suggested a passage from the rst to the second of these regimes at a uence of 6.6 x 109 W/cm2 which is comparable to the intensities used here. 11



However, Herrmann et al. 27 showed that the melting in their NP threading experiment in which spatially conned bridges were formed between a chain of gold NPs depended on peak power and not average power of the melting laser and as a result suggested that the melting was due to electromagnetic hot spots. With respect to the uences used in this work Herrmann et al. 27 used much lower values and yet achieved melting similar to that shown in Figure 4 (d). In any case it is clear from the above discussion that at intermediate laser uences it is not possible to consider only the laser uences without also taking into account the presence of electromagnetic hot spots. In order to evaluate whether non-isotropic melting occurs via local concentration and amplication of light, i.e. by the formation of hot spots, we have performed nite integral technique (FIT) calculations. The FIT method, which is based on the solution of the Maxwell equations in their integral form, 41 allows calculation of the electromagnetic eld distribution to be performed for both the near and far elds. In this work we concentrate on the electriceld distributions in the near eld to assess the spatial extention and location of the hot spots as well as the numerical extent of the amplication of the eld. The FIT calculations were performed for 400 and 600 nm light illuminating 4 NPs of 10 nm diameter separated by 1 nm, embedded in water in accordance with the model developed in our previous publication. 34 Furthermore, the electric eld vector of the illuminating light is aligned along the interparticle axis of the chain of particles and the direction of propagation of the light is perpendicular to this axis. These two representative wavelengths were chosen in order to help us discuss the mechanisms of melting outlined above as 400 nm corresponds to the experimental interband melting wavelength while 600 nm is the maximum of the calculated longitudinal plasmon for 4 NPs in the above model. 34 Figure 5 shows the results of the FIT calculations, reporting evident hot spots in the regions between the NPs. In the case of illumination with 600 nm light, a local enhancement of almost 2 orders of magnitude of the eld near the surfaces of the NPs facing the interparticle gap leads to a local eld on the order of 1012 W/cm2 . In this intensity regime, non-linear 12


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Figure 5: Concentration of the light in the near eld for (a) 400 nm and (b) 600 nm light illuminating 4 spherical gold NPs. eects such as multiphoton absorption, plasma formation, impact ionization of water, and attraction between NPs due to light trapping must be considered. 2732 By contrast a much smaller enhancement (factor of 5) is observed in the case of 400 nm which means that hot spots play a smaller role in the melting in this case. Therefore, localized melting is more important for plasmonic melting wavelengths where the hot spots can induced the formation of bridges between particles whereas at 400 nm the melting of the aggregate is more isotropic, leading to the coalesce into larger particles. The present work concentrates on the dierent melting mechanisms induced when changing the melting light wavelength to correspond either with interband or plasmonic excitation. For 400 nm light the melting is both isotropic and not self-limiting in the sense that even when the nanostructures change shape due to melting they continue to absorb this light as it excites interband transitions in the metal. This leads to complete melting of the particles and formation of larger spherical particles as observed. In contrast, excitation at 570 nm involves 3 contributions: interband excitation as well as both transverse and longitudinal plasmon resonances. The structures which contribute most to the longitudinal resonance at 13



this wavelength are those containing only a few NPs as discussed above, 34 thus irradiation leads to melting in the hot spot regions of dimer and trimers. After the initial fusion, the extended/longitudinal plasmon resonance will strongly shift to the red however the transverse plasmon and interband transition will continue to be excited and may allow further melting to convert the particles into regular shapes (rods and triangular nanoplates). Finally, for heating on the red side of the longitudinal plasmon at 620 nm we propose that local melting takes place due to lattice softening at/near the hot spots between particles and the resulting formation of bridges between the particles, which is a similar mechanism to that proposed by Herrmann et al. 27 for the threading of NPs. This mechanism is strongly self-limiting because as soon as the bridges between NPs are formed the longitudinal plasmonic resonance shifts into the IR meaning that such structures no longer absorb the melting light thus inhibiting further melting. In conclusion, we have presented a method to control the morphology of femtosecond laser melting of spherical gold nanoparticle aggregates by careful manipulation of both the wavelength and uence of the melting laser beam. The outcome of the photoinduced melting has been characterized both by spectroscopic and electron microscopy techniques and shows that it is possible to produce larger spherical NPs (400 nm melting), nanorods and nanoprisms (570 nm melting) and larger necklace linked 1D bridged structures (620 nm melting). The mechanism behind the morphological control is related to the wavelength dependent light concentration of dierent aggregate geometries. Calculations performed here show that the presence of hot spots can increase the local eld by up to two orders of magnitude leading to localized melting of the structures. The calculations also show that the spatial distribution and extent of the light concentration is strongly wavelength dependent. The combination of this controlled melting with the self-assembly of nanoparticles on surfaces could nd applications in nanofabrication techniques.

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Acknowledgement DC and PO'K acknowledge funding from PRIN project no. 2015CL3APH.

References (1) Daniel, M.-C.; ; Astruc, D. Gold Nanoparticles: Assembly, Supramolecular Chemistry, Quantum-Size-Related Properties, and Applications toward Biology, Catalysis, and Nanotechnology. Chem. Rev. 2004, 104, 293346. (2) Hartland, G. V. Optical Studies of Dynamics in Noble Metal Nanostructures. Chem.

Rev. 2011, 111, 38583887. (3) Dreaden, E. C.; Alkilany, A. M.; Huang, X.; Murphy, C. J.; El-Sayed, M. A. The golden age: gold nanoparticles for biomedicine. Chem. Soc. Rev. 2012, 41, 27402779. (4) Govorov, A. O.; Richardson, H. H. Generating heat with metal nanoparticles. Nano

Today 2007, 2, 30 38. (5) Baou, G.; Rigneault, H. Femtosecond-pulsed optical heating of gold nanoparticles.

Phys. Rev. B 2011, 84, 035415. (6) Huang, X.; El-Sayed, M. A. Gold nanoparticles: Optical properties and implementations in cancer diagnosis and photothermal therapy. J. Adv. Res. 2010, 1, 13 28. (7) Hühn, D.; Govorov, A.; Gil, P. R.; Parak, W. J. Photostimulated Au Nanoheaters in Polymer and Biological Media: Characterization of Mechanical Destruction and Boiling.

Adv. Funct. Mater. 2012, 22, 294303. (8) Jaque, D.; Martinez Maestro, L.; del Rosal, B.; Haro-Gonzalez, P.; Benayas, A.; Plaza, J. L.; Martin Rodriguez, E.; Garcia Sole, J. Nanoparticles for photothermal therapies. Nanoscale 2014, 6, 94949530. 15



(9) Minai, L.; Zeidan, A.; Yeheskely-Hayon, D.; Yudovich, S.; Kviatkovsky, I.; Yelin, D. Experimental Proof for the Role of Nonlinear Photoionization in Plasmonic Phototherapy.

Nano Lett. 2016, 16, 46014607. (10) Ahijado-Guzmán, R.; González-Rubio, G.; Izquierdo, J. G.; Bañares, L.; LópezMontero, I.; Calzado-Martín, A.; Calleja, M.; Tardajos, G.; Guerrero-Martínez, A. Intracellular pH-Induced Tip-to-Tip Assembly of Gold Nanorods for Enhanced Plasmonic Photothermal Therapy. ACS Omega 2016, 1, 388395. (11) Qiu, J.; Wei, W. D. Surface Plasmon-Mediated Photothermal Chemistry. J. Phys.

Chem. C 2014, 118, 2073520749. (12) Jin, R.; Cao, Y.; Mirkin, C. A.; Kelly, K. L.; Schatz, G. C.; Zheng, J. G. Photoinduced Conversion of Silver Nanospheres to Nanoprisms. Science 2001, 294, 19011903. (13) Jin, R.; Cao, Y.; Hao, E.; Metraux, G.; Schatz, G.; Mirkin, C. Controlling anisotropic nanoparticle growth through plasmon excitation. Nature 2003, 425, 487490. (14) Link, S.; Burda, C.; Nikoobakht, B.; El-Sayed, M. A. Laser-Induced Shape Changes of Colloidal Gold Nanorods Using Femtosecond and Nanosecond Laser Pulses. J. Phys.

Chem. B 2000, 104, 61526163. (15) Inasawa, S.; Sugiyama, M.; Yamaguchi, Y. Laser-Induced Shape Transformation of Gold Nanoparticles below the Melting Point: The Eect of Surface Melting. J. Phys.

Chem. B 2005, 109, 31043111. (16) Albrecht, W.; Deng, T.-S.; Goris, B.; van Huis, M. A.; Bals, S.; van Blaaderen, A. Single Particle Deformation and Analysis of Silica-Coated Gold Nanorods before and after Femtosecond Laser Pulse Excitation. Nano Lett. 2016, 16, 18181825. (17) Zuev, D. A.; Makarov, S. V.; Mukhin, I. S.; Milichko, V. A.; Starikov, S. V.; Morozov, I. A.; Shishkin, I. I.; Krasnok, A. E.; Belov, P. A. Fabrication of Hybrid Nanostruc16


Page 16 of 19

Page 17 of 19 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


tures via Nanoscale Laser-Induced Reshaping for Advanced Light Manipulation. Adv.

Mater. 2016, 28, 30873093. (18) González-Rubio, G.; González-Izquierdo, J.; Bañares, L.; Tardajos, G.; Rivera, A.; Altantzis, T.; Bals, S.; Peña-Rodríguez, O.; Guerrero-Martínez, A.; Liz-Marzán, L. M. Femtosecond Laser-Controlled Tip-to-Tip Assembly and Welding of Gold Nanorods.

Nano Lett. 2015, 15, 82828288. (19) González-Rubio, G.; Guerrero-Martínez, A.; Liz-Marzán, L. M. Reshaping, Fragmentation, and Assembly of Gold Nanoparticles Assisted by Pulse Lasers. Acc. Chem. Res.

2016, 49, 678686. (20) González-Rubio, G.; Díaz-Núñez, P.; Rivera, A.; Prada, A.; Tardajos, G.; GonzálezIzquierdo, J.; Bañares, L.; Llombart, P.; Macdowell, L. G.; Alcolea Palafox, M.; LizMarzán, L. M.; Peña-Rodríguez, O.; Guerrero-Martínez, A. Femtosecond laser reshaping yields gold nanorods with ultranarrow surface plasmon resonances. Science 2017,

358, 640644. (21) Mafuné, F.; Kohno, J.-y.; Takeda, Y.; Kondow, T. Nanoscale Soldering of Metal Nanoparticles for Construction of Higher-Order Structures. J. Am. Chem. Soc. 2003,

125, 16861687. (22) Kim, S. J.; Jang, D.-J. Laser-induced nanowelding of gold nanoparticles. Appl. Phys.

Lett. 2005, 86, 03312. (23) A. Hu, Y. Z.; Duley, W. Femtosecond Laser-Induced Nanowelding: Fundamentals and Applications. Open Surf. Sci. J. 2011, 3, 4249. (24) Hu, A.; Peng, P.; Alari, H.; Zhang, X. Y.; Guo, J. Y.; Zhou, Y.; Duley, W. W. Femtosecond laser welded nanostructures and plasmonic devices. J. Laser Appl. 2012,

24, 042001 .

17



(25) Garnett, E. C.; Cai, W.; Cha, J. J.; Mahmood, F.; Connor, S. T.; Greyson Christoforo, M.; Cui, Y.; McGehee, M. D.; Brongersma, M. L. Self-limited plasmonic welding of silver nanowire junctions. Nat. Mater. 2012, 11, 241249. (26) Huang, H.; Liu, L.; Peng, P.; Hu, A.; Duley, W. W.; Zhou, Y. Controlled joining of Ag nanoparticles with femtosecond laser radiation. J. Appl. Phys. 2012, 112, 123519. (27) Herrmann, L. O.; Valev, V. K.; Tserkezis, C.; Barnard, J. S.; Kasera, S.; Scherman, O. A.; Aizpurua, J.; Baumberg, J. J. Threading plasmonic nanoparticle strings with light. Nat. Comm. 2014, 5, 4568, Article. (28) Boulais, t.; Lachaine, R.; Meunier, M. Plasma-Mediated Nanocavitation and Photothermal Eects in Ultrafast Laser Irradiation of Gold Nanorods in Water. J. Phys. Chem.

C 2013, 117, 93869396. (29) Labouret, T.; Palpant, B. Nonthermal model for ultrafast laser-induced plasma generation around a plasmonic nanorod. Phys. Rev. B 2016, 94, 245426. (30) Alabastri, A.; Tuccio, S.; Giugni, A.; Toma, A.; Liberale, C.; Das, G.; Angelis, F. D.; Fabrizio, E. D.; Zaccaria, R. P. Molding of Plasmonic Resonances in Metallic Nanostructures: Dependence of the Non-Linear Electric Permittivity on System Size and Temperature. Materials 2013, 6, 48794910. (31) Alabastri, A.; Toma, A.; Malerba, M.; De Angelis, F.; Proietti Zaccaria, R. High Temperature Nanoplasmonics: The Key Role of Nonlinear Eects. ACS Photonics 2015,

2, 115120. (32) Alabastri, A.; Malerba, M.; Calandrini, E.; Manjavacas, A.; De Angelis, F.; Toma, A.; Proietti Zaccaria, R. Controlling the Heat Dissipation in Temperature-Matched Plasmonic Nanostructures. Nano Lett. 2017, 17, 54725480.

18


Page 18 of 19

Page 19 of 19 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


(33) Diaz Fernandez, Y. A.; Gschneidtner, T. A.; Wadell, C.; Fornander, L. H.; Lara Avila, S.; Langhammer, C.; Westerlund, F.; Moth-Poulsen, K. The conquest of middle-earth: combining top-down and bottom-up nanofabrication for constructing nanoparticle based devices. Nanoscale 2014, 6, 1460514616. (34) Fratoddi, I. et al. Gold nanoparticles functionalized by rhodamine B isothiocyanate: A new tool to control plasmonic eects. J. Colloid Interface Sci. 2018, 513, 10 19. (35) Ghosh, S. K.; Pal, T. Interparticle Coupling Eect on the Surface Plasmon Resonance of Gold Nanoparticles: From Theory to Applications. Chemical Reviews 2007, 107, 47974862. (36) Jain, P. K.; El-Sayed, M. A. Plasmonic coupling in noble metal nanostructures. Chem.

Phys. Lett. 2010, 487, 153 164. (37) Halas, N. J.; Lal, S.; Chang, W.-S.; Link, S.; Nordlander, P. Plasmons in Strongly Coupled Metallic Nanostructures. Chem. Rev. 2011, 111, 39133961. (38) Hartland, G. V. Measurements of the material properties of metal nanoparticles by time-resolved spectroscopy. Phys. Chem. Chem. Phys. 2004, 6, 52635274. (39) Hu, M.; Petrova, H.; Hartland, G. V. Investigation of the properties of gold nanoparticles in aqueous solution at extremely high lattice temperatures. Chem. Phys. Lett.

2004, 391, 220 225. (40) Petrova, H.; Perez Juste, J.; Pastoriza-Santos, I.; Hartland, G. V.; Liz-Marzan, L. M.; Mulvaney, P. On the temperature stability of gold nanorods: comparison between thermal and ultrafast laser-induced heating. Phys. Chem. Chem. Phys. 2006, 8, 814821. (41) Weiland, T. Discretization Method for the Solution of Maxwell's Equations for SixComponent Fields. AEU-Archiv fur Elektronik und Ubertragungstechnik 1977, 31, 116.

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