Letter www.acsami.org
Subcooled-Water Nonstickiness of Condensate Microdrop SelfPropelling Nanosurfaces Juan Li,†,‡,§ Yuting Luo,†,§ Jie Zhu,† Hong Li,† and Xuefeng Gao* †
Division of Nanobionic Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, P. R. China ‡ School of Physics and Information Technology, Shaanxi Normal University, Shanxi 710119, China S Supporting Information *
ABSTRACT: We report perfect humidity-tolerant subcooled-water nonstickiness on condensate microdrop self-propelling (CMDSP) surfaces. As exemplified by a CMDSP nanoneedle surface, we find that impinged subcooled drops can instantly rebound and simultaneously take away surface condensate. Remarkably, continuously poured subcooled water can also shed off on the nanosample surface. In sharp contrast, they instantly freeze on the contrast flat hydrophobic surface. Such a superior performance may be ascribed to nanostructure-induced extremely low solid−liquid interface adhesion and prevention of phase transition from the liquid subcooled water to the solid ice. These findings help in the development of low-adhesive superhydrophobic surfaces suitable for a cold and humid environment.
KEYWORDS: superhydrophobic, nanostructure, condensate microdrop self-propelling, subcooled-water nonstickiness, antifreezing
I
utilization and thermal management.17−20 In our opinion, such a surface also should own humidity-tolerant subcooled-water nonstickiness. Thus, it is significant to experimentally explore its feasibility and understand its mechanism, which has not been reported yet. Here, we demonstrate that novel superhydrophobic surfaces with a CMDSP function indeed own perfect humidity-tolerant subcooled-water nonstickiness. First, we synthesize a type of exemplified CMDSP surface consisting of fluorosilane-modified Cu(OH)2-clustered ribbed nanoneedles. A special setup is designed for exploring interactions between the condensed sample surface and the impinged subcooled-water drop. Our experiments verify that impinged subcooled drops can instantly bounce off the nanosample surface and take away surface condensates, the residence time of which is 13 ms. Remarkably, continuously poured subcooled-water flow can also instantly shed off the nanosample surface, without any water pinning and freezing. In sharp contrast, both subcooled-water drops and flow can instantly freeze on the flat surface with identical lowsurface-energy chemistry. Further analyses indicate that the CMDSP surfaces can not only own extremely low adhesion to condensed microdrops and impacted macrodrops but also eliminate the risk of droplet pinning caused by emerging ice crystals on the top of the building blocks.
nspired from nature and benefiting from the advancement of various top-down and bottom-up nanofabrication technologies, great breakthroughs have been made in the creation of various superwettability surfaces, especially superhydrophobic surfaces.1 However, it is still a great challenge to achieve superhydrophobic surfaces with subcooled-water nonstickiness that can work in a cold and humid environment.2 In principle, to achieve such a surface, the key lies in how to control fine structures so as to minimize its surface adhesion to both condensate drops and impinged macroscopic subcooled-water drops. It has recently been reported that moisture unavoidably can penetrate the microscale valleys of hierarchical structured surfaces (including natural lotus leaves) with low-adhesive superhydrophobicity to macroscopic water drops.3−5 Clearly, the trapped Wenzel-state condensates are highly adhesive, which can prevent the rebounding of impinged subcooledwater drops (e.g., freezing rain) and facilitate their solidification.2 Very recently, a type of novel superhydrophobic surface with a condensate microdrop self-propelling (CMDSP) function has been developed on the basis of fine control over small-scale interspaces and tip sizes of nanoscale building blocks.6−20 Differing from the gravity-driven shedding of macroscopic water drops, tiny condensate microdrops suspended on the CMDSP surfaces can self-remove in a jumping way via their coalescence-released excess surface energy. Such a surface has attracted intensive interest because of its value in basic research and technological innovations such as moisture self-cleaning,14 energy-effective frost prevention,15,16 and enhancement of heat transfer for efficient energy © XXXX American Chemical Society
Received: October 13, 2015 Accepted: November 19, 2015
A
DOI: 10.1021/acsami.5b09719 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Letter
ACS Applied Materials & Interfaces Figure 1a shows the scanning electronic microscopy (SEM) top (left) and side (right) views of the as-synthesized
To explore whether such a CMDSP surface really possesses humidity-tolerant subcooled-water nonstickiness, we first need to find an appropriate evaluation method and build up the corresponding characterization setup. To our knowledge, the usual methods of evaluating the water nonstickiness of superhydrophobic surfaces mainly include measurement of the static contact angle, sliding angle, adhesive force, and droprebounding ability. However, measured static contact angles cannot indicate the nonstickiness of superhydrophobic surfaces, the robustness of which cannot also be reflected by the measured sliding angles for slightly deposited water drops.21 In view of the difficulty in accurately modulating the temperature of subcooled water and maintaining its temperature stability due to unavoidable heat exchange with an ambient environment, we suppose that, as for the latter two methods, measuring the rebounding ability of an impinging subcooled-water drop to the CMDSP surface appears to be more suitable in this case. Accordingly, we customize a testing setup, as shown in Figure 2a, which includes a subcooled-water drop generation and
Figure 1. (a) SEM top (right) and side (left) views of the assynthesized Cu(OH)2-clustered ribbed nanoneedles. Inset: Magnified image of a single nanoneedle tip. (b) Optical side view showing selfpropelled jumping of condensate microdrops. (c) Optical bird’s-eye views showing the self-propelled jumping details of two (top row) or multiple (bottom row) adjacent condensate microdrops via mutual coalescence. Such a nanostructured surface owns an excellent ability of preventing moisture penetration and extremely low solid−liquid interface adhesion. Scale bars: 100 μm.
Cu(OH)2-clustered ribbed nanoneedles, which can be obtained by facile electrochemical deposition of copper foils (99.99%, 3 × 4 × 0.2 cm3) in a solution of 2 M KOH at 10 °C for 25 min under a current density of 1.5 mA cm−2 (using an electrochemical workstation, Chenhua 660C, China) followed by fluorosilane modification, according to our previous work.20 These morphologies are taken by using a high-resolution scanning electronic microscope (Hitachi S4800, Japan) after the nanosamples are sputtered with a 15-nm-thick gold layer. Evidently, these self-standing ribbed nanoneedles present not only a microscopic 3D rugged feature but also radial nanoneedle clusters with needle-to-needle interspaces tapering from the top down. The average diameter of the nanoneedles tapers from ∼800 nm at the base down to ∼150 nm at the tip, while the average length is ∼8 μm. After low-surface-energy fluorosilane modification, the nanostructured surface can exhibit the desired CMDSP function. From the side view of nanostructured samples with a substrate temperature of ∼5 °C, an environment temperature of ∼25 °C, and a relative humidity of ∼60%, we can easily observe the self-propelled jumping events of condensate microdrops (Figure 1b), using a highspeed high-resolution 3D imager (Keyence VW-9000, Japan). Figure 1c further shows two sets of optical image sequences at a bird’s-eye view, where two (top row) and multiple (bottom row) adjacent condensate microdrops can self-remove via their mutual coalescence. This property may be ascribed to the nanostructure-induced and extremely low solid−liquid interface adhesion, where the coalescence-released excess surface energy can sufficiently drive the self-jumping of merged microdrops.11,20 In fact, our recent study has clearly revealed how tiny condensate drops bridge among the nanoneedles and grow into suspended microdrops via self-transport and/or selfexpansion modes.20
Figure 2. (a) Schematic of our setup of using impinged subcooledwater drops to evaluate the nonstickiness of the CMDSP surfaces. (b) Optical images showing dynamic interactions between the impinged subcooled-water drop (−7 °C) and the CMDSP surface (top) and the contrast flat surface (bottom), respectively. Clearly, the subcooledwater drop can instantly bounce off the CMDSP surface and simultaneously take away the surface condensate (leaving a bare region denoted by the orange dotted circle), which is in sharp contrast to its quick freezing on the contrast flat surface.
injection system, a sample-cooling system, and an imaging system. To obtain a subcooled-water drop (e.g., with a nominal temperature of −7 °C), water stored in the stainless steel syringe needle (Legato 100, KDS, USA) is refrigerated for ∼5 min by a thermoelectric cooler (LTD-240, Tianjin Jinie Industry and Trade Co., Ltd., China) with the corresponding temperature and then injected by the pump (SNS021/011, Dataphysics, Germany) at a flow speed of 2 μL/s until a 10 μL subcooled-water drop can detach from the needle tip. To be able to explore the nonstickiness robustness of our nanosample surface to impinging subcooled water and meanwhile reduce the heat dissipation of the tested subcooled-water drop, we choose the release height of 10 cm as an example. To minimize B
DOI: 10.1021/acsami.5b09719 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Letter
ACS Applied Materials & Interfaces perturbation of air flow, the whole device is isolated by a transparent PMMA box, where the air temperature and relative humidity are 20 °C and ∼60%, respectively. To more intuitively show interactions of the impinging drop and condensed nanostructured surface (with a substrate temperature of −5 °C), the titled angle of all samples, attached to the cooling stage, is fixed at 5°. Although the temperature of our refrigerated water drops is very hard to accurately determine, our contrast experiments can verify that they are indeed subcooled, which can easily freeze on the flat surface (see movie S1 in the Supporting Information). Our subsequent measurements demonstrate that the CMDSP surfaces indeed present perfect humidity-tolerant nonstickiness to impinged subcooled-water drops, as shown in Figure 2b. For the CMDSP surface, we easily find that the impinged subcooled-water drops can instantly retract and rebound without any water pinning after spreading to the maximum, the residence time of which is 13 ms. Remarkably, the condensate on the CMDSP surface can be simultaneously taken away by the impinged subcooled-water drop, leaving a bare region, denoted by an orange dotted circle (as shown in the top row of Figure 2b and movie S2 in the Supporting Information). In sharp contrast, the impinged subcooled-water drop can quickly freeze on the flat hydrophobic surface (see movie S1 in the Supporting Information). The tiplike morphology, as shown in the bottom row of Figure 2b, can also verify that the subcooled-water drop has been solidified in its spreading stage. Evidently, the CMDSP sample owns perfect nonstickiness to impinged subcooled-water drops even after experiencing the condensation pretreatment. It should be pointed out that the temperature of subcooledwater drops is very hard to tune toward lower temperature using our current setup. Besides, the impinging experiment of subcooled-water drops is very difficult to elucidate if such a performance is effective to the whole film layer. Accordingly, we want to further explore the property of the whole film layer using continuously poured subcooled water with lower temperature. To simplify our experiment, we choose −20 °C water as an example. Compared to the stainless steel syringe needle with narrow channels, plastic containers with larger volume and smooth hydrophobic inner walls theoretically may increase the energy barrier for heterogeneous nucleation of ice crystals to support lower-temperature subcooled water. In this case, subcooled water with a nominal temperature of −20 °C can be achieved by simply placing 330 mL Nestle purified water bottles filled with degassed pure water (Milli-Q, 18 MΩ) in the freezing chamber of the refrigerator for 3 h. Then, we directly pour the subcooled water from a height of ∼10 cm within ∼10 s onto the CMDSP and contrast flat surfaces with a tilted angle of 5° and a substrate temperature of −5 °C in an ambient environment, which is real-time recorded by a high-speed highresolution 3D imager. As shown in Figure 3, the CMDSP surface (left) presents perfect nonstickiness to continuously poured subcooled water, which is in sharp contrast with the quick freezing of subcooled-water flow and formed ice layer on the flat surface (right). Why such a CMDSP surface can own perfect humiditytolerant nonstickiness to subcooled water? We suppose that such a superior performance may be ascribed to nanostructureinduced, extremely low solid−liquid adhesion and prevention of phase transition from the liquid subcooled water to the solid ice. To better understand its mechanism, we provide illustrative schematics, as shown in Figure 4. First, the subcooled-water
Figure 3. Optical images showing the perfect nonstickiness of the CMDSP surface (left) to the continuously poured subcooled water (−20 °C), in sharp contrast to its instant freezing on the contrast flat surface (right).
Figure 4. (a) Schematics showing that an impinged subcooled-water drop can instantly spread, retract, and rebound off the CMDSP surface, taking away superficial condensate. (b) Schematic showing that the instantly formed solid−liquid interface on the nanostructured surface almost can be fully separated by a heat-insulated air layer, preventing the release of latent heat and the heterogeneous nucleation of ice crystals. (c) Schematic showing the tight solid−liquid contact nature on the contrast flat surface, benefiting the rapid release of latent heat and the heterogeneous nucleation of ice crystals. Such perfect subcooled-water nonstickiness of CMDSP surfaces may be ascribed to the nanostructure-induced, humidity-tolerant, and extremely low solid−liquid adhesion and prevention of phase transition from the liquid-state subcooled water to the solid ice.
drop impacting the CMDSP surface can instantly rebound after its maximal spread, simultaneously taking away surface condensates (Figure 4a). This is because the CMDSP surfaces, consisting of nanoscale building blocks with small-scale interspaces and tip sizes, can not only avoid moisture penetration but also minimize their interface adhesion with the suspended condensate microdrops11−13,20 or impinged macroscopic water drops.22 It should also be pointed out that such a tiplike nanostructured surface can own a remarkable ability to inhibit the nucleation of ice crystals, which often requires at least tens of minutes for icing.23 As shown in Figure 4b, the subcooled water can only contact the inorganic nanoneedle tips, where the instantly formed solid−liquid C
DOI: 10.1021/acsami.5b09719 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
ACS Applied Materials & Interfaces
■
interface is almost fully separated by the air layer, which is a type of known heat-insulated medium with far lower thermal conductivity. In principle, feeble heat conduction between the subcooled-water droplet and substrate is still unavoidable because of their temperature difference. However, as for a transient solid−liquid contact of only an order of magnitude of milliseconds, it is extremely difficult for the subcooled-water drops to release their latent heat or initiate heterogeneous nucleation on the tips of sharp nanoneedles.23−26 In sharp contrast, the impinged subcooled water can form a tight solid− liquid contact with the contrast hydrophobic flat surface during their spreading process, as shown in Figure 4c. No doubt that this would benefit the rapid release of latent heat and the nucleation of ice crystals, which is the reason why subcooled water can rapidly freeze on the flat surface.23−26 Clearly, the remarkable nucleation-inhibiting ability of CMDSP surfaces can eliminate the risk of droplet pinning caused by emerging ice crystals on the top of the building blocks. Accordingly, CMDSP nanostructured surfaces, characterized by small-scale interspaces and tip sizes, can effectively prevent the pinning and freezing of subcooled water, especially in the cold and humid environment. In conclusion, we have verified that CMDSP surfaces indeed own perfect humidity-tolerant subcooled-water nonstickiness. Combined experiments and theoretical analyses have revealed that such a remarkable property may be ascribed to nanostructure-induced, extremely low solid−liquid interface adhesion and prevention of phase transition from the liquid subcooled water to the solid ice. In principle, any CMDSP surface, consisting of nanoscale building blocks with small-scale interspaces and tip sizes, may be nonsticky to subcooled water, even upon being exposed to a cold and humid environment. Clearly, our work offers a very facile and energy-effective strategy of preventing the pinning and freezing of subcooled water on material surfaces like airplane wings. Besides, this insight is also meaningful to guide the development of robust low-adhesive superhydrophobic surfaces suitable for a cold and humid environment.13,15,27 Currently, our group is utilizing such a strategy to develop multifunctional superhydrophobic aluminum alloys, which would be very promising for solving the high-energy-consuming issues of current devices such as the wings of aircrafts and the heat exchangers of air conditioners and heat pumps. In addition, the subcooled-water nonstickiness of such a CMDSP surface may be further improved by combining some emerging techniques, such as shortening the contact time of impinged water drops by the delicate design of surface morphologies28,29 and inducing spontaneous droplet ejection via manipulating the dynamics of the air cushion.30
■
Letter
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Author Contributions §
These authors contributed equally.
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
■
REFERENCES
This work was supported by the National Basic Research Program of China (Grant 2012CB933200), Key Research Program of the Chinese Academy of Sciences (Grant KJZDEW-M01), National Natural Science Foundation of China (Grant 21573276), Natural Science Foundation of Jiangsu Province (Grant BK20130355), and Director Program of Suzhou Institute of Nano-Tech and Nano-Bionics (Grant 07CA021006).
(1) Wang, S.; Liu, K.; Yao, X.; Jiang, L. Bioinspired Surfaces with Superwettability: New Insight on Theory, Design, and Applications. Chem. Rev. 2015, 115, 8230−8293. (2) Wang, Y.; Xue, J.; Wang, Q.; Chen, Q.; Ding, J. Verification of Icephobic/Anti-Icing Properties of a Superhydrophobic Surface. ACS Appl. Mater. Interfaces 2013, 5, 3370−3375. (3) Zheng, Y.; Han, D.; Zhai, J.; Jiang, L. In Situ Investigation on Dynamic Suspending of Microdroplet on Lotus Leaf and Gradient of Wettable Micro- and Nanostructure From Water Condensation. Appl. Phys. Lett. 2008, 92, 084106. (4) Wier, K. A.; McCarthy, T. J. Condensation on Ultrahydrophobic Surfaces and Its Effect on Droplet Mobility: Ultrahydrophobic Surfaces Are Not Always Water Repellant. Langmuir 2006, 22, 2433−2436. (5) Lafuma, A.; Quere, D. Superhydrophobic States. Nat. Mater. 2003, 2, 457−460. (6) Chen, C.-H.; Cai, Q.; Tsai, C.; Chen, C.-L.; Xiong, G.; Yu, Y.; Ren, Z. Dropwise Condensation on Super Hydrophobic Surfaces with Two-Tier Roughness. Appl. Phys. Lett. 2007, 90, 173108. (7) Chen, X.; Wu, J.; Ma, R.; Hua, M.; Koratkar, N.; Yao, S.; Wang, Z. Nanograssed Micropyramidal Architectures for Continuous Dropwise Condensation. Adv. Funct. Mater. 2011, 21, 4617−4623. (8) Feng, J.; Pang, Y.; Qin, Z.; Ma, R.; Yao, S. Why Condensate Drops Can Spontaneously Move Away on Some Superhydrophobic Surfaces but Not on Others. ACS Appl. Mater. Interfaces 2012, 4, 6618−6625. (9) Feng, J.; Qin, Z.; Yao, S. Factors Affecting the Spontaneous Motion of Condensate Drops on Superhydrophobic Copper Surfaces. Langmuir 2012, 28, 6067−6075. (10) He, M.; Zhou, X.; Zeng, X.; Cui, D.; Zhang, Q.; Chen, J.; Li, H.; Wang, J.; Cao, Z.; Song, Y.; Jiang, L. Hierarchically Structured Porous Aluminum Surfaces for High-Efficient Removal of Condensed Water. Soft Matter 2012, 8, 6680−6683. (11) Tian, J.; Zhu, J.; Guo, H.-Y.; Li, J.; Feng, X.-Q.; Gao, X. Efficient Self-Propelling of Small-Scale Condensed Microdrops by Closely Packed ZnO Nanoneedles. J. Phys. Chem. Lett. 2014, 5, 2084−2088. (12) Luo, Y.; Li, J.; Zhu, J.; Zhao, Y.; Gao, X. Fabrication of Condensate Microdrop Self-Propelling Porous Films of Cerium Oxide Nanoparticles on Copper Surfaces. Angew. Chem., Int. Ed. 2015, 54, 4876−4879. (13) Zhao, Y.; Luo, Y.; Li, J.; Yin, F.; Zhu, J.; Gao, X. Condensate Microdrop Self-Propelling Aluminum Surfaces Based on Controllable Fabrication of Alumina Rod-Capped Nanopores. ACS Appl. Mater. Interfaces 2015, 7, 11079−11082. (14) Wisdom, K. M.; Watson, J. A.; Qu, X.; Liu, F.; Watson, G. S.; Chen, C.-H. Self-Cleaning of Superhydrophobic Surfaces by Self-
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.5b09719. Movie showing the distinct dynamics of impinged subcooled-water drops onto the surface of the flat hydrophobic (movie S1) (AVI) Movie showing the distinct dynamics of impinged subcooled-water drops onto the CMDSP sample surface (movie S2) (AVI) D
DOI: 10.1021/acsami.5b09719 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Letter
ACS Applied Materials & Interfaces Propelled Jumping Condensate. Proc. Natl. Acad. Sci. U. S. A. 2013, 110, 7992−7997. (15) Xu, Q.; Li, J.; Tian, J.; Zhu, J.; Gao, X. Energy-Effective FrostFree Coatings Based on Superhydrophobic Aligned Nanocones. ACS Appl. Mater. Interfaces 2014, 6, 8976−8980. (16) Zhang, Q.; He, M.; Chen, J.; Wang, J.; Song, Y.; Jiang, L. AntiIcing Surfaces Based on Enhanced Self-Propelled Jumping of Condensed Water Microdroplets. Chem. Commun. 2013, 49, 4516− 4518. (17) Miljkovic, N.; Enright, R.; Nam, Y.; Lopez, K.; Dou, N.; Sack, J.; Wang, E. N. Jumping-Droplet-Enhanced Condensation on Scalable Superhydrophobic Nanostructured Surfaces. Nano Lett. 2013, 13, 179−187. (18) Hou, Y.; Yu, M.; Chen, X.; Wang, Z.; Yao, S. Recurrent Filmwise and Dropwise Condensation on a Beetle Mimetic Surface. ACS Nano 2015, 9, 71−81. (19) Zhao, Y.; Luo, Y.; Zhu, J.; Li, J.; Gao, X. Copper-Based Ultrathin Nickel Nanocone Films with High-Efficiency Dropwise Condensation Heat Transfer Performance. ACS Appl. Mater. Interfaces 2015, 7, 11719−11723. (20) Zhu, J.; Luo, Y.; Tian, J.; Li, J.; Gao, X. Clustered RibbedNanoneedle Structured Copper Surfaces with High-Efficiency Dropwise Condensation Heat Transfer Performance. ACS Appl. Mater. Interfaces 2015, 7, 10660−10665. (21) Tian, J.; Zhang, Y.; Zhu, J.; Yang, Z.; Gao, X. Robust Nonsticky Superhydrophobicity by the Tapering of Aligned ZnO Nanorods. ChemPhysChem 2014, 15, 858−861. (22) Lai, Y.; Gao, X.; Zhuang, H.; Huang, J.; Lin, C.; Jiang, L. Designing Superhydrophobic Porous Nanostructures with Tunable Water Adhesion. Adv. Mater. 2009, 21, 3799−3803. (23) Guo, P.; Zheng, Y.; Wen, M.; Song, C.; Lin, Y.; Jiang, L. Icephobic/Anti-Icing Properties of Micro/Nanostructured Surfaces. Adv. Mater. 2012, 24, 2642−2648. (24) Cao, L.; Jones, A. K.; Sikka, V. K.; Wu, J.; Gao, D. Anti-Icing Superhydrophobic Coatings. Langmuir 2009, 25, 12444−12448. (25) Bahadur, V.; Mishchenko, L.; Hatton, B.; Taylor, J. A.; Aizenberg, J.; Krupenkin, T. Predictive Model for Ice Formation on Superhydrophobic Surfaces. Langmuir 2011, 27, 14143−14150. (26) Mishchenko, L.; Hatton, B.; Bahadur, V.; Taylor, J. A.; Krupenkin, T.; Aizenberg, J. Design of Ice-Free Nanostructured Surfaces Based on Repulsion of Impacting Water Droplets. ACS Nano 2010, 4, 7699−7707. (27) Lv, J.; Song, Y.; Jiang, L.; Wang, J. Bio-Inspired Strategies for Anti-Icing. ACS Nano 2014, 8, 3152−3169. (28) Bird, J.; Dhiman, R.; Kwon, H.-M.; Varanasi, K. Reducing the Contact Time of a Bouncing Drop. Nature 2013, 503, 385−388. (29) Liu, Y.; Moevius, L.; Xu, X.; Qian, T.; Yeomans, J.; Wang, Z. Pancake Bouncing on Superhydrophobic Surfaces. Nat. Phys. 2014, 10, 515−519. (30) Schutzius, T.; Jung, S.; Maitra, T.; Graeber, G.; Köhme, M.; Poulikakos, D. Spontaneous Droplet Trampolining on Rigid Superhydrophobic Surfaces. Nature 2015, 527, 82−85.
E
DOI: 10.1021/acsami.5b09719 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
