Co-reporter:Sanghyeon Kim, Sung-Kon Kim, Pengcheng Sun, Nuri Oh, and Paul V. Braun
Nano Letters November 8, 2017 Volume 17(Issue 11) pp:6893-6893
Publication Date(Web):October 20, 2017
DOI:10.1021/acs.nanolett.7b03290
Li-iodine chemistry is of interest for electrochemical energy storage because it has been shown to provide both high power and high energy density. However, Li-iodine batteries are typically formed using Li metal and elemental iodine, which presents safety and fabrication challenges (e.g., the high vapor pressure of iodine). These disadvantages could be circumvented by using LiI as a starting cathode. Here, we present fabrication of a reduced graphene oxide (rGO)/LiI composite cathode, enabling for the first time the use of LiI as the Li-ion battery cathode. LiI was coated on rGO by infiltration of an ethanolic solution of LiI into a compressed rGO aerogel followed by drying. The free-standing rGO/LiI electrodes show stable long-term cycling and good rate performance with high specific capacity (200 mAh g–1 at 0.5 C after 100 cycles) and small hysteresis (0.056 V at 1 C). Shuttling was suppressed significantly. We speculate the improved electrochemical performance is due to strong interactions between the active materials and rGO, and the reduced ion and electron transport distances provided by the three-dimensional structured cathode.Keywords: cathode; hysteresis; lithium iodide; Lithium iodine battery; reduced graphene oxide aerogel; shuttling;
Co-reporter:Masao Miyake, Makoto Suginohara, Naoto Narahara, Tetsuji Hirato, and Paul V. Braun
Chemistry of Materials November 28, 2017 Volume 29(Issue 22) pp:9734-9734
Publication Date(Web):October 26, 2017
DOI:10.1021/acs.chemmater.7b03466
Single crystal semiconductors almost always exhibit better optoelectrical properties than their polycrystalline or amorphous counterparts. While three-dimensionally (3D) nanostructured semiconductor devices have been proposed for numerous applications, in the vast majority of reports, the semiconductor is polycrystalline or amorphous, greatly reducing the potential for advanced properties. While technologies for 3D structuring of semiconductors via use of a 3D template have advanced significantly, approaches for epitaxially growing nanostructured single crystal semiconductors within a template remain limited. Here, we demonstrate the epitaxial growth of 3D-structured ZnO through colloidal templates formed from 225 and 600 nm diameter colloidal particles via a low-temperature (∼80 °C) hydrothermal process using a flow reactor. The effects of the pH of the reaction solution as well as the additive used on the 3D epitaxy process are investigated. The optical and electrical properties of the epitaxially grown nanostructured ZnO are probed by reflectance, photoluminescence, and Hall effect measurements. It is found that the epitaxially grown nanostructured ZnO generally exhibits properties superior to those of polycrystalline ZnO. The demonstrated hydrothermal epitaxy process should be applicable to other chemical solution-based deposition techniques and help extend the range of materials that can be grown into a 3D nanostructured single-crystalline form.
Co-reporter:Christian R. Ocier, Neil A. Krueger, Weijun Zhou, and Paul V. Braun
ACS Photonics April 19, 2017 Volume 4(Issue 4) pp:909-909
Publication Date(Web):February 28, 2017
DOI:10.1021/acsphotonics.6b01001
Visibly transparent porous silicon dioxide (PSiO2) and PSiO2/titanium dioxide (TiO2) optical elements were fabricated by thermal oxidation, or a combination of thermal oxidation and atomic layer deposition infilling, of an electrochemically etched porous silicon (PSi) structure containing an electrochemically defined porosity profile. The thermally oxidized PSiO2 structures are transparent at visible wavelengths and can be designed to have refractive indices ranging from 1.1 to 1.4. The refractive index can be increased above 2.0 through TiO2 infilling of the pores. Applying this oxidation and TiO2 infilling methodology enabled tuning of a distributed Bragg reflector (DBR) formed from PSi across the visible spectrum. At the maximum filling, the DBR exhibited a transmission of 2% at 620 nm. Simulations match well with measured spectra. In addition to forming DBR filters, phase-shaping gradient refractive index (GRIN) elements were formed. As a demonstration, a 4 mm diameter radial GRIN PSiO2 element with a parabolic, lens-like phase profile with a calculated focal length of 1.48 m was formed. The calculated focal length was reduced to 0.80 m upon the addition of TiO2. All the structures showed broad transparency in the visible and were stable to the materials conversion process.Keywords: distributed Bragg reflector; gradient refractive index; phase-shaping optics; spectral filter;
Co-reporter:Runyu Zhang;Joseph Cohen;Shanhui Fan
Nanoscale (2009-Present) 2017 vol. 9(Issue 31) pp:11187-11194
Publication Date(Web):2017/08/10
DOI:10.1039/C7NR03567E
Rhenium–Nickel (RexNi100−x) based 3D metallic inverse opals (IOs) were realized via colloidal crystal templated electrodeposition from an aqueous electrolyte. By varying the electrodeposition parameters, x could be varied from 0 to 88. Under reducing conditions, the rhenium-rich IOs were structurally stable to temperatures of at least 1000 °C for 5 h and for at least 12 h after coating with a thin layer of Al2O3. This demonstrated level of thermal stability is significantly improved compared to previously reported electrodeposited refractory inverse opals with similar characteristic dimensions. A strong frequency dependence in the optical reflection, which ranged from ∼5% around 1.5 μm to ∼65% around 5 μm, is predicted by simulations and experimentally observed, indicating the potential of this structure as a high temperature spectrally selective optical absorber/emitter. The elastic modulus of the ReNi IO structure is ∼35 GPa and the hardness is ∼0.8 GPa. Both these properties are much higher than those of Ni inverse opals and other periodically porous materials with similar characteristic pore dimensions. We suggest this work provides a promising approach for thermally stable mesostructured materials for high temperature catalyst supports, refractory photonics and mechanical applications including high temperature filtration, and high temperature actuators.
Co-reporter:Dr. Tsung-Han Tsai;Dr. Mohammad A. Ali;Zhelong Jiang; Paul V. Braun
Angewandte Chemie 2017 Volume 129(Issue 18) pp:5083-5088
Publication Date(Web):2017/04/24
DOI:10.1002/ange.201700166
AbstractMaterials which selectively transport molecules along defined paths offer new opportunities for concentrating, processing and sensing chemical and biological agents. Here, we present the use of traveling ionic waves to drive molecular transport and concentration of hydrophilic molecules entrained within a hydrogel. The traveling ionic wave is triggered by the spatially localized introduction of ions, which through a dissipative ion exchange process, converts quaternary ammonium groups in the hydrogel from hydrophilic to hydrophobic. Through a reaction–diffusion process, the hydrophobic region expands with a sharp transition at the leading edge; it is this sharp gradient in hydrophilicity that drives the transport of hydrophilic molecules dispersed within the film. The traveling wave moved up to 450 μm within 30 min, while the gradient length remained 20 μm over this time. As an example of the potential of molecular concentration using this approach, a 70-fold concentration of a hydrophilic dye was demonstrated.
Co-reporter:Sanghyeon Kim;Jinyun Liu;Ke Sun;Junjie Wang;Shen J. Dillon
Advanced Functional Materials 2017 Volume 27(Issue 35) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/adfm.201702783
FeF2 is considered a promising conversion compound for the positive electrode in lithium-ion batteries due to its high thermodynamic reduction potential (2.66 V vs Li/Li+) and high theoretical specific capacity (571 mA h g−1). However, the sluggish reaction kinetics and rapid capacity decay caused by side reactions during cycling limit its practical application. Here, the fabrication of Ni-supported 3D Al2O3-coated FeF2 electrodes is presented, and it is shown that these structured electrodes significantly overcome these limitations. The electrodes are prepared by iron electrodeposition on a Ni support, followed by a facile fluorination process and Al2O3 coating by atomic layer deposition. The 3D FeF2 electrode delivers an initial discharge capacity of 380 mA h g−1 at a current density of 200 mA g−1 at room temperature. The 3D scaffold improves the reaction kinetics and enables a high specific capacity by providing an efficient electron pathway to the insulating FeF2 and short Li diffusion lengths. The Al2O3 coating significantly improves the cycle life, probably by preventing side reactions through limiting direct electrode–electrolyte contact. The fabrication method presented here can also be applied for synthesis of other metal fluoride materials on different 3D conductive templates.
Co-reporter:Huigang Zhang;Tan Shi;David J. Wetzel;Ralph G. Nuzzo
Advanced Materials 2016 Volume 28( Issue 4) pp:742-747
Publication Date(Web):
DOI:10.1002/adma.201504780
Co-reporter:Neil A. Krueger, Aaron L. Holsteen, Seung-Kyun Kang, Christian R. Ocier, Weijun Zhou, Glennys Mensing, John A. Rogers, Mark L. Brongersma, and Paul V. Braun
Nano Letters 2016 Volume 16(Issue 12) pp:7402-7407
Publication Date(Web):October 31, 2016
DOI:10.1021/acs.nanolett.6b02939
The emergence and growth of transformation optics over the past decade has revitalized interest in how a gradient refractive index (GRIN) can be used to control light propagation. Two-dimensional demonstrations with lithographically defined silicon (Si) have displayed the power of GRIN optics and also represent a promising opportunity for integrating compact optical elements within Si photonic integrated circuits. Here, we demonstrate the fabrication of three-dimensional Si-based GRIN micro-optics through the shape-defined formation of porous Si (PSi). Conventional microfabrication creates Si square microcolumns (SMCs) that can be electrochemically etched into PSi elements with nanoscale porosity along the shape-defined etching pathway, which imparts the geometry with structural birefringence. Free-space characterization of the transmitted intensity distribution through a homogeneously etched PSi SMC exhibits polarization splitting behavior resembling that of dielectric metasurfaces that require considerably more laborious fabrication. Coupled birefringence/GRIN effects are studied by way of PSi SMCs etched with a linear (increasing from edge to center) GRIN profile. The transmitted intensity distribution shows polarization-selective focusing behavior with one polarization focused to a diffraction-limited spot and the orthogonal polarization focused into two laterally displaced foci. Optical thickness-based analysis readily predicts the experimentally observed phenomena, which strongly match finite-element electromagnetic simulations.Keywords: birefringence; Microlenses; silicon photonics; transformation optics;
Co-reporter:Jinyun Liu, Xi Chen, Jinwoo Kim, Qiye Zheng, Hailong Ning, Pengcheng Sun, Xingjiu Huang, Jinhuai Liu, Junjie Niu, and Paul V. Braun
Nano Letters 2016 Volume 16(Issue 7) pp:4501-4507
Publication Date(Web):June 20, 2016
DOI:10.1021/acs.nanolett.6b01711
High volumetric energy density secondary batteries are important for many applications, which has led to considerable efforts to replace the low volumetric capacity graphite-based anode common to most Li-ion batteries with a higher energy density anode. Because most high capacity anode materials expand significantly during charging, such anodes must contain sufficient porosity in the discharged state to enable the expansion, yet not excess porosity, which lowers the overall energy density. Here, we present a high volumetric capacity anode consisting of a three-dimensional (3D) nanocomposite formed in only a few steps which includes both a 3D structured Sn scaffold and a hollow Sn sphere within each cavity where all the free Sn surfaces are coated with carbon. The anode exhibits a high volumetric capacity of ∼1700 mA h cm–3 over 200 cycles at 0.5C, and a capacity greater than 1200 mA h cm–3 at 10C. Importantly, the anode can even be formed into a commercially relevant ∼100 μm thick form. When assembled into a full cell the anode shows a good compatibility with a commercial LiMn2O4 cathode. In situ TEM observations confirm the electrode design accommodates the necessary volume expansion during lithiation.
Co-reporter:Sung-Kon Kim;Jiung Cho;Jeffrey S. Moore;Ho Seok Park
Advanced Functional Materials 2016 Volume 26( Issue 6) pp:903-910
Publication Date(Web):
DOI:10.1002/adfm.201504307
The electrodes of a hybrid electrochemical capacitor which utilize the quinone (Q)-hydroquinone (QH2) couple, a prototypical organic redox system known to provide fast and reversible proton-coupled electron-transfer reactions, are deterministically mesostructured via a colloidal templating strategy to provide good ion and electron transport pathways, enabling a high rate performance. Specifically, a conducting polymer, polypyrrole (PPy), is functionalized with a pseudocapacitive material, a Q/QH2-containing catechol derivative, by noncovalent interactions. The mesostructure of this hybrid material is formed into an ordered 3D porous structure by a polystyrene colloidal crystal template-assisted electrosynthesis. The catechol derivative is sufficiently bound to the PPy through noncovalent interactions to provide a volumetric capacitance as high as ≈130 F cm−3 and a capacitance retention of ≈75% over 10 000 charging/discharging cycles. When compared with a randomly structured electrode, the deterministically structured electrode exhibits an improved rate performance due to the mesostructure facilitated electron and ion transport.
Co-reporter:James H. Pikul, Jinyun Liu, Paul V. Braun, William P. King
Journal of Power Sources 2016 Volume 315() pp:308-315
Publication Date(Web):31 May 2016
DOI:10.1016/j.jpowsour.2016.03.034
•Ultra-high power density is achieved in primary microbatteries.•Integration of high capacity materials enables high energy density.•Conformal electrodeposition in mesostructured electrodes is demonstrated.•Dense lithium metal electrodeposition is demonstrated.Microbatteries are increasingly important for powering electronic systems, however, the volumetric energy density of microbatteries lags behind that of conventional format batteries. This paper reports a primary microbattery with energy density 45.5 μWh cm−2 μm−1 and peak power 5300 μW cm−2 μm−1, enabled by the integration of large volume fractions of high capacity anode and cathode chemistry into porous micro-architectures. The interdigitated battery electrodes consist of a lithium metal anode and a mesoporous manganese oxide cathode. The key enabler of the high energy and power density is the integration of the high capacity manganese oxide conversion chemistry into a mesostructured high power interdigitated bicontinuous cathode architecture and an electrodeposited dense lithium metal anode. The resultant energy density is greater than previously reported three-dimensional microbatteries and is comparable to commercial conventional format lithium-based batteries.
Co-reporter:T. Patrick Xiao, Osman S. Cifci, Samarth Bhargava, Hao Chen, Timo Gissibl, Weijun Zhou, Harald Giessen, Kimani C. Toussaint Jr., Eli Yablonovitch, and Paul V. Braun
ACS Photonics 2016 Volume 3(Issue 5) pp:
Publication Date(Web):April 25, 2016
DOI:10.1021/acsphotonics.6b00066
The greatest source of loss in conventional single-junction photovoltaic cells is their inefficient utilization of the energy contained in the full spectrum of sunlight. To overcome this deficiency, we propose a multijunction system that laterally splits the solar spectrum onto a planar array of single-junction cells with different band gaps. As a first demonstration, we designed, fabricated, and characterized dispersive diffractive optics that spatially separated the visible (360–760 nm) and near-infrared (760–1100 nm) bands of sunlight in the far field. Inverse electromagnetic design was used to optimize the surface texture of the thin diffractive phase element. An optimized thin film fabricated by femtosecond two-photon absorption 3D direct laser writing shows an average splitting ratio of 69.5% between the visible and near-infrared light over the 380–970 nm range at normal incidence. The splitting efficiency is predicted to be 80.4% assuming a structure without fabrication errors. Spectral-splitting action is observed within an angular range of ±1° from normal incidence. Further design optimization and fabrication improvements can increase the splitting efficiency under direct sunlight, increase the tolerance to angular errors, allow for a more compact geometry, and ultimately incorporate a greater number of photovoltaic band gaps.
Co-reporter:Jinwoo Kim;Larry K. Aagesen;Jun Hee Choi;Jaewon Choi;Ha Seong Kim;Jinyun Liu;Chae-Ryong Cho;Jin Gu Kang;Ali Ramazani;Katsuyo Thornton
Advanced Materials 2015 Volume 27( Issue 31) pp:4551-4559
Publication Date(Web):
DOI:10.1002/adma.201502265
Co-reporter:Chunjie Zhang; Amit Sitt; Hyung-Jun Koo; Kristopher V. Waynant; Henry Hess; Brian D. Pate
Journal of the American Chemical Society 2015 Volume 137(Issue 15) pp:5066-5073
Publication Date(Web):March 16, 2015
DOI:10.1021/jacs.5b00240
Materials which induce molecular motion without external input offer unique opportunities for spatial manipulation of molecules. Here, we present the use of polyacrylamide hydrogel films containing built-in chemical gradients (enthalpic gradients) to direct molecular transport. Using a cationic tertiary amine gradient, anionic molecules were directionally transported up to several millimeters. A 40-fold concentration of anionic molecules dosed in aerosol form on a substrate to a small region at the center of a radially symmetric cationic gradient was observed. The separation of mixtures of charged dye molecules was demonstrated using a boronic acid-to-cationic gradient where one molecule was attracted to the boronic acid end of the gradient, and the other to the cationic end of the gradient. Theoretical and computational analysis provides a quantitative description of such anisotropic molecular transport, and reveals that the gradient-imposed drift velocity is in the range of hundreds of nanometers per second, comparable to the transport velocities of biomolecular motors. This general concept of enthalpy gradient-directed molecular transport should enable the autonomous processing of a diversity of chemical species.
Co-reporter:Junjie Wang, Hui Zhou, Jagjit Nanda, and Paul V. Braun
Chemistry of Materials 2015 Volume 27(Issue 8) pp:2803
Publication Date(Web):March 26, 2015
DOI:10.1021/cm504365s
Ni scaffolded mesostructured 3D Fe2O3 electrodes were fabricated by colloidal templating and pulsed electrodeposition. The scaffold provided short pathways for both lithium ions and electrons in the active phase, enabling fast kinetics and thus a high power density. The scaffold also resulted in a reduced voltage hysteresis. The electrode showed a reversible capacity of ∼1000 mAh g–1 at 0.2 A g–1 (∼0.2 C) for about 20 cycles, and at a current density of 20 A g–1 (∼20 C), the deliverable capacity was about 450 mAh g–1. The room-temperature voltage hysteresis at 0.1 A g–1 (∼0.1 C) was 0.62 V, which is significantly smaller than that normally reported in the literature. The hysteresis further reduced to 0.42 V at 45 °C. Potentiostatic electrochemical impedance spectroscopy (PEIS) studies indicated that the small voltage hysteresis may be due to a reduction in the Li2O/Fe interfacial area in the electrode during cycling relative to conventional conversion systems.
Co-reporter:Sung-Kon Kim, Euiyeon Jung, Matthew D. Goodman, Kenneth S. Schweizer, Narihito Tatsuda, Kazuhisa Yano, and Paul V. Braun
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 17) pp:9128
Publication Date(Web):April 13, 2015
DOI:10.1021/acsami.5b01147
We report a three-dimensional (3D) porous carbon electrode containing both nanoscale and microscale porosity, which has been hierarchically organized to provide efficient ion and electron transport. The electrode organization is provided via the colloidal self-assembly of monodisperse starburst carbon spheres (MSCSs). The periodic close-packing of the MSCSs provides continuous pores inside the 3D structure that facilitate ion and electron transport (electrode electrical conductivity ∼0.35 S m–1), and the internal meso- and micropores of the MSCS provide a good specific capacitance. The capacitance of the 3D-ordered porous MSCS electrode is ∼58 F g–1 at 0.58 A g–1, 48% larger than that of disordered MSCS electrode at the same rate. At 1 A g–1 the capacitance of the ordered electrode is 57 F g–1 (95% of the 0.24 A g–1 value), which is 64% greater than the capacitance of the disordered electrode at the same rate. The ordered electrode preserves 95% of its initial capacitance after 4000 charging/discharging cycles.Keywords: colloid; energy storage; hierarchical structure; porous carbon; supercapacitor;
Co-reporter:Jinyun Liu, Sean J. Kelly, Eric S. Epstein, Zeng Pan, Xingjiu Huang, Jinhuai Liu, Paul V. Braun
Journal of Power Sources 2015 Volume 299() pp:40-48
Publication Date(Web):20 December 2015
DOI:10.1016/j.jpowsour.2015.08.078
•Three-dimensionally scaffold-based anodes are fabricated.•Thin nanosheets provide efficient pathways for electron and ion transportation.•The Co3O4 anodes show attractive C-rate performance.•The robust electrode structure provides high capacity retention.Advances in secondary batteries are required for realization of many technologies. In particular, there remains a need for stable higher energy batteries. Here we suggest a new anode concept consisting of an ultrathin Co3O4 nanosheet-coated Ni inverse opal which provides high charge–discharge rate performance using a material system with potential for high energy densities. Via a hydrothermal process, about 4 nm thick Co3O4 nanosheets were grown throughout a three-dimensional Ni scaffold. This architecture provides efficient pathways for both lithium and electron transfer, enabling high charge–discharge rate performance. The scaffold also accommodates volume changes during cycling, which serves to reduce capacity fade. Because the scaffold has a low electrical resistance, and is three-dimensionally porous, it enables most of the electrochemically active nanomaterials to take part in lithiation–delithiation reactions, resulting in a near-theoretical capacity. On a Co3O4 basis, the Ni@Co3O4 electrode possesses a capacity of about 726 mAh g−1 at a current density of 500 mA g−1 after 50 cycles, which is about twice the theoretical capacity of graphite. The capacity is 487 mAh g−1, even at a current density of 1786 mA g−1.
Co-reporter:Jinyun Liu, Nan Li, Matthew D. Goodman, Hui Gang Zhang, Eric S. Epstein, Bo Huang, Zeng Pan, Jinwoo Kim, Jun Hee Choi, Xingjiu Huang, Jinhuai Liu, K. Jimmy Hsia, Shen J. Dillon, and Paul V. Braun
ACS Nano 2015 Volume 9(Issue 2) pp:1985
Publication Date(Web):January 31, 2015
DOI:10.1021/nn507003z
Stability and high energy densities are essential qualities for emerging battery electrodes. Because of its high specific capacity, silicon has been considered a promising anode candidate. However, the several-fold volume changes during lithiation and delithiation leads to fractures and continuous formation of an unstable solid-electrolyte interphase (SEI) layer, resulting in rapid capacity decay. Here, we present a carbon–silicon–carbon (C@Si@C) nanotube sandwich structure that addresses the mechanical and chemical stability issues commonly associated with Si anodes. The C@Si@C nanotube array exhibits a capacity of ∼2200 mAh g–1 (∼750 mAh cm–3), which significantly exceeds that of a commercial graphite anode, and a nearly constant Coulombic efficiency of ∼98% over 60 cycles. In addition, the C@Si@C nanotube array gives much better capacity and structure stability compared to the Si nanotubes without carbon coatings, the ZnO@C@Si@C nanorods, a Si thin film on Ni foam, and C@Si and Si@C nanotubes. In situ SEM during cycling shows that the tubes expand both inward and outward upon lithiation, as well as elongate, and then revert back to their initial size and shape after delithiation, suggesting stability during volume changes. The mechanical modeling indicates the overall plastic strain in a nanotube is much less than in a nanorod, which may significantly reduce low-cycle fatigue. The sandwich-structured nanotube design is quite general, and may serve as a guide for many emerging anode and cathode systems.Keywords: capacity; Li-ion battery; nanotube; plastic strain; silicon anode;
Co-reporter:James H. Pikul;Hailong Ning;Runyu Zhang;Xuejiao Li;Sheng Xu;Junjie Wang;William P. King;John A. Rogers
PNAS 2015 Volume 112 (Issue 21 ) pp:6573-6578
Publication Date(Web):2015-05-26
DOI:10.1073/pnas.1423889112
As sensors, wireless communication devices, personal health monitoring systems, and autonomous microelectromechanical systems
(MEMS) become distributed and smaller, there is an increasing demand for miniaturized integrated power sources. Although thin-film
batteries are well-suited for on-chip integration, their energy and power per unit area are limited. Three-dimensional electrode
designs have potential to offer much greater power and energy per unit area; however, efforts to date to realize 3D microbatteries
have led to prototypes with solid electrodes (and therefore low power) or mesostructured electrodes not compatible with manufacturing
or on-chip integration. Here, we demonstrate an on-chip compatible method to fabricate high energy density (6.5 μWh cm−2⋅μm−1) 3D mesostructured Li-ion microbatteries based on LiMnO2 cathodes, and NiSn anodes that possess supercapacitor-like power (3,600 μW cm−2⋅μm−1 peak). The mesostructured electrodes are fabricated by combining 3D holographic lithography with conventional photolithography,
enabling deterministic control of both the internal electrode mesostructure and the spatial distribution of the electrodes
on the substrate. The resultant full cells exhibit impressive performances, for example a conventional light-emitting diode
(LED) is driven with a 500-μA peak current (600-C discharge) from a 10-μm-thick microbattery with an area of 4 mm2 for 200 cycles with only 12% capacity fade. A combined experimental and modeling study where the structural parameters of
the battery are modulated illustrates the unique design flexibility enabled by 3D holographic lithography and provides guidance
for optimization for a given application.
Co-reporter:Sung-Kon Kim;Hyung-Jun Koo;Aeri Lee
Advanced Materials 2014 Volume 26( Issue 30) pp:5108-5112
Publication Date(Web):
DOI:10.1002/adma.201401525
Co-reporter:Ming Fu;Kundan Chaudhary;Jonathan G. Lange;Ha Seong Kim;Jamie J. Juarez;Jennifer A. Lewis
Advanced Materials 2014 Volume 26( Issue 11) pp:1740-1745
Publication Date(Web):
DOI:10.1002/adma.201304809
Co-reporter:Chunjie Zhang;Gerry G. Cano
Advanced Materials 2014 Volume 26( Issue 32) pp:5678-5683
Publication Date(Web):
DOI:10.1002/adma.201401710
Co-reporter:Jinyun Liu;Hui Gang Zhang;Junjie Wang;Jiung Cho;James H. Pikul;Eric S. Epstein;Xingjiu Huang;Jinhuai Liu;William P. King
Advanced Materials 2014 Volume 26( Issue 41) pp:7096-7101
Publication Date(Web):
DOI:10.1002/adma.201402552
Co-reporter:Robert H. Coridan, Kevin A. Arpin, Bruce S. Brunschwig, Paul V. Braun, and Nathan S. Lewis
Nano Letters 2014 Volume 14(Issue 5) pp:2310-2317
Publication Date(Web):March 28, 2014
DOI:10.1021/nl404623t
WO3 thin films have been deposited in a hierarchically structured core–shell morphology, with the cores consisting of an array of Si microwires and the shells consisting of a controlled morphology WO3 layer. Porosity was introduced into the WO3 outer shell by using a self-assembled microsphere colloidal crystal as a mask during the deposition of the WO3 shell. Compared to conformal, unstructured WO3 shells on Si microwires, the hierarchically structured core–shell photoanodes exhibited enhanced near-visible spectral response behavior, due to increased light absorption and reduced distances over which photogenerated carriers were collected. The use of structured substrates also improved the growth rate of microsphere-based colloidal crystals and suggests strategies for the use of colloidal materials in large-scale applications.
Co-reporter:Paul V. Braun
Chemistry of Materials 2014 Volume 26(Issue 1) pp:277
Publication Date(Web):October 11, 2013
DOI:10.1021/cm4023437
This Perspective overviews many of the developments in templated porous three-dimensional photonics, with a particular focus on functional architectures, and provides suggestions for future opportunities for research. A significant diversity of 3D structures is available today with characteristic dimensions appropriate for providing strong light–matter interactions, in no small part due to recent advances in 3D patterning techniques. However, the optical functionality of these structures has generally remained limited. Advances in materials chemistry have the opportunity to dramatically increase the function of templated 3D photonics, and a few examples of highly functional templated 3D photonics for sensing, solar energy harvesting, optical metamaterials, and light emission are presented as first examples of success.Keywords: metamaterials; optoelectronics; photonic band gap; photonic crystal; self-assembly; three-dimensional;
Co-reporter:Hyung-Jun Koo, Kristopher V. Waynant, Chunjie Zhang, Richard T. Haasch, and Paul V. Braun
Chemistry of Materials 2014 Volume 26(Issue 8) pp:2678
Publication Date(Web):March 27, 2014
DOI:10.1021/cm5004388
We report a general diffusion based method to form micrometer-scale lateral chemical gradients in polymer brushes via selective alkylation. A quaternized brush gradient is derived from a concentration gradient of alkylating agent formed by diffusion in permeable media around a microchannel carrying the alkylating agent. Polymer brushes containing both charge and aromatic gradients are formed using the alkylating agents, methyl iodide and benzyl bromide, respectively. The gradients are quantitatively characterized by confocal Raman spectroscopy and qualitatively by fluorescence microscopy. The length and gradient strength can be controlled by varying the diffusion time, concentrations, and solvents of the alkylating agent solutions. This microfluidic brush gradient generation method enables formation of 2-D chemical potential gradients with a diversity of shapes.
Co-reporter:Jinwoo Kim, Ha Seong Kim, Jun Hee Choi, Hyeongtag Jeon, Yohan Yoon, Jinyun Liu, Jea-Gun Park, and Paul V. Braun
Chemistry of Materials 2014 Volume 26(Issue 24) pp:7051
Publication Date(Web):December 1, 2014
DOI:10.1021/cm5034645
Significant efforts have been made over the past few decades to realize functional three-dimensional photonic crystal devices including zero-threshold lasers, waveguides, light-emitting diodes (LEDs), and solar cells; however, progress has been limited because of difficulties in creating three-dimensional photonic crystals from single-crystal materials. Most have been formed from polycrystalline materials and thus have generally exhibited poor electronic properties. Realization of materials containing complex three-dimensional mesostructures, in single-crystal form, remains a significant challenge. Here, we demonstrate the epitaxial growth of three-dimensionally mesostructured Cu2O by bottom-up electrodeposition through a 3D silica colloidal template. Not only is the templated Cu2O single crystal, but when the electrodeposition continues past the colloidal template, the crystallinity of the overlying solid Cu2O appears to be improved because the template blocks threading dislocations, resulting in substantial reductions in the dislocation density of the overlying solid Cu2O.
Co-reporter:Hyung-Jun Koo, Kristopher V. Waynant, Chunjie Zhang, and Paul V. Braun
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 16) pp:14320
Publication Date(Web):June 24, 2014
DOI:10.1021/am503609x
We present a facile microfluidic method for forming narrow chemical gradients in polymer brushes. Co-flow of an alkylating agent solution and a neat solvent in a microfluidic channel forms a diffusion-driven concentration gradient, and thus a gradient in reaction rate at the interface of the two flows, leading to a quaternization gradient in the underlying poly(2-(dimethylamino)ethyl methacrylate) polymer brush. The spatial distribution of the quaternized polymer brush is characterized by confocal Raman microscopy. The quaternization gradient length in the polymer brush can be varied with the injection flow rate and the distance from the co-flow junction. A chemical gradient in the polymer brush as narrow as 5 μm was created by controlling these parameters. The chemical gradient by laminar co-flow is compared with numerical calculations that include only one adjustable parameter: the reaction rate constant of the polymer brush quaternization. The calculated chemical gradient agrees with the experimental data, which validates the numerical procedures established in this study. Flow of multiple laminar streams of reactive agent solutions enables single-run fabrication of brush gradients with more than one chemical property. As one example, four laminar streams—neat solvent/benzyl bromide solution/propargyl bromide solution/neat solvent—generate multistep gradients of aromatic and alkyne groups. Because the alkyne functional group is a click-reaction available site, the alkyne gradient could allow small gradient formation with a wide variety of chemical properties in a polymer brush.Keywords: amine alkylation; chemical gradient; click reaction; laminar flow; microfluidics; polymer brush
Co-reporter:Hyung-Jun Koo, Sung-Kon Kim and Paul V. Braun
RSC Advances 2014 vol. 4(Issue 40) pp:20927-20931
Publication Date(Web):28 Apr 2014
DOI:10.1039/C4RA01154F
Graphene based electrical conductors are under consideration for numerous applications in energy storage, energy conversion devices, electronics and sensors. Here, we report a facile and versatile method for fabrication of graphene based composite microwires ranging from ∼20 to 250 μm in diameter via size reduction during dehydration of extruded larger diameter graphene oxide-loaded agarose hydrogel fibers. The graphene oxide is effectively reduced to graphene by chemical and thermal treatment. After dehydration and reduction, the resulting graphene composite microwires exhibit high electrical conductivities of up to 1.8 S m−1.
Co-reporter:Corissa K. Lee, Charles E. Diesendruck, Enjiong Lu, Austin N. Pickett, Preston A. May, Jeffrey S. Moore, and Paul V. Braun
Macromolecules 2014 Volume 47(Issue 8) pp:2690-2694
Publication Date(Web):April 4, 2014
DOI:10.1021/ma500195h
A spiropyran mechanophore (force-sensitive molecule), which is fluorescent in its mechanically activated state, is used to investigate swelling-induced mechanochemistry in cross-linked poly(methyl methacrylate). The spiropyran is incorporated as a cross-linker. A correlation is observed between solvent-induced polymer swelling and fluorescence intensity, suggesting that the forces during swelling are sufficient to drive the electrocyclic ring-opening of spiropyran to its colored and fluorescent merocyanine form. Control experiments and solvatochromic studies validate that activation is indeed due to swelling-induced mechanical forces and not solvent effects. Systematic studies varying solvents and cross-linking densities provide insight into how altering swelling parameters influences the mechanophore response at the molecular level.
Co-reporter:Hailong Ning, Neil A. Krueger, Xing Sheng, Hohyun Keum, Chen Zhang, Kent D. Choquette, Xiuling Li, Seok Kim, John A. Rogers, and Paul V. Braun
ACS Photonics 2014 Volume 1(Issue 11) pp:1144
Publication Date(Web):October 21, 2014
DOI:10.1021/ph500230j
Here we demonstrate, via a modified transfer-printing technique, that electrochemically fabricated porous silicon (PSi) distributed Bragg reflectors (DBRs) can serve as the basis of high-quality hybrid microcavities compatible with most forms of photoemitters. Vertical microcavities consisting of an emitter layer sandwiched between 11- and 15-period PSi DBRs were constructed. The emitter layer included a polymer doped with PbS quantum dots, as well as a heterogeneous GaAs thin film. In this structure, the PbS emission was significantly redistributed to a 2.1 nm full-width at half-maximum around 1198 nm, while the PSi/GaAs hybrid microcavity emitted at 902 nm with a sub-nanometer full-width at half-maximum and quality-factor of 1058. Modification of PSi DBRs to include a PSi cavity coupling layer enabled tuning of the total cavity optical thickness. Infiltration of the PSi with Al2O3 by atomic layer deposition globally red-shifted the emission peak of PbS quantum dots up to ∼18 nm (∼0.9 nm per cycle), while introducing a cavity coupling layer with a gradient optical thickness spatially modulated the cavity resonance of the PSi/GaAs hybrid such that there was an ∼30 nm spectral variation in the emission of separate GaAs modules printed ∼3 mm apart.Keywords: distributed Bragg reflector; gradient refractive index; silicon photonics; silicon/III−V hybrid; vertical cavity emitter
Co-reporter:Jun Ma, Bibek R. Parajuli, Marc G. Ghossoub, Agustin Mihi, Jyothi Sadhu, Paul V. Braun, and Sanjiv Sinha
Nano Letters 2013 Volume 13(Issue 2) pp:618-624
Publication Date(Web):January 3, 2013
DOI:10.1021/nl304190s
We report measurements and modeling of thermal conductivity in periodic three-dimensional dielectric nanostructures, silicon inverse opals. Such structures represent a three-dimensional “phononic crystal” but affect heat flow instead of acoustics. Employing the Stober method, we fabricate high quality silica opal templates that on filling with amorphous silicon, etching and recrystallizing produce silicon inverse opals. The periodicities and shell thicknesses are in the range 420–900 and 18–38 nm, respectively. The thermal conductivity of inverse opal films are relatively low, ∼0.6–1.4 W/mK at 300 K and arise due to macroscopic bending of heat flow lines in the structure. The corresponding material thermal conductivity is in the range 5–12 W/mK and has an anomalous ∼T1.8 dependence at low temperatures, distinct from the typical ∼T3 behavior of bulk polycrystalline silicon. Using phonon scattering theory, we show such dependence arising from coherent phonon reflections in the intergrain region. This is consistent with an unconfirmed theory proposed in 1955. The low thermal conductivity is significant for applications in photonics where they imply significant temperature rise at relatively low absorption and in thermoelectrics, where they suggest the possibility of enhancement in the figure of merit for polysilicon with optimal doping.
Co-reporter:Mark D. Losego, Ian P. Blitz, Richard A. Vaia, David G. Cahill, and Paul V. Braun
Nano Letters 2013 Volume 13(Issue 5) pp:2215-2219
Publication Date(Web):April 17, 2013
DOI:10.1021/nl4007326
Because interfaces impede phonon transport of thermal energy, nanostructuring can transform fully dense solids into ultralow thermal conductivity materials. Here we report a simple self-assembly approach to synthesizing organoclay nanolaminates with cross-planar thermal conductivities below 0.10 W m–1 K–1—a 5-fold decrease compared to unmodified clay. These organoclays are produced via alkylammonium cation exchange with colloidally dispersed montmorillonite clay sheets followed by solvent casting. Time-domain thermoreflectance (TDTR) is used to evaluate the thermal conductivity of the organoclay nanolaminates. Variations in both organic layer thickness and cation chemistry are investigated. At these interface densities (1.0–1.5 interfaces/nm), we demonstrate that thermal conductivity is relatively independent of nanolaminate spacing. A simple series resistance model describes the behavior and gives an interfacial thermal conductance value of ≈150 MW m–2 K–1 for the organic/clay interface, consistent with similar organic–inorganic interfaces. The wide range of compositional substitutions and structural variations possible in these materials, make organoclays a versatile new platform for investigating the underlying physics of nanolaminate structures.
Co-reporter:Chunjie Zhang, Mark D. Losego, and Paul V. Braun
Chemistry of Materials 2013 Volume 25(Issue 15) pp:3239
Publication Date(Web):July 9, 2013
DOI:10.1021/cm401738p
Phenylboronic acids (PBAs) are being considered for glucose sensing and controlled insulin release, because of their affinity for diol-containing molecules. The interaction of immobilized PBAs in a hydrogel matrix with glucose can lead to volumetric changes that have been used to monitor glucose concentration and release insulin. Although the interaction of PBAs with diol-containing molecules has been intensively studied, the response of PBA-modified hydrogels as a function of the specific PBA chemistry is not well understood. To understand the interaction of immobilized PBAs with glucose in hydrogel systems under physiological conditions, the glucose-dependent volumetric changes of a series of hydrogel sensors functionalized with different classes of PBAs were investigated. The volume change induced by PBA-glucose interactions is converted to the diffracted wavelength shift by a crystalline colloidal array embedded in the hydrogel matrix. The PBAs studied contain varying structural parameters such as the position of the boronic acid on the phenyl ring, different substituents on PBAs and different linkers to the hydrogel backbone. The volumetric change of the PBA modified hydrogels is found to be highly dependent on the chemical structure of the immobilized PBAs. The PBAs that appear to provide linear volumetric responses to glucose are found to also have slow response kinetics and significant hysteresis, while PBAs that show nonlinear responses have fast response kinetics and small hysteresis. Electron-withdrawing substituents, which reduce the pKa of PBAs, either increase or decrease the magnitude of response, depending on the exact chemical structure. The response rate is increased by PBAs with electron-withdrawing substituents. Addition of a methylene bridge between the PBA and hydrogel backbone leads to a significant decrease in the response magnitude. PBAs with specific desirable features can be selected from the pool of available PBAs and other PBA derivatives with desired properties can be designed according to the findings reported here.Keywords: boronic acid; glucose responsive; hydrogel; photonic crystal; sensor;
Co-reporter:Matthew D. Goodman;Kevin A. Arpin;Agustin Mihi;Narihito Tatsuda;Kazuhisa Yano
Advanced Optical Materials 2013 Volume 1( Issue 4) pp:300-304
Publication Date(Web):
DOI:10.1002/adom.201300120
Co-reporter:Corissa K. Lee, Brett A. Beiermann, Meredith N. Silberstein, Joanna Wang, Jeffrey S. Moore, Nancy R. Sottos, and Paul V. Braun
Macromolecules 2013 Volume 46(Issue 10) pp:3746-3752
Publication Date(Web):May 14, 2013
DOI:10.1021/ma4005428
Spiropyran (SP) mechanophore was synthesized into the soft or hard phase of segmented polyurethanes (SPU) and used as a molecular probe of force and orientation. Upon either tensile stretching or irradiation with UV light the SP-linked segmented polyurethane (SP-SPU) adopt a deep purple coloration and are fluorescent, demonstrating the force and UV-induced formation of the open merocyanine (MC) form of the mechanophore. Order parameters calculated from the anisotropy of the fluorescence polarization of merocyanine (MC) were used to characterize the orientation in each phase. Exploiting the ability of SP to be force activated, the SP-SPUs were also mechanically activated to track the force and orientation in each domain of segmented polyurethane during uniaxial tensile loading.
Co-reporter:Hailong Ning;Agustin Mihi;Joseph B. Geddes III;Masao Miyake
Advanced Materials 2012 Volume 24( Issue 23) pp:OP153-OP158
Publication Date(Web):
DOI:10.1002/adma.201104769
Co-reporter:Huigang Zhang and Paul V. Braun
Nano Letters 2012 Volume 12(Issue 6) pp:2778-2783
Publication Date(Web):May 14, 2012
DOI:10.1021/nl204551m
Silicon-based lithium ion battery anodes are attracting significant attention because of silicon’s exceptionally high lithium capacity. However, silicon’s large volume change during cycling generally leads to anode pulverization unless the silicon is dispersed throughout a matrix in nanoparticulate form. Because pulverization results in a loss of electric connectivity, the reversible capacity of most silicon anodes dramatically decays within a few cycles. Here we report a three-dimensional (3D) bicontinuous silicon anode formed by depositing a layer of silicon on the surface of a colloidal crystal templated porous nickel metal scaffold, which maintains electrical connectivity during cycling due to the scaffold. The porous metal framework serves to both impart electrical conductivity to the anode and accommodate the large volume change of silicon upon lithiation and delithiation. The initial capacity of the bicontinuous silicon anode is 3568 (silicon basis) and 1450 mAh g–1 (including the metal framework) at 0.05C. After 100 cycles at 0.3C, 85% of the capacity remains. Compared to a foil-supported silicon film, the 3D bicontinuous silicon anode exhibits significantly improved mechanical stability and cycleability.
Co-reporter:Soo Hyoun Cho, Scott R. White, and Paul V. Braun
Chemistry of Materials 2012 Volume 24(Issue 21) pp:4209
Publication Date(Web):October 4, 2012
DOI:10.1021/cm302501b
Polymers that respond in a productive fashion to their environment are under active development as they offer significant advantages over traditional materials. For example, polymers with the ability to self-heal and recover a significant fraction of their initial properties after being subjected to a damage event are of significant interest. Here we study the effect of healing agent viscosity and catalyst activity on self-healing at and near room temperature. The viscosity of the PDMS healing agent was varied from 14 to 40 000 cP, and the tin-based catalysts di-n-butyltin dilaurate, dimethyl-dineodacanoate tin, di-n-butyl bis(2-ethylenehexanoate), tin II oleate, and tetrakis(acetoxydibutyl tinoxy)silane were studied. Both vinyl ester and epoxy matrices were investigated. By optimizing the viscosity of the PDMS healing agent and the catalytic activity, as well as selection of the appropriate adhesion promoter, a PDMS-based self-healing system which healed at room temperature was obtained.Keywords: catalytic activity; epoxy; microcapsules; PDMS; phase separation; room temperature; self-healing; tin catalyst; viscosity;
Co-reporter:Nihan Yonet-Tanyeri;Rachel C. Evans;Huilin Tu
Advanced Materials 2011 Volume 23( Issue 15) pp:1739-1743
Publication Date(Web):
DOI:10.1002/adma.201003705
Co-reporter:Aaron C. Jackson;Jonathan A. Bartelt
Advanced Functional Materials 2011 Volume 21( Issue 24) pp:4705-4711
Publication Date(Web):
DOI:10.1002/adfm.201101574
Abstract
A self-healing approach for optically transparent thermoplastic polymers, based on plasticizer-induced solvent welding, is reported. For the specific system investigated, dibutylphthalate (DBP) filled urea-formaldehyde capsules are dispersed in a polymethylmethacrylate (PMMA) matrix. Upon a damage event, DBP is released into the crack, and locally plasticizes and swells the polymer, enabling it to remend. Two challenges are addressed to maintain optical transparency: minimization of light scatter from the capsules in the polymer matrix and minimization of light scatter from the healed polymer. PMMA films containing DBP capsules have good transmissive properties as a result of the close index match between PMMA and DBP. The transmission properties are better than, for example, when DBP capsules are dispersed into a poorly index matched matrix, such as polystyrene. In the DBP PMMA system, the healed material is inherently index matched to the polymer matrix and thus the polymer's original optical properties are largely restored. Self-healing using both small capsules, 1.5 μm in diameter, and large capsules, 75 μm in diameter is demonstrated. Smaller capsules are particularly important for thin polymer films which are not thick enough to hold the larger capsules. Polymer films with smaller capsules also have very good transmission properties due to a minimization of light scattering by the small size of the capsules. Large capsules enable healing of larger damage events, but do inherently result in some light scattering. This plasticizer-based approach to self-healing is shown to enable recovery of the protective properties and a portion of the mechanical properties of a polymeric film.
Co-reporter:Kevin A. Arpin, Mark D. Losego, and Paul V. Braun
Chemistry of Materials 2011 Volume 23(Issue 21) pp:4783
Publication Date(Web):October 18, 2011
DOI:10.1021/cm2019789
Tungsten inverse opal photonic crystals were fabricated using a template directed electrodeposition method. The electrodeposition was accomplished using a molten salt solution at elevated temperatures. Following template removal, the tungsten inverse opals were conformally coated with hafnia or alumina via atomic layer deposition. This surface passivation layer increased the thermal stability of the tungsten microarchitectures by limiting surface diffusion. Alumina protected tungsten inverse opals were thermally stable up to 1000 °C for at least 12 h in forming gas (5% H2 in Ar). Hafnia protected inverse opals were thermally stable up to 1400 °C for at least 12 h in forming gas. We expect that this surface passivation technique can also be implemented to increase the thermal stability of other refractory metal microarchitectures. The demonstrated thermal stability is an important property for the realization of metallic photonic crystals as narrow band emitters for thermophotovoltaics.Keywords: electrodeposition; thermophotovoltaics; tungsten inverse opal;
Co-reporter:Aaron C. Jackson;Jonathan A. Bartelt;Kamil Marczewski;Nancy R. Sottos
Macromolecular Rapid Communications 2011 Volume 32( Issue 1) pp:82-87
Publication Date(Web):
DOI:10.1002/marc.201000468
Co-reporter:Kevin A. Arpin, James H. Pikul, William P. King, Hongyou Fan and Paul V. Braun
Soft Matter 2011 vol. 7(Issue 21) pp:10252-10257
Publication Date(Web):06 Sep 2011
DOI:10.1039/C1SM06078C
The ability to pattern functional nanoparticle arrays in multiple dimensions will enable future devices which exhibit functions that cannot be realized using unstructured nanoparticle arrays. Here we demonstrate the unique assembly properties of dynamic micellar nanoparticles by combining a top down lithographic nanopatterning technique with a solution-based bottom up self-assembly. The templates for the directed self-assembly of the micelles consisted of arrays of cylindrical recess features fabricated by nanoimprint lithography. Silica was coated on this patterned substrate and subsequently selectively functionalized with a positively charged molecular monolayer (N-(3-Trimethoxysilylpropyl) diethylenetriamine) to regulate the micelle-surface interactions. The self-assembled block co-polymer polystyrene-b-poly(4-vinyl pyridine) (PS480k–PVP145k) micelles were approximately 325nm in diameter in aqueous solutions (pH = 2.5) and 50nm in diameter in the dry state. The average number of micelles assembled per feature increased from less than 1 to 12 with increasing feature diameter in the range of 200nm–1μm. Using a 2D model for maximum packing of circles in circular host features, the effective sphere size of the micelles during assembly was calculated to be 250nm in diameter. Thus, the micelles exhibited three characteristic sizes during assembly, 325nm in bulk solution, 250nm during assembly, and 50nm in the dry state. This dramatic variation in nanoparticle volume during the assembly process offers unique opportunities for forming nanometre scale, multidimensional arrays not accessible using hard sphere building blocks.
Co-reporter:Dr. Agustín Mihi;Chunjie Zhang ; Paul V. Braun
Angewandte Chemie International Edition 2011 Volume 50( Issue 25) pp:5712-5715
Publication Date(Web):
DOI:10.1002/anie.201100446
Co-reporter:Dr. Agustín Mihi;Chunjie Zhang ; Paul V. Braun
Angewandte Chemie 2011 Volume 123( Issue 25) pp:5830-5833
Publication Date(Web):
DOI:10.1002/ange.201100446
Co-reporter:Kevin A. Arpin;Agustin Mihi;Harley T. Johnson;Alfred J. Baca;John A. Rogers;Jennifer A. Lewis
Advanced Materials 2010 Volume 22( Issue 10) pp:1084-1101
Publication Date(Web):
DOI:10.1002/adma.200904096
Abstract
Materials exhibiting multidimensional structure with characteristic lengths ranging from the nanometer to the micrometer scale have extraordinary potential for emerging optical applications based on the regulation of light–matter interactions via the mesoscale organization of matter. As the structural dimensionality increases, the opportunities for controlling light–matter interactions become increasingly diverse and powerful. Recent advances in multidimensional structures have been demonstrated that serve as the basis for three-dimensional photonic-bandgap materials, metamaterials, optical cloaks, highly efficient low-cost solar cells, and chemical and biological sensors. In this Review, the state-of-the-art design and fabrication of multidimensional architectures for functional optical devices are covered and the next steps for this important field are described.
Co-reporter:Jeong-Ho Park
Advanced Materials 2010 Volume 22( Issue 4) pp:496-499
Publication Date(Web):
DOI:10.1002/adma.200902465
Co-reporter:Corissa K. Lee ; Douglas A. Davis ; Scott R. White ; Jeffrey S. Moore ; Nancy R. Sottos
Journal of the American Chemical Society 2010 Volume 132(Issue 45) pp:16107-16111
Publication Date(Web):October 26, 2010
DOI:10.1021/ja106332g
Spiropyran (SP) mechanophores (mechanochemically reactive units) can impart the unique functionality of visual stress detection to polymers and have potential for use in smart materials with self-sensing capabilities. These color-generating mechanophores were incorporated into polyurethane via step growth polymerization. Polyurethane, which is inherently a versatile engineering polymer, possesses an optimized balance of mechanical toughness and elasticity to allow for investigation of the kinetics of the mechanochemical response of the SP mechanophore in the bulk polymer via fluorescence and absorbance measurements. The stress-induced 6-π electrocyclic ring-opening to the colored merocyanine (MC) form of the mechanophore was quantified by measuring the change in absorbance of the polymer, while it was held at constant strain. The closing kinetics of the mechanophore was also studied by fluorescence imaging. Finally, the effects of mechanical strain on the equilibrium between the SP and MC forms are reported and discussed.
Co-reporter:Yoonho Jun ; Dongguk Yu ; Matthew C. George
Journal of the American Chemical Society 2010 Volume 132(Issue 29) pp:9958-9959
Publication Date(Web):June 30, 2010
DOI:10.1021/ja1023628
We demonstrate an optical interference-based photochemical method for the high-resolution localization of nanoparticles inside colloidal crystals or other porous structures. The method specifically relies on photoinduced inversion of the colloidal crystal surface charge to drive the localized deposition of charged gold nanoparticles. 4-Bromomethyl-3-nitrobenzoic acid (BNBA) was used as a photocleavable linker, and dansylamide was attached to BNBA to increase the absorption at 351 nm. Two-beam interference lithography was used for high-resolution optical patterning of the colloidal crystals; the resulting pattern was then decorated with functional nanoparticles. The periodicity of the pattern was 400 nm, and the width of the gold nanoparticle decorated region was ∼200 nm. Our strategy of using photoswitching in a refractive-index-matched porous medium followed by the attachment of nanoparticles to the photoswitched region should be applicable to wide classes of charged nanoparticles.
Co-reporter:Xindi Yu;Lei Shi;Dezhuan Han;Jian Zi
Advanced Functional Materials 2010 Volume 20( Issue 12) pp:1910-1916
Publication Date(Web):
DOI:10.1002/adfm.201000135
Abstract
A 2D polystyrene colloidal crystal self-assembled on a flat gold surface supports multiple photonic and plasmonic propagating resonance modes. For both classes of modes, the quality factors can exceed 100, higher than the quality factor of surface plasmons (SP) at a polymer–gold interface. The spatial energy distribution of those resonance modes are carefully studied by measuring the optical response of the hybrid plasmonic–photonic crystal after coating with dielectric materials under different coating profiles. Computer simulations with results closely matching those of experiments provide a clear picture of the field distribution of each resonance mode. For the SP modes, there is strong confinement of electromagnetic energy near the metal surface, while for optical modes, the field is confined inside the spherical particles, far away from the metal. Coating of dielectric material on the crystal results in a large shift in optical features. A surface sensor based on the hybrid plasmonic–photonic crystal is proposed, and it is shown to have atomic layer sensitivity. An example of ethanol vapor sensing based on physisorption of ethanol onto the sensor surface is demonstrated.
Co-reporter:Jinsub Shin, Paul V. Braun, Wonmok Lee
Sensors and Actuators B: Chemical 2010 Volume 150(Issue 1) pp:183-190
Publication Date(Web):21 September 2010
DOI:10.1016/j.snb.2010.07.018
Polymer hydrogels can exhibit large reversible volume changes in response to external stimuli, and thus are regarded as excellent materials for chemical sensors. In this report, we demonstrate a mechanically robust and fast response photonic crystal pH sensor fabricated by templated photo-polymerization of hydrogel monomers within the interstitial space of a self-assembled colloidal photonic crystal. Throughout a rigorous optimization of the photo-polymerization, pH sensors showing a response time of less than 10 s upon a pH change were fabricated. Repeated pH changes revealed that the sensor has a long lifetime (>6 months) without degradation of the response time or reproducibility in pH-driven color change.
Co-reporter:Abigail T. Juhl, John D. Busbee, John J. Koval, Lalgudi V. Natarajan, Vincent P. Tondiglia, Richard A. Vaia, Timothy J. Bunning, and Paul V. Braun
ACS Nano 2010 Volume 4(Issue 10) pp:5953
Publication Date(Web):October 7, 2010
DOI:10.1021/nn100885x
Layered polymer/nanoparticle composites have been created through the one-step two-beam interference lithographic exposure of a dispersion of 25 and 50 nm silica particles within a photopolymerizable mixture at a wavelength of 532 nm. The polymerizable mixture is composed of pentaerythritol triacrylate (monomer), 1-vinyl-2-pyrrolidinone (monomer), and photoinitiator. In the areas of constructive interference, the monomer begins to polymerize via a free-radical process and concurrently the nanoparticles move into the regions of destructive interference. The effects of exposure time, power density, nanoparticle size, and periodicity on the final nanocomposite structure were measured with transmission electron microscopy to determine the mechanism for particle segregation. Diffraction from the sample was monitored as well, though its magnitude was not a good predictor of nanostructure in this relatively low index contrast system. Exposure time did not have a strong effect on the final structure. The best nanoparticle sequestration was observed at reduced laser power density, smaller interferogram periodicity, and decreased nanoparticle size, indicating that particle segregation is dominated by diffusion-limited nanoparticle transport directed by a matrix containing a gradient of polymerization kinetics.Keywords: directed assembly; holography; nanocomposite; nanoparticles; photopolymerization
Co-reporter:Soo Hyoun Cho;Scott R. White
Advanced Materials 2009 Volume 21( Issue 6) pp:645-649
Publication Date(Web):
DOI:10.1002/adma.200802008
Co-reporter:Soo Hyoun Cho;Scott R. White
Advanced Materials 2009 Volume 21( Issue 6) pp:
Publication Date(Web):
DOI:10.1002/adma.200990020
Co-reporter:John D. Busbee;Abigail T. yuhl;Lalguldi V. Natarajan;Vincent P. Tongdilia;Timothy J. Bunning;Richard A. Vaia
Advanced Materials 2009 Volume 21( Issue 36) pp:3659-3662
Publication Date(Web):
DOI:10.1002/adma.200900298
Co-reporter:Dara Van Gough, Abigail T. Juhl, Paul V. Braun
Materials Today 2009 Volume 12(Issue 6) pp:28-35
Publication Date(Web):June 2009
DOI:10.1016/S1369-7021(09)70178-6
Programming three dimensional nanostructures into materials is becoming increasingly important given the need for ever more highly functional solids. Applications for materials with complex programmed structures include solar energy harvesting, energy storage, molecular separation, sensors, pharmaceutical agent delivery, nanoreactors and advanced optical devices. Here we discuss examples of molecular and optical routes to program the structure of three-dimensional nanomaterials with exquisite control over nanomorphology and the resultant properties and conclude with a discussion of the opportunities and challenges of such an approach.
Co-reporter:Dara Van Gough, Alejandro Wolosiuk and Paul V. Braun
Nano Letters 2009 Volume 9(Issue 5) pp:1994-1998
Publication Date(Web):March 26, 2009
DOI:10.1021/nl900264n
A size selective nanorattle was formed by encapsulating soybean peroxidase (SBP) within a ZnS mesoporous hollow sphere. Once encapsulated within the mesoporous hollow sphere, the SBP remained active against molecules smaller than the 3 nm diameter of the mesopores in the shell wall, while molecules larger than the mesopores, which could not pass into the hollow sphere, did not interact with the SBP. Specifically, encapsulated SBP catalyzed the oxidation of Amplex Ultra-Red, a small fluorogen, in the presence of hydrogen peroxide, encapsulated SBP was deactivated by sodium azide, and no reaction was observed between encapsulated SBP and a greater than 3 nm diameter protease.
Co-reporter:Xindi Yu, Huigang Zhang, John K. Oliverio and Paul V. Braun
Nano Letters 2009 Volume 9(Issue 12) pp:4424-4427
Publication Date(Web):2017-2-22
DOI:10.1021/nl9027236
An innovative and versatile nanofabrication technique based on template assisted three-dimensional (3D) nanolithography is presented that takes advantage of the irreversibility of conformal growth and conformal etching at locations with negative surface curvatures in 3D templates. Using colloidal crystals as templates, nanoring particles are generated with quantity much higher than conventional methods. Relying on the same principle, metallodielectric photonic crystals with discrete metal elements are fabricated that show strong absorption in the near-IR and transmission at longer wavelengths.
Co-reporter:Jyh-Tsung Lee ; Matthew C. George ; Jeffrey S. Moore
Journal of the American Chemical Society 2009 Volume 131(Issue 32) pp:11294-11295
Publication Date(Web):July 28, 2009
DOI:10.1021/ja904554m
We demonstrate a facile method for fabricating novel 3D microfluidic channels by using two-photon-activated chemistry to locally switch the interior surface of a porous host from a hydrophobic state to a hydrophilic state. The 3D structures can be infilled selectively with water and/or hydrophobic oil with a minimum feature size of only a few micrometers. We envision that this approach may enable the fabrication of complex microfluidic structures that cannot be easily formed via current technologies.
Co-reporter:Dongyeon Son, Alejandro Wolosiuk and Paul V. Braun
Chemistry of Materials 2009 Volume 21(Issue 4) pp:628
Publication Date(Web):January 22, 2009
DOI:10.1021/cm8017852
The effect of surface chemistry of SiO2 colloids dispersed in a nonionic surfactant based lyotropic liquid crystal (LLC) on the double direct templating of hollow mesostructured ZnS capsules was investigated. In double direct templating, a LLC templates the mineralization of ZnS on the surface of a colloidal particle. Removal of the colloid results in a periodically mesostructured hollow capsule. After ZnS mineralization and a subsequent etching of the sacrificial SiO2 core, the ZnS mesostructure was imaged using transmission electron microscopy (TEM). The highest quality mesostructure was observed for poly(acrylic acid) (PAA) functionalized colloids, while other surface chemistries, including bare silica, poly(ethylene glycol), amine, and thiol surface chemistries yielded much less favorable results. In the PAA system, the order of the hexagonally arranged 3 nm mesopores in the ZnS shell closely matched that of the lyotropic liquid crystal template. Detailed TEM revealed the presence of regions where the mesopores lay parallel to the colloidal surface and others where they were perpendicularly arranged. We suspect the PAA functionalization favored both the nucleation of ZnS and organization of the LLC template responsible for templating mesostructured ZnS shell around the colloidal particle.
Co-reporter:Andrew Brzezinski, Ying-Chieh Chen, Pierre Wiltzius and Paul V. Braun
Journal of Materials Chemistry A 2009 vol. 19(Issue 48) pp:9126-9130
Publication Date(Web):06 Nov 2009
DOI:10.1039/B914318A
Atomic layer deposition in complex three-dimensional porous materials is useful for manipulating properties such as pore size, pore connectivity, density, and dielectric constant. In order to calculate a material's properties it is necessary to determine the material distribution. A generally applicable algorithm for determining the material distribution and pore connectivity is presented. Calculations using the algorithm compared favorably with experimental results for the important case of infilling dielectric material into three-dimensional photonic crystal templates.
Co-reporter:MatthewC. George Dr. ;PaulV. Braun
Angewandte Chemie 2009 Volume 121( Issue 46) pp:8758-8761
Publication Date(Web):
DOI:10.1002/ange.200904089
Co-reporter:MatthewC. George Dr. ;PaulV. Braun
Angewandte Chemie International Edition 2009 Volume 48( Issue 46) pp:8606-8609
Publication Date(Web):
DOI:10.1002/anie.200904089
Co-reporter:
Nature Photonics 2008 2(11) pp:
Publication Date(Web):2008-11-01
DOI:10.1038/nphoton.2008.209
Researchers have demonstrated the first photonic-crystal system with light emitters that experience three-dimensional photonic and electronic confinement.
Co-reporter:MatthewC. George;ErikC. Nelson;JohnA. Rogers ;PaulV. Braun
Angewandte Chemie 2008 Volume 121( Issue 1) pp:150-154
Publication Date(Web):
DOI:10.1002/ange.200804171
Co-reporter:MatthewC. George;ErikC. Nelson;JohnA. Rogers ;PaulV. Braun
Angewandte Chemie International Edition 2008 Volume 48( Issue 1) pp:144-148
Publication Date(Web):
DOI:10.1002/anie.200804171
Co-reporter:Andrew Brzezinski, Ying-Chieh Chen, Pierre Wiltzius and Paul V. Braun
Journal of Materials Chemistry A 2009 - vol. 19(Issue 48) pp:NaN9130-9130
Publication Date(Web):2009/11/06
DOI:10.1039/B914318A
Atomic layer deposition in complex three-dimensional porous materials is useful for manipulating properties such as pore size, pore connectivity, density, and dielectric constant. In order to calculate a material's properties it is necessary to determine the material distribution. A generally applicable algorithm for determining the material distribution and pore connectivity is presented. Calculations using the algorithm compared favorably with experimental results for the important case of infilling dielectric material into three-dimensional photonic crystal templates.
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