bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tuneable Thermal Emission Using Chalcogenide Metasurface
Authors: Cao Tun , Zhang Xinyu , Dong Weiling , Lu Li , Zhou Xilin , Zhuang Xin , Deng Junhong , Cheng Xing , Li Guixin , Simpson Robert E. 
Published: June 2018

AbstractModulation of thermal radiation is an essential element of infrared sensing and imaging, thermal infrared light sources, camouflage, and thermophotovoltaics. Recently, tuneable thermal emission of nanophotonic structures has been demonstrated. However, most of the current strategies involve controlling single spectral thermal emission in the far‐infrared region, and blue shifting their resonances to the shorter wavelength region is rarely explored. Moreover, fast modulation of multispectral thermal radiation remains challenging. In this work, the dynamic control of multispectral thermal emission from 2 to 4 µm from an ultrathin reconfigurable metasurface is experimentally presented based on Au/SiO2/Ge2Sb2Te5/Au multilayer. This metadevice contains several integrated thermal emitters of various wavelengths, each of which consists of gold (Au) squares array with different widths. A tuning of multispectral absorptivity (emissivity) can be achieved by transiting the state of Ge2Sb2Te5 from amorphous to crystalline. A heat‐transfer model is developed to demonstrate that the reversible switching of multispectral thermal emission can be achieved in just 300 ns. The experimental demonstration along with the theoretical framework lays the foundation for designing high‐speed reconfigurable multispectral thermal emitters, which, as expected, will initiate a new route to thermal engineering.
Optically Driven Soft Micro Robotics
Authors: Nocentini Sara , Parmeggiani Camilla , Martella Daniele , Wiersma Diederik S. 
Published: June 2018

AbstractThe miniaturization of robots and actuators down to the micrometer length scale constitutes a fascinating technological challenge. Their development faces fabrication issues due to the small dimensions and their design must take into account how physics laws behave on those length scales. Last but not least, a major issue is energy delivery and management. In this scenario, light emerges as a versatile tool for the fabrication and, even more importantly, as an energy source. Optically driven micromachines—in which optical stimuli can be efficiently converted into mechanical work—have been realized in various contexts. This Review collects recent advances in this field, focusing on optical micro robots realized in soft polymers. Starting from an overview of the photoresponsive materials that have been employed, the various designs and realizations of such devices are shown exhibiting tasks and capabilities like swimming, walking, and the manipulation of microscopic objects. In the last part, frontiers studies in the integration of polymeric structures with biological organisms are shown. In many of the reported studies, untethered operation is a key issue, seen as a fundamental requirement toward the development of smart robots that can autonomously perform tasks and respond to their environment.
Superradiantly Limited Linewidth in Complementary THz Metamaterials on Si‐Membranes
Authors: Keller Janine , Haase Johannes , Appugliese Felice , Rajabali Shima , Wang Zhixin , Paravicini‐Bagliani Gian Lorenzo , Maissen Curdin , Scalari Giacomo , Faist Jérôme 
Published: June 2018

AbstractComplementary double split ring THz resonators fabricated on a 10 µm thin Si‐membrane are studied. The linewidths of the fundamental LC mode and dipolar mode are drastically narrowing with increased resonator spacing. The extracted decay rate of the LC mode as a function of the resonator density shows a linear dependence, evidencing a collective superradiant effect of the resonator array. Furthermore, it is shown that a metamaterial can be designed for a low superradiant broadening of the resonance at high resonator densities, that is, in the metamaterial condition. The use of a thin membrane as a substrate is crucial, since it shifts the THz surface plasmon polaritons modes to much higher frequencies, preventing them to couple to the LC mode and unveiling the superradiant broadening mechanism for a large range of lattice spacings. At higher frequencies, not interfering with the high Q LC mode, other additional modes, which are ascribed to photonic crystal modes, form in the Si‐membrane. The angle‐dependent band structure is mapped and corresponding simulated electric field distributions are shown.
Organic Photodetectors with Gain and Broadband/Narrowband Response under Top/Bottom Illumination Conditions
Authors: Wang Wenbin , Du Mingde , Zhang Miao , Miao Jianli , Fang Ying , Zhang Fujun 
Published: June 2018

AbstractOrganic photodetectors (OPDs) possessing broadband/narrowband photodetection capability and gain have great potential in integrated optoelectronics products. In this work, OPDs with a device structure of ITO/poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/thick active layer/semitransparent Al electrode exhibit the extraordinary functions, gain and bidirectional photodetection capability with tunable spectral response range. For the binary OPDs with poly(3‐hexylthiophene‐2,5‐diyl) (P3HT):[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) (100:1, wt/wt) as active layer, the OPDs exhibit narrowband response from 620 to 700 nm with full‐width at half maximum (FWHM) of ≈30 nm under bottom illumination condition and broadband response from 300 to 700 nm under top illumination condition, respectively. To further confirm and optimize the extraordinary functions of OPDs, ternary devices are fabricated with P3HT:poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dit‐hiophene‐co‐3‐fluor‐othieno[3,4‐b]thiophene‐2‐carboxylate] (PTB7‐Th):PC71BM (50:50:1, wt/wt) as active layer. The narrowband response can be adjusted to near infrared (NIR) region from 760 to 860 nm. The broadband response can be extended to NIR region with response range from 300 to 860 nm. Meanwhile, external quantum efficiency (EQE) spectral shape of the ternary OPDs becomes flatter under top illumination condition and can be kept constant under different bias. The ternary OPDs exhibit similar EQE values of ≈2000% and specific detectivity larger than 1011 Jones at −50 V bias under bottom and top illumination conditions.
Optically Addressable Photoaligned Semiconductor Nanorods in Thin Liquid Crystal Films for Display Applications
Authors: Zhang Wanlong , Schneider Julian , Chigrinov Vladimir G. , Kwok Hoi Sing , Rogach Andrey L. , Srivastava Abhishek K. 
Published: June 2018

AbstractThe local optical anisotropy of 1D semiconductor nanorods (NRs), which results in anisotropic absorption and polarized emission, is important for various applications. Thin films of photoaligned, oriented NRs offer not only polarized emission but also anisotropic absorption at the macroscopic scale. Based on this anisotropic absorption, two kinds of optically addressable photoemissive displays are presented, which employ polarized backlight in combination with a liquid crystal (LC) based polarization rotator to control the down conversion emission intensity of a photoaligned NR/liquid crystal polymer (LCP) composite film. The first alternative “fixed information display” utilizes pattern aligned NRs, with an orthogonal easy axis in two domains, resulting in optical contrast in neighboring domains. The second option “random information display” employs unidirectionally aligned NR films as a projection screen to display any information coded by a LC cell. It is also shown that the NR/LCP composite film can align LC in bulk, and therefore, can be integrated into a LC cell, fabricating a robust photoemissive NR display device.
A Broadband Plasmonic Metasurface Superabsorber at Optical Frequencies: Analytical Design Framework and Demonstration
Authors: Nagarajan Arvind , Vivek Kumar , Shah Manav , Achanta Venu Gopal , Gerini Giampiero 
Published: June 2018

AbstractPlasmonic metasurface based superabsorbers exhibit high absorbance. While the absorption peak can be tuned by the geometry/size of the sub‐wavelength resonator, broadband absorption can be obtained by harnessing spectrally shifted resonances of multiple resonators of various size/shapes in a unit cell. Metal dispersion hinders high‐performance broadband absorption at optical frequencies and careful designing is essential to achieve good structures. A novel analytical framework is proposed for designing a broadband superabsorber which is much faster than the time consuming full‐wave simulations that are employed so far. Analytical expressions are derived for the wavelength dependency of the design parameters, which are then used in the optimization of broadband absorption. Numerical simulations report an average polarization‐independent absorption of ≈97% in the 450–950 nm spectral region with a near unity absorption (99.36%) in the 500–850 nm region. Experimentally, an average absorption over 98% is demonstrated in the 450–950 nm spectral region at 20° incident angle. The designed superabsorber is polarization insensitive and has a weak launch angle dependency. The proposed framework simplifies the design process and provides a quicker optimal solution for high‐performance broadband superabsorbers.
Ultrasoft and Highly Stretchable Hydrogel Optical Fibers for In Vivo Optogenetic Modulations
Authors: Wang Lulu , Zhong Cheng , Ke Dingning , Ye Fengming , Tu Jie , Wang Liping , Lu Yi 
Published: June 2018

AbstractOptogenetics has been widely applied as a cell‐specific technique with high temporal resolution for the modulation of neural circuitry in vivo, offering potential novel treatments for neuropsychiatric diseases. However, to date, the most widely used optogenetics waveguides remain silica optical fibers, which may lead to a mismatch in the mechanical properties between the implants and neural tissues. To resolve this issue, alginate‐polyacrylamide hydrogel optical fibers can be fabricated in a simplified one‐step process, and they show significantly improved characteristics for the in vivo optogenetic applications, including low light‐propagation loss and Young's modulus, and high stretchability. After the expression of AAV‐CaMKIIα‐ChR2‐mCherry, blue light pulses are delivered into hippocampus using a hydrogel‐optrode array, and frequency‐dependent neural responses can be observed. Moreover, optogenetic stimulation through the chronic implanted hydrogel optical fibers in the primary motor cortex can considerably modulate the animal's behavior. Hydrogel fibers significantly alleviate tissue response at the implant/neural interface, compared with that observed using the silica optical fibers. Taken together, the results of this study demonstrate the feasibility and advantages of the hydrogel optical fiber use for chronic optogenetic modulation in free‐moving animals. Hydrogel implant use may allow the development of novel therapeutic strategies for the treatment of neuropsychiatric disorders.
The True Value of Disorder
Authors: López Cefe 
Published: June 2018

AbstractBorder regions between areas where physical problems involve very few bodies with well‐described interactions or immensely many (amenable to statistical description) are prone to fall in the category usually associated with complexity. Disorder is an important factor to consider when examining complexity. Disordered optical materials per se would not qualify as complex but when disorder is partial or merely incipient or nonlinear interactions are included, an entirely new character is added. Here, attention is paid to three examples of these kinds of optical systems. The propagation of light through diffusive media and image formation behind an opaque screen is proposed as a problem where an exact computable solution can be expected but is impractical. Analysis shows that the problem is akin to condensed matter physics concepts related to narrow leads conductance. Another condensed matter related phenomenon brought to photonics is that of localization: disorder can induce a cessation of transport when interference of scattered fields is destructive in all directions forcing light to be exponentially confined. Finally, random lasers are a problem where a disordered, open, photonic system is governed by immensely many modes interacting nonlinearly.
Solar Redox Flow Batteries: Mechanism, Design, and Measurement
Authors: Cao Liuyue , Skyllas‐Kazacos Maria , Wang Da‐Wei 
Published: June 2018

AbstractThe increasing public awareness of the energy crisis since the 1970s has promoted the ongoing development of energy conversion and storage systems. As a supplement to photovoltaics, photoelectrochemical cells (PECs) are among the promising solar electricity generation systems. However, the intrinsic intermittence of sunlight can never guarantee continuous electricity supply. Therefore, PECs are being developed to convert solar energy to chemical energy in the forms of fuels such as H2 and other organic chemicals. However, this technology requires massive storage systems for the solar fuels/chemicals, and complementary conversion systems for electricity generation from the solar fuels. Redox flow batteries (RFBs) are capable of large‐scale real‐time electricity storage and conversion. Both PECs and RFBs have been investigated for more than three decades, yet the integration of these two systems has not reached maturity. Hence, this review aims to give a critical overview of the state‐of‐the‐art progress in solar redox flow batteries, from the aspects of the working mechanism, device engineering, and performance evaluation.
High‐Efficiency Polymer:Nonfullerene Solar Cells with Quaterthiophene‐Containing Polyimide Interlayers
Authors: Park Euyoung , Seo Jooyeok , Han Hyemi , Kim Hwajeong , Kim Youngkyoo 
Published: June 2018

AbstractInterfacial layers (interlayers) are one of the emerging approaches in organic solar cells with bulk heterojunction (BHJ) layers because the solar cell efficiency can be additionally improved by their presence. However, less attention is paid to the use of interlayers for polymer:nonfullerene solar cells, which have strong advantages over polymer:fullerene solar cells. In addition, most polymers used for the interlayers possess a low glass transition temperature (Tg). Here, it is demonstrated that two types of quarterthiophene‐containing polyimides (PIs) with high Tg (>198 °C), which are synthesized using pyromellitic dianhydride (PMDA) and cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride (CTCDA), can act as an interfacial layer in the polymer:nonfullerene solar cells with the BHJ layers of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and 3,9‐bis(2‐methylene(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene) (ITIC), or (3‐(1,1‐dicyanomethylene)‐1‐methyl‐indanone)‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]‐dithiophene) (IT‐M). Interestingly, the efficiency and stability of devices are improved by the PMDA‐based PI interlayers with a stretched chain structure but degraded by the CTCDA‐based PI interlayers with a bended chain structure.
Tailoring the Edge Sites of 2D Pd Nanostructures with Different Fractal Dimensions for Enhanced Electrocatalytic Performance
Authors: Yan Yucong , Li Xiao , Tang Min , Zhong Hao , Huang Jingbo , Bian Ting , Jiang Yi , Han Yu , Zhang Hui , Yang Deren 
Published: June 2018

AbstractThe important role of edge sites in atomically thin 2D materials serving as catalysts is already of concerned in plenty of material systems and catalytic reactions, whereas comprehensive study of the edge sites in 2D noble‐metal nanocatalysts is still lacking. Herein, for the first time, a controllable etching approach to tailor the fractal dimensions and edge sites of Pd nanosheets is developed and the edge sites in these 2D nanostructures from both structural and chemical aspects are investigated. The as‐tailored 2D Pd nanostructures with extra edge sites exhibit substantially enhanced electrocatalytic performance for the formic acid oxidation reaction (FAOR). Moreover, careful analysis of the results from electrocatalytic measurements reveals that the specific activities for the edge sites in the 2D nanostructures far exceed the activities for the low‐index planes of Pd and even dominate the overall activity exhibited by the 2D noble‐metal catalysts.
Stretchable Multiresponsive Hydrogel with Actuatable, Shape Memory, and Self‐Healing Properties
Authors: Zhang Feng , Xiong Ligui , Ai Yongjian , Liang Zhe , Liang Qionglin 
Published: June 2018

AbstractSmart hydrogels with responsive behaviors have attracted tremendous attention. However, it is still a challenge to synthesize stretchable hydrogels capable of changing their original properties in response to multiple external stimuli. Here, integration of actuation function, shape memory, and self‐healing capability in a highly stretchable hydrogel under triple external triggers is achieved by rationally engineering multiple functional moieties. The hydrogel exhibits high stretchability (average relative strain (mm/mm) is >15) and excellent fatigue resistance during 100 loading cycles of 100% strain. Incorporating a moisture‐insensitive polymer film with the hydrogel, hydroactuated functionality is demonstrated. Moreover, shape memory and self‐healing abilities of the hydrogel are realized by the formation of ionic crosslinking or dynamic borate ester in conditions of multivalent cations and pH, respectively. Deformable plastic flowers are displayed in this work as a proof‐of‐concept, and it is believed that this smart hydrogel could be used in plenty of frontier fields, such as designing electronic devices, soft robotics, and actuators.
Cobalt Nanoparticles/Black Phosphorus Nanosheets: An Efficient Catalyst for Electrochemical Oxygen Evolution
Authors: Shi Fangbing , Geng Zhibin , Huang Keke , Liang Qingshuang , Zhang Yuan , Sun Yu , Cao Jungang , Feng Shouhua 
Published: June 2018

AbstractBlack phosphorus (BP) nanosheet (NS) is an emerging oxygen evolution reaction (OER) electrocatalyst with both high conductivity and abundant active sites. However, its ultrathin structure suffers instability because of the lone pair electrons exposed at the surface, which badly restricts durability for achieving long‐term OER catalysis. Herein, a facile solvothermal reduction route is designed to fabricate Co/BP NSs hybrid electrocatalyst by in situ growth of cobalt nanoparticles on BP NSs. Notably, electronic structure engineering of Co/BP NSs catalyst is observed by electron migration from BP to Co due to the higher Fermi level of BP than that of Co. Because of the preferential migration of the active lone pairs from the defect of BP NSs, the stability and high hole mobility can be effectively retained. Consequently, Co/BP NSs electrocatalyst exhibits outstanding OER performance, with an overpotential of 310 mV at 10 mA cm−2, and excellent stability in alkaline media, indicating the potential for the alternatives of commercial IrO2. This study provides insightful understanding into engineering electronic structure of BP NSs by fully utilizing defect and provides a new idea to design hybrid electrocatalysts.
N‐Type Surface Doping of MAPbI3 via Charge Transfer from Small Molecules
Authors: Perry Erin E. , Labram John G. , Venkatesan Naveen R. , Nakayama Hidenori , Chabinyc Michael L. 
Published: June 2018

AbstractOrganic hole and electron transport materials are regularly employed as electron‐ and hole‐blocking layers in perovskite thin‐film solar cells. In order to optimize charge extraction in the device, these organic layers can be doped using organic small molecules. However, to date there is little work carried out on direct doping of perovskite surfaces. In this report, the change in electrical properties of thin films of MAPbI3 by surface doping the film with an organic dopant molecule: cobaltocene (Co(C5H5)2) is studied. By varying the quantity of cobaltocene deposited, the conductivity of MAPbI3 thin films is observed to be tunable over several orders of magnitude. A tunable shift in the Fermi level illustrating that charge transfer doping enables control over the interfacial energy levels, is observed. An increase in photoconductivity is seen at intermediate doping levels, indicating passivation of surface traps confirmed by increased photoluminescence. This model system provides a means to understand more complex heterointerfaces of doped organic blends at perovskite surfaces.
Photothermal Heating and Cooling of Nanostructures
Authors: Crane Matthew J. , Zhou Xuezhe , Davis E. James , Pauzauskie Peter J. 
Published: June 2018

AbstractA vast range of insulating, semiconducting, and metallic nanomaterials have been studied over the past several decades with the aim of understanding how continuous‐wave or pulsed laser radiation can influence their chemical functionality and local environment. Many fascinating observations have been made during laser irradiation including, but not limited to, the superheating of solvents, mass‐transport‐mediated morphology evolution, photodynamic therapy, morphology dependent resonances, and a range of phase transformations. In addition to laser heating, recent experiments have demonstrated the laser cooling of nanoscale materials through the emission of upconverted, anti‐Stokes photons by trivalent rare‐earth ions. This Focus Review outlines the analytical modeling of photothermal heat transport with an emphasis on the experimental validation of anti‐Stokes laser cooling. This general methodology can be applied to a wide range of photothermal applications, including nanomedicine, photocatalysis, and the synthesis of new materials. The review concludes with an overview of recent advances and future directions for anti‐Stokes cooling.
Rational Design of Ternary Composite Photoanode BiVO4/PW12/NiTsPc for Improved Photoelectrochemical Water Oxidation
Authors: Xi Lu , Zhang Qian , Sun Zhixia , Song Chunli , Xu Lin 
Published: June 2018

AbstractDespite recent efforts to improve BiVO4 semiconductor photoanodes, the electron‐hole recombination in BiVO4 photoanodes is still a critical problem in efficient photoelectrochemical water oxidation. In this work, a dual modification of BiVO4 photoanodes is performed utilising the polyoxometalate compound H3PW12O40 (PW12), acting as electron shuttle (electron capture and transfer), and nickel (II) phthalocyanine tetrasulfonic acid (NiTsPc), acting as hole extractor (accelerating hole transport). As for the photoelectrochemical water oxidation, the BiVO4/PW12/NiTsPc photoanode displays a 5.4‐fold improvement in photocurrent density at 1.23 V (vs. RHE) as compared to the pristine BiVO4 photoanode, under illumination of simulated solar light. Furthermore, we demonstrate that the recombination of electron‐hole pairs could be remarkably suppressed in the dual modified BiVO4 photoanode, by means of the electrochemical impedance spectroscopy measurements together with hydrogen peroxide as the hole scavenger. Additionally, the energy band distributions among PW12, BiVO4, and NiTsPc allow the photoelectron to transfer from BiVO4 to PW12 and the hole from BiVO4 to NiTsPc, which is responsible for the improved photoactivity of BiVO4. This work provides a new insight into effectively improving BiVO4 photoanode by rational design of dual modification.