Role of Contact and Contact Modification on Photo-response in a Charge Transfer Complex Single Nanowire Device

We investigated the feasibility of obtaining large photoresponse in metal-semiconductor-metal(MSM) type single nanowire device where one contact can be blocking type. We showed that suitable modification of the blocking contact by deposition of a capping metal using focused electron beam(FEB) can lead to considerable enhancement of the photoresponse. The work was done in a single Cu:TCNQ nanowire device fabricated by direct growth of nanowires(NW) from pre-patterned Cu electrode which makes the contact ohmic with the other contact made from Au. Analysis of the data shows that the large photoresponse of the devices arises predominantly due to reduction of the barriers at the Au/NW blocking contact on illumination. This is caused by the diffusion of the photo generated carriers from the nanowires to the contact region. When the barrier height is further reduced by treating the contact with FEB deposited Pt, this results in a large enhancement in the device photoresponse.

Fabrication and photo-response of monolithic 90°hybrid-photodetector array chip for QPSK detection

A quadrature phase-shift keying(QPSK)coherent photodetector chip consisting of a 4×4 multimode interference 90°optical hybrid and a four-channel evanescent photodetector array is designed and fabricated with its photo-response in the L-band characterized.The metal organic chemical vapor deposition regrowth method is adopted to realize active–passive monolithic integration.The chip exhibits a low dark current below 100 nA for each photodetector in the array,a low excess loss of 0.85 dB,a common mode ratio rejection better than 13.6 dB,and a phase deviation within±10°over the 40 nm wavelength span.

Photo-responsive droplet manipulation slippery lubricant-infused porous surface with ultra-high durability

Photo-responsive slippery lubricant-infused porous surface(SLIPS) for droplet manipulation is flexible, noncontact and non-destructive in droplet manipulation, which has promising applications in flexible robotics, microfluidics,biomedicine, and chemical analysis. However, the repeated manipulations for droplets of SLIPSs are quite limited in the works reported so far, the poor durability of droplet manipulation severely limits the practical application of the surfaces. In this paper, an Fe3O4-doped polydimethylsiloxane(PDMS)-based SLIPS is proposed and implemented to achieve ultra-high repeated droplet manipulation numbers under near-infrared ray(NIR) laser irradiation. Firstly, a micron columnar array structure with micro-pits on the top side, as well as, a wall structure out of the array is designed on SLIPS to reserve the lubricant. Secondly, the prototype of the SLIPS is fabricated by a 3-step ultraviolet(UV) lithography, and subsequently immersed in silicone oil for more than 96 h to obtain the ultra-high durability slippery lubricant-infused porous surface(UD-SLIPS). With a power of 25 m W–85 m W NIR laser, the repeated manipulation of microdroplets(≤ 5 μL) in the scale of 1 cm can exceed more than 3000 times which is far beyond that in previous reports. Finally, the droplet manipulation performance of this photo-responsive UD-SLIPS and the influence of infusion time on durability are investigated. The mechanism of the PDMS swelling effect is found to be the key factor in improving the droplet manipulation durability of SLIPS. The findings of this work would be of great significance for the development of highly durable photo-responsive functional surfaces for droplet manipulation.

A Concise Review of Gold Nanoparticles-Based Photo-Responsive Liposomes for Controlled Drug Delivery

The focus of drug delivery is shifting toward smart drug carriers that release the cargo in response to a change in the microenvironment due to an internal or external trigger. As the most clinically successful nanosystem, liposomes naturally come under the spotlight of this trend. This review summarizes the latest development about the design and construction of photo-responsive liposomes with gold nanoparticles for the controlled drug release. Alongside, we overview the mechanism involved in this process and the representative applications.

How light affect the magnetotactic behavior and reproduction of ellipsoidal multicellular magnetoglobules?

Magnetotactic bacteria(MTB)synthesize intracellular magnetic organelles,magnetosomes,which consist of magnetic crystals that are enveloped in a membrane.Magnetosomes are organized into a chain(s)and confer on cells a magnetic dipolar moment.This magnetic property allows MTB cells to align and swim along geomagnetic field lines,a movement referred to as magnetotaxis.Some MTB species change their swim direction in response to illumination by UV,violet and blue light.Here we analyzed the polarity of morphology,magnetism,and motion in Mediterranean multicellular magnetotactic prokaryotes,also called,magnetoglobules or MMP.The magnetoglobules were assembled from 60-80 cells into an asymmetric ellipsoidal morphology with a relative narrow and large end.They swam dominantly northward,parallel to the direction of the magnetic field,with the narrow-end as the leading side.In response to a reversal in the direction of the magnetic field,they aligned quickly along the magnetic field lines and kept swimming northward.Interestingly,under constant illumination,385-nm UV light,magnetoglobules changed their swimming direction southward anti-parallel to the direction of the magnetic field,with the large-end as the leading side.The change from a northward to southward direction occurred along with an increase of swimming speed.A minimum of 35-mW/cm^(2) irradiance of UV light was sufficient to trigger the swimming re-orientation.UV radiation also triggered the unidirectional division of magnetoglobules.Together these results revealed a coordination of the polarity of magnetoglobule morphology,magnetic moment,and swimming orientation,in response to magnetic and optical stimuli.The UV triggered the reversal of magnetotaxis and magnetoglobule division indicating the ecological significance of light for multicellular magnetotactic prokaryotes.

PRNU Extraction from Stabilized Video:A Patch Maybe Better than a Bunch

This paper presents an algorithm to solve the problem of Photo-Response Non-Uniformity(PRNU)noise facing stabilized video.The stabilized video undergoes in-camera processing like rolling shutter correction.Thus,misalignment exists between the PRNU noises in the adjacent frames owing to the global and local frame registration performed by the in-camera processing.The misalignment makes the reference PRNU noise and the test PRNU noise unable to extract and match accurately.We design a computing method of maximum likelihood estimation algorithm for extracting the PRNU noise from stabilized video frames.Besides,unlike most prior arts tending to match the PRNU noise in whole frame,we propose a new patch-based matching strategy,aiming at reducing the influence from misalignment of frame the PRNU noise.After extracting the reference PRNU noise and the test PRNU noise,this paper adopts the reference and the test PRNU overlapping patch-based matching.It is different from the traditional matching method.This paper conducts different experiments on 224 stabilized videos taken by 13 smartphones in the VISION database.The area under curve of the algorithm proposed in this paper is 0.841,which is significantly higher than 0.805 of the whole frame matching in the traditional algorithm.Experimental results show good performance and effectiveness the proposed strategy by comparing with the prior arts.

In-situ growth of ZnS/FeS heterojunctions on biomass-derived porous carbon for efficient oxygen reduction reaction

It is an urgent task to develop highly efficient non-noble metal electrocatalysts in the direction of ORR,but still a huge and long-term challenge.Herein,an efficient one-step pyrolysis of Sichuan pepper powder,2,2-bipyridine,FeCl3,Na SCN,and ZnCl2 at 900℃ provides the FeS/ZnS@N,S-C-900 hybrid catalyst.Transmission electron microscopy(TEM)images and Mott-Schottky curves clearly reveal the in-situ constructed abundant FeS/ZnS-based p-n junctions dispersed on the biomass-derived porous carbon surface of FeS/ZnS@N,S-C-900.The as-prepared FeS/ZnS@N,S-C-900 hybrid exhibits superior ORR performance in comparison with Pt/C in 0.1 M KOH with high onset(Eonset)and half-wave potentials(E1/2)of 1.00 and 0.880 V vs.RHE,large limiting current density(JL)of 5.60 mA cm-2,and robust durability and methanol tolerance.Impressively,upon the light irradiation,FeS/ZnS@N,S-C-900 produces a photocurrent as high as ca.0.3μA cm-2,resulting in further improvement over Eonset,E1/2,and JLof FeS/ZnS@N,S-C-900 to1.10 V vs.RHE,0.885 V vs.RHE,and 6.02 mA cm-2.Experiment in combination with theoretical calculations demonstrate the significant effect of FeS/ZnS heterojunction on the enhanced ORR catalytic activity of FeS/ZnS@N,S-C-900.This work is useful for the development of advanced heterojunction-based ORR catalysts for various energy conversion devices.

Organoborane cyclophanes with flexible linkers: Dynamic coordination and photo-responsive fluorescence

Stimuli-responsive macrocycles are of importance for synthetic chemistry and smart materials. In this manuscript, we report two novel organoborane cyclophanes, which were successfully synthesized by ruthenium-catalyzed olefin metathesis. They are composed of one/two boron-doped helicene π-skeletons and flexible alkyl chain linkers, thus representing a new kind of non-conjugated organoborane macrocycles. Their cyclic structures and photophysical properties, as well as Lewis acidity were theoretically and experimentally investigated. Notably, two enantiomers in one single crystal are observed for one organoborane cyclophane, owning to the presence of helical π-framework in its cyclic structure. Moreover, their Lewis acid-base adducts may dissociate in the excited state and thus display intriguing photo-responsive fluorescence properties, which can be further modulated by temperature. This study thus provides a novel design strategy for non-conjugated organoborane macrocycles, which may promote the development of stimuli-responsive macrocyclic materials with fascinating properties.

Preparation of Photo-responsive DNA Supramolecular Hydrogels and Their Application as UV Radiometers

Ultraviolet light(UV)is an essential component of ambient light,but high dose UV would damage genome DNA.While semiconductors and soft materials have been employed to detect the UV,the complex process and the instrumental requirement have limited the application in daily life.In this study,taking advantage of sequence designability,a series of hydrogels with different gel-sol transition rates was constructed under the same UV intensity by introducing competing hybridization to tune the stability of the molecular network.Through estimating the transition time between each system under UV light irradiation,the intensity of UV could be roughly estimated,which provided a convenient method for the visual detection of UV.

The visible light-triggered nonvolatile memory performances in melamine-decorated <110>-oriented lead halide perovskites: A photo-responsive structural evolution insight

The exploration of novel photo/thermal-responsive nonvolatile memorizers will be beneficial for energysaving memories.Herein,new<110>-oriented perovskites using single template melamine,i.e.,[(MLAI-H_(2))(PbX_(4))]_n(X=Br (α-1),Cl (α-2),MLAI=melamine) have been prepared and their structures upon irradiation of visible light have been investigated.They have been fabricated as nonvolatile memory devices with structures of ITO/[(MLAI-H_(2))(PbX_(4))]_n/PMMA/Ag (device-1:X=Br,device-2:X=Cl),which can exhibit unique visible light-triggered binary nonvolatile memory performances.Interestingly,the silent or working status can be monitored by visible chromisms.Furthermore,the light-triggered binary resistive switching mechanisms of these ITO/[(MLAI-H_(2))(PbX_(4))]_n/PMMA/Ag memory devices have been clarified in terms of EPR,fluorescence,and single-crystal structural analysis.The presence of light-activated traps in<110>-oriented[(MLAI-H_(2))(PbX_(4))]_n perovskites are dominated in the appearance of light-triggered resistive switching behaviors,based on which the inverted internal electrical fields can be established.According to the structural analysis,the more distorted PbX_6octahedra,higher corrugated<110>-oriented perovskite sheets,and more condensed organic-inorganic packing in Br-containing perovskite are beneficial for the stabilization of light-activated traps,which lead to the better resistive switching behavior of device-1.This work can pave a new avenue for the establishment of novel energy-saving nonvolatile memorizers used in aerospace or military industries.

Azobenzene Based Photo-responsive Mechanical Actuator Fabricated by Intermolecular H-bond Interaction

Photo-responsive mechanical actuator is a class of stimuli-responsive materials transferring light to mechanical energy through macroscopic transformation.To fabricate photo-responsive mechanical actuator,soft polymeric materials crosslinked with functional bridging structures are desired.Supramolecular interaction is a relatively common way to fabricate crosslinked materials due to its excellent self-assembly performance.And azobenzene and derivatives are ideal candidates of photo-responsive materials because of the unique photo-induced trans-cis isomerization.Here,a new kind of crosslinked materials based on supramolecular interaction between 4,4'-dihydroxyazobenzene and chitosan is reported.Under 355 nm irradiation,the macroscopic bending of polymeric materials occurs rapidly due to the photo-isomerization of 4,4-dihydroxyazobenzene.Meanwhile,the photo-responsive mechanical actuator can also lift weight which is up to 200 times that of the actuator itself,and convert energy from light to mechanical work efficiently.This report suggests a new kind of photo-responsive actuator based on supramolecular interaction and may be helpful to contribute a theoretical basis to the design and synthesis of photo-responsive mechanical actuator suitable for large-scale manufacturing industrialization in future.

Azobenzene-based ultrathin peptoid nanoribbons for the potential on highly efficient artificial light-harvesting

The development of artificial light-harvesting systems based on long-range ordered ultrathin organic nanomaterials(i.e., below3 nm), which were assembled from stimuli-responsive sequence-controlled biomimetic polymers, remains challenging. Herein,we report the self-assembly of azobenzene-containing amphiphilic ternary alternating peptoids to construct photo-responsive ultrathin peptoids nanoribbons(UTPNRs) with a thickness of ~2.3 nm and the length in several micrometers. The pendants hydrophobic conjugate stacking mechanism explained the formation of one-dimensional ultrathin nanostructures, whose thickness was highly dependent on the length of side groups. The photo-isomerization of azobenzene moiety endowed the aggregates with a reversible morphology transformation from UTPNRs to spherical micelles(46.5 nm), upon the alternative irradiation with ultraviolet and visible light. Donor of 4-(2-hydroxyethylamino)-7-nitro-2,1,3-benzoxadiazole(NBD) and acceptor of rhodamine B(RB) were introduced onto the hydrophobic and hydrophilic regions, respectively, to generate photocontrollable artificial light-harvesting systems. Compared with the spheres-based systems, the obtained NBD-UTPNRs@RB composite proved a higher energy transfer efficiency(90.6%) and a lower requirement of RB acceptors in water. A proof-ofconcept use as fluorescent writable ink demonstrated the potential of UTPNRs on information encryption.

Dithienylmaleimide-based D-A Conjugated Polymer Film:Photo-responsive Behavior and Application in Electrical Memory and Logic Gates

Solid-stated smart polymers responsive to external stimuli have attracted much attention for potential application in the field of photoelectron devices,logic gates,sensor,data storage and security.However,it is a bigger challenge for polymers than that for small molecules in solid state to acquire stimuli-responsive properties,because polymers with high molecular weight are not as easy to change the packing structure as small molecules under external stimulation.Here,a D-A type alternating copolymer PTMF-o containing 3,4-bisthienylmaleimide(A unit)and fluorene(D unit)is designed and synthesized.Upon irradiation of sunlight,PTMF-o film exhibits a photo-response with the color altering from purple to colorless.It is attributed to the structure of copolymer transformed from ring-opening form(PTMF-o)to ring-closure form(PTMF-c),resulting from the oxidative photocyclization of 3,4-bisthienylmaleimide unit.Consequently,the ability of charge transfer(CT)from fluorene to 3,4-bisthienylmaleimide unit in PTMF-o can be easily weakened by light stimuli.PTMF-o film displays a WORM-type resistive storage performance for the strong CT.Interestingly,after exposure,the electrical memory behavior in situ transfers into FLASH type,due to weak CT in PTMF-c.PTMF-o film can also be employed as smart material to construct NAND and NOR logic gates by using light as input condition.The work provides a simple way to modify the electronic properties of polymers and realize stimuli-response in solid states.

Hypoxia-induced activity loss of a photo-responsive microtubule inhibitor azobenzene combretastatin A4

The conformation-dependent activity of azo-benzene combretastatin A4(Azo-CA4)provides a unique approach to reduce the side-effects of chemotherapy,due to the light-triggered conformation transition of its azobenzene moiety.Under hypoxic tumor microenviron-ment,however,the high expression of azoreductase can reduce azobenzene to aniline.It was postulated that the Azo-CA4 might be degraded under hypoxia,resulting in the decrease of its anti-tumor activity.The aim of this study was to verify such hypothesis in HeLa cells in vitro.The quantitative drug concentration analysis shows the ratio-metric formation of degradation end-products,confirming the bioreduction of Azo-CA4.The tubulin staining study indicates that Azo-CA4 loses the potency of switching off microtubule dynamics under hypoxia.Furthermore,the cell cycle analysis shows that the ability of Azo-CA4 to induce mitotic arrest is lost at low oxygen content.Therefore,the cytotoxicity of Azo-CA4 is compromised under hypoxia.In contrast,combretastatin A4 as a positive control maintains the potency to inhibit tubulin polymer-ization and break down the nuclei irrespective of light irradiation and oxygen level.This work highlights the influence of hypoxic tumor microenvironment on the anti-tumor potency of Azo-CA4,which should be considered during the early stage of designing translational Azo-CA4 delivery systems.

A Photo-responsive Catalytic Vesicle with GPx Activity

Glutathione peroxidase (GPx) is a vital antioxidant enzyme involved in the reduction of reactive oxygen species and protects cells from oxidative damage.Consequently enormous efforts have been devoted to developing artificial catalysts with GPx function.Besides the research on enhancing the catalytic activity of GPx mimics,the design and construction of smart GPx models has also inspired great interest.Herein,a novel photo-responsive seleniumcontaining vesicular GPx model was successfully constructed by supramolecular self-assembly of the cationic surfactant PyC10AZoC10Py with benzeneseleninic acid (PhSeO2H) through hydrophobic and electrostatic interactions in aqueous media.This selenium-containing vesicular catalyst showed remarkable GPx-like activity,which is 692times more effective than PhSeO2H for the reduction of cumene hydroperoxide (CUOOH) by 4-nitrobenzenethiol (NBT).Interestingly,when an equimolar amount of α-CD was added,the GPx-like activity of the catalytic vesicle declines remarkably due to the vesicle disaggregation in the presence ofα-CD.Whereas the biomimetic system was irradiated by UV light at 365 nm,the catalytic vesicle was formed again and the GPx-like activity recovered.

Photo-responsive polymer materials for biological applications

Photo-responsive polymer materials from zero-dimensional micelles, two-dimensional surfaces to three-dimensional hydrogels have been designed, synthesized and applied for various biological fields including drug delivery and cell manipulation. Many remarkable works have been reported, revealing the advantages of photo-responsive polymers such as noninvasion and spatiotemporal control. In this review, we briefly summarized the remarkable progress of photo-responsive polymers with irreversible or reversible moieties and their further biological applications. The future opportunities and challenges of photo-responsive polymer materials are also proposed.

Migration of endothelial cells into photo-responsive hydrogels with tunable modulus under the presence of pro-inflammatory macrophages

Cell migration in three-dimensional environment is extremely important for tissue regeneration and other biological processes.In this work,a model system was developed to study how endothelial cells(ECs)migrate into photo-responsive hydrogels under the presence of pro-inflammatory macrophages.The hydrogel was synthesized from hyaluronic acid grafted with coumarin and methacrylate moieties by both carbon–carbon covalent linking and coumarin dimerization under UV irradiation at 365 nm.The structure of the hydrogel was conveniently modulated by UV irradiation at 254nm to decompose the coumarin dimers,leading to the significant decrease of modulus and increase of swelling ratio and mesh size.Under the presence of M1 macrophages,ECs were induced to migrate into the hydrogels with a different degree.A significant larger net displacement of ECs was found in the softer hydrogel obtained by irradiation with UV at 254nm than in the stiffer original one at day 7.

Photo-responsive metal/semiconductor hybrid nanostructure:A promising electrocatalyst for solar light enhanced fuel cell reaction

Direct alcohol fuel cells(DAFCs)have received wide attention as a new type of clean energy device because of their high energy conversion efficiency,portability,non-toxicity and pollution-free.Anode catalysts are the key factors affecting the performance of DAFCs.Recently studies show that using the optical activity of semiconductor materials as the carriers of traditional precious metal electrocatalysts,under the illumination of light sources,can greatly improve the electrocatalytic activity and stability of electrodes.In this review,the research progress of photo-responsive metal/semiconductor hybrids as the electrocatalysts for DAFCs in recent years is summarized,including:(1)Mechanism and advantages of photo-assistant electrochemical alcohol oxidation reaction,(2)me tal/semiconductor electrocatalyst for the different type of fuel cell reactions,(3)different kind of metals in photo-responsive metal/semiconductor hybrid nanostructure,(4)the personal prospects of the photo-responsive metal/semiconductor electrode for future application in DAFCs.

Recent Process of Photo-responsive Materials with Aggregation-induced Emission

The research of photo-responsive materials,with changed absorption and emission under light stimulus,has drawn more and more attention due to their wide applications.However,most of them suffered from the notorious aggregation-caused quenching(ACQ)effect,which often led to the unconspicuous luminescent change in photo-responsive process.To solve this problem,the strategy of combining aggregation-induced emission(AIE)and photochromic properties was utilized,which largely enriched the phenomenon and application of photo-responsive materials.This short review summarized the recent progress of photo-responsive AIE materials with changed UV absorbance or PL phenomenon under UV-irradiation,including the types of molecular structures,internal mechanisms and the practical applications.Also,some outlooks were given on the further exploration of this field at the end of this paper.

High responsivity and fast response 8×8β-Ga_(2)O_(3)solar-blind ultraviolet imaging photodetector array

In this work,an 8×8 Ga_(2)O_(3)solar-blind ultraviolet photodetector array is introduced for image sensing application.The 2-in wafer-scaled Ga_(2)O_(3)thin film was grown by metalorganic chemical vapor deposition technique;and the photodetector array was fabricated through ultraviolet photolithography,lift-off,and electron-beam evaporation.In addition to the high solar-blind/visible rejection ratio of 104,every photodetector cell in the array has high performance and fast response speed,such as responsivity of 49.4 A W^(-1),specific detectivity of 6.8×10^(14)Jones,external quantum efficiency of 1.9×10^(4)%,linear dynamic range of 117.8 d B,and response time of 41 ms,respectively,indicating the high photo-response performance of the photodetector.Moreover,the photodetector array displayed uniform responsivity with a standard deviation of~6%,and presented a sensing image of low chromatic aberration,owing to the high resolution of the photodetector array.In a word,this work may contribute to developing Ga_(2)O_(3)-based optoelectronic device applications.