Oxygen vacancies enable the visible light photoactivity of chromium-implanted TiO2 nanowires

Although computational studies have demonstrated that metal ion doping can effectively narrow the bandgap of TiO_(2),the visible-light photoactivity of metal-doped TiO_(2) photoanodes is still far from satisfactory.Herein,we report an effective strategy to activate the visible-light photoactivity of chromiumimplanted TiO_(2) via the incorporation of oxygen vacancies.The chromium-doped TiO_(2) activated by oxygen vacancies(Cr-TiO_(2)-vac)exhibited an incident photon-to-electron conversion efficiency(IPCE)of~6.8%at450 nm,which is one of the best values reported for metal-doped TiO_(2).Moreover,Cr-TiO_(2)-vac showed no obvious photocurrent decay after 100 h under visible-light illumination.

A strategy of enhancing the photoactivity of TiO_2 containing nonmetal and transition metal dopants

An effective structural codoping approach is proposed to modify the photoelectrochemical （PEC） properties of anatase TiO2 by being doped with nonmetal （N or/and C） and transition metal （Re） elements. The electronic structures and for- mation energies of different doped systems are investigated using spin-polarized density functional theory. We find that （C, Re） doped TiO2, with a low formation energy and a large binding energy, reduces the band gap to a large extent, thus it could contribute to the significant enhancement of the photocatalytic activity in the visible-light region. It should be pointed out that, to be successful, the proper proportion of the dopants C and Re should be controlled, so that reasonable PEC properties can be achieved.

Synergetic effects of lanthanum,nitrogen and phosphorus tri-doping on visiblelight photoactivity of TiO_2 fabricated by microwave-hydrothermal process

Effects of La, N, and P doping on the structural, electronic and optical properties of TiO_2 synthesized from TiCl_4 hydrolysis via a microwave-hydrothermal process were investigated by X-ray diffraction, transmission electron microscopy, N_2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy, electron paramagnetic resonance, UV-vis absorbance spectroscopy, photoelectrochemical measurements, and photoluminescence spectroscopy. The results showed that the presence of La in the tri-doped TiO_2 played a predominant role in inhibiting the recombination of the photogenerated electrons and holes. The existence of the substitutional N, interstitial N, and oxygen vacancies in TiO_2 lattices led to the band gap narrowing. It was P-doping rather than La or N doping that played a key role in inhibiting both anatase-to-rutile phase transformation and crystal growth, in stabilizing the mesoporous textural properties, and in increasing the content of surface bridging hydroxyl. Moreover, the tri-doping significantly enhanced the surface Ti^（4＋）-O^（2-）-Ti^（4＋）-O^（-·） species. All above-mentioned factors cooperated to result in the enhanced photoactivity of the tri-doped TiO_2. As a result, it exhibited the highest photoactivity towards the degradation of 4-chlorophenol（4-CP） under visible-light irradiation among all samples, which was much superior to commercial P25 TiO_2.

Preparation and photoactivity of thermosensitive polymer supported metallophthalocyanine

A novel reactive metallophthalocyanine derivative,zinc tetra(2,4-dichloro-1,3,5-triazine)aminophthalo-cyanine(Zn-TDTAPc),was prepared and immobilized on poly(N-isopropylacrylamide)(PNIPAAm) by covalent bonding to obtain a thermosensitive polymer(Zn-TDTAPc-g-PNIPAAm).Compared with zinc tetraaminophthalocyanine(Zn-TAPc),Zn-TDTAPc-g-PNIPAAm exhibits excellent solubility in water and in most organic solvents.Furthermore,it has a special thermosensitive property in water and the lower critical solution temperature(LCST) is 34.1℃.It was found that both dissolved and precipitated Zn-TDTAPc-g-PNIPAAm present high photoactivity evidenced by the experiment of photocatalytic degra-dation of 1,3-diphenylisobenzofuran(DPBF) in the presence of Zn-TDTAPc-g-PNIPAAm.These proper-ties suggest that it can be used potentially in photodynamic therapy(PDT).

Protection of Photoactivity of Photosensitizers by Amphiphilic Polysaccharide Micelles

Photosensitizer （photosan）-encapsulated micelles were prepared by self-assembly of Photosan with two amphiphilic polysaccharide derivatives, including the cholesteryl conjugated sodium alginate derivative （CSAD） and the deoxycholic acid group conjugated chitosan derivative （DA-Chit）. The results of UV-Vis and fluorescence spectroscopy indicated that the hydrogen bonding strength dominated the micelle formation. Methyl viologen was used as a model quencher of photosan. Using the steady-state fluorescence technology, the quenching constants were determined to be 2.05, 1.88 and 0.30 L/mmol for the free photosan, the photosan-CSAD micelle and the photosan-DA-Chit micelle, respectively. This suggested that photosan was protected from quenching of methyl viologen by the polysaccharide micelles. In addition, the protection effect of the photosan-DA-Chit micelle was significantly stronger than that of the photosan-CSAD micelle. The photosan-DA-Chit micelle is thus anticipated for protection of photoactivity of photosan during the blood circulation process in vivo.

Reduced graphene oxide/silicon nanowire hetero- structures with enhanced photoactivity and superior photoelectrochemical stability

Silicon nanowires （SiNWs） have been widely studied as light harvesting antennas in photocatalysts due to their ability to absorb broad-spectrum solar radiation, but they are typically limited by poor photoelectrochemical stability. Here, we report the synthesis of reduced graphene oxide-SiNW （rGO-SiNW） heterostructures to achieve greatly improved photocatalytic activity and stability. The SiNWs were synthesized through a metal-assisted electroless etching process and functionalized with reduced graphene oxide （rGO） flakes through a chemical absorption process. Here, the rGO not only functions as a physical protection layer to isolate the SiNWs from the harsh electrochemical environment but also serves as a charge mediator to facilitate the charge separation and transport processes. Furthermore, the rGO may also function as a redox catalyst to ensure efficient utilization of photo-carriers for the desired chemical reactions. Photocatalytic dye degradation studies show that the photoactivity of the heterostructures can be significantly enhanced with an initial activation process and maintained without apparent decay over repeated reaction cycles. Electrochemical and photo- electrochemical studies indicate that the enhanced photoactivity and photostability can be attributed to the more efficient separation of photoexcited charge carriers in SiNWs and the reduced self-oxidation of the surface of the SiNWs during the photocatalytic dye degradation process. The ability to significantly improve the photocatalytic activity and stability in rGO-SiNW heterostructures can not only lead to more opportunities for the application of silicon-based photocatalysts/ photoelectrodes for solar energy harvesting but also provide new insights into the stabilization of other unstable photocatalytic

Enhanced visible light photoactivity of TiO_(2)/SnO_(2) films by tridoping with Y/F/Ag ions

The Y,F,and Ag tridoped TiO_(2)/SnO_(2) composite nanocrystalline film(YFAg–TS)with prominent photocatalytic performance was prepared by the modified sol–gel method and was characterized by utilizing X-ray diffraction(XRD),differential thermal and thermogravimetric(DTA–TG)analysis,scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),Brunauer–Emmett–Teller(BET)method,ultraviolet–visible diffuse reflectance spectroscopy(UV–vis DRS),and photoluminescence(PL).The XRD and DTA–TG results expose that the YFAg–TS catalyst is a mixed phase consisting of anatase,rutile,and chlorargyrite,which is beneficial to improving the photocatalytic performance of TiO_(2).The SEM,TEM,and BET results disclose that the YFAg–TS film has smaller nanoparticles,higher specific surface area,and narrower pore size compared with pure TiO_(2) film.The XRD and TEM results exhibit that a part of yttrium can enter the TiO_(2) lattice to induce lattice distortion.The XPS results confirm the presence of Y^(3+)state in the YFAg–TS sample,and Y^(3+)ions can act as the trapping site of electrons to expedite the separation of electrons and holes.The UV–vis DRS results reveal that the YFAg–TS film has an obvious absorption edge shift and a narrower bandgap(2.70 eV)compared with pure TiO_(2) film.The PL results show that the YFAg–TS film has the highest photogenerated electrons and holes separation efficiency and charges transfer efficiency among all samples.The photocatalytic activity of the YFAg–TS was assessed by monitoring the degradation of methyl green and formaldehyde solution.The results manifest that the YFAg–TS film has high stability and excellent photocatalytic performance.The possible synergistic photocatalytic mechanism of YFAg–TS films has been discussed in this paper.

Photoactive Naphthalene Diimide Functionalized Titanium-Oxo Clusters with High Photoelectrochemical Responses

Photoactive functionalized titanium-oxo clusters(TOCs)are regarded as an important model compound for dye-sensitized titanium dioxide solar cells.However,the dyes used for sensitizing TOCs are still limited.Herein,two cyclic TOCs are reported,namely,[Ti_(6)(μ_(3)-O)_(2)(Oi-Pr)_(8))(LA)_(2)]·i-PrOH(S1)and[Ti_(6)(μ_(3)-O)2(Oi-Pr)_(8))(LV)_(2)]·i-PrOH(S2),which are functionalized by photoactive naphthalene diimide(NDI)chromophores.Their molecular structures and photophysical and photochemical properties were systematically studied.As shown by ultraviolet-visible(UV-vis)spectra and photocurrent study results,the band gap and the photocurrent response of S1 and S2 were derived from NDI ligands which extend the absorption edge of S1 and S2 approaching 500 nm and afford high photocurrent densities of 2.12μA/cm^(2)and 1.95μA/cm^(2)for S1 and S2,respectively,demonstrating the significance of the photoactive ligand in modulating photoresponse of TOCs.This work is expected to enrich the structural library of photoactive TOCs and provide insights into understanding the structure-property relationships of sensitized clusters.

Synthesis and Photoinitiated Crosslinking of Active Poly(lactic acid) Materials

Acrylate-terminated poly（lactic acid）（DPLA） was synthesized by polycondensation, using lactic acid, polyalcohol and acrylic acid as the raw materials. The prepolymer products in each process were characterized by FT-IR, 1 H-NMR, GPC and DSC. DPLAs were then formulated with reactive diluent and diphenyl ketone as photoinitiator and photopolymerized into film（FPLA）. Thermal stability and degradation properties of the UV curing PLA film were studied. The results showed that the structures of prepolymer and the performances of the film could be adjusted by changing the types and content of the branching agent polyalcohol. After crosslinking modification, the degradation rate of FPLA was reduced and FPLA had better thermal stability than the pure PLA.

Long-Term Activity of Thermoplastic Gel Electrolyte in a Photo-Electrochemical Assembly Involving Poly Bithiophene (PBTh) as Photoactive Working Electrode

Evidence for the long period of a sustainable function of a thermoplastic gel electrolyte (TPGE) consists of polyethylene glycol (PEG)/I2/I- in propylene carbonate (PC) was recorded. The studied photoactive assembly consists of PBTH/FTO/TPGE I2/I-/Platinized FTO. The study showed that the assembly regenerates the expected photoelectrochemical (PEC) quantities such as photocurrent, and other dielectric properties with infrequent use through an elapsed period of 18 months. The behavior of PBTh/occluded with CdS was mentored during this period and showed a similar result. PEC studies indicated the presence of p-p type hole accumulations interface, evident from the initial sharp rise in photocurrent. The change of open circuit potential (dVoc) indicates that the shortest electron lifetime is 100 ms. The behavioral outcome of the assemblies within the period of study refracts stability of the electrode and the long life cycle of the electrolyte.

DESIGN AND STUDY OF NEW AZOBENZENE LIQUID CRYSTAL/POLYMER MATERIALS

Discussion is presented on the use of the photoisomerization of azobenzene chromophore in the design andpreparation of novel functional materials. The two systems reviewed are azobenzene polymer-stabilized liquid crystals andazobenzene elastomers. In the first case, a polymer network containing azobenzene moieties is used to optically induce andstabilize a long-range liquid crystal orientation without the need of treating the surfaces of the substrates. This optical andrubbing-free approach was applied to nematic and ferroelectric liquid crystals. In the second case, an azobenzene side-chainliquid crystalline polymer is grafted onto a styrene-butadiene-styrene triblock copolymer to yield a photoactive thermoplasticelastomer. Coupled mechanical and optical effects make possible the formation of dimaction gratings that may be useful formechanically tunable optical devices.

Damage threshold influenced by polishing imperfection distribution under 355-nm laser irradiation

A systematic interpretation of laser-induced damage in the nanosecond regime is realized with a defect distribution buried inside the redeposited layer arising from a polishing process. Under the 355-nm laser irradiation, the size dependence of the defect embedded in the fused silica can be illustrated through the thermal conduction model. Considering CeO2 as the major initiator, the size distribution with the power law model is determined from the damage probability statistics. To verify the accuracy of the size distribution, the ion output scaling with depth for the inclusion element is obtained with the secondary ion mass spectrometer. For CeO2 particulates in size of the depth interval with ion output satisfied in the negative exponential form, the corresponding density is consistent with that of the identical size in the calculated size distribution. This coincidence implies an alternative method for the density analysis of photoactive imperfections within optical components at the semi-quantitative level based on the laser damage tests.

Antimicrobial technology in orthopedic and spinal implants

Infections can hinder orthopedic implant function and retention.Current implant-based antimicrobial strategies largely utilize coating-based approaches in order to reduce biofilm formation and bacterial adhesion.Several emerging antimicrobial technologies that integrate a multidisciplinary combination of drug delivery systems,material science,immunology,and polymer chemistry are in development and early clinical use.This review outlines orthopedic implant antimicrobial technology,its current applications and supporting evidence,and clinically promising future directions.

Influence of Thickness and Annealing Temperature on the Optical Properties of Spin-Coated Photoactive P3HT:PCBM Blend

Influence of annealing temperature and thickness on the optical characteristics of the blend of poly (3-hexylthiophene) (P3HT) and Phenyl C61 butyric acid methylester (PCBM) layer has been investigated in this report. Photoactive polymer material (P3HT:PCBM) was deposited on indium tin oxide (ITO) substrate by spin-coating. The morphology of P3HT:PCBM composite layer was investigated by Atomic Force Microscope (AFM). The surface roughness was found to reduce after heat treatment. The absorption of the composite layer was found to increase with its number of layer (thickness). On the other hand, the photoluminescence (PL) quenching, which indicates efficient charge separation in the bulk heterojunction, was found higher for the thinner layer. Absorption was also found to increase with the annealing temperature. Therefore, to optimize the thickness of the P3HT:PCBM photoactive layer that will provide best absorption while providing efficient charge separation, annealing at optimized temperature might be an effective tool.

Investigation on Lanthanum Fluoride as a Novel Cathode Buffer Material Layer for the Enhancement of Stability and Performance of Organic Solar Cell

This article presents the investigation on very thin Lanthanum Fluoride (LaF3) layer as a new cathode buffer layer (CBL) for organic solar cell (OSC). OSCs were fabricated with poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) polymer blend at 1:1 ratio. Electron-beam evaporation at room temperature was used to deposit 3 and 5 nm thick LaF3 layer. A very smooth surface of LaF3 with an average roughness of 0.2 nm has been observed by the Atomic Force Microscope (AFM) that is expected to prevent diffusion of cathode metal ion through it and thereby enhance the lifetime and stability of OSC. Huge enhancement of JSC and VOC was also observed for 3 nm-thick LaF3 CBL. Several excellent features of the LaF3 layer such as, transporting electron through tunneling, blocking of holes to the cathode, minimizing recombination, protecting the photoactive polymer from ambient oxygen, and reducing degradation/oxidation of any low work function layer at the cathode interface, might have contributed to the performance enhancement of OSC. The experimental findings indicate the promise of LaF3 to be an excellent CBL material for OSC.

Optical, Photoelectrochemical, and Electrochemical Impedance Studies on Photoactive Organic/Inorganic/Interface Assemblies of Poly 2,2 Bithiophene/Poly 3-(2-Thienyl) Aniline (PThA)/TiO₂

Particles of TiO2 modified with poly 3-(2-thienyl) aniline (PThA) and occluded in poly 2,2 bithiophene (PBTh), were subjected to optical, electrochemical impedance spectroscopic (EIS) and photoelectrochemical (PEC) investigation in aqueous, acetate, citrate, and phosphate electrolytes. EIS studies revealed that the assembly film of TiO2/PThA/PBTh possess porous-type structure. They also confirmed the approximate value of Ef obtained from electrochemical studies. Both EIS and optical studies indicated that ac conductivity is much greater than dc conductivity. Guided by the properties of PBTh, no large changes in the energy band structure occurred due to occlusion of TiO2 in PBTh films. Occlusion of TiO2/PThA into the network structure of PBTh inhibits the energy dissipation process and impeded charge polarization process of the material. Photoelectrochemical outcome suggested possible band alignments between the organic film and TiO2 and formation of hybrid sub-bands. Inclusion of TiO2 in the thiophene-based polymers enhanced the charge separation and consequently charge transfer processes and widen the absorption in visible light range.

Photoactive donor-acceptor conjugated macrocycles:New opportunities for supramolecular chemistry

The design and synthesis of photoactive macrocyclic molecules continue to attract attention because such species play important roles in supramolecular chemistry as well as photoelectronic applications.Donoracceptor(D-A)conjugated macrocycles are an emerging class of photoactive molecules due to their D-A conjugated structural characteristics and tunable optical properties.In addition,the well-defined cavities in such D-A macrocycles endow them with versatile host-guest properties.In this review,we provide a comprehensive summary of D-A conjugated macrocycle chemistry,detailing recent progress in the area of synthetic methods,optical properties,host-guest chemistry and applications of the underlying chemistry to chemical sensors,bioimaging and photoelectronic devices.Our objective is to provide not only a review of the fundamental findings,but also to outline future research directions where D-A conjugated macrocycles and their constructs may have a role to play.

Fabrication of Zn-Ti layered double hydroxide by varying cationic ratio of Ti^(4+) and its application as UV absorbent

ZnTi-layered double hydroxides（LDHs） with varying Zn/Ti ratio have been synthesized by coprecipitation of zinc and titanium salts from homogeneous solution.The obtained ZnTi-LDHs possess high crystallinity and hierarchical structure with improved UV-absorbance property.The UV-vis spectra show that the UV absorbing properties of ZnTi-LDHs is stronger and broader than both MgAl-LDH and ZnAl-LDH due to the existence of Ti.Moreover,the UV absorption property increased with the content of Ti,which can be ascribed to the decrease in the band gap energy,as clearly confirmed by density functional theory calculations.When irradiated by UV rays,the property of the samples with generated free radicals（OH^·and O2^·） was evaluated by means of electron spin resonance（EPR）.ZnTi-LDHs generated a relatively lower active radicals in contrast with TiO2 and ZnO,which implied an increased safety used as sunscreens.Therefore,this work provides a detailed understanding of UV shielding properties of ZnTiLDHs which was unrevealed previously,and demonstrates the expansive application prospects of ZnTiLDHs in the field of sunscreens.

Fabrication and Significant Photoelectrochemical Activity of Titania Nanotubes Modified with Thin Indium Tin Oxide Film

Ordered titanium dioxide nanotubes （TiOaNTs） modified with indium tin oxide （ITO） films were obtained via magnetron sputtering, in which ITO plate was used as a target, onto the as-anodized titania support followed by the calcination process. The morphology of fabricated material with deposited oxide was investigated using scanning electron microscopy. Raman and UV-Vis spectroscopies were utilized to characterize crystalline phase and optical properties of prepared samples, whereas X-ray photoelectron spectroscopy allowed determining the binding energy of present elements. In the case of titanium, three various oxidation states were identified and also the presence of indium and tin was confirmed. The electrochemical test carried out when the sample was exposed to light allows for selection of the most photoactive material. The highest photocurrent was registered when only 5-nm ITO layer was sputtered, and it equals 256 and 133 μA cm^-2 for the electrode material immersed in 0.5 M KOH and K2SO4 electrolytes, respectively, that is accordingly 3.5 and 4.4 times higher than the one observed for pristine titania. Furthermore, ITO-modified titania exhibits excellent photostability upon prolonged illumination that is of key importance for possible application in light-driven processes.