Research advances of light-driven hydrogen evolution using polyoxometalate-based catalysts

With the increasing concerns to energy shortage and environmental problems in modern society,the development of cheap,clean,and sustainable energy alternatives has been attracting tremendous attention globally.Among various strategies of renewable energy exploration,solar-driven water splitting into its compositional elements H2 and O2 is an ideal approach to convert and store renewable solar energy into chemical bonds.In recent few decades,as an emerging new type of catalysts,polyoxometalates(POMs)have been widely utilized for water splitting due to their versatile synthetic methodology and highly tunable physicochemical and photochemical properties.This critical review addresses the research advances of light-driven hydrogen evolution using polyoxometalate-based catalysts,including plenary POMs,transition-metal-substituted POMs,POM@MOF composites,and POM-semiconductor hybrids,under UV,near UV and visible light irradiation.In addition,the catalytic mechanism for each reaction system has been thoroughly discussed and summarized.Finally,a comprehensive outlook of this research area is also prospected.

Dye-Enhanced Self-Electrophoretic Propulsion of Light-Driven TiO_2–Au Janus Micromotors

Light-driven synthetic micro-/nanomotors have attracted considerable attention in recent years due to their unique performances and potential applications. We herein demonstrate the dye-enhanced self-electrophoretic propulsion of light-driven Ti O_2–Au Janus micromotors in aqueous dye solutions. Compared to the velocities of these micromotors in pure water, 1.7, 1.5, and 1.4 times accelerated motions were observed for them in aqueous solutions of methyl blue(10-5g L^(-1)), cresol red(10^(-4)g L^(-1)),and methyl orange(10^(-4)g L^(-1)), respectively. We determined that the micromotor speed changes depending on thetype of dyes, due to variations in their photodegradation rates. In addition, following the deposition of a paramagnetic Ni layer between the Au and Ti O_2 layers, the micromotor can be precisely navigated under an external magnetic field. Such magnetic micromotors not only facilitate the recycling of micromotors, but also allow reusability in the context of dye detection and degradation.In general, such photocatalytic micro-/nanomotors provide considerable potential for the rapid detection and ‘‘on-thefly'' degradation of dye pollutants in aqueous environments.

Wheel-shaped icosanuclear Cu-containing polyoxometalate catalyst: Mechanistic and stability studies on light-driven hydrogen generation

In this paper,we report the synthesis and characterization of a wheel-shaped icosanuclear Cu-containing polyoxometalate(POM),K_(12)Li_(13)[Cu_(2)0Cl(OH)_(24)(H_(2)O)_(12)(P_(8)W_(48)O_(184))]·22H_(2)O(K_(12)Li_(13)-Cu_(2)0P_(8)W_(48)).The resulting cation-exchanged tetrabutylammonium salt of the polyoxoanion Cu_(2)0P_(8)W_(48)(TBA-Cu_(2)0P_(8)W_(48))exhibits high efficiency for visible-light-driven H_(2) production in the presence of an[Ir(ppy)2(dtbbpy)][PF_(6)]photosensitizer and a triethanolamine electron donor.Under optimal conditions,the turnover number for H_(2) production reaches~2892 after 5 h of photocatalysis and thereafter continuously increases to~13400 in a long-term 120 h reaction,representing the best performance among all reported transition-metal-substituted POM catalysts.Mechanistic studies confirm the existence of reductive and oxidative quenching processes,of which the reductive quenching pathway is dominant.Various stability tests demonstrate that the TBA-Cu_(2)0P_(8)W_(48) catalyst slowly dissociates Cu ions under turnover conditions;however,both the starting TBA-Cu_(2)0P_(8)W_(48) and its molecular decomposition products are dominant active species for efficient and long-term H_(2) production.

Current–Voltage Characteristics of the Aziridine-Based Nano-Molecular Wires: a Light-Driven Molecular Switch

Using nonequilibrium Green＇s function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-（4-nitrophenyl）-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene molecular optical switch. The title molecule can convert between closed and open forms by visible or ultraviolet irradiation. The I-V characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian orbitals, HOMO-LUMO gaps, effect of electrode materials Y（111）（Y =Au, Ag and Pt） on electronic transport and different molecular geometries corresponding to the closed and open forms through the molecular device are discussed in detail. Based on the results, as soon as possible the open form translates to the closed form, and there is a switch from the ON state to the OFF state（low resistance switches to high resistance）. Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.

Recent advancement and future challenges of photothermal catalysis for VOCs elimination:From catalyst design to applications

Photothermal catalysis realizes the synergistic effect of solar energy and thermochemistry,which also has the potential to improve the reaction rate and optimize the selectivity.In this review,the research progress of photothermal catalytic removal of volatile organic compounds(VOCs)by nano-catalysts in recent years is systematically reviewed.First,the fundamentals of photothermal catalysis and the fabrication of catalysts are described,and the design strategy of optimizing photothermal catalysis performance is proposed.Second,the performance for VOC degradation with photothermal catalysis is evaluated and compared for the batch and continuous systems.Particularly,the catalytic mechanism of VOC oxidation is systematically introduced based on experimental and theoretical study.Finally,the future limitations and challenges have been discussed,and potential research directions and priorities are highlighted.A broad view of recent photothermal catalyst fabrication,applications,challenges,and prospects can be systemically provided by this review.

A novel dicobalt-substituted tungstoantimonate polyoxometalate: Synthesis,characterization,and photocatalytic water oxidation properties

The one-pot assembly reaction of a trilacunary,lone-pair-containing[B-α-SbW9O33]9.precursor with Co2+ions in an aqueous medium led to the isolation of a novel{SbO3(H2O)3}bridging,dicobalt-substituted,sandwich-type tungstoantimonate{Co2Sb2(H2O)10[B-β-SbW9O33]2}^4–(1a).This compound was structurally characterized in the solid state by single-crystal X-ray diffraction,elemental analyses,thermogravimetric analysis,and IR spectroscopy.The most remarkable feature was that 1a comprises two trilacunary[B-β-SbW9O33]9^-fragments trapping a novel,centrally symmetric,rhomb-like{Co2Sb2}belt with 10 terminal water molecules.When combined with the photosensitizer[Ru(bpy)3]^2+and the sacrificial electron acceptor S2O82.,1a exhibited efficient catalytic activity for water oxidation with a remarkable turnover number(TON)of 193,initial turnover frequency(TOFinitial)of 5.3 s^-1,O2 yield of 30.8%,and quantum yield(ФQY)of 36.2%under light-driven conditions.

Preparation of Polyaniline/ZnO Films by Electrochemical Polymerization

A series of polyaniline (PANI)/zinc oxide (ZnO) nano-particle (diameter 70 nm) composite films were prepared by electrochemical polymerization in the presence of ZnO nanoparticle. Furthermore, PANI-ZnO/PVA (PVA = polyvinyl alcohol) double-layer system was prepared. We first report preparations of a photocatalyst/conducting polymer light absorber by using ZnO nano-particles.

Visible light-driven oxidation of non-native substrate by laccase attached on Ru-based metal-organic frameworks

Light-induced electron transfer can broaden the substrate range of metalloenzyme.However,the efficiency of photo-enzyme coupling is limited by the poor combination of photosensitizer or photocatalyst with enzyme.Herein,we prepared the nano-photocatalyst MIL-125-NH_(2)@Ru(bpy)by in site embedding ruthenium pyridine-diimine complex[Ru(bpy)_(3)^(2+)into metal organic frameworks MIL-125-NH_(2)and associated it with multicopper oxidase(MCO)laccase.Compared to[Ru(bpy)_(3)]^(2+),the coupling efficiency of MIL-125-NH_(2)@Ru(bpy)_(3)for enzymatic oxygen reduction increased by 35.7%.A series of characterizations confirmed that the amino group of laccase formed chemical bonds with the surface defects or hydrophobic groups of MIL-125-NH_(2)@Ru(bpy)_(3).Consequently,the tight binding accelerated the quenching process and electron transfer between laccase and the immobilized ruthenium pyridine-diimine complex.This work would open an avenue for the synthesis of MOFs photocatalyst towards photo-enzyme coupling.

Near-infrared light-driven Janus capsule motors： Fabrication, propulsion, and simulation

We report a fuel-free, near-infrared （NIR）-driven Janus microcapsule motor. The Janus microcapsule motors were fabricated by template-assisted polyelectrolyte layer-by-layer assembly, followed by spraying of a gold layer on one side. The NIR-powered Janus motors achieved high propulsion with a maximum speed of 42μm.s-1 in water. The propulsion mechanism of the Janus motor was attributed to the self-thermophoresis effect： The asymmetric distribution of the gold layer generated a local thermal gradient, which in turn generated thermophoretic force to propel the Janus motor. Such NIR-propelled Janus capsule motors can move efficiently in cell culture medium and have no obvious effects on the cell at the power of the NIR laser, indicating considerable promise for future biomedical applications.

Light-driven crystallization of polystyrene micro-spheres

We investigate the dynamic crystallization processes of colloidal photonic crystals, which are potentially invaluable for solving a number of existing and emerging technical problems in regards to controlled fabrication of crystals, such as size normalization, stability improvement, and acceleration of synthesis. In this paper, we report systematic high-resolution optical observation of the spontaneous crystallization of monodisperse polystyrene(PS) micro-spheres in aqueous solution into close-packed arrays in a static line optical tweezers. The experiments demonstrate that the crystal structure is mainly affected by the minimum potential energy of the system; however, the crystallization dynamics could be affected by various mechanical, physical, and geometric factors. The complicated dynamic transformation process from 1D crystallization to 2D crystallization and the creation and annihilation of dislocations and defects via crystal relaxation are clearly illustrated.Two major crystal growth modes, the epitaxy growth pattern and the inserted growth pattern, have been identified to play a key role in shaping the dynamics of the 1D and 2D crystallization process. These observations offer invaluable insights for in-depth research about colloidal crystal crystallization.

Cytochrome P450s in algae:Bioactive natural product biosynthesis and light-driven bioproduction

Algae are a large group of photo synthetic organisms responsible for approximately half of the earth’s total photosynthesis.In addition to their fundamental ecological roles as oxygen producers and as the food base for almost all aquatic life,algae are also a rich source of bioactive natural products,including several clinical drugs.Cytochrome P450 enzymes(P450s) are a superfamily of biocatalysts that are extensively involved in natural product biosynthesis by mediating various types of reactions.In the post-genome era,a growing number of P450 genes have been discovered from algae,indicating their important roles in algal life-cycle.However,the functional studies of algal P450s remain limited.Benefitting from the recent technical advances in algae cultivation and genetic manipulation,the researches on P450s in algal natural product biosynthesis have been approaching to a new stage.Moreover,some photoauto trophic algae have been developed into "photo-bioreactors" for heterologous P450s to produce high-value added pharmaceuticals and chemicals in a carbon-neutral or carbon-negative manner.Here,we comprehensively review these advances of P450 studies in algae from 2000 to 2021.

Light-driven soft actuator based on graphene and WSe2 nanosheets composite for multimodal motion and remote manipulation

Remote controlled soft actuators have attracted ever-increasing interest in industrial,medical,robotics,and engineering fields.Soft actuators are charming than normal tools in executing dedicate tasks due to small volume and flexible body they have.However,it remains a challenge to design soft actuator that can adapt to multi-environments under remote stimuli with promising nano materials.Herein,we have developed a kind of near-infrared laser driven soft actuators with multi locomotive modes based on WSe2 and graphene nanosheets heterojunction.Different locomotion modes are driven by photothermal effect induced deformation to adapt to different working conditions.Moreover,the specially designed gripper driven by pulsed laser can lift a heavy load which is four times of its weight.This work broadens the choice of advanced nanomaterials for photothermal conversion of soft actuators.It is promising to realize applications including photothermal therapy and complex environment detection through the combination of the intelligent robot design and optical fiber system.

Visible-light-driven photocatalytic degradation of rhodamine B using Bi_(2)WO_(6)/GO deposited on polyethylene terephthalate fabric

The environmental repercussions of wastewater from the dye process mean that it is very important to obtain an eco-friendly photocatalyst that would degrade wastewater.Herein,bismuth tungstate/graphene oxide(Bi_(2)WO_(6)/GO)composites are fabricated through in-situ hydrothermal reaction and then the Bi_(2)WO_(6)/GO photocatalysts are deposited onto polyethylene terephthalate(PET)fabric.The obtained Bi_(2)WO_(6)/GO deposited PET fabrics are then characterized through XPS,Raman,SEM,TEM,XRD,UV-vis,BET method and photoluminescence spectroscopy(PL)to investigate their chemical and crystal structures,morphology,optical property,surface area and photochemical properties.Photocatalytic performance is studied through examining the rate of degrading rhodamine B(RhB)under visible light.Surface of PET fibers is densely covered with Bi_(2)WO_(6)/GO.Bi_(2)WO_(6)/GO deposited PET fabrics show a broad absorption band in the visible spectra.Removal rate of RhB on the Bi_(2)WO_(6)/GO deposited PET fabric is the highest with the GO content of 2 g/L(labeled as Bi_(2)WO_(6)/2 g/LGO).The result of active species experiment shows that superoxide radicals(·O_(2)^(−))plays a major role in the degradation of RhB.Moreover,Bi_(2)WO_(6)/2 g/LGO deposited PET fabric shows excellent cycle stability of photocatalytic degradation for RhB.The findings in this work can be extended to preparation other types of composite on the textile for photocatalysis,which can be applied to remove dyes in the wastewater produced by the textile or leather industry.

Bidirectional Light-Driven Ion Transport through Porphyrin Metal–Organic Framework-Based van der Waals Heterostructures via pH-Induced Band Alignment Inversion

Heterogeneous two-dimensional layered membranes reconstructed fromnatural or synthetic van derWaals materials enable novel ion transport mechanisms by coupling with the chemical and optoelectronic properties of the layered constituents.Here,we report a light-driven and pH-dependent bidirectional ion transport phenomenon through porphyrin metal–organic framework(PMOF)and transition metal dichalcogenides-based multilayer van der Waals heterostructures with sub-nanometer ionic channels.

Solar Energy for Value-Added Chemical Production by LightPowered Microbial Factories

The light-driven material-microorganism biohybrid system has the potential to transfer solar energy for chemical production.However,few studies have reported the construction of biohybrid systems using light-responsive materials with nonmodel strains that have been widely used in practical industrial production for value-added chemicals,especially with regard to the mechanism of action of photogenerated charges in the cytoplasm,probably due to the complexity of their anabolic pathways.Herein,a biohybrid system as a research mode was constructed by electrostatically self-assembling a highly efficient light-harvesting material of graphite-phase nitrided carbon(g-C_(3)N_(4))nanosheets with nonmodel strains(Phaffia rhodozyma)for synthesis of nutritional chemical astaxanthin.The biohybrid interface enabled efficient separation,transfer,and transport of photogenerated charges from g-C_(3)N_(4) into the interior of P.rhodozyma,which improved the substance metabolism and the energy metabolism of P.rhodozyma.Notably,photogenerated charges can significantly promote the accumulation of precursors along the astaxanthin anabolic pathway and enhance the cytoplasmic redox environment and ATP levels in the interior of P.rhodozyma,even under adverse conditions(such as enzyme inhibitors),thus increasing the yield of astaxanthin compared to the traditional culture of P.rhodozyma.This study not only provides new ideas for converting solar energy into value-added chemicals,but it also provides guidance for regulating microbial synthesis plants.

Photo-thermoelectric generator integrated in graphene-based actuator for self-powered sensing function

Smart actuators integrated with sensing functions are taking a significant role in constructing intelligent robots.However,the detection of sensing signals in most actuators requires external electrical power,lacking in the self-powered feature.Herein,we report a graphene-based light-driven actuator with self-powered sensing function,which is designed by integrating a photothermoelectric generator into the actuator intelligently.When one part of the actuator is irradiated by near-infrared light,it shows a deformation with bending curvature up to 1.5 cm^(−1),owing to the mismatch volume changes between two layers of the actuator.Meanwhile,the temperature difference across the actuator generates a voltage signal due to the photo-thermoelectric effect.The Seebeck coefficient is higher than 40μV/K.Furthermore,the self-powered voltage signal is consistent with the deformation trend,which can be used to characterize the deformation state of actuator without external electrical power.We further demonstrate a gripper and a bionic hand.Their deformations mimic the motions of human hand(or finger),even making complex gestures.Concurrently,they can output self-powered voltage signals for sensing.We hope this research will pave a new way for selfpowered devices,state-of-the-art intelligent robots,and other integrated multi-functional systems.

Light hybrid micro/nano-robots:From propulsion to functional signals

Untethered motile micro/nanorobots(MNRs)that can operate in hard-to-reach small space and perform noninvasive tasks in cellular level hold bright future in healthcare,nanomanufacturing,biosensing,and environmental remediation.Light,as a flexible encoding method with tunable freedom of intensity,wavelength,polarization,and propagation direction,endows unique spatialtemporal precision and dexterity to the manipulation of MNRs.Meanwhile,light has been extensively investigated as functional signals in bioimaging,phototherapy,as well as photoelectrochemical reactions.The hybridization of light and other actuation method ushers in novel MNRs with broadened design space,improved controllability,and advanced functionality.In this review,the fundamental mechanisms of light-driven MNRs will be revisited.On top of it,light hybrid systems,coupling with magnetic,electric,chemical,or ultrasound field,will be reviewed,with light for propulsion or as functional signal.The rational hybridization of multiple stimulus in MNRs not only promises simple combination of two driving forces,but more importantly,motivates rethinking of light-driven MNRs for unprecedented applications.

基于非对称PVA/墨水/PE双层膜的光驱动柔性致动器和多功能传感器

聚乙烯醇/中国墨水混合物被均匀涂覆在聚乙烯薄膜上制备了结构稳定的双层软驱动器.由于两层材料的热膨胀系数的显著差异,在氙灯照射下,驱动器能以较快的响应速度实现较大的弯曲变形.通过改变光的强度以及结合尺蠖的仿生结构设计,机器人可以在不同的表面(如纸张和树叶)上实现各种形式的运动.同时在光的驱动下,它可以实现物体的捕获、表情的改变、象鼻的收缩与卷曲以及仿生花朵的开闭等.此外,基于双层驱动器良好的光热转换和灵敏的压力传感性能,它可以实现人体运动监测(如关节弯曲、呼吸、吞咽等),还能与光电转换装置集成.这种多功能、多驱动模式软机器人在可穿戴设备、交通运输、光电转换设备等应用领域具有巨大潜力.

A novel Cu_(1.5)Mn_(1.5)O_(4)photothermal catalyst with boosted surface lattice oxygen activation for efficiently photothermal mineralization of toluene

Developing a novel photothermal catalyst for efficient mineralization of volatile organic compounds(VOCs)is of great significance to control air pollution.Herein,for the first-time,a spinel Cu_(1.5)Mn_(1.5)O_(4)nanomaterial with enhanced surface lattice oxygen activation was successfully obtained by a novel light-driven in situ reconstruction strategy from its precursor(CuMnO_(2))for efficient toluene mineralization.X-ray diffraction(XRD)and high-resolution transmission electron microscopy(HRTEM)analyses confirm that the CuMnO_(2)phase was converted into spinel Cu1.5Mn1.5O4 phase under full spectrum light irradiation.Ultraviolet–visible–near infrared ray(UV–vis–NIR)spectroscopy,X-ray photoelectron spectroscopy(XPS)analysis,and density functional theory(DFT)calculations determine that the strong near-infrared absorption ability and low dissociation energy of oxygen bond in Cu_(1.5)Mn_(1.5)O_(4)are beneficial to its surface lattice oxygen activation.Furthermore,O2-temperature programmed desorption(TPD)and in situ diffuse reflectance infrared transform spectroscopy(DRIFTS)further indicate that the surface lattice oxygen of the Cu_(1.5)Mn_(1.5)O_(4)is easily activated under light irradiation,which can promote ring opening of toluene.This research endows a new design of photothermal nanomaterial with enhanced lattice oxygen activation for deep oxidation of VOCs.