Surface-modified Ag@Ru-P25 for photocatalytic CO_(2) conversion with high selectivity over CH_(4) formation at the solid–gas interface

Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO_(2) reduction to solar fuels.A surface-modified Ag@Ru-P25 photocatalyst with H_(2)O_(2) treatment was designed in this study to convert CO_(2) and H_(2)O vapor into highly selective CH4.Ru doping followed by Ag nanoparticles(NPs)cocatalyst deposition on P25(TiO_(2))enhances visible light absorption and charge separation,whereas H_(2)O_(2) treatment modifies the surface of the photocatalyst with hydroxyl(–OH)groups and promotes CO_(2) adsorption.High-resonance transmission electron microscopy,X-ray photoelectron spectroscopy,X-ray absorption near-edge structure,and extended X-ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst,while thermogravimetric analysis,CO_(2) adsorption isotherm,and temperature programmed desorption study were performed to examine the significance of H_(2)O_(2) treatment in increasing CO_(2) reduction activity.The optimized Ag1.0@Ru1.0-P25 photocatalyst performed excellent CO_(2) reduction activity into CO,CH4,and C2H6 with a~95%selectivity of CH4,where the activity was~135 times higher than that of pristine TiO_(2)(P25).For the first time,this work explored the effect of H_(2)O_(2) treatment on the photocatalyst that dramatically increases CO_(2) reduction activity.

Scalable Membraneless Direct Liquid Fuel Cells Based on a Catalyst-Selective Strategy

This perspective presents a membraneless direct liquid fuel cell(DLFC)concept based on a catalyst-selective strategy.The membraneless DLFCs are operated at low temperatures by employing a non-precious cathode catalyst with a high catalytic selectivity.The uniqueness is that the inexpensive cathode catalyst only catalyzes the oxygen reduction reaction but does not catalyze the oxidation reaction of a specific fuel.Therefore,during the operation of DLFCs,the liquid fuel can enter the cathode freely without any concern of fuel crossover.This catalyst-selective approach tactfully avoids the use of high-cost or technically unviable ion-exchange polymer membranes in DLFCs.The catalyst-selective operating principle also overcomes the scalability issue of the traditional laminar-flow membraneless DLFCs.Through a proper management of the anode and cathode catalysts in the cell,a variety of inexpensive,renewable alcohols,and small-molecule organics can be employed as anode fuels.This innovative approach of membraneless alkaline DLFCs offers a great opportunity for the development of inexpensive energy-generation systems for both mobile and stationary applications.In addition to summarizing the principle and the research progress of the unique membraneless DLFC platform,the challenges and future research directions are presented.

Optical Patterning of Two-Dimensional Materials

Recent advances in the field of two-dimensional(2D)materials have led to new electronic and photonic devices enabled by their unique properties at atomic thickness.Structuring 2D materials into desired patterns on substrates is often an essential and foremost step for the optimum performance of the functional devices.In this regard,optical patterning of 2D materials has received enormous interest due to its advantages of high-throughput,site-specific,and on-demand fabrication.Recent years have witnessed scientific reports of a variety of optical techniques applicable to patterning 2D materials.In this minireview,we present the state-of-the-art optical patterning of 2D materials,including laser thinning,doping,phase transition,oxidation,and ablation.Several applications based on optically patterned 2D materials will be discussed as well.With further developments,optical patterning is expected to hold the key in pushing the frontiers of manufacturing and applications of 2D materials.

Efficient predictions of formation energies and convex hulls from density functional tight binding calculations

Defects in materials significantly alter their electronic and structural properties,which affect the per-formance of electronic devices,structural alloys,and functional materials.However,calculating all the possible defects in complex materials with conventional Density Functional Theory(DFT)can be compu-tationally prohibitive.To enhance the efficiency of these calculations,we interfaced Density Functional Tight Binding(DFTB)with the Clusters Approach to Statistical Mechanics(CASM)software package for the first time.Using SiC and ZnO as representative examples,we show that DFTB gives accurate results and can be used as an efficient computational approach for calculating and pre-screening formation ener-gies/convex hulls.Our DFTB+CASM implementation allows for an efficient exploration(up to an order of magnitude faster than DFT)of formation energies and convex hulls,which researchers can use to probe other complex systems.

Nitrate additives for lithium batteries:Mechanisms,applications,and prospects

Lithium-metal batteries(LMBs)are considered as one of the most promising energy storage devices due to the high energy density and low reduction potential of the Li-metal anode.However,the growth of lithium dendrites results in accumulated dead Li and safety issues,limiting the practical application of LMBs.LiNO_(3)is a well-known additive in lithium-sulfur batteries to regulate the solid-electrolyte interphase(SEI),effectively suppressing the redox shuttle of polysulfides.Recently,other nitrates have been investigated in various electrolyte and battery systems,yielding improved SEI stability and cycling performance.In this review,we provide an overview of various nitrates,including LiNO_(3)for lithium batteries,focusing on their mechanisms and performance.We first discuss the effect of nitrate anions on SEI formation,as well as the cathode-electrolyte interphase(CEI).The solvation behavior regulated by nitrates is also extensively explored.Some strategies to improve the solubility of LiNO_(3)in ester-based electrolytes are then summarized,followed by a discussion of recent progress in the application of nitrates in different systems.Finally,further research directions are presented,along with challenges.This review provides a comprehensive understanding of nitrates and affords new and interesting ideas for the design of better electrolytes and battery systems.

Opto-thermoelectric pulling of light-absorbing particles

Optomechanics arises from the photon momentum and its exchange with low-dimensional objects.It is well known that optical radiation exerts pressure on objects,pushing them along the light path.However,optical pulling of an object against the light path is still a counter-intuitive phenomenon.Herein,we present a general concept of optical pulling-opto-thermoelectric pulling(OTEP)—where the optical heating of a light-absorbing particle using a simple plane wave can pull the particle itself against the light path.This irradiation orientation-directed pulling force imparts self-restoring behaviour to the particles,and three-dimensional(3D)trapping of single particles is achieved at an extremely low optical intensity of 10^(−2)mWμm^(−2).Moreover,the OTEP force can overcome the short trapping range of conventional optical tweezers and optically drive the particle flow up to a macroscopic distance.The concept of selfinduced opto-thermomechanical coupling is paving the way towards freeform optofluidic technology and lab-on-achip devices.

Light-driven single-cell rotational adhesion frequency assay

The interaction between cell surface receptors and extracellular ligands is highly related to many physiological processes in living systems.Many techniques have been developed to measure the ligand-receptor binding kinetics at the single-cell level.However,few techniques can measure the physiologically relevant shear binding affinity over a single cell in the clinical environment.Here,we develop a new optical technique,termed single-cell rotational adhesion frequency assay(scRAFA),that mimics in vivo cell adhesion to achieve label-free determination of both homogeneous and heterogeneous binding kinetics of targeted cells at the subcellular level.Moreover,the scRAFA is also applicable to analyze the binding affinities on a single cell in native human biofluids.With its superior performance and general applicability,scRAFA is expected to find applications in study of the spatial organization of cell surface receptors and diagnosis of infectious diseases.

Atomistic modeling and rational design of optothermal tweezers for targeted applications

Optical manipulation of micro/nanoscale objects is of importance in life sciences,colloidal science,and nanotechnology.Optothermal tweezers exhibit superior manipulation capability at low optical intensity.However,our implicit understanding of the working mechanism has limited the further applications and innovations of optothermal tweezers.Herein,we present an atomistic view of opto-thermo-electro-mechanic coupling in optothermal tweezers,which enables us to rationally design the tweezers for optimum performance in targeted applications.Specifically,we have revealed that the non-uniform temperature distribution induces water polarization and charge separation,which creates the thermoelectric field dominating the optothermal trapping.We further design experiments to systematically verify our atomistic simulations.Guided by our new model,we develop new types of optothermal tweezers of high performance using low-concentrated electrolytes.Moreover,we demonstrate the use of new tweezers in opto-thermophoretic separation of colloidal particles of the same size based on the difference in their surface charge,which has been challenging for conventional optical tweezers.With the atomistic understanding that enables the performance optimization and function expansion,optothermal tweezers will further their impacts.

Opto-thermoelectric microswimmers

Inspired by the“run-and-tumble”behaviours of Escherichia coli(E.coli)cells,we develop opto-thermoelectric microswimmers.The microswimmers are based on dielectric-Au Janus particles driven by a self-sustained electrical field that arises from the asymmetric optothermal response of the particles.Upon illumination by a defocused laser beam,the Janus particles exhibit an optically generated temperature gradient along the particle surfaces,leading to an opto-thermoelectrical field that propels the particles.We further discover that the swimming direction is determined by the particle orientation.To enable navigation of the swimmers,we propose a new optomechanical approach to drive the in-plane rotation of Janus particles under a temperature-gradient-induced electrical field using a focused laser beam.Timing the rotation laser beam allows us to position the particles at any desired orientation and thus to actively control the swimming direction with high efficiency.By incorporating dark-field optical imaging and a feedback control algorithm,we achieve automated propelling and navigation of the microswimmers.Our optothermoelectric microswimmers could find applications in the study of opto-thermoelectrical coupling in dynamic colloidal systems,active matter,biomedical sensing,and targeted drug delivery.

Optothermally Assembled Nanostructures

CONSPECTUS:Nanofabrication is one of the core techniques in rapidly evolving nanoscience and nanotechnology.Conventional top-down nanofabrication approaches such as photolithography and electron beam lithography can produce high-resolution nanostructures in a robust way.However,these methods usually involve multistep processing and sophisticated instruments and have difficulty in fabricating three-dimensional complex structures of multiple materials and reconfigurability.Recently,bottom-up techniques have emerged as promising alternatives to fabricating nanostructures via the assembly of individual building blocks.In comparison to top-down lithographical methods,bottom-up assembly features the on-demand construction of superstructures with controllable configurations at single-particle resolution.The size,shape,and composition of chemically synthesized building blocks can also be precisely tailored down to the atomic scale to fabricate multimaterial architectural structures of high flexibility.Many techniques have been reported to assemble individual nanoparticles into complex structures,such as self-assembly,DNA nanotechnology,patchy colloids,and optically controlled assembly.Among them,the optically controlled assembly has the advantages of remote control,site-specific manipulation of single components,applicability to a wide range of building blocks,and arbitrary configurations of the assembled structures.In this Account,we provide a concise review of our contributions to the optical assembly of architectural materials and structures using discrete nanoparticles as the building blocks.By exploiting entropically favorable optothermal conversion and controlling optothermal−matter interactions,we have developed optothermal assembly techniques to manipulate and assemble individual nanoparticles.Our techniques can be operated both in solution and on solid substrates.First,we discuss the opto-thermoelectric assembly(OTA)of colloidal particles into superstructures by coordinating thermophoresis and interparticle depletion bonding in the solution.Localized laser heating generates a temperature gradient field,where the thermal migration of ions creates a thermoelectric field to trap charged particles.The depletion of ion species at the gap between closely positioned particles under optical heating provides strong interparticle bonding to stabilize colloidal superstructures with precisely controlled configurations and interparticle distances.Second,we discuss bubble-pen lithography(BPL)for the rapid printing of nanoparticles using an optothermal microbubble.The long-range convection flow induced by the optothermal bubble drags the colloidal particles to the substrate with a high velocity.BPL represents a general method for printing all kinds of building blocks into desired patterns in a high-resolution and high-throughput way.Third,we present the optothermally-gated photon nudging(OPN)technique,which manipulates and assembles particles on a solid substrate.Our solid-phase optical control of particles synergizes the modulation of particle−substrate interactions by optothermal effects and photon nudging of the particles by optical scattering forces.Operated on the solid surfaces without liquid media,OPN can avoid the undesired Brownian motion of nanoparticles in solutions to manipulate individual particles with high accuracy.In addition,the assembled structures can be actively reassembled into new configurations for the fabrication of tunable functional devices.Next,we discuss applications of the optothermally assembled nanostructures in surfaceenhanced Raman spectroscopy,color displays,biomolecule sensing,and fundamental research.Finally,we conclude this Account with our perspectives on the challenges,opportunities,and future directions in the development and application of optothermal assembly.