Improved Charge Separation and CO2 Affinity of In2O3 by K Doping with Accompanying Oxygen Vacancies for Boosted CO2 Photoreduction.

The CO2 photocatalytic conversion efficiency of the semiconductor photocatalyst is always inhibited by the sluggish charge transfer and undesirable CO2 affinity. In this work, we prepare a series of K-doped In2O3 catalysts with concomitant oxygen vacancies (OV) via a hydrothermal method, followed by a low-temperature sintering treatment. Owing to the synergistic effect of K doping and OV, the charge separation and CO2 affinity of In2O3 are synchronously promoted. Particularly, when P/P0 = 0.010, at room temperature, the CO2 adsorption capacity of the optimal K-doped In2O3 (KIO-3) is 2336 cm3·g-1, reaching about 6000 times higher than that of In2O3 (0.39 cm3·g-1). As a result, in the absence of a cocatalyst or sacrificial agent, KIO-3 exhibits a CO evolution rate of 3.97 µmol·g-1·h-1 in a gas-solid reaction system, which is 7.6 times that of pristine In2O3 (0.52 µmol·g-1·h-1). This study provides a novel approach to the design and development of efficient photocatalysts for CO2 conversion by element doping.

Construction of an In2O3/Bi2S3 Z-Scheme Heterojunction for Enhanced Photocatalytic CO2 Reduction.

Photocatalytic conversion of CO2 to hydrocarbon fuel is a potential strategy to solve energy shortage and mitigate the greenhouse effect. Here, direct Z-scheme heterojunction photocatalysts (In2O3/Bi2S3) without an electron mediator are prepared by a simple hydrolysis method. The In2O3/Bi2S3 composite photocatalysts show greatly boosted photoactivity on CO2 conversion to CO compared with the pristine In2O3 and Bi2S3. The highest CO evolution rate of 2.67 µmol·g-1·h-1 is achieved by In2O3/Bi2S3-3, without any sacrificial agent or cocatalyst, which is about 3.87 times that of In2O3 (0.69 µmol·g-1·h-1). The boosted photocatalytic performance of In2O3/Bi2S3 composite catalysts can be ascribed to the establishment of a Z-scheme heterojunction, improving the photoabsorption and facilitating charge separation and transfer. This study provides a reference for designing and fabricating high-efficiency Z-scheme heterojunction photocatalysts for photocatalytic CO2 reduction.

Boosting the activity for organic pollutants removal of In2O3 by loading Ag particles under natural sunlight irradiation.

A novel photocatalyst In2O3 with loading Ag particles is prepared via a facile one-step annealing method in air atmosphere. The Ag/In2O3 exhibits considerable photoactivity for decomposing sulfisoxazole (SOX), tetracycline hydrochloride (TC), and rhodamine B (RhB) under natural sunlight irradiation, which is much higher than that of pristine In2O3 and Ag species. After natural sunlight irradiation for 100 min, 70.6% of SOX, 65.6% of TC, and 81.9% of RhB are degraded over Ag/In2O3, and their corresponding chemical oxygen demand (COD) removal ratio achieve 95.4%, 38.4%, and 93.6%, respectively. A batch of experiments for degrading SOX with adjusting pollutant solution pH and adding coexisting anions over Ag/In2O3 are carried out to estimate its practical application prospect. Particularly, the as-prepared Ag/In2O3 possesses a superior stability, which exhibits no noticeable deactivation in decomposing SOX after eight cycles' reactions. In addition, the Ag/In2O3 coated on a frosted glass plate, also possesses a superior activity and stability for SOX removal, which solve the possible second pollution of residual powdered catalyst in water. Ag particles on In2O3 working as electron accepter improve charge separation and transfer efficiency, as well as the photo-absorption and organic pollutants affinity, leading to the boosted photoactivity of Ag/In2O3. The photocatalytic mechanism for degrading SOX and degradation process over Ag/In2O3 has been systemically investigated and proposed. This work offers an archetype for the rational design of highly efficient photocatalysts by metal loading.

Tuning colour centres at a twisted hexagonal boron nitride interface.

The colour centre platform holds promise for quantum technologies, and hexagonal boron nitride has attracted attention due to the high brightness and stability, optically addressable spin states and wide wavelength coverage discovered in its emitters. However, its application is hindered by the typically random defect distribution and complex mesoscopic environment. Here, employing cathodoluminescence, we demonstrate on-demand activation and control of colour centre emission at the twisted interface of two hexagonal boron nitride flakes. Further, we show that colour centre emission brightness can be enhanced by two orders of magnitude by tuning the twist angle. Additionally, by applying an external voltage, nearly 100% brightness modulation is achieved. Our ab initio GW and GW plus Bethe-Salpeter equation calculations suggest that the emission is correlated to nitrogen vacancies and that a twist-induced moiré potential facilitates electron-hole recombination. This mechanism is further exploited to draw nanoscale colour centre patterns using electron beams.

Realization of Curved Circular Nanotubes Using In Situ Monitored Self-Assembly.

Curved fluidic channels with a circular cross-section play an important role in biology, chemistry, and medicine. However, in nanofluidics, a problem that is largely unsolved is the lack of an effective fabrication method for curved circular nanotubes (10-1000 nm). In this work, an electron-beam-induced self-assembly process was applied to achieve fine curved nanostructures for the realization of nanofluidic devices. The diameter of the tube could be precisely controlled by an atomic layer deposition process. Fluid transported through the nanochannels was verified and characterized using a dark-field microscope under an optical diffraction limit size. The fluid flow demonstrates that the liquid's evaporation (vapor diffusion) in the nanochannel generates compressed vapor, which pumps the liquid and pushes it forward, resulting in a directional flow behavior in the ∼100 nm radius of tubes. This phenomenon could provide a useful platform for the development of diverse nanofluidic devices.

Kirigami Engineering of Suspended Graphene Transducers.

The low mass density and high mechanical strength of graphene make it an attractive candidate for suspended-membrane energy transducers. Typically, the membrane size dictates the operational frequency and bandwidth. However, in many cases it would be desirable to both lower the resonance frequency and increase the bandwidth, while maintaining overall membrane size. We employ focused ion beam milling or laser ablation to create kirigami-like modification of suspended pure-graphene membranes ranging in size from microns to millimeters. Kirigami engineering successfully reduces the resonant frequency, increases the displacement amplitude, and broadens the effective bandwidth of the transducer. Our results present a promising route to miniaturized wide-band energy transducers with enhanced operational parameter range and efficiency.

Construction of BiOIO3/AgIO3 Z-Scheme Photocatalysts for the Efficient Removal of Persistent Organic Pollutants under Natural Sunlight Illumination.

The efficient removal of persistent organic pollutants (POPs) in natural waters is vital for human survival and sustainable development. Photocatalytic degradation is a feasible and cost-effective strategy to completely disintegrate POPs at room temperature. Herein, we develop a series of direct Z-scheme BiOIO3/AgIO3 hybrid photocatalysts via a facile deposition-precipitation method. Under natural sunlight irradiation, the light intensity of which is ∼40 mW/cm2, a considerable rate constant of 0.185 min-1 for photodecomposing 40 mg/L MO is obtained over 0.5 g/L Bi@Ag-5 composite photocatalyst powder, about 92.5 and 5.3 times higher than those of pristine AgIO3 and BiOIO3. The photoactivity of Bi@Ag-5 for photodecomposing MO under natural sunlight illumination surpasses most of the reported photocatalysts under Xe lamp illumination. After natural sunlight irradiation for 20 min, 95% of MO, 82% of phenol, 78% of 2,4-DCP, 54% of ofloxacin, and 88% of tetracycline hydrochloride can be photodecomposed over Bi@Ag-5. Relative to the commercial photocatalyst TiO2 (P25), Bi@Ag-5 exhibits greatly higher photoactivity for the treatment of MO-phenol-tetracycline hydrochloride mixture pollutants in the scale-up experiment of 500 mL of solution, decreasing COD, TOC, and chromaticity value by 52, 19, and 76%, respectively, after natural sunlight irradiation for 40 min. The photodegradation process and mechanism of MO have been systematically investigated and proposed. This work provides an archetype for designing efficient photocatalysts to remove POPs.

Electron Beam Maneuvering of a Single Polymer Layer for Reversible 3D Self-Assembly.

Reversible self-assembly that allows materials to switch between structural configurations has triggered innovation in various applications, especially for reconfigurable devices and robotics. However, reversible motion with nanoscale controllability remains challenging. This paper introduces a reversible self-assembly using stress generated by electron irradiation triggered degradation (shrinkage) of a single polymer layer. The peak position of the absorbed energy along the depth of a polymer layer can be modified by tuning the electron energy; the peak absorption location controls the position of the shrinkage generating stress along the depth of the polymer layer. The stress gradient can shift between the top and bottom surface of the polymer by repeatedly tuning the irradiation location at the nanoscale and the electron beam voltage, resulting in reversible motion. This reversible self-assembly process paves the path for the innovation of small-scale machines and reconfigurable functional devices.

Core-shell structured Z-scheme Ag2S/AgIO3 composites for photocatalytic organic pollutants degradation.

Constructing direct Z-scheme system is a promising strategy to boost the photocatalytic performance for pollution waters restoration, but it is of great challenge because of the requirement of appropriately staggered energy band alignment and intimate interfacial interaction between semiconductors. Herein, a class of core-shell structured Ag2S-AgIO3 Z-scheme heterostructure photocatalysts are designed and developed. Ag2S is generated by the in-situ ion exchange reaction and anchored on the surface of AgIO3, so the intimate interface between AgIO3 and Ag2S is realized. Integration of AgIO3 and Ag2S extends the ultraviolet absorption of AgIO3 to Vis-NIR region, and also promote the charge separation and migration efficiency, contributing to the enhanced photocatalysis activity for composite catalysts. The optimal Ag2S-AgIO4-4 catalyst exhibits a MO photo-degradation rate constant of 0.298 h-1, which reaches 5.77 and 11.4-folds higher than that of AgIO3 (0.044 h-1) and Ag2S (0.024 h-1). The as-obtained composite catalyst exhibits universally photocatalytic activity in disintegrating diverse industrial pollutants and pharmaceuticals. Particularly, driven by natural sunlight, the Ag2S-AgIO4-4 can effectively decompose MO. A plausible Z-scheme photocatalytic mechanism and reaction pathways of MO degradation over composite catalyst are systemically investigated and proposed.

Increasing electron density by surface plasmon resonance for enhanced photocatalytic CO2 reduction.

The photocatalytic CO2 reduction reaction is a multi-electron process, which is greatly affected by the surface electron density. In this work, we synthesize Ag clusters supported on In2O3 plasmonic photocatalysts. The Ag-In2O3 compounds show remarkedly enhanced photocatalytic activity for CO2 conversion to CO compared to pristine In2O3. In the absence of any co-catalyst or sacrificial agent, the CO evolution rate of optimal Ag-In2O3-10 is 1.56 µmol/g/h, achieving 5.38-folds higher than that of In2O3 (0.29 µmol/g/h). Experimental verification and DFT calculation demonstrate that electrons transfer from Ag clusters to In2O3 on Ag-In2O3 compounds. In Ag-In2O3 compounds, Ag clusters serving as electron donators owing to the SPR behaviour are not helpful to decline photo-induced charge recomnation rate, but can provide more electron for photocatalytic reaction. Overall, the Ag clusters promote visible-light absorption and accelerate photocatalytic reaction kinetic for In2O3, resulting in the photocatalytic activity enhancement of Ag-In2O3 compounds. This work puts insight into the function of plasmonic metal on enhancing photocatalysis performance, and provides a feasible strategy to design and fabricate efficient plasmonic photocatalysts.

Hybridized Radial and Edge Coupled 3D Plasmon Modes in Self-Assembled Graphene Nanocylinders.

Current graphene-based plasmonic devices are restricted to 2D patterns defined on planar substrates; thus, they suffer from spatially limited 2D plasmon fields. Here, 3D graphene forming freestanding nanocylinders realized by a plasma-triggered self-assembly process are introduced. The graphene-based nanocylinders induce hybridized edge (in-plane) and radial (out-of-plane) coupled 3D plasmon modes stemming from their curvature, resulting in a four orders of magnitude stronger field at the openings of the cylinders than in rectangular 2D graphene ribbons. For the characterization of the 3D plasmon modes, synchrotron nanospectroscopy measurements are performed, which provides the evidence of preservation of the hybridized 3D graphene plasmons in the high precision curved nanocylinders. The distinct 3D modes introduced in this paper, provide an insight into geometry-dependent 3D coupled plasmon modes and their ability to achieve non-surface-limited (volumetric) field enhancements.

Optimizing the Electronic Structure of ZnS via Cobalt Surface Doping for Promoted Photocatalytic Hydrogen Production.

Developing highly efficient semiconductor photocatalysts for H2 evolution is intriguing, but their efficiency is subjected to the following three critical issues: limited light absorption, low carrier separation efficiency, and sluggish H2 evolution kinetics. Element surface doping is a feasible strategy to synchronously break through the above limitations. In this study, we prepared a series of Co-surface-doped ZnS photocatalysts to systematically investigate the effects of Co surface doping on photocatalytic activity and electronic structure. The implantation of Co results in the emergence of the impurity level above the valence band (VB) and the upshifted conduction band (CB) and enhances its visible light absorption. Co gradient doping inhibits the combination and facilitates the migration of carriers. S atoms are proven to be reactive active sites for photocatalytic H2 evolution over both ZnS and Co-doped ZnS. Co doping alters the surface electronic structure and decreases the absolute value for the hydrogen binding free energy (ΔGH) of the adsorbed hydrogen atom on the catalyst. As a consequence, Co-surface-doped ZnS shows boosted photocatalytic H2 evolution activity relative to the undoped material. This work provides insights into the mechanistic understanding of the surface element doping modification strategy to developing efficient photocatalysts.

Electron Irradiation Driven Nanohands for Sequential Origami.

Sequence plays an important role in self-assembly of 3D complex structures, particularly for those with overlap, intersection, and asymmetry. However, it remains challenging to program the sequence of self-assembly, resulting in geometric and topological constrains. In this work, a nanoscale, programmable, self-assembly technique is reported, which uses electron irradiation as "hands" to manipulate the motion of nanostructures with the desired order. By assigning each single assembly step in a particular order, localized motion can be selectively triggered with perfect timing, making a component accurately integrate into the complex 3D structure without disturbing other parts of the assembly process. The features of localized motion, real-time monitoring, and surface patterning open the possibility for the further innovation of nanomachines, nanoscale test platforms, and advanced optical devices.

Self-Assembled 3D Nanosplit Rings for Plasmon-Enhanced Optofluidic Sensing.

Plasmonic sensors are commonly defined on two-dimensional (2D) surfaces with an enhanced electromagnetic field only near the surface, which requires precise positioning of the targeted molecules within hotspots. To address this challenge, we realize segmented nanocylinders that incorporate plasmonic (1-50 nm) gaps within three-dimensional (3D) nanostructures (nanocylinders) using electron irradiation triggered self-assembly. The 3D structures allow desired plasmonic patterns on their inner cylindrical walls forming the nanofluidic channels. The nanocylinders bridge nanoplasmonics and nanofluidics by achieving electromagnetic field enhancement and fluid confinement simultaneously. This hybrid system enables rapid diffusion of targeted species to the larger spatial hotspots in the 3D plasmonic structures, leading to enhanced interactions that contribute to a higher sensitivity. This concept has been demonstrated by characterizing an optical response of the 3D plasmonic nanostructures using surface-enhanced Raman spectroscopy (SERS), which shows enhancement over a 22 times higher intensity for hemoglobin fingerprints with nanocylinders compared to 2D nanostructures.

Dibenzothiophene-S,S-Dioxide-Based Conjugated Polymers: Highly Efficient Photocatalyts for Hydrogen Production from Water under Visible Light.

Three dibenzothiophene-S,S-dioxide-based alternating copolymers were synthesized by facile Suzuki polymerization for visible light-responsive hydrogen production from water (> 420 nm). Without addition of any cocatalyst, FluPh2-SO showed a photocatalytic efficiency of 3.48 mmol h-1 g-1 , while a larger hydrogen evolution rate (HER) of 4.74 mmol h-1 g-1 was achieved for Py-SO, which was ascribed to the improved coplanarity of the polymer that facilitated both intermolecular packing and charge transport. To minimize the possible steric hindrance of FluPh2-SO by replacing 9,9'-diphenylfluorene with fluorene, Flu-SO exhibited a more red-shifted absorption than FluPh2-SO and yielded the highest HER of 5.04 mmol h-1 g-1 . This work highlights the potential of dibenzothiophene-S,S-dioxide as a versatile building block and the rational design strategy for achieving high photocatalytic efficiency.

Advanced Continuous Flow Platform for On-Demand Pharmaceutical Manufacturing.

As a demonstration of an alternative to the challenges faced with batch pharmaceutical manufacturing including the large production footprint and lengthy time-scale, we previously reported a refrigerator-sized continuous flow system for the on-demand production of essential medicines. Building on this technology, herein we report a second-generation, reconfigurable and 25 % smaller (by volume) continuous flow pharmaceutical manufacturing platform featuring advances in reaction and purification equipment. Consisting of two compact [0.7 (L)×0.5 (D)×1.3 m (H)] stand-alone units for synthesis and purification/formulation processes, the capabilities of this automated system are demonstrated with the synthesis of nicardipine hydrochloride and the production of concentrated liquid doses of ciprofloxacin hydrochloride, neostigmine methylsulfate and rufinamide that meet US Pharmacopeia standards.

Self-Assembled Three-Dimensional Graphene-Based Polyhedrons Inducing Volumetric Light Confinement.

The ability to transform two-dimensional (2D) materials into a three-dimensional (3D) structure while preserving their unique inherent properties might offer great enticing opportunities in the development of diverse applications for next generation micro/nanodevices. Here, a self-assembly process is introduced for building free-standing 3D, micro/nanoscale, hollow, polyhedral structures configured with a few layers of graphene-based materials: graphene and graphene oxide. The 3D structures have been further modified with surface patterning, realized through the inclusion of metal patterns on their 3D surfaces. The 3D geometry leads to a nontrivial spatial distribution of strong electric fields (volumetric light confinement) induced by 3D plasmon hybridization on the surface of the graphene forming the 3D structures. Due to coupling in all directions, resulting in 3D plasmon hybridization, the 3D closed box graphene generates a highly confined electric field within as well as outside of the cubes. Moreover, since the uniform coupling reduces the decay of the field enhancement away from the surface, the confined electric field inside of the 3D structure shows two orders of magnitude higher than that of 2D graphene before transformation into the 3D structure. Therefore, these structures might be used for detection of target substances (not limited to only the graphene surfaces, but using the entire volume formed by the 3D graphene-based structure) in sensor applications.

In Situ Monitored Self-Assembly of Three-Dimensional Polyhedral Nanostructures.

The self-assembly of 3D nanostructures is a promising technology for the fabrication of next generation nanodevices and the exploration of novel phenomena. However, the present techniques for assembly of 3D nanostructures are invisible and have to be done without physical contact, which bring great challenges in controlling the shapes with nanoscale precision. This situation leads to an extremely low yield of self-assembly, especially in 3D nanostructures built with metal and semiconductor materials. Here, an in situ self-assembly process using a focused ion beam (FIB) microscopy system has been demonstrated to realize 3D polyhedral nanostructures from 2D multiple pieces. An excited ion beam in the FIB microscopy system offers not only a visualization of the nanoscale self-assembly process but also the necessary energy for inducing the process. Because the beam energy that induces the self-assembly can be precisely adjusted while monitoring the status of the self-assembly, it is possible to control the self-assembly process with sub-10 nm scale precision, resulting in the realization of diverse 3D nanoarchitectures with a high yield. This approach will lead to state-of-the-art applications utilizing properties of 3D nanostructures in diverse fields.

A Rapid Total Synthesis of Ciprofloxacin Hydrochloride in Continuous Flow.

Within a total residence time of 9 min, the sodium salt of ciprofloxacin was prepared from simple building blocks via a linear sequence of six chemical reactions in five flow reactors. Sequential offline acidifications and filtrations afforded ciprofloxacin and ciprofloxacin hydrochloride. The overall yield of the eight-step sequence was 60 %. No separation of intermediates was required throughout the synthesis when a single acylation reaction was applied to remove the main byproduct, dimethylamine.

Silole-Containing Polymer Nanodot: An Aqueous Low-Potential Electrochemiluminescence Emitter for Biosensing.

A novel D-A conjugated polymer backbone containing silole and 9-octyl-9H-carbazole units was synthesized via Sonogashira reaction. This silole-containing polymer (SCP) was further used to prepare SCP dots with a nanoprecipitation method, which showed an electrochemiluminescence (ECL) emission at relatively low potential in aqueous solution. The strong anodic ECL emission could be observed at +0.4 V (vs Ag/AgCl) with a peak value at +0.78 V in the presence of tri-n-propylamine (TPrA) as a co-reactant, which came from the band gap emission of the excited SCP dots. The ECL emission could be quenched via resonance energy transfer from the excited SCP dots to an acceptor. Thus, a low-potential anodic ECL sensing strategy was proposed for ECL detection of the acceptor-related analytes. Using dopamine as the analyte, whose electro-oxidation product could act as the energy acceptor to quench the ECL emission of SCP dots, the ECL detection method showed a detection limit of 50 nM and high anti-interference ability. This work demonstrates an example of polymer dots as an ECL emitter and its potential application in ECL detection methodology.