Search

Sunlight is an abundant and clean energy source, the harvesting of which could make a significant contribution to society's increasing energy demands. Metal halide perovskites (MHP) have recently received attention for solar fuel generation through photocatalysis and solar-driven electrocatalysis. However, MHP photocatalysis is limited by low solar energy conversion efficiency, poor stability, and impractical reaction conditions. Compared to photocatalysis, MHP solar-driven electrocatalysis not only exhibits higher solar conversion efficiency but also is more stable when operating under practical reaction conditions. In this Perspective, we outline three leading types of MHP solar-driven electrocatalysis device technologies now in the research spotlight, namely, (1) photovoltaic-electrochemical (PV-EC), (2) photovoltaic-photoelectrochemical (PV-PEC), and (3) photoelectrochemical (PEC) approaches for solar-to-fuel reactions, including water-splitting and the CO2 reduction reaction. In addition, we compare each technology to show their relative technical advantages and limitations and highlight promising research directions for the rapidly emerging scientific field of MHP-based solar-driven electrocatalysis. ispartof: JOURNAL OF PHYSICAL CHEMISTRY LETTERS vol:13 issue:1 pages:25-41 ispartof: location:United States status: published

A kind of polyurethane rubber (PU)/n-octadecane (n-OD)@silicon dioxide (SiO2)-polymethyl acrylate (PHEMA) form-stable phase change material (PCM) was fabricated in this paper. n-OD@SiO2-PHEMA microcapsules were prepared in one-pot, through interfacial hydrolysis polycondensation of alkoxy silanes and radical polymerization of HEMA. Then, n-OD@SiO2-PHEMA microcapsules were added into PU matrix to obtain PU/n-OD@SiO2-PHEMA composites. SiO2-PHEMA hybrid shell not only provides a shelter for core material, but also increases interfacial bonding between microcapsules with PU and effectively improves the mechanical properties of composites. The morphologies, chemical compositions and crystal structures of microcapsules and composites were characterized by SEM, TEM, FT-IR and XRD methods. The thermal and mechanical properties of the microcapsules and composites were characterized by differential scanning calorimetry and mechanical performance tests. The results show that the thermal and mechanical properties of PU/n-OD@SiO2-PHEMA composites were better than those of neat PU. The PU/n-OD@SiO2-PHEMA composites endow the microcapsules with improved thermal reliability and leakage proof property. The composites were found as form-stable PCM with low leakage rate. The phase change latent heat of the PU/n-OD@SiO2-PHEMA composites was up to 85.1 J/g and the composites can be used for thermal energy storage.

In this paper, partly esterified β-cyclodextrin derivative had been synthesized by esterification of β-cyclodextrin and maleic anhydride. Then, it is amidated by diethanolamine. β-Cyclodextrin copolymer had been prepared from amidated β-cyclodextrin derivative, cholic acid and epichlorohydrin in sodium hydroxide aqueous solution. β-Cyclodextrin hydrogel had been prepared through radical polymerization of β-cyclodextrin copolymer, N-isopropylacrylamide and acrylic acid. The structures, compositions and morphology of the hydrogel were characterized by infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry and field-emission scanning electron microscope. Its properties were tested and analyzed by ultraviolet spectroscopy, thermogravimetric analysis and swelling experiments. The results show that the β-cyclodextrin hydrogel owns sustained release performance, temperature and pH sensitivities.

A facile strategy for hydrophobic films based on oil-infused polystyrene microspheres with the unit of γ-methacryloxypropyltrimethoxysilane is demonstrated. Specifically, the rough polystyrene microspheres with unit of γ-methacryloxypropyltrimethoxysilane are synthesized by suspension polymerization. These hydrophobic films were used, for the first time, as rough substrates for loading low surface tension silicone oils as lubricating liquids for the fabrication of polystyrene films. The properties of the films can be well tuned by adjusting the toluene and γ-methacryloxypropyltrimethoxysilane balance of the polystyrene microspheres and the mass ratio of toluene to γ-methacryloxypropyltrimethoxysilane reached 7 : 1.5 was found to be the most effective. The hydrophobic films could easily repel water and the water contact angle of the film was 150° before infusing oil and reached 139° after infusing oil. The morphology, structure and composition of polystyrene microspheres were characterized by SEM and FTIR. The content of trapped lubricant was quantified by silicone oil decomposition and measured by thermogravimetric analysis. Bacterial attachment tests showed that silicone oil infusion inhibited the attachment and growth of E. coli. The resulting films maintain water repellency and slipperiness after freezing, water flowing, and friction.

Lyotropic chromonic liquid crystals (LCLCs) confined in cylindrical cavity can form an escaped-twisted (ET) configuration, resulting from the saddle-splay elastic constant is great much than twist ...

In a cylindrical cavity with a degenerate planar anchoring, the lyotropic chromonic nematic liquid crystals without intrinsic chirality tend to exhibit an escaped twisted configuration for the larg...

In this study, a macroinitiator of β-CD-ONa was prepared by a substitution reaction of β-cyclodextrin (β-CD) with sodium (Na). The macroinitiator was then used in the ring-opening polymerization of octamethylcyclotetrasiloxane (D4) to obtain a star polymer, in which β-CD is the core and polysiloxane is the arm. FTIR, NMR, TGA, CA, etc., were used to characterize the structure and properties of star polymers. The results indicated that there were four polysiloxane arms attached to each β-CD core, and the star polymer had good thermal stability. With the increase in D4 monomer dosage, the hydrophobicity of the star polymer slightly improved, but the reaction time had no significant effect on hydrophobicity. When the star polymer was coated onto polyethylene terephthalate membrane, the transmittance increased from 87.6% to 92.8%, and the haze did not change significantly. Furthermore, the surface of star polymer porous membranes was prepared by the static breath-figure method using n-hexane as solvent at 30 °C. The results showed uniform pore distribution and increased hydrophobicity.

Accurate and efficient gas monitoring is still a challenge because the existing sensing techniques mostly lack specific identification of gases or hardly meet the requirement of real-time readout. Herein, we present a strategy of conductometric response-triggered surface-enhanced Raman spectroscopy (SERS) for such gas monitoring, via designing and using ultrathin oxide-wrapped plasmonic metal nanoparticles (NPs). The oxide wrapping layer can interact with and capture target gaseous molecules and produce the conductometric response, while the plasmonic metal NPs possess strong SERS activity. In this strategy, the conductometric gas sensing is performed throughout the whole monitoring process, and once a conductometric response is generated, it will trigger SERS measurements, which can accurately recognize molecules and hence realize gas monitoring. The feasibility of this strategy has been demonstrated via using ultrathin SnO2 layer-wrapped Au NP films to monitor gaseous 2-phenylethanethiol molecules. It has been shown that the monitoring is rapid, accurate, and quantifiable. There exist optimal values of working temperature and SnO2 layer thickness, which are about 100 °C and 2.5 nm, respectively, for monitoring gaseous 2-phenylethanethiol. The monitoring signal intensity has a linear relation with the gas concentration in the range from 1 to 100 ppm on a logarithmic scale. Furthermore, the monitoring limits are at the ppm level for some typical gases, such as 2-phenylethanethiol, cyclohexanethiol, 1-dodecanethiol, and toluene. This study establishes the conductometric response-triggered SERS, which enables accurate gas recognition and real-time monitoring.

The gemini-like surfactants have been constructed by compounding N-erucamidopropyl-N,N-dimethylamine (UC22AMPM) and o-phthalic acid (o-PA), m-phthalic acid (m-PA), or p-phthalic acid (p-PA), and are denoted as o-EAPA, m-EAPA, and p-EAPA, respectively. It is well known that inorganic salts have significant effects on surfactant aggregates, and herein the effects of sodium chloride (NaCl) on gemini-like surfactants is explored by rheological and dynamic light scattering measurements, and cryo-TEM. It is found that the viscoelasticity of the EAPA systems first increases and then decreases with an increase of the NaCl concentration. And the optimal NaCl concentrations for these three systems are in the order of o-EAPA < m-EAPA < p-EAPA due to different spacer distances between the two carboxyl groups in the phthalic acid. Similar trends in the N,N-dimethyl oleoaminde-propylamine (DOAPA) and o-PA, m-PA, or p-PA systems were also observed. The results show that an appropriate NaCl concentration will promote gemini-like surfactants to form wormlike micelles (WLMs). Upon further increasing the NaCl concentration, the WLMs transform into vesicles. Excessive NaCl concentration will cause the surfactant systems to reach their cloud point and make the surfactants precipitate out. The mechanism of the effects of NaCl is that Cl- reduces the electrostatic repulsion between the headgroups of the surfactants. This work is helpful in understanding the effects of inorganic salts on the surfactants and this study is useful for exploring the practical applications of gemini-like surfactants.

In this paper, hydroxyl terminated polysiloxane was first prepared by ring-opening polymerization of octamethylcyclotetrasiloxane (D4), which was then modified with acryloyl chloride to obtain acryloyloxy polysiloxane. A light-scattering material was synthesized by copolymerization of acryloyloxy polysiloxane and methyl methacrylate (MMA). The results showed that the transmittance of the material was 88% and the haze was 93% when the ratio of MMA to light-scattering agent was 100:1, the amount of initiator was 0.3%, and the post-polymerization temperature was 50 °C. The TGA data indicated that the material had excellent heat resistance. Therefore, it has a wide range of applications in the field of light-emitting diodes.

A facile and general strategy is presented for homogenous and ultrathin metal sulfide wrapping on plasmonic metal (PM) nanoparticles (NPs) based on a thiourea-induced isotropic shell growth. This strategy is typically implemented just via adding the thiourea into pre-formed PM colloidal solutions containing target metal ions. The validity of this strategy is demonstrated by taking the wrapped NPs with Au core and CuS shell or Au@CuS NPs as an example. They are successfully fabricated via adding the thiourea and Cu2+ solutions into pre-formed Au NP colloidal solution. The CuS shell layer is highly homogenous (

The block copolymer PS-b-PMMA was prepared by atom transfer radical polymerization (ATRP). Amphiphilic copolymer could be formed by hydrolysis of the block copolymer at acidic conditions. The products were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectro-scopy and gel permeation chromatography. The results illustrated the successful preparation of amphiphilic copolymer. The porous membranes were prepared by the breath figure method and characterized their surface morphology. The results showed that there was a regular and uniform porous morphology on the surface of the amphiphilic copolymer film. When the concentration of the polymer solution was 25 mg/mL, the pore size of the PS-b-PMAA copolymer membrane was about 1 nm. After immersing the polymer film in silicone oil for a period of time, the water contact angle reached 108.7°. The microbial adhesion test was used to study the adhesion of microporous membrane surface to microorganisms. The results showed that the surface of the oil film could effectively improve the antibacterial property of the polymer surface.

In order to intrinsically boost the photocatalytic performance of WO3/CdS, the charge transfer route can be modulated from conventional type-Ⅱ to Z-scheme by incorporating of hydrogen ions into WO3/CdS to form H0.53WO3/CdS. This work indicates that only when charge transfer of WO3/CdS is type-Ⅱ, can H0.53WO3/CdS composite be formed in-situ. Subsequently, the Z-scheme photocatalytic mechanism plays its prominent roles in gradually improving photocatalytic H2 evolution performance. H0.53WO3/CdS has high photocatalytic activity for hydrogen production, which is much higher than that of WO3/CdS. This work will provides an in-depth understanding of charge separation and transfer processes and steer charge flow in a Z-scheme manner for efficient solar-to-chemical energy applications.

This work demonstrated the 12 fold-enhanced solar water splitting over the type-II core-shell nanostructured TiO2 rutile photoanodes by orienting the charge flow and accelerating the hole transport to water-oxidation sites. Such nanoheterostructured photoanodes were designed rationally and prepared by a facile strategy to enwrapping an amorphous Ta2OxNy layer on surface of TiO2 nanorods grown on the FTO glass substrates, consequently the incident photon-to-current conversion efficiency was increased from 2.2% to 22.6% in a two-electrode system under 390 nm light irradiation. The activity results showed that under AM 1.5 G illumination, the photocurrent output of TiO2@Ta2OxNy photoanodes reached a stable density of 1.32 mA cm−2 at 1.23 V vs RHE, and which is 12 times and ca. 4.3 times than that of the pristine TiO2 and TiO2@Ta2O5 counterparts, respectively. Correspondingly, the oxygen evolution rate was improved from 20.3 to 112.7 mmol m−2 h−1. A solar-to-chemical energy conversion efficiency of ca. 1.49% was achieved at 1.23 V vs RHE.

Lithium–sulfur (Li–S) batteries have received significant attention due to the high theoretical specific capacity of sulfur (1675 mA h g–1). However, the practical applications are often handicapped by sluggish electrochemical kinetics and the “shuttle effect” of electrochemical intermediate polysulfides. Herein, we propose an in-situ copolymerization strategy for covalently confining a sulfur-containing copolymer onto reduced graphene oxide (RGO) to overcome the aforementioned challenges. The copolymerization was performed by heating elemental sulfur and isopropenylphenyl-functionalized RGO to afford a sulfur-containing copolymer, that is, RGO-g-poly(S-r-IDBI), which is featured by a high sulfur content and uniform distribution of the poly(S-r-IDBI) on RGO sheets. The covalent confinement of poly(S-r-IDBI) onto RGO sheets not only enhances the Li+ diffusion coefficients by nearly 1 order of magnitude, but also improves the mechanical properties of the cathodes and suppresses the shuttle effect of polysul...

TiO2@Ni(OH)2 core-shell microspheres were synthesized by a facile strategy to obtain a perfect 3D flower-like nanostructure with well-arranged Ni(OH)2 nanoflakes on the surfaces of TiO2 microspheres; this arrangement led to a six-fold enhancement in photocatalytic hydrogen evolution. The unique p-n type heterostructure not only promotes the separation and transfer of photogenerated charge carriers significantly, but also offers more active sites for photocatalytic hydrogen production. A photocatalytic mechanism is proposed based on the results of electrochemical measurements and X-ray photoelectron spectroscopy.

We present the on-chip fabrication of bilayer Au NP-decorated WO3 nanoporous thin films (B-Au/WO3) via layer-by-layer stacking of a sacrificial colloidal template with periodic Au sputtering deposition. Technical analysis shows that the B-Au/WO3 film is homogeneous and consists of a hexagonally ordered bowl-like structure, whose surface is uniformly decorated with crystalline Au NPs. The B-Au/WO3 sensing film shows a sensitivity of 96.0, a response time of 9.0 s and a recovery time of 16.0 s for 1 ppm NO2 at a low operating temperature of 150 °C. This significantly exceeds performances of bare WO3 counterpart. Also, the B-Au/WO3 sensor demonstrates obviously enhanced sensing responses over operating temperature ranges of 75–225 °C and perfect selectivity to NO2 gas. We proposed a combined sensing mechanism, the surface Au NPs dominated chemical sensitization and inter-bedded Au NP-induced electronic sensitization, to explain the perfect sensing performances in sensitivity, response, and selectivity. The template-mediated approach focuses on precise single-layer control and facilitates direct integration of the sensing film onto the required sensor substrate. The addressed on-chip fabrication strategy along with Au NPs decoration technique might provide promising applications in construction of advanced chemiresistive gas sensors, photocatalysts and electrochromic smart windows.

The composite with heavily incorporated HxWO3 (H0.53WO3/CdS) was successfully synthesized by a facile method of photo-assisted in situ reduction and applied in photocatalytic water splitting into H2. Its photocatalytic activity is about 70 times greater than that of pure CdS. Such a heterostructure shows wide spectral response in the UV-vis-NIR range, which is attributed to the LSPR of H0.53WO3. In the vis-NIR-driven photocatalytic water reduction process, a unique dual path for generating H2 from water is constructed, which is contributed by the synergistic photocatalysis effect between the charge-carrier separation driven by the Z-scheme and hot electron injection induced by LSPR (Localized Surface Plasmon Resonance).

This study aimed to investigate the wear failure changes of spindle hook teeth and the reasons for such failure during field work. Spindle samples were obtained from a fixed position of the spindle bar under different field picking area conditions and combined with the spatial distribution characteristics of cotton bolls in Xinjiang. After cutting a spindle sample, a scanning electron microscope and an energy spectrum analyzer were used to characterize the micromorphology and element composition of the hook tooth surface and cross section under different working area conditions. The wear parameters of the hook teeth were then extracted. The results showed that the thickness of the coating on the surface of the hook tooth used in this study was between 66.1 µm and 74.4 µm. The major chemical element was chromium, with a small amount of nickel. During the field picking process, failure of the coating on the surface of the hook teeth initially appeared on the tooth tip and tooth edge, and then spread to the entire hook tooth surface. The wear failure of the hook teeth resulted from abrasive wear, oxidative wear, and fatigue peeling. As the picking area increased, the wear area of the hook teeth increased exponentially, while the wear width increased linearly. When the field picking area reached 533.33 ha, the maximum change rate of the wear area was 2.33 × 103 µm2/ha, and the wear width was 1.84 µm/ha. During field work, the thickness of the coating decreased from the cutting surface to the tooth edge, and the wear rate gradually increased. The wear rate at Position 1 was the slowest, at 0.01 µm/ha, and the wear rate at Position 5 was the fastest, at 0.25 µm/ha.

Flexoelectric effect and dielectric effect in uniform lying helix (ULH) cholesteric liquid crystals under cell boundary conditions of periodic anchoring at the bottom and vertical anchoring at the top are studied. They can be quantitatively analyzed by theoretically simulation of the polar angle and the tilt angle. It is found that a good ULH texture can be formed inside under periodic boundary conditions and the bulk director is not affected by the surface anchoring strength. The induced rotation angle of the helical axis by the flexoelectric effect is slightly non-uniform with the position, and the coupling of the flexoelectric effect and dielectric effect increases the inhomogeneous change. Our results will provide an accurate theory basis for the formation of a good ULH texture and the influence of dielectric effect on the optical axis.

In recent years, applications such as marine search and rescue, border patrol, etc. require electro-optical equipment to have both high resolution and precise geographic positioning abilities. The step and stare working based on a composite control system is a preferred solution. This paper proposed a step and stare system composed of two single-axis fast steering mirrors and a two-axis gimbal. The fast steering mirrors (FSMs) realize image motion compensation and the gimbal completes pointing control. The working principle and the working mode of the system are described first. According to the imaging optical path, the algorithm and control flow of the line of sight (LOS) and image motion compensation are developed. The proposed method is verified through ground imaging and flight tests. Under the condition of flight, the pointing accuracy of the target can be controlled within 15 m. The proposed algorithm can achieve effective motion compensation and get high-resolution images. This achieves high resolution and accurate LOS simultaneously.

A simple and cost-effective route to fabricating gold-coated glass nano-stings' arrays is presented for highly efficient surface enhanced Raman spectroscopy (SERS) chips via reactive ion etching of the glass slide covered with polystyrene (PS) colloidal monolayer and sputtering deposition of gold on it. The as-fabricated SERS chips consist of the nearly-hemispherical particles with submicron-size, which are hexagonally arranged into the ordered arrays. There are many short and long Au-coated glass nano-stings standing vertically on the hemispherical particles, showing high density tips (up to 7.0 × 103 μm-2). The formation of such gold-coated glass hierarchically structured array is attributed to the geometry of PS colloidal monolayer and the nanoscale roughness of glass slide's surface. Further, it has been demonstrated that such gold-coated glass array chip is highly SERS-active and can be utilized to detect trace organophosphorous toxicant with the limit below ppt level and good reproducibility in measurements. The intensity of the Raman peak shows the linear relation, in logarithmic scale, with the organophosphorous concentration from ppt to ppm level, exhibiting the possibility of quantitative detection in a large concentration range. This work has demonstrated the cost-effective method to fabricate the high performance SERS chips for trace detection of toxic molecules.

Detection of trace harmful small gaseous molecules (h-SGMs), based on surface enhanced Raman spectroscopy (SERS), has been expected to be a useful strategy but is challenging due to the extremely small Raman cross section (RCS) and weak metal affinity of the h-SGMs. Here, a new strategy, ultrathin layer solid transformation-enabled (ULSTE)-SERS, is proposed. It uses the chemical reaction between the target h-SGM and an ultrathin layer of solid sensing matter coated on a plasmonic metal SERS substrate. This reaction in situ produces a new solid matter with large RCS, which ensures the detection of trace h-SGMs via SERS. The validity of this strategy has been demonstrated by detecting trace H2S gas with an ultrathin CuO layer wrapped around Au nanoparticles. Furthermore, this strategy allows fast and ultrasensitive detection. The detection limit can be down to ppb (even ppt) levels with 10 min preprocessing. Importantly, this strategy has good universality for various other h-SGMs, such as SO2, CS2, CH3SH, and HCl, etc., using appropriate sensing matter. Additionally, the ULSTE-SERS is also suitable for unstable molecules and fast portable detection due to the stable solid layer. This work provides highly efficient SERS-based detection of trace h-SGMs, which is easily applied in practical situations.

Eu3+-doped CdMoO4 luminescent ultra-thin films were fabricated by a facile aqueous solution method. The thin films were characterized by means of X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the results showed that Eu3+ions are doped into CdMoO4 and the luminescent thin films are dense and smooth. Photoluminescence (PL) spectra, UV–vis absorption spectra and lifetimes were also used to characterize luminescent properties of the resulting films. The optimal doping concentration was found to be 10 mol% for the Eu3+-doped CdMoO4 luminescent ultra-thin films.

High-Pb solders have been used as die-attach and interconnect materials for decades in discrete power components. Because of the known harmful effects of Pb to human health and the environment, as well as the demand of the wide-band-gap SiC/GaN power devices serving under high power density and high junction temperature, alternative Pb-free solders/materials and solutions have been studied intensively. Pb-free alternatives to replace high-Pb solders are still in their infancy. The exemption of using high-Pb solders has been extended to 2021, although it may be terminated anytime if a new technology or material were to be accepted industry-wide. The potential high-temperature Pb-free materials, including solders (AuSn/AuSi/AuGe, ZnAl and BiAgX®), Ag-sintering material, and transient liquid-phase bonding (TLPB) material, are reviewed in this paper with an emphasis on BiAgX® solders. The extremely high cost of Au-based solders limits their applications, although they have been used in high-temperature electronics. Zn-Al has a high melting temperature, good mechanical properties, and good thermal performance. However, the high reactivity makes Zn-Al solders only available in wire and preform. BiAgX® solder (available in paste, wire and preform) has been developed to replace the high-Pb solders for use in low-power discrete components, with relatively low cost and better reliability than the high-lead counterpart. Ag-sintering material and TLPB material form joints by atomic diffusion (either solid diffusion for sintering or solid–liquid interdiffusion for TLPB). The challenges in mass-production and the cost have restricted their success to be widely used in industry. Although it is likely that none of these materials/technologies are ideal to satisfy all the requirements of the variety of high temperature Pb-free die attach applications in terms of processing/reliability/cost, each solution has the potential to satisfy a niche within this broader categorization.

With automotive electronics booming, more sensors and power moderators are increasingly required for electrical vehicles and self-driving cars. Lead-free tin-silver-copper (SnAgCu), also known as SAC , has been a popular choice for surface-mount technology (SMT) assembly solder alloy in the electronics industry.

Photoelectrochemical (PEC) water splitting has been demonstrated as a promising way to acquire clean hydrogen energy. However, the efficiency has been limited by the high recombination rate of photogenerated electron-hole pairs. Herein, we provided a simple approach to construct a novel SnO2 quantum dots (QDs) modified TiO2 nanorod arrays (NAs) by the calcination of SnCl2 -adsorbed TiO2 NAs. The photocurrent density of SnO2 QDs/TiO2 NAs exhibits about 5 times higher than that of parent TiO2 NAs at a bias of 0.4 V vs. Ag/AgCl. SnO2 QDs/TiO2 NAs also show a high photoelectrocatalytic activity for overall water splitting with an actual yield of H2 and O2 to be 27.85 and 11.87 μmol cm-2 h-1 , respectively. The excellent performance of photoanode for PEC water splitting could be attributed to its Z-scheme heterostructure for good separation efficiency and transport rate of photogenerated charge carries.

Graphene oxide was prepared by improving Hummers method and then modified by 4,4′-oxydianiline to get aminated graphene oxide, which was used to construct redox initiator system with dibenzoyl peroxide for synthesis of poly(methyl methacrylate) grafted to graphene oxide by in situ polymerization. Nanocomposites used grafted polymer as fillers with loadings from 0.5 to 1.0 wt % of poly(methyl methacrylate) were obtained by solution blending. The structures, properties and morphology of graphene oxide, grafted poly(methyl methacrylate) and composites are characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectra, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical thermal analysis and bacterial adhesion examination respectively. The initial decomposition temperature and the glass transition temperature of the nanocomposites are improved by addition of grafted poly(methyl methacrylate). Furthermore, there is a significant enhancement of the decreasing of the surface bacterial adhesion of prepared nanocomposites.

A flexible route is developed for fabrication of large area α-Cu2S nanorod arrays (NRAs) on the basis of one-step laser ablation of a copper foil in CS2 liquid. It has been demonstrated that the obtained products are the high-temperature phase α-Cu2S and consist of the nanorods vertically standing on the Cu foil, exhibiting the array. The nanorods were about 1 μm in length and around 100 nm in thickness and built by stacking the nearly spherical and ⟨110⟩-oriented nanoparticles (NPs) up. Such array can be peeled off from the foil and remain freestanding. Further, it has been found that the ablation duration, the laser power, and the foil surface state are crucial to the formation of the Cu2S NRA. The formation of such oriented NP-stacked Cu2S NRAs is attributed to the laser-induced generation of α-Cu2S NPs and the NPs' deposition/oriented connection growth on the surface-vulcanized copper foil. Importantly, the visible photocurrent response of the α-Cu2S NRAs is 8 times higher than that of the Cu2S NPs' film with the equivalent thickness and also larger than that of previously reported Cu2S, showing significantly enhanced photoelectric performances. As an application, such NRAs have exhibited markedly enhanced visible photocatalytic activity and highly stable recycling performances, compared with the α-Cu2S NPs. Further studies have revealed that the enhanced performances are attributed to the structurally enhanced light trapping effect of the NRAs as well as short and smooth carrier diffusion path in the oriented NP-stacked nanorods. This work provides a new and simple method for fabrication of the large area Cu2S NRAs with high and stable photoelectric performances.

A flexible route is presented for the controlled decoration of the Au nanoparticles (NPs) on the spherical MoS2 particles, just by dropping the HAuCl4 aqueous solution into the hydrothermal reactio...

Strong sunlight harvesting and efficient charge separation are of great significances for solar energy utilization of metal oxides, but it is a challenge to realize these two aspects simultaneously. Here, we strategize oxygen-vacancy-rich (or defective)-SnO2 wrapped gold nanoparticles (Au@D-SnO2 NPs) for this. The designed NPs are fabricated just by adding precursors into boiling pre-prepared Au colloidal solution and then re-dispersing the reacted NPs in water, based on surface alloying and selective oxidation. Typically, the fabricated Au@D-SnO2 NPs (with 12 nm thick shell) exhibit strong absorption in full solar spectrum (200–2000 nm) with an energy absorption efficiency as high as 84%. Meanwhile, the photocurrent response of the typical NPs is 2.3 and 13.6 times as high as that of Au@SnO2 NPs (with poor oxygen vacancies) and commercial SnO2 NPs, respectively, showing efficient charge separation. Such excellent performance is attributed to the synergistic effect of surface plasmon resonance (SPR) of the Au core and the band gap narrowing induced by the abundant oxygen vacancies. Further, the excellent photocatalytic performance of the Au@D-SnO2 NP catalyst has been demonstrated via exemplary photocatalytic removal of gaseous ammonia. The catalytic rate is about 4.2 and 25 times as high as that of the Au@SnO2 NP and the commercial SnO2 NP catalysts, respectively. It is expected that such excellent photocatalytic performance will also be obtained on other defective oxides wrapped metal structures. This work provides a preparation method for Au@D-SnO2 NPs, which can be used for efficient solar energy utilization.

In order to study the interaction between the sodium dodecyl sulfate (SDS)/ n-hexylamine (NHA) composite aqueous solution, the supramolecular system had been constructed at the optimal molar ratio of 1:1 at high mass concentration. Based on the experimental results, supramolecular system formation mechanism was proposed according to the determination of its rheology, Cryo-TEM, Dynamic light scattering (DLS). SDS and NHA form vesicles via hydrogen bonding and electrostatic repulsion. The phase behavior of the system transforms from unilamellar vesicles under relative low mass concentration to multilamellar vesicles when the mass concentration increases to 200 mM. Meanwhile, temperature and inorganic salts were used to observe the effects of hydrogen bonding and electrostatic repulsion on vesicles. When temperature rises to 55℃, the vesicle basically disappears. When inorganic salt concentration reaches 150 mM, the vesicle gradually transforms into fibrous structure. From the perspective of fluidity state, the influence of temperature on vesicles is more than that of inorganic salts.

Surface single-atom tailoring of a gold nanoparticle, that is, adding, removing, or replacing one surface atom on a structure-resolved nanoparticle in a controlled manner, is very exciting yet challenging and has not been hitherto achieved. Herein we report the first realization of the introduction of a single sulfur atom onto the surface of the structure-unraveled Au60S6(SCH2Ph)36 nanoparticle. Single-crystal X-ray crystallography reveals that the as-obtained nanoparticle consists of one Au17 kernel protected by one Au20S3(SCH2Ph)18 and one unprecedented Au23S4(SCH2Ph)18 motif with the introduced sulfur atom included as a tetrahedral-coordinated μ4-S. The introduced sulfur leads to the changes of both internal structure and crystallographic arrangement. Unlike the case of 6HLH arrangement in Au60S6(SCH2Ph)36 crystals, the “ABAB” arrangement in Au60S7(SCH2Ph)36 crystals enhances the solid photoluminescence of amorphous Au60S7(SCH2Ph)36 and brings a slight redshift of the maximum emission. The extensive ne...

Controllable and flexible fabrication of ultrathin and uniform oxide layer-wrapped noble metal nanoparticles (NPs) has been expected. Here a new strategy is presented for them based on colloidal electrostatic attraction and self-assembly on the metal NPs via one-step laser ablation of noble metal targets in the hydrolysis-induced hydroxide sol solutions at room temperature. The Au NPs, with several tens of nanometers in size, are taken as core part and TiO2 as shell-layer to demonstrate the validity of the presented strategy. It has been shown that the TiO2 shell-wrapped Au NPs are obtained after laser ablation of Au target in the hydrolysis-induced Ti(OH)4 sol solution. The Au NPs are about 35 nm in mean size, and the TiO2 shell layers are amorphous in structure and about 2.5 nm in thickness. The shell thickness is nearly independent of the Au NPs’ size. Further experiments have shown that the thickness and crystallinity of the shell-layer can be tuned and controlled via changing the temperature or pH va...

Spherical MoS2 nanoparticles are fabricated by laser ablation of MoS2 target in water. The obtained nanoparticles are mostly nearly perfectly spherical in shape with smooth surface, and tens to hundreds of nanometers in diameters. Such spherical MoS2 nanoparticles are built by concentrically curved {002} planes and show onion-like structure. Further examination has revealed that there exist shrinkage cavities (or voids) in the central part of the MoS2 nanoparticles or small pores dispersed in the particles and a few tadpole-like long-tailed nanoparticles in the products, indicating the marks of melting and molten liquid droplets’ solidification during laser ablation. A model is thus presented based on laser-induced MoS2 liquid droplets’ generation and inward {002}-oriented growth via radial solidification, which reveals the growth mechanism of the spherical MoS2 nanoparticles with onion-like structure. Interestingly, such onion-like structured spherical MoS2 nanoparticles have exhibited much higher surfac...

A very simple route is developed for fast fabrication of nanosized amorphous titanium dioxide (TiO2) hollow spheres (THPs) just via dropping the pure four titanium chloride (TiCl4) liquid droplets into deionized water at around room temperature. The THPs, at around 80 nm in mean diameter, can be formed within a few seconds after dropping TiCl4 droplets into water. The shell layers of the obtained THPs are amorphous and porous in structure with a porosity of 58–80% and show a linear increase in thickness with the size of THPs. Further experiments have revealed that the reaction temperature, initial pH value, and size of the TiCl4 droplet are crucial to the formation, size, productivity, and microstructure of the THPs. A model is proposed on the basis of the fragmentation of liquid droplets, hydrolysis-induced formation, and inward growth of TiO2 shell layers, which can well describe the formation of the THPs. Importantly, such amorphous nanoscaled THPs have exhibited some strong hollow structure-enhanced p...

For a long time, there has been global concern over the environment and energy problems. Recently, the problems, which have brought about serious effect on the global living condition, have been in the “spotlight” and given impetus to the universal’s efforts to head for the same direction: stem the worst warming and strive for the renewable energy source. Hydrogen peroxide (H2O2) is undoubtedly a good choice, which holds the promise as a clean, efficient, safe and transferrable energy carrier. Octahedral coordination polymer, Cd3(C3N3S3)2, was found to be a robust photocatalyst for H2O2 generation under visible light irradiation. To further improve the H2O2 generation efficiency, adhering the octahedron to reduced graphene (rGO) was applied as the strategy herein. The study shows that by adhering Cd3(C3N3S3)2 to rGO, the formation of H2O2 is 2.5-fold enhanced and its deformation is concurrently suppressed. This work not only demonstrates the effectiveness of adhering Cd3(C3N3S3)2 polymer to rGO for the improvement of the polymer’s photocatalytic performance, but also proposes a general way for the fabrication of graphene/coordination compound hybrids for maximizing their synergy.

A simple synthetic route is presented for fabricating gold nanoparticle (NP)-decorated bismuth oxychloride (BiOCl) nanosheets in one step based on laser ablation of a gold target in a hydrochloric acid solution of bismuth nitrate without surfactant. After laser ablation, BiOCl nanosheets with attached Au NPs are obtained. The nanosheets are sub-micron in the planar dimension and around 20 nm thick, and the Au NPs are a mean size of approximately 20 nm. Further experiments reveal that such Au-NP-decorated nanosheets could be formed at a large Cl/Bi molar ratio range (0.01 to 3) in solution. The formation of the BiOCl nanosheets is attributed to the Au plasma plume-induced local fast hydrothermal reaction, which drives the planar growth of BiOCl. Importantly, these Au-NP-decorated BiOCl nanosheets exhibit high photodegradation activity on rhodamine B, a typical organic pollutant, compared with bare nanosheets under visible light irradiation, and show highly stable and recyclable performance. This is attributed to the plasmonic properties of Au NPs, which increase optical absorption and promote separation of electron-hole pairs in the NP-decorated BiOCl nanosheets. This work provides not only a new plasmonic photocatalyst for the oxidative degradation of organic pollutants, but also a general method for fabrication of the metal-NP-decorated nanosheets of other layer-structured oxychlorides.

A facile temperature regulation strategy is developed for fabrication of Au concave nanocrystals with specific shapes via seed-assisted growth at 25 °C or lower. It has been found that the reaction temperature, even with minor changes, can significantly influence the shape of the nanocrystals, which evolves from the concave trisoctahedral to calyptriform, coral and dendritic structures with the decrease of temperature from 25 °C to 5 °C. The size and optical absorbance spectra of the nanocrystals can be determined just by the addition amount of Au seeds. The formation of the Au concave nanocrystals is attributed to the preferential growth of the nuclei in 〈110〉 and 〈111〉 directions, along which the growth rates are of different temperature dependences. Importantly, the concave trisoctahedral and calyptriform Au nanocrystal-built films have exhibited strong surface enhanced Raman scattering (SERS) activity towards the lindane molecules, with the enhancement factor higher than 107, due to their high density of sharp corners/edges or the tip effect. The Raman peak intensity versus lindane concentration is subject to a linear double logarithmic relation from 30 ppb to 300 ppm, which is attributed to the Freundlich adsorption of lindane molecules on the Au nanocrystals. This work provides not only a simple route for the fabrication of the Au nanocrystals with various specific structures but also efficient SERS substrates for trace detection of organochlorine pesticide residues.

Rapid, ultrasensitive and reliable detection of mercury ions (Hg2+) by surface enhanced Raman spectroscopy (SERS) is of importance, but is restricted by the extremely low Raman cross section of the Hg2+. Here, we report a facile methodology that can realize such detection based on the organometallic Cu(CH4N2S)Cl · 0.5H2O nanobelts and SERS. In the assay, Hg2+ react with the nanobelts coated on a SERS active gold nanoparticle (NP) film to form ultrafine HgS NPs in situ. Subsequently, solid HgS is SERS determined to mirror the presence of Hg2+. Importantly, such detection is rapid and ultrasensitive. Within 10 min, limit of detection (LoD) of ppt level can be realized. The high detection efficiency is attributed to the superhydrophilicity, rich micropores and ultrathin nature of the organometallic nanobelts besides the strong SERS effect of Au NP film. In addition, this detection is highly resistant to various metal ions (Cu2+, Fe3+, Bi3+, Cr3+, Na+, Ni2+, Cd2+, etc) and is highly reliable in actual water (lake and tap water). Finally, influences of some substrate parameters and detection conditions on the test results are revealed. The optimal thickness of the gold NP film is about 80 nm, and the optimal wavelength of excitation light is about 633 nm. A small amount of Cu(CH4N2S)Cl · 0.5H2O nanobelts or a large volume of Hg2+ contaminated solution contributes to low LoDs. We believe that this work provides a rapid and sensitive detection for Hg2+.

In Enhanced oil recovery methods, CO2 is an excellent injecting fluid than water because of its prominent properties which includes non-flammability, non-polarity and non-toxicity. The reservoir pressure is over minimum miscibility pressure (MMP), it also provides for miscible displacement process of multi-contact. The CO2 injection process has been widely practiced in oil industry in the last decades. In the fractured or heterogeneous reservoirs, the injected gas will mostly passage through the fractures or high permeability layers which present the minimum flow resistance, leaving much of crude oil unrecovered in the low permeability rock-matrix. In this research, a composite polymer gel was proposed for harsh reservoir conditions, such as high salinity (NaCl 15.0 wt%, Ca2+ 0.8wt% and Mg2+ 0.8wt %), acid conditions (pH 3.25) and analyzed systematically at laboratory scale, consisting of polymer, cross linker and nanoparticles (silica dioxide). The gel system was characterized by different parameters like viscosity (μ), loss modulus (G″) and elastic modulus (G′) by varying polymer concentration, cross-linker concentration, silica dioxide (SiO2) concentration by using macro-rheology. The micro-rheology was used to calculate mean square displacement (MSD) and elasticity index (EI) of composite gel system. The bottle testing method was used for characterizing the gelation time of composite, gelation code and synergistic mechanism. The macro-rheological results of composite polymer gel proved that elastic modulus (G′) and loss modulus (G″) of composite gel system tends to increase with increment in silica dioxide (SiO2), polymer, cross linker and salinity concentrations. The results of G′ and G″ showed that composite gel have good elasticity at high salinity and acidic conditions. The gelation time observed was 6 days, which is sufficient to pump the gel into targeted zone. The gel code obtained was G at the temperature of 60°C. The elasticity index (EI) in micro-rheological results showed that gel has good elasticity, and MSD curve showed gelling fluid is elastic fluid and bears good stability. The composite polymer gel bears very low syneresis in acid conditions for 60 days at the temperature of 60°C, and having good thermal stability. The laboratory scale research indicates that newly formulated composite polymer gel can be efficiently applied to heterogeneous reservoirs for harsh reservoir conditions and CO2 shut-off problems, and can decrease the water or gas breakthrough problems by plugging the highly permeable channels and increasing the sweep efficiency from low permeable reservoir to produce the residual oil and ultimately increase the production of oil.

Profile control treatment is an effective technology to improve reservoir heterogeneity and decrease the watercut. Polymer gel has become the most widely used profile control agent. The most commonly used polymer in polymer gels is HPAM, which has poor adaptability in high temperature and high salinity reservoirs resulting in poor gel performance. Amphiphilic polymers have good viscosifying action in high temperature and high salinity reservoirs due to the polymer chain entanglement and hydrophobic chain association. In this paper, one amphiphilic polymer (PADC) was developed by introducing a betaine type functional monomer. In order to further improve the anti-temperature performance of PADC, the idea of using inorganic nanoparticles for enhancement was proposed. Based on this, a composite gel with good temperature and salt resistance was developed by adding crosslinking agent. The effects of nanosilica particle concentration, polymer concentration and crosslinking agent concentration on the gel performance of the composite gel were investigated systematically. The results showed that salt viscosifying action ability was related to the ionic strength. The higher the ionic strength, the larger the polymer molecular hydraulics radius. At the same time, the strength of hydrophobic association was improved and formed a denser spatial network structure. The synergistic effects made PADC have the characteristic of salt viscosifying action. It was also found that the viscoelasticity of the polymer solution changed from a viscous system to an elastic system by adding nano-silica, and apparent viscosity increased significantly. We have demonstrated that nano-silica surface will adsorb free polymer moleculesin solution, and form molecular brushes due to charge attraction and hydrogen bonding. The molecular brushes will adsorb and combine with the spatial network structure formed by the amphiphilic polymer. A significant improvement in the gel strength of composite polymer gel compared with organic polymer gel. Our work indicates that the composite gel based on amphiphilic polymer has significantly potential applications in high temperature and high salinity reservoirs, it has certain reference significance for stabilizing oil output and controlling water content for the similar reservoirs.

In order to improve the shear resistance of amphiphilic polymer gel, cyclodextrin polymer is selected to construct inclusion polymer gel named as CADC inclusion gel. The critical shear condition was determined to be 4000 rpm and 7 min through rheological method. Under this condition, variety of instruments such as rheometer, scanning electron microscope (SEM) were used to prove CADC inclusion gel has more excellent shear stability than amphiphilic polymer gel. This is because the cyclodextrin structure in CADC inclusion gel can reorganize amphiphilic polymer which has been broken via host-guest inclusion effect. At the same time, the sand pack tube was used to test plugging performance of the sheared CADC inclusion gel. The formation of such host-guest inclusion gel solves the problem of poor shear resistance ability of amphiphilic polymer gel. It has great potentials to replace the amphiphilic polymer gel for water shutoff applications in oilfield.

In order to investigate the effect of host-guest inclusion on the stability of emulsion, two host-guest inclusion complexes (CDP-APC16 and CDP-APP4 respectively) were constructed by using cyclodextrin polymer (CDP) and amphiphilic polymers(named APC16, APP4). The optimal inclusion ratios of APP4 and APC16 with CDP were explored and the O/W emulsion were prepared by APC16, APP4, CDP-APC16 and CDP-APP4. The stability of these four types of emulsion were analyzed by laser particle size analyzer and rheometer etc. The mechanism of inclusion complex emulsion stability was discussed by interfacial viscosity and interfacial viscoelasticity. The CDP including hydrophobic chain can form a more stable network structure and the free hydrophobic chain of CDP-APC16 easily insert into oil phase to emulsify the oil. The longer hydrophobic chain length of APC16 is easier to be included by CDP than that of APP4.Therefore, the CDP-APC16 inclusion complex emulsion show better stability. The inclusion complex shows a prospect application in tertiary oil recovery.

Polyimide/silver composite films were successfully prepared by in situ polymerization. A precursor, AgNO3 was used as the source of the silver nanoparticles. The structure and morphology of resulting films were characterized by FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Consequently, the silver nanoparticles were well dispersed in polyimide matrix. Meanwhile, thermal properties from thermal gravimetric analyses (TGA) and mechanical properties from tensile test which confirmed composites were kept good performance as compared to pure polyimide. In addition, the antimicrobial activity of polyimide/silver composite films against three different bacteria, B. subtilis, S. aureus, and E. coil, illustrated excellent activity. This composite is potential useful as antimicrobial material with good thermal performance in a wide variety of biomedical and general use applications.

The micro/nanostructured orderly porous In2O3 ultrathin film and its gas sensing devices are fabricated via the solution-dipping monolayer organic colloidal template. Such In2O3 thin film is of about 200 nm in the apparent thickness and ordered porous structure. The porous In2O3 film-based sensor has exhibited ultrahigh response to H2S at room temperature, more than two orders of magnitude higher than the previously reported highest value. Further experiments have demonstrated that the ambient humidity plays a crucial role in the ultra-highly enhanced gas sensing to H2S at room temperature. A sensing mechanism based on ambient humidity-induced H2S hydrolyzation is presented, including hydrolyzation-induced desorption of the chemisorbed oxygen and formation of water thin film on the In2O3 surface, which can well explain the ultrahigh sensing of In2O3 to H2S at room temperature. An In2O3-based gas sensor array is thus designed for quantitative detection of H2S in the real environment with common interferential gases. This work gives a systematic and deep study of the humidity effects on responses of the In2O3-based sensors to H2S, and reveals the sensing mechanism of In2O3 films to H2S at room temperature, indicating practical significance in designing and fabrication of the In2O3 film-based H2S sensors.

This paper mainly focuses on the synergistic effect of Sn and N dopants to enhance the photocatalytic performance of anatase TiO2 under visible light or simulated solar light irradiation. The Sn and N co-doped TiO2 (SNT-x) photocatalysts were successfully prepared by the facile sol-gel method and the post-nitridation route in the temperature range of 400-550 °C. All the as-prepared samples were characterized in detail by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, transmission electron microscopy, X-ray photoelectron and electron spin resonance spectroscopy and photoelectrochemical measurements. The characterization results reveal that the co-incorporation of Sn and N atoms remarkably modifies the electronic structure of TiO2, which gives rise to a prominent separation of photogenerated charge carriers and more efficient interfacial charge-transfer reactions in a photocatalytic process. The enhanced photocatalytic activity is attributed to the intensified active oxygen species including hydroxyl radicals (˙OH) and superoxide anion radicals (O2˙(-)) for degradation of organic pollutants. And the result of photocatalytic hydrogen production further confirms the existence of the synergistic effect in the SNT-x samples, because they exhibit higher photocatalytic activity than the sum of N/TiO2 and Sn/TiO2. This work provides a paradigm to consolidate the understanding of the synergistic effect of metal and non-metal co-doped TiO2 in domains of photocatalysis and photoelectrochemistry.

Emulsions stabilized by the supramolecular systems with sodium polyacrylic acid and amphiphilic polymers with different hydrophobic monomer contents were investigated. Multiple-light scattering was used to characterize the stability of emulsions. Optical microscopy and particle size analyzer were utilized to determine the droplet size distributions. The glass-etching micro model and microscopy were used to observe the emulsion stability in the porous media. To explore the stability mechanisms of emulsions, the rheology of the external phase and the oil/water interface were determined with the Physica MCR301 Rheometer. Emulsions formed by the supramolecular systems exhibit a better stability than the individual amphiphilic polymer systems. Moreover, the stability of emulsions formed by the supramolecular systems increases with the hydrophobic monomer content of amphiphilic polymers. The results can be attributed to the large viscous effect of the external phase and the high strength of the oil/water interfacial film in the emulsions. The results provide a theoretical foundation for future studies of the oil displacement efficiency by amphiphilic polymer supramolecular systems in tertiary oil recovery.

In recent years, with the further development of old oilfields, in order to further improve the oil recovery, they must be conformance controlled. Among various types of conformance control methods, polymer gels composed of polymers and crosslinkers have attracted widespread attention because of their efficiency and low costs. Among them, organic chromium gels with their good formation adaptability and high stability have been fully developed in recent decades. This review introduces the different types of polymers and crosslinkers used in the preparation of organic chromium gels, and the mechanisms of affecting their performance are analyzed. On this basis, the organic chromium gels for different formation conditions are introduced, including nanoparticle-reinforced and compound organic chromium gels. At the same time, evaluation methods of organic chromium gels are introduced, while the focus is on the in-situ measurement method (mirco-rheology) of gel formation time developed in recent decades. Based on the currently developed organic chromium gel and the analysis of the development status in oilfields, future directions like the use of supramolecular organic chromium gel and shear organic chromium gel are suggested.

Emulsion formation is inevitable during polymer flooding. In order to study the mechanism of the emulsion stability formed by inclusion complex and crude oil, the optimal inclusion ratio of inclusion complex was determined, and then, the properties of the emulsion such as particle size, stability, and interface film strength were tested by microscope, laser particle size analyzer, rheometer, and stability analyzer. Test results show that the addition of cyclodextrin polymer in inclusion complex have a positive effect on the stability of the emulsion. There are two main mechanisms which cyclodextrin polymers enhance the stability of emulsions. Firstly, with the addition of the cyclodextrin polymer, the viscosity of the external phase is increased, making it difficult for emulsion to coalesce and demulsify. Secondly, the cyclodextrin polymer and the hydrophobic chain of the amphiphilic polymer are adsorbed at the oil-water interface together, which enhances the interface film strength. The stability mechanism of the emulsion formed by the inclusion complex and crude oil has laid a foundation for its application in oil displacement.