Construction of Nickel Single Atoms by Using the Inherent Confined Space in Template-Occupied Mesoporous Silica.

Due to their maximum atomic use of metal sites, single-atom catalysts (SACs) exhibit excellent catalytic activity in a variety of reactions. Although many techniques have been reported for the production of SACs, the construction of single atoms through a convenient strategy is still challenging. Here, we provide a facile method to prepare nickel SACs by utilizing the inherent confined space between the template and silica walls in template-occupied mesoporous silica KIT-6 (TOK). After the introduction of nickel-containing precursors into the inherent confined space of the TOK by solid-phase grinding, Ni SACs can be produced promptly during calcination. Single Ni atoms create a covalent Ni-O-Si structure in the TOK, as indicated by density functional theory (DFT) calculations and experimental data. This synthetic approach is easy to scale up, and 10 g of sample can be effortlessly synthesized using ball milling. The resultant Ni SACs were applied to the oxygen evolution reaction and exhibited higher catalytic activity and stability than the comparative sample synthesized in the absence of confined space.

Efficient liquid phase photothermal catalysis realized by Ag2O/Bi4O5I2via heat-localization in a microreactor.

By constructing a Ag2O/Bi4O5I2 p-n heterojunction and applying a heat-localization microreactor, efficient photocatalysis enhanced by both photoinduced carrier separation and the photothermal effect was realized. This work focuses on the utilization of near-infrared light to broaden the absorption spectrum and accelerate the transportation of carriers. Through the production and localization of heat, it provides a novel thought for full-spectrum photocatalysis.

Elevating the Photocatalytic Performance of BiOCl by Promoting Light Utilization: From Co doping to the Microreactor.

Owing to its unique layered structure, BiOCl demonstrates high photocatalytic activity. However, its wide bandgap hinders the absorption of visible light. Doping modification is an effective method to expand the light absorption edge of photocatalysts by creating a doping energy level within the bandgap. Herein, Co as a variable valence element was used to dope the BiOCl nanosheets through a simple hydrothermal approach. As a result, the absorption edge of Co-BiOCl extends to the visible light region, and the photocatalytic performance was enhanced by 3.02 times. To overcome the shortcoming of photons being consumed easily in the bulk reactor, a planar microreactor was introduced to reduce the attenuation of light and accelerate the mass transfer. By comparison to the bulk reactor, a maximum of 15.3-fold additional activity promotion emerged. This work combines doping modification and reactor improvement to realize highly efficient photocatalysis in practical application.

Infrared light induced sustainable enhancement of photocatalytic efficiency by thermoelectric effect.

Hindering the recombination of photoinduced electron-hole pairs is of significance for enhancing photocatalytic performance. Applying a voltage to separate carriers offers an option to realize it. Thermoelectric materials own the ability to continuously sustain a voltage when a temperature difference exists between its two sides. However, maintaining the thermoelectric effect without wasting additional energy remains a challenge. Herein, a C3N4/Polyaniline/Poly(vinylidene fluoride) cilia array was fabricated to reach efficient photocatalysis through thermoelectric effect and photothermal effect. The cilia array structure offers more than 40% of light absorbance compared to the film. Hence, the infrared light in sunlight, which was usually omitted in photocatalysis, was transformed into heat. Through the unique design which draws upon the huge difference in thermal conductivity of air and water, a temperature gap was formed between the top and bottom sides of the cilia array by half-submerging it in water. Therefore, the photocatalytic efficiency was improved by 84.4%. This work achieves an energy-saving method to enhance photocatalytic performance by activating thermoelectric effect through infrared light, shedding light on the application of multi-modes enhanced photocatalysis.

Low-Energy Photons Dual Harvest for Photocatalytic Hydrogen Evolution: Bimodal Surface Plasma Resonance Related Synergism of Upconversion and Pyroelectricity.

Utilization of low-energy photons for efficient photocatalysis remains a challenging pursuit. Herein, a strategy is reported to boost the photocatalytic performance, by promoting low-energy photons dual harvest through bimodal surface plasmon resonance (SPR)-enhanced synergistically upconversion and pyroelectricity. It is achieved by introducing triplet-triplet annihilation upconversion (TTA-UC) materials and plasmonic material (Au nanorods, AuNRs) into composite fibers composed of pyroelectric substrate (poly(vinylidene fluoride)) and photocatalyst Cd0.5 Zn0.5 S. Interestingly, the dual combination of TTA-UC and AuNRs SPR in the presence of polyvinylidene fluoride substrate with pyroelectric property promotes the photocatalytic hydrogen evolution performance by 2.88 folds with the highest average apparent quantum yield of 7.0% under the low-energy light (λ > 475 nm), which far outweighs the role of separate application of TTA-UC (34%) and AuNRs SPR (76%). The presence of pyroelectricity plays an important role in the built-in electric field as well as the accordingly photogenerated carrier behavior in the composite photocatalytic materials, and the pyroelectricity can be affected by AuNRs with different morphologies, which is proved by the Kelvin probe force microscopy and photocurrent data. This work provides a new avenue for fully utilizing low-energy photons in the solar spectrum for improving photocatalytic performance.

Fly ash derived calcium silicate hydrate as a highly efficient and fast adsorbent for Cu(ii) ions: role of copolymer functionalization.

The environmental issues caused by heavy metal accumulation from polluted water are becoming serious and threaten human health and the ecosystem. The adsorption technology represented by calcium silicate hydrate has attracted much attention, but suffers from high manufacturing costs and poor stability bottlenecks. Here, we have proposed a "trash-to-treasure" conversion strategy to prepare a thin sheet calcium silicate hydrate material (ACSH) using solid waste fly ash as silicon source and a small amount of Acumer2000 as modifier. The obtained materials showed fast adsorption rates, superior adsorption capacities and remarkable long-term stability for Cu(ii) removal. Under the conditions of 0.5 g L-1 adsorbent concentration and 100 mL Cu(ii) solution with a concentration of 100 mg L-1, ACSH can adsorb 95.6% Cu(ii) within 5 min. The adsorption isotherms conformed to Langmuir models and the maximum adsorption capacity was 532 mg g-1. Using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, specific surface area and pore structure analysis, it was found that the excellent adsorption performance could be attributed to the ultrahigh surface area (356 m2 g-1), abundant pores and multiple active sites induced by Acumer2000 modification. Moreover, the encapsulation effect from carboxylate and long carbon chains in Acumer2000 endowed modified samples with strong corrosion resistance to CO2, which effectively inhibited the formation of by-product CaCO3 and retained the remarkable adsorption performance for more than 100 days. Interestingly enough, the advantages of ACSH in economy and performance could been maintained in ACSH based adsorptive membranes. This work is of great significance for solid waste utilization as well as the preparation of high quality, cost-effective and long-term stability calcium silicate hydrate materials.

Construction of an Interfacial Photocatalytic Mode Based on Carbonized Mushrooms to Enhance Infrared Light-Assisted Photocatalytic Water Splitting Performance.

To find a more efficient way to generate photocatalytic hydrogen, we developed the interfacial photocatalytic mode, in which the photocatalytic reaction can be transferred to a high-energy interfacial area. The new interfacial mode in this work is assembled with the help of carbonized mushrooms, which is an ideal water transporter as well as an excellent photothermal converter. The higher temperature from efficient light-to-heat conversion performance and thermal localization promote the efficiency of hydrogen evolution, and some effects peculiar to the interfacial mode can make the departure of hydrogen from the active sites of the photocatalyst smoother. As a result, the active sites can be exposed in a timely manner to allow the progress of the next cycle of the photocatalytic reaction to be smoother. The efficiency of interfacial photocatalytic hydrogen production can reach >10 times that of the corresponding sample in the traditional bulk water mode. This work has allowed further exploration of the construction of the interfacial photocatalytic mode, provided a reliable experimental basis for the development of the interfacial mode, and illuminated a new path for the development of photocatalytic water splitting.

Efficient photocatalytic H2production realized by MnxCd1-xSeIn situheterojunction.

Fast recombination of photoinduced carriers inhibits the performance of photocatalysts. By constructing heterojunctions, built-in electric fields can be formed to separate electrons and holes and finally enhance the photocatalytic efficiency. Herein, a MnxCd1-xSein situheterojunction was fabricated by a facile solvothermal method to draw upon this advantage. Absorption spectra show that the light absorption of CdSe raises up obviously after the doping of Mn2+. Best performance was achieved when the doping percent of Mn2+was 50%. This Mn0.5Cd0.5Se sample exhibits a 7.2 folds increase in hydrogen evolution against pure CdSe owing to the fast electron transportation. Moreover, it proves well stability in an 18 h cycling test and gains a 6.7% apparent quantum yield under 420 nm light. In summary, this work constructs anin situheterojunction to enhance the photocatalytic hydrogen evolution efficiency and sheds light on a feasible way for the application of photocatalysis.

Interfacial Design to Enhance Photocatalytic Hydrogen Evolution via Optimizing Energy and Mass Flows.

Energy and mass transfer in photocatalytic systems plays a significant role in photocatalytic water splitting, but relevant research has long been ignored. Here, an interfacial photocatalytic mode for photocatalytic hydrogen production is exploited to optimize the energy and mass flows and mainly includes a heat-insulating layer, a water-channel layer, and a photothermal photocatalytic layer. In this mode, the energy flow is optimized for efficient spreading, conversion, and utilization. A low-loss path (ultrathin water film) and an efficient heat localized zone are constructed, where light energy, especially infrared-light energy, can transfer to the target functional membrane surface with low loss and the thermal energy converted from light can be localized for further use. Meanwhile, the optimization of the mass flow is achieved by improving the desorption capacity of the products. The generated hydrogen bubbles can rapidly leave from the surface of the photocatalyst, along with the active sites being released timely. Consequently, the photocatalytic hydrogen production rate can be increased up to about 6.6 times that in a conventional photocatalytic mode. From the system design aspect, this work provides an efficient strategy to improve the performance of photocatalytic water splitting by optimizing the energy and mass flows.

Sustainable Internal Electric Field for Enhanced Photocatalysis: From Material Design to Energy Utilization.

The intrinsic internal electric field in a ferroelectric photocatalyst is beneficial for improving the photocatalytic properties because of its positive effect on the separation and migration of photogenerated carriers. However, this kind of internal electric field is static and easily saturated by inner and outer shielding effects, seriously restricting its potential in photocatalysis. To overcome this problem, a sustainable internal electric field was introduced into photocatalysis based on piezoelectric and pyroelectric effect, which exhibits good capability in consistently boosting photocatalytic activity, thus becoming a hot research topic. In this Perspective we summarize the recent significant progress in the construction of sustainable internal electric fields for facilitating photocatalysis from material design to energy utilization. Moreover, the fascinating influence of sustainable internal electric fields on carrier behavior is also discussed. Finally, a summary and outlook for building a sustainable internal electric field to further enhance photocatalytic performance are provided.

Biochemical Effects of Silver Nanomaterials in Human Hepatocellular Carcinoma (HepG2) Cells.

In dose-response and structure-activity studies, human hepatic HepG2 cells were exposed to between 0.01 and 300 ug/ml of different silver nanomaterials and AgNO3 for 3 days. Treatment chemicals included a custom synthesized rod shaped nano Ag, a glutathione capped nano Ag, polyvinylpyrrolidone (PVP) capped nano Ag (75 nm) from Nanocomposix and AgNO3. Various biochemical parameters were then evaluated to study cytotoxicity, cell growth, hepatic function and oxidative stress. Few indications of cytotoxicity were observed between 0.1 ug/ml and 6 ug/ml of any nano Ag. At 10 ug/ml and above, Ag containing nanomaterials caused a moderate to severe degree of cytotoxicity in HepG2 cells. Lactate dehydrogenase and aspartate transaminase activity alterations were the most sensitive cytotoxicity parameters. Some biochemical parameters were altered by exposures to both nano Ag and AgNO3 (statistically significant increases in alkaline phosphatase, gamma glutamyltranspeptidase, glutathione peroxidase and triglycerides; in contrast both glutathione reductase and HepG2 protein concentration were both decreased). Three parameters were significantly altered by nano Ag but not by AgNO3 (decreases in glucose 6-phosphate dehydrogenase and thioredoxin reductase and increases in catalase). Cytotoxicity per se did not appear to fully explain the patterns of biological responses observed. Some of the observations with the three nano Ag (increases in alkaline phosphatase, catalase, gamma glutamyltranspeptidase, as well as decreases in glucose 6-phosphate dehydrogenase and glutathione reductase) are in the same direction as HepG2 responses to other nanomaterials composed of TiO2, CeO2, SiO2, CuO and Cu. Therefore, these biochemical responses may be due to micropinocytosis of nanomaterials, membrane damage, oxidative stress and/or cytotoxicity. Decreased G6PDH (by all three nano Ag forms) and GRD activity (only nano Ag R did not cause decreases) support and are consistent with the oxidative stress theory of Ag nanomaterial action.

Construction of Infrared-Light-Responsive Photoinduced Carriers Driver for Enhanced Photocatalytic Hydrogen Evolution.

Infrared light, more than 50% of the solar light energy, is long-termly ignored in the photocatalysis field due to its low photon energy. Herein, infrared-light-responsive photoinduced carriers driver is first constructed taking advantage of pyroelectric effect for enhancing photocatalytic hydrogen evolution. In order to give full play to its role, the photocatalytic reaction is localized on the surface and interface of the composite based on a new semi-immersion type heat collected photocatalytic microfiber system. The system is consisted of distinctive pyroelectric substrate poly(vinylidene fluoride-co-hexafluropropylene (PVDF-HFP), typical photothermal material carbon nanotube (CNT), and representative photocatalyst CdS. The transient photocurrent, electrochemical impedance spectroscopy, time-resolved photoluminescence and pyroelectric potential characterizations indicate that the infrared-light-responsive carriers driver significantly promotes the photogenerated charge separation, accelerates carrier migration, and prolongs carrier lifetime. The photocatalytic hydrogen evolution efficiency is remarkably improved more than five times with the highest average apparent quantum yield of 16.9%. It may open up new horizons to photocatalytic technology for the more efficient use of infrared light.

Fabrication of Metal-Organic Frameworks inside Silica Nanopores with Significantly Enhanced Hydrostability and Catalytic Activity.

Because of their diverse structure, high porosity, and tunable functionality, metal-organic frameworks (MOFs) are of great interest for diverse applications, including catalysis. However, the poor hydrostability of most reported MOFs hinders their catalytic applications seriously. In addition, the development of an effective method to improve the catalytic activity of MOFs is another challenge. Here, we report for the first time the development of a double-solvent strategy to fabricate MOFs inside silica nanopores. A typical MOF (MOF-5) and a mesoporous silica with two-dimensional hexagonal pore regularity (SBA-15) were first attempted. The double-solvent strategy is based on a hydrophobic solvent and a hydrophilic solution containing MOF precursors with a volume equal to or less than the pore volume of the support so that the MOF can be formed selectively in the channels of support. Our results show that upon confinement in silica nanopores the hydrostability of MOF-5 is apparently improved. The framework of MOF-5 is destroyed obviously in a humid environment for 15 min, but that confined in SBA-15 is well preserved after 8 h. Moreover, the catalytic activity of the composite MOF-5@SBA-15 is superior to that of pure MOF-5 regarding activity and reaction rate. Under the catalysis of MOF-5@SBA-15, the conversion of benzyl bromide in the Friedel-Crafts alkylation reaction can reach 100% at 80 °C for 3 h, which is much higher than that of pure MOF-5 (61%) and SBA-15 (0%). We also demonstrate that the double-solvent strategy can be successfully extended to other MOFs, such as HKUST-1 and ZIF-8. Our work might open up an avenue for the improvement of stability and performance of MOFs, which is highly expected for a variety of applications.

Oriented Built-in Electric Field Introduced by Surface Gradient Diffusion Doping for Enhanced Photocatalytic H2 Evolution in CdS Nanorods.

Element doping has been extensively attempted to develop visible-light-driven photocatalysts, which introduces impurity levels and enhances light absorption. However, the dopants can also become recombination centers for photogenerated electrons and holes. To address the recombination challenge, we report a gradient phosphorus-doped CdS (CdS-P) homojunction nanostructure, creating an oriented built-in electric-field for efficient extraction of carriers from inside to surface of the photocatalyst. The apparent quantum efficiency (AQY) based on the cocatalyst-free photocatalyst is up to 8.2% at 420 nm while the H2 evolution rate boosts to 194.3 µmol·h-1·mg-1, which is 58.3 times higher than that of pristine CdS. This concept of oriented built-in electric field introduced by surface gradient diffusion doping should provide a new approach to design other types of semiconductor photocatalysts for efficient solar-to-chemical conversion.

Selectivity Enhancement in Heterogeneous Photocatalytic Transformations.

Photocatalysis has been invariably considered as an unselective process (especially in water) for a fairly long period of time, and the investigation on selective photocatalysis has been largely neglected. In recent years, the field of selective photocatalysis is developing rapidly and now extended to several newer applications. This review focuses on the overall strategies which can improve the selectivity of photocatalysis encompassing a wide variety of photocatalysts, and modifications thereof, as well as the related vital processes of industrial significance such as reduction and oxidation of organics, inorganics, and CO2 transformation. Comprehensive and successful strategies for enhancing the selectivity in photocatalysis are abridged to reinvigorate and stimulate future investigations. In addition, nonsemiconductor type photocatalysts, such as Ti-Si molecular sieves and carbon quantum dots (CQDs), are also briefly appraised in view of their special role in special selective photocatalysis, namely epoxidation reactions, among others. In the end, a summary and outlook on the challenges and future directions in the research field are included in the comprehensive review.

Controllable self-assembly of NaREF4 upconversion nanoparticles and their distinctive fluorescence properties.

The paper presents the growth of hexagonal NaYF4:Yb(3+), Tm(3+) nanocrystals with tunable sizes induced by different contents of doped Yb(3+) ions (10%-99.5%) using the thermal decomposition method. These nanoparticles, which have different sizes, are then self-assembled at the interface of cyclohexane and ethylene and transferred onto a normal glass slide. It is found that the size of nanoparticles directs their self-assembly. Due to the appropriate size of 40.5 nm, 15% Yb(3+) ions doped nanoparticles are able to be self-assembled into an ordered inorganic monolayer membrane with a large area of about 10 × 10 µm(2). More importantly, the obvious short-wave (300-500 nm) fluorescence improvement of the ordered 2D self-assembly structure is observed to be relative to disordered nanoparticles, which is because intrinsic absorption and scattering of upconversion nanoparticles leads to the self-loss of fluorescence, especially the short-wave fluorescence inside the disordered structure, and the relative emission of short-wave fluorescence is reduced. The construction of a 2D self-assembly structure can effectively avoid this and improve the radiated short-wave fluorescence, especially UV photons, and is able to direct the design of new types of solid-state optical materials in many fields.

A bio-inspired inner-motile photocatalyst film: a magnetically actuated artificial cilia photocatalyst.

A new type of inner-motile photocatalyst film is explored to enhance photocatalytic performance using magnetically actuated artificial cilia. The inner-motile photocatalyst film is capable of generating flow and mixing on the microscale because it produces a motion similar to that of natural cilia when it is subjected to a rotational magnetic field. Compared with traditional photocatalyst films, the inner-motile photocatalyst film exhibits the unique ability of microfluidic manipulation. It uses an impactful and self-contained design to accelerate interior mass transfer and desorption of degradation species. Moreover, the special cilia-like structures increase the surface area and light absorption. Consequently, the photocatalytic activity of the inner-motile photocatalyst film is dramatically improved to approximately 3.0 times that of the traditional planar film. The inner-motile photocatalyst film also exhibits high photocatalytic durability and can be reused several times with ease. Furthermore, this feasible yet versatile platform can be extended to other photocatalyst systems, such as TiO2, P25, ZnO, and Co3O4 systems, to improve their photocatalytic performance.

Expeditious organic-free assembly: morphologically controlled synthesis of iron oxides using microwaves.

A microwave hydrothermal method is developed for the synthesis of iron oxides, α-Fe2O3, ß-FeOOH, and the junction of α-Fe2O3-ß-FeOOH. This method is absolutely organic-free, and various structures could be obtained simply by changing the use of the iron source and NaOH. The as-prepared sea urchin-like ß-FeOOH exhibits excellent catalytic performance for the degradation of methylene blue (MB) in the presence of H2O2.

Legionella pneumophila transcriptional response following exposure to CuO nanoparticles.

Copper ions are an effective antimicrobial agent used to control Legionnaires' disease and Pontiac fever arising from institutional drinking water systems. Here, we present data on an alternative bactericidal agent, copper oxide nanoparticles (CuO-NPs), and its efficacy on Legionella pneumophila. In broth cultures, the CuO-NPs caused growth inhibition, which appeared to be concentration and exposure time dependent. The transcriptomic response of L. pneumophila to CuO-NP exposure was investigated by using a whole-genome microarray. The expression of genes involved in metabolism, transcription, translation, DNA replication and repair, and unknown/hypothetical proteins was significantly affected by exposure to CuO-NPs. In addition, expression of 21 virulence genes was also affected by exposure to CuO-NP and further evaluated by quantitative reverse transcription-PCR (qRT-PCR). Some virulence gene responses occurred immediately and transiently after addition of CuO-NPs to the cells and faded rapidly (icmV, icmW, lepA), while expression of other genes increased within 6 h (ceg29, legLC8, legP, lem19, lem24, lpg1689, and rtxA), 12 h (cegC1, dotA, enhC, htpX, icmE, pvcA, and sidF), and 24 h (legP, lem19, and ceg19), but for most of the genes tested, expression was reduced after 24 h of exposure. Genes like ceg29 and rtxA appeared to be the most responsive to CuO-NP exposures and along with other genes identified in this study may prove useful to monitor and manage the impact of drinking water disinfection on L. pneumophila.

Speedy fabrication of diameter-controlled Ag nanowires using glycerol under microwave irradiation conditions.

Diameter-controlled Ag nanowires were rapidly fabricated (1 min) using inexpensive, abundant, and environmentally-friendly glycerol as both a reductant and solvent under non-stirred microwave irradiation conditions; no Ag particles were formed using conventional heating methods. The temperature and pressure of the reaction systems were monitored to investigate the role of microwaves in the assembly of nanowires.