Z-Scheme Modulated Charge Transfer on InVO4 @ZnIn2 S4 for Durable Overall Water Splitting.

The charge transfer within heterojunction is crucial for the efficiency and stability of photocatalyst for overall water splitting (OWS). Herein, InVO4 nanosheets have been employed as a support for the lateral epitaxial growth of ZnIn2 S4 nanosheets to produce hierarchical InVO4 @ZnIn2 S4 (InVZ) heterojunctions. The distinct branching heterostructure facilitates active site exposure and mass transfer, further boosting the participation of ZnIn2 S4 and InVO4 for proton reduction and water oxidation, respectively. The unique Z-scheme modulated charge transfer, visualized by simulation and in situ analysis, has been proved to promote the spatial separation of photoexcited charges and strengthen the anti-photocorrosion capability of InVZ. The optimized InVZ heterojunction presents improved OWS (153.3 µmol h-1  g-1 for H2 and 76.9 µmol h-1  g-1 for O2 ) and competitive H2 production (21090 µmol h-1  g-1 ). Even after 20 times (100 h) of cycle experiment, it still holds more than 88% OWS activity and a complete structure.

Incorporation of dumbbell-shaped and Y-shaped cross-linkers in adjustable pullulan/polydopamine hydrogels for selective adsorption of cationic dyes.

Hydrogel adsorbents have attracted considerable attention due to their sludge minimization, good water permeability and renewable performance. Here, a promising strategy for the one-step preparation of pullulan/polydopamine hybird hydrogels (PPGels) was presented. Dumbbell-shaped cross-linker neopentyl glycol diglycidyl ether (NGDE, 2 arms) and Y-shaped cross-linker trimethylolpropane triglycidyl ether (TTE, 3 arms) were selected to study the relationship between cross-linker structure and hydrogel performances. The NGDE possessing less molecular repulsive force and higher reactivity demonstrated more effective cross-linking with the pullulan, which leaded to a decrease in pore size of the hydrogel. Meanwhile, the introduction of polydopamine significantly enhanced the adsorption ability and gave the resulting hybrid gel the specific selectivity toward cationic dyes (96 mg/g for crystal violet, 25.8 mg/g for methylene blue and barely not adsorption for azophloxine). Our data suggested that the electrostatic interaction played a vital role in the dye adsorption process, and the adsorption data could be explained by pseudo-second-order model and Langmuir isotherm model. Furthermore, the obtained PPGel could be easily separated after adsorption. This study describes the relationship between cross-linker structure and properties of pullulan/polydopamine hybrid gels, which provides a new strategy to create polysaccharide-based adsorbents for wastewater remediation.

Ultrathin ZnIn2 S4 Nanosheets Anchored on Ti3 C2 TX MXene for Photocatalytic H2 Evolution.

Photocatalysts derived from semiconductor heterojunctions that harvest solar energy and catalyze reactions still suffer from low solar-to-hydrogen conversion efficiency. Now, MXene (Ti3 C2 TX ) nanosheets (MNs) are used to support the in situ growth of ultrathin ZnIn2 S4 nanosheets (UZNs), producing sandwich-like hierarchical heterostructures (UZNs-MNs-UZNs) for efficient photocatalytic H2 evolution. Opportune lateral epitaxy of UZNs on the surface of MNs improves specific surface area, pore diameter, and hydrophilicity of the resulting materials, all of which could be beneficial to the photocatalytic activity. Owing to the Schottky junction and ultrathin 2D structures of UZNs and MNs, the heterostructures could effectively suppress photoexcited electron-hole recombination and boost photoexcited charge transfer and separation. The heterostructure photocatalyst exhibits improved photocatalytic H2 evolution performance (6.6 times higher than pristine ZnIn2 S4 ) and excellent stability.

Dramatic red fluorescence enhancement and emission red shift of carbon dots following Zn/ZnO decoration.

Metal atom doping, an easy and convenient method, can optimize and tune the physical-chemical properties and photometrics of carbon dots (CDs). However, there are few reports on the preparation of metal-decorated CDs that give red emission and a high photoluminescence quantum yield (PLQY). Here, we demonstrate a zinc (existing in human body) ion-doping strategy to observably enhance the PLQY and lengthen the CD emission wavelength. The prepared Zn/ZnO-decorated CDs (Zn-CDs) produced red fluorescence (623 nm) with a superior PLQY of 40.3%. Through a series of analyses, Zn-CDs were confirmed to contain an oxidation state and reduction state of Zn doping into the internal defects and surface of Zn-CDs. More valuably, the Zn-CDs had excellent chemical stability, photo-stability, long-term storage stability, and high biocompatibility, and therefore could be used as a robust red fluorescence probe for high-quality cellular imaging.

Nitrogen-doped carbon dots as a fluorescent probe for the highly sensitive detection of Ag+ and cell imaging.

An easy hydrothermal synthesis strategy was applied to synthesize green-yellow emitting nitrogen-doped carbon dots (N-CDs) using 1,2-diaminobenzene as the carbon source, and dicyandiamide as the dopant. The nitrogen-doped CDs resulted in improvement in the electronic characteristics and surface chemical activities. N-CDs exhibited bright fluorescence emission and could response to Ag+ selectively and sensitively. Other ions produced nearly no interference. A N-CDs based fluorescent probe was then applied to sensitively determine Ag+ with a detection limit of 5 × 10-8  mol/L. The method was applied to the determination of Ag+ dissolved in water. Finally, negligibly cytotoxic, excellently biocompatibile, and highly fluorescent carbon dots were applied for HepG2 cell imaging and the quenched fluorescence by adding Ag+ , which indicated its potential applications.

Salecan-Based pH-Sensitive Hydrogels for Insulin Delivery.

Stimuli-responsive polymeric hydrogels are promising and appealing delivery vehicles for protein/peptide drugs and have made protein/peptide delivery with both dosage- and spatiotemporal-controlled manners possible. Here a series of new Salecan-based pH-sensitive hydrogels were fabricated for controlled insulin delivery via the graft copolymerization reaction between Salecan and 2-acrylamido-2-methyl-1-propanesulfonic acid. In this study, on one hand, Salecan played a key role in modifying the structure and the pore size of the developing hydrogel. On the other hand, Salecan tuned the water content and the water release rate of the obtained hydrogel, leading to a controllable release rate of the insulin. More importantly, in vitro release experiments validated that the release of insulin from this intelligent system could be also tailored by the environmental pH of the release medium. For SGA2, the amount of encapsulated insulin released at gastric conditions (pH 1.2) was relatively low (about 26.1 wt % in 24 h), while that released at intestinal conditions (pH 7.4) increased significantly (over 50 wt % in 6 h). Furthermore, toxicity assays demonstrated that the designed hydrogel carriers were biocompatible. These characteristics make the Salecan-based hydrogel a promising candidate for protein/peptide drug delivery device.

Interfacial tuning in FeP/ZnIn2S4 Ohm heterojunction: Enhanced photocatalytic hydrogen production via Zn-P charge bridging.

Interfacial regulation is key to photocatalytic performance, yet modulating interfacial charge transfer in heterostructures remains challenging. Herein, a novel nanoflower-like FeP/ZnIn2S4 Ohm heterostructure is first designed, with Zn atoms in ZnIn2S4 (ZIS) acting as potential anchoring sites around P atoms, forming liganded Zn-P bonds. Combining 1D FeP nanowires and 2D ZIS nanosheets enhances the mobility of photogenerated electrons. The synergistic chain-type "electron pickup" mechanism of the Ohm heterojunction coupled with the Zn-P bond speeds up electron transport at the interface. The Ohm heterojunction initiates an internal electric field, creating a driving force to further transfer photogenerated electrons through the Zn-P rapid electron transport channel to FeP, which acts as a reservoir for active sites to release H2. The optimized FeP/ZIS demonstrates a remarkable H2 evolution rate at 4.36 mmol h-1 g-1, 3.6 times that of pristine ZIS. This work provides novel insights into optimizing photocarrier dynamics via interfacial microenvironment modulation.

Boosted visible-light-driven degradation over stable ternary heterojunction as a plasmonic photocatalyst: Mechanism exploration, pathway and toxicity evaluation.

The incorporation of plasmonic metals into semiconductors forming heterojunction photocatalysts is a promising route to enhance the photocatalytic performance in visible light. In this work, we reported the visible-light-driven one-dimensional (1D) nanostick silver/silver sulfide (Ag/Ag2S) photocatalyst combining with two-dimensional (2D) nanosheet reduced graphene oxide intersected by hollow structure (h-RGO) was prepared via a feasible approach at room temperature. The density of Ag depositing on the surface of Ag2S was easily tuned by the concentration of sodium borohydride and the silicon dioxide nanospheres were employed as templates in the preparation of h-RGO by the layer-by-layer (LBL) assembly. The ternary plasmonic Ag/Ag2S/h-RGO photocatalysts exhibited better photocatalytic performance for degradation of naphthalene (95.95%) and 1-naphthol (98.65%) under visible light than the pure Ag2S, composite Ag/Ag2S and composite Ag/Ag2S/RGO. Localized surface plasmon resonance of Ag, heterojunction formed between Ag/Ag2S and RGO and the unique characteristics of h-RGO, which included higher specific surface areas, more efficient reflections of light and more active sites than RGO for boosting separation efficiency of charge carriers, were all responsible for such enhancement. By combining the characterization results with various computations, the mechanism, potential degradation pathways and the toxicity of the generated intermediates for photodegradation were examined. In addition to offering profound insight into the expansion of effective plasmonic photocatalysts with novel structures, the current study is beneficial to ease the environmental crisis to a certain extent.

Insights into the role of ·OH generated in Fe2+/CaO2/coal slime system for efficient extracellular polymeric substances degradation to improve dewaterability of sewage sludge.

The disposal of massive sewage sludge and coal slime is a problem facing municipalities in China. A hypothesis for the co-disposal of sludge and coal slime is proposed to improve dewaterability by utilizing the beneficial role of coal slime as a filter assist and CaO2 enhanced system in this research. Results showed that capillary suction time, specific resistance to filtration and water content decreased dramatically from 49.3 s, 13.2 × 1012 m/kg and 84.85% to 19.1 s, 1.0 × 1012 m/kg and 50.07%, respectively, under the optimal conditions with 0.3/0.1/0.3-Fe2+/CaO2/coal slime g/g DS. The hydroxyl radicals generated in the Fe2+/CaO2 process acted on extracellular polymeric substances (EPS), resulting in a drop in the ratio of α-helix/(ß-sheet + random coil) in the secondary structure of EPS proteins and a reduction in the concentration of aromatic proteins and tryptophan-like substances in TB-EPS, thereby enhancing the sludge dewaterability. Furthermore, coal slime as the skeleton building material induced a rise in sludge particle size and contact angle, lowering the hydrophilicity, compressibility of sludge and providing more channels to facilitate water flow. This work verified the promising application prospect of the Fe2+/CaO2/coal slime combined system in the enhancement of sludge dewaterability.

Photocatalytic degradation mechanism of phenanthrene over visible light driven plasmonic Ag/Ag3PO4/g-C3N4 heterojunction nanocomposite.

Visible light driven plasmonic Ag/Ag3PO4/g-C3N4 heterojunction nanocomposite with regular morphology was prepared via a modified facile method. The two-dimensional ultrathin g-C3N4 nanosheet is uniformly wrapped on the surface of Ag3PO4 nanopolyhedron. A charge transfer bridge was built between Ag3PO4 nanopolyhedron and g-C3N4 nanosheet due to the reduction of Ag nanoparticles. This structure can inhibit the recombination of photogenerated electron-hole pairs and promote the transfer of photogenerated carriers, so as to produce more active species for participating in the photocatalytic reaction. In addition, the surface plasmon resonance (SPR) of appropriate Ag nanoparticles enhanced the absorption and utilization of visible light. Compared with Ag3PO4 and Ag/Ag3PO4, Ag/Ag3PO4/g-C3N4 showed higher photocatalytic activity. Under visible light irradiation, the degradation rate of phenanthrene (PHE) was 0.01756 min-1, which was 3.14 times and 2.38 times that of Ag3PO4 and Ag/Ag3PO4, respectively. After four cycles of photocatalytic reaction, the Ag/Ag3PO4/g-C3N4 photocatalyst still maintained high photocatalytic activity. The active sites of PHE were predicted by Gaussian simulation calculation and combined with intermediate products identification of GC-MS, the possible degradation pathway of PHE was speculated. This research has reference significance for the construction of plasmonic heterojunction photocatalyst in the field of environmental pollution remediation.

Sheet-on-sheet TiO2/Bi2MoO6 heterostructure for enhanced photocatalytic amoxicillin degradation.

Developing sheet-on-sheet (2D/2D) heterostructure with built-in electric field (BIEF) is effective in boosting the performance of photocatalysts for emerging contaminants degradation. Herein, the 2D/2D microtopography and (-)TiO2/(+)Bi2MoO6 BIEF were precisely integrated into hierarchical nanosheets, which can provide the basis and driving force for charge transfer both in in-plane and interface of heterojunction. The prepared photocatalyst (TiO2/Bi2MoO6) showed high-efficiency and stable performance for photocatalytic amoxicillin (AMX) degradation, which was 18.2 and 5.7 times higher than TiO2 and Bi2MoO6, respectively. More importantly, TiO2/Bi2MoO6 showed more efficient photocatalytic activity and photogenerated charge separation than TiO2@Bi2MoO6 (different morphology). Besides, four possible pathways of AMX degradation were proposed depending on Gaussian calculations and intermediates analysis by GC-MS and HPLC-TOFMS. This work sheds light on the design and construction of unique 2D/2D heterostructure photocatalysts for AMX degradation.

Efficient Noble-Metal-Free Catalysts Supported by Three-Dimensional Ordered Hierarchical Porous Carbon.

Development of heterogeneous catalysts has attracted increasing attention, owing to their remarkable catalytic performance and recyclability. Herein, we report well-developed heterogeneous catalysts with a three-dimensional ordered hierarchical structure, constructed from nickel or cobalt nanoparticles embedded in porous carbon. The obtained catalysts were fully characterized by several techniques. On account of the uniform distribution of metal nanoparticles in the porous carbon matrix and large diffusion channels that allow for effective mass transport, the catalysts exhibited superior catalytic performance for styrene epoxidation reaction. In particular, the catalysts showed good catalytic activity, high selectivity and excellent recyclability toward the styrene epoxidation. Thus, this facile approach developed allows for fabricating advanced heterogeneous catalysts with high catalytic activities for useful practical applications.

Naphthalene-benzoindole derived two novel fluorometric pH-Responsive probes for environmental systems and bioimaging.

In this work, we designed a kind of novel fluorescent probes based on naphthalene-benzoindole conjugate derived for sensitively monitoring the pH fluctuation in environment and biological systems. In the spectral method, these two probes both show significant red shift, color change and fluorescence quenching due to the effect of intramolecular charge transfer (ICT) mechanism. Moreover, we found that the probe bearing with carboxyl group displayed a more hydrophilicity than the one bearing with hydrogen atom instead, and the former exhibits a faster response and higher fluorescence intensity. Besides, the probe bearing with carboxyl group shows lower cytotoxicity, evidences by the vitro study. It indicates that this probe has great potential in application in living cell imaging as well as pH-fluctuation monitoring.

Fenton-like catalyst Fe3O4@polydopamine-MnO2 for enhancing removal of methylene blue in wastewater.

Fenton technology has been proven an effective way to remove dyes from wastewater. However, the demanding pH of reaction condition restricted its wide application. In this study, we report a novel Fenton-like catalyst (Fe3O4@PDA-MnO2) facilely synthesized by polydopamine (PDA) coating and MnO2 depositing onto the surface of Fe3O4 nanoparticles. This method for preparing magnetic Fe3O4@PDA-MnO2 catalyst could avoid the agglomeration of MnO2 nanoparticles and make the catalyst collect easily from the solution. The resultant Fe3O4@PDA-MnO2 nanoparticles possess core-shell nanostructure. Fe3O4@PDA-MnO2 catalyst could cooperate with hydrogen peroxide to form a Fenton-like reagent for the removal of methylene blue (MB) and performed excellent catalytic activities towards MB, including high degradation efficiency of 97.36% after 240 min. Besides, Fe3O4@PDA-MnO2 can retain excellent reusability after 5 using-cycles. More importantly, the catalyst can be used in a wide pH range from 2 to 12 in Fenton systems, demonstrating that the degradation process is independent on pH which is different from most reported studies. Also, Fe3O4@PDA-MnO2 could still keep more than 75% removal efficiency of MB in industrial wastewater treatment application. Therefore, the synthesized Fe3O4@PDA-MnO2 would be a promising device for the removal of dyes from wastewater.

Polysaccharide metallohydrogel obtained from Salecan and trivalent chromium: Synthesis and characterization.

Here, a new kind of Salecan derived polysaccharide metallohydrogel was reported. Successful fabrication of Salecan metallohydrogel was verified by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and rheological measurements. Scanning electron microscope investigations have been conducted to elucidate the morphology of Salecan/Cr3+ gel (SCgel). We found that the pore size of metallohydrogel can be tailored by adjusting the Cr3+ dose during gel formation. After that, swelling and de-swelling behaviors were systematically studied. The increasing of chromium ion concentration and the presence of saline solutions will cause the decrease of swelling percentage. It is assumed that the decreasing hydrophilicity of Salecan, the increase of crosslinking density, and the complexation of the carboxylate group with saline ions are the main syneresis mechanisms. Altogether, this study opens a new avenue to prapare Salecan-based hydrogel.

Selective determination of Ag+ using Salecan derived nitrogen doped carbon dots as a fluorescent probe.

We report that nitrogen doped carbon dots (N-CDs) represent a viable fluorescent probe for the determination of Ag+. The N-CDs can be fairly easily prepared by a hydrothermal treatment method using Salecan and dicyandiamide as the precursors, display excitation/emission maxima of 350/438nm. The N-CDs have an average diameter of about 3.8nm. The N-CDs exhibited blue fluorescence (quantum yield of 13.2%) and could response to Ag+ selectively and sensitively. Other ions nearly had no interference. The probe has excellent selectivity, high sensitivity, and a linear response range that extends from 0 to 40µM. The limit of detection is as low as 1.12×10-7mol/L. The method was applied to the determination of Ag+ dissolved in water.

Preparation of a Salecan/poly(2-acrylamido-2-methylpropanosulfonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride) Semi-IPN Hydrogel for Drug Delivery.

Salecan is a water-soluble bacterial polysaccharide consisting of glucopyranosyl units linked by α-1,3 and ß-1,3 glycosidic bonds. salecan is suitable for the development of hydrogels for biomedical applications, given its outstanding physicochemical and biological profiles. In this study we designed a new semi-interpenetrating polymer network hydrogel that introduces the salecan polysaccharide into a stimuli-responsive poly(2-acrylamido-2-methylpropanosulfonic acid-co-[2-(methacryloxy)ethyl]trimethylammonium chloride) (PAM) hydrogel matrix for controlled insulin release. We found that salecan not only tunes the structure and pore size of the PAM hydrogels, but also endows them with adjustable water release rates. More importantly, in vitro drug loading/release assays demonstrated that insulin is efficiently loaded into the resulting hydrogels and can be released in an on-demand manner by controlling the pH and salecan dose. Furthermore, cell viability and cell adhesion experiments verified the cell compatibility of these hydrogel carriers. Together, these results make salecan-incorporated PAM hydrogels promising materials for drug delivery.

Design of Salecan-containing semi-IPN hydrogel for amoxicillin delivery.

Salecan is a new linear extracellular ß-glucan. The unique structure and beneficial properties of Salecan makes it an appealing material in biomedical applications. In this work, novel drug devices based on Salecan in a hydrogel matrix of poly(N-(3-dimethylaminopropyl)acrylamide-co-acrylamide) (Salecan/PDA) were fabricated via free radical polymerization for controlled release of amoxicillin. It was demonstrated that amoxicillin was efficiently encapsulated into the developed hydrogels and released in a Salecan dose-dependent and pH-sensitive manner. Furthermore, cell toxicity and adhesion assays confirmed that these drug carriers were biocompatible. Altogether, this study opens a new avenue to fabricate hydrogel devices for controlled delivery of drug.

Synthesis and characterization of a novel cationic hydrogel base on salecan-g-PMAPTAC.

Salecan is a biological macromolecular and biocompatible polysaccharide that has been investigated for recent years. Herein, we report a novel cationic hydrogel fabricated by graft-polymerizing 3-(methacryloylamino)propyl-trimethylammonium chloride (MAPTAC) onto salecan chains. The obtained hydrogels were transparent, solid-elastic, macro-porous, ion-sensitive, and non-cytotoxic. The swelling ratios increased with salecan content, while mechanical strength does the opposite. Moreover, drug delivery test was studied as a potential application. Diclofenac sodium (DS) and insulin were selected as model drugs. Interestingly, in drug loading process, DS molecules exhibited highly affinity to these cationic hydrogels. Almost all the DS molecules in loading solution were absorbed and spread into the hydrogel. For drug release profiles, insulin-loaded hydrogel showed an initial rapid release and a sustained release. As a comparison, DS-loaded hydrogel exhibited a more sustained release profile. Results suggested salecan-g-PMAPTAC hydrogel could be a good candidate for anionic drug loading and delivery.

Synthesis and characterization of a multi-sensitive polysaccharide hydrogel for drug delivery.

Salecan is a novel water soluble polysaccharide produced by a salt-tolerant strain Agrobacterium sp. ZX09. Poly(dimethylaminoethyl methacrylate) (PDMAEMA) is a pH, thermo, and ionic strength multi-sensitive polymer with anti-bacterial property. Here, we report a semi-interpenetrating polymer network (semi-IPN) hydrogel based on salecan and PDMAEMA. The obtained hydrogel is simultaneous sensitive to pH, ionic strength and temperature: the swelling ratio maximizes at pH 1.2 and shrinks at pH value greater than 3; besides, water content of the hydrogel decreases as the ionic strength increases; in terms of temperature, the hydrogel swells/deswells at temperatures below/above 40°C. Cytotoxicity test shows the hydrogel is non-cytotoxic to COS-7 cells. Protein drug insulin was selected as model drug to test the in vitro release behavior of the hydrogel. Results show the release rate increases with the swelling ratio of the hydrogel. In addition, when the temperature is higher than the lower critical solution temperature (LCST) of PDMAEMA, the hydrogel shrinks to extrude more drug molecules. Moreover, the release rate and release amount were higher in acid condition (pH 1.2) than at pH 7.4. In summary, this polysaccharide hydrogel is a promising material for drug delivery.