Decade Milestone Advancement of Defect-Engineered g-C3N4 for Solar Catalytic Applications.

Over the past decade, graphitic carbon nitride (g-C3N4) has emerged as a universal photocatalyst toward various sustainable carbo-neutral technologies. Despite solar applications discrepancy, g-C3N4 is still confronted with a general fatal issue of insufficient supply of thermodynamically active photocarriers due to its inferior solar harvesting ability and sluggish charge transfer dynamics. Fortunately, this could be significantly alleviated by the "all-in-one" defect engineering strategy, which enables a simultaneous amelioration of both textural uniqueness and intrinsic electronic band structures. To this end, we have summarized an unprecedently comprehensive discussion on defect controls including the vacancy/non-metallic dopant creation with optimized electronic band structure and electronic density, metallic doping with ultra-active coordinated environment (M-Nx, M-C2N2, M-O bonding), functional group grafting with optimized band structure, and promoted crystallinity with extended conjugation π system with weakened interlayered van der Waals interaction. Among them, the defect states induced by various defect types such as N vacancy, P/S/halogen dopants, and cyano group in boosting solar harvesting and accelerating photocarrier transfer have also been emphasized. More importantly, the shallow defect traps identified by femtosecond transient absorption spectra (fs-TAS) have also been highlighted. It is believed that this review would pave the way for future readers with a unique insight into a more precise defective g-C3N4 "customization", motivating more profound thinking and flourishing research outputs on g-C3N4-based photocatalysis.

Precise Defect Engineering on Graphitic Carbon Nitrides for Boosted Solar H2 Production.

Defect engineering has been regarded as an "all-in-one strategy" to alleviate the insufficient solar utilization in g-C3 N4 . However, without appropriate modification, the defect benefits will be partly offset due to the formation of deep localized defect states and deteriorated surface states, lowering the photocarrier separation efficiency. To this end, the defective g-C3 N4 is designed with both S dopants and N vacancies via a dual-solvent-assisted synthetic approach. The precise defect control is realized by the addition of ethylene glycol (EG) into precursor formation and molten sulfur into the pyrolysis process, which simultaneously induced g-C3N4. with shallow defect states. These shallow defect energy levels can act as a temporary electron reservoir, which are critical to evoke the migrated electrons from CB with a moderate trapping ability, thus suppressing the bulky photocarrier recombination. Additionally, the optimized surface states of DCN-ES are also demonstrated by the highest electron-trapping resistance (Rtrapping ) of 9.56 × 103 Ω cm2 and the slowest decay kinetics of surface carriers (0.057 s-1 ), which guaranteed the smooth surface charge transfer rather than being the recombination sites. As a result, DCN-ES exhibited a superior H2 evolution rate of 4219.9 µmol g-1 h-1 , which is 29.1-fold higher than unmodified g-C3 N4 .

Tailoring activation of CoNiO nanoparticles/porous carbon nanofibers by atomic doping for high performance supercapacitors.

Metal-organic framework (MOF) materials are rich in active sites and have a high specific surface area, which make them potential electrode materials. In this work, a simple immersion method combined with a carbonization treatment process is applied to prepare MOF derived composite materials (CoNiO/PCNFs). Among them, cobalt-based MOFs (Co-MOFs) are selected as the precursor and doped with Ni atoms, and the ratio of Co and Ni is tailored to acquire a high-performance electrode. The electrochemical results show that when the ratio of Co to Ni is 2 : 2, the prepared CoNiO/PCNFs-2 electrode has high capacitance (912.4 F g-1 at 1 A g-1) and superior rate capability (retention is above 50% at 100 A g-1). Additionally, it is highly stable at 20 A g-1 (nearly no degradation after 6000 cycles). Density Functional Theory (DFT) calculations indicate that the Ni doping models present lower formation energy and better -OH group adsorption properties. Moreover, the density of electronic state (DOS) and differential charge density distribution demonstrate that Ni doping effectively enhances the charge transport during the charging and discharging processes, which is beneficial to enhance the energy storage of the electrode materials. In conclusion, this work presents a strategy to design MOF-derived composite electrodes. The experimental tests and theoretical calculations explore the energy storage process and prove that the CoNiO/PCNF electrode materials have great potential for applications.

Microfluidic synthesis of Janus-structured QD-encoded magnetic microbeads for multiplex immunoassay.

Uniform and monodisperse quantum dot (QD)-encoded magnetic microbeads with Janus structure were produced in a microfluidic device via photopolymerization. UV light through a microscope objective was used to solidify the microbeads which showed sharp interfaces and excellent magnetic responses. QDs with different emission peaks (450 nm for blue and 640 nm for red) were mixed at different ratios to provide three spectral codes. The QD-encoded microbeads can be distinguished by analyzing their fluorescent images in HSV color space. After hydrolysis of the anhydride group in alkaline solution, protein was immobilized on microbeads via activation of carboxyl groups using (1-ethyl-3(3-dimethylaminoprophyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS). A microhole array in polydimethylsiloxane (PDMS) substrates with a specific size was fabricated to trap individual microbeads in a single microhole. The combination of Janus-structured QD-encoded magnetic microbeads and microhole arrays facilitates both flexibility, binding kinetics, sensitivity for suspension assay, and fluorescence mapping analysis for conventional biochips, thus providing a novel platform for multiplex bioanalysis. The capability of this integration for multiplex immunoassays was verified using three kinds of IgG and their corresponding anti-IgG. A detection limit of 0.07 ng/mL was achieved for human IgG, indicating practical applications in various fields.

Role of Mo doping and the interfacial interaction mechanism of Ni-Mo-S electrodes: experimental and computational study.

The metal element doping strategy is often used to optimize the electrode materials of supercapacitors as they can provide rich redox active sites and high conductivity; however, the synergistic effect between different metallic ions and the interfacial interaction mechanism during the energy storage process are still unclear. In this work, Mo-doped Ni-Mo-S (NMS) nanoflowers are prepared by one-step electrodeposition, and the ratios of Ni : Mo are tailored. Dynamics analysis shows that the Mo element occupies a prominent position in the capacitive behavior contribution. Meanwhile, density functional theory (DFT) reveals that Mo doping influences the electronic structure of the NMS materials and their affinity towards OH- in the electrolyte. All the electrodes (NMS-0, NMS-0.5, NMS-1, NMS-2, NMS-3, and NMS-4) exhibit excellent specific capacitance (1640.8, 1665.8, 1456.2, 1414.6, 1515.4 and 1214.6 F g-1, respectively) and good cycling stability (80.8%, 84.5%, 75.4%, 78.2%, 93.1% and 99.6%, respectively) for 5000 cycles. This work proposes an efficient method to synthesize NMS materials and theoretically studies the effect of the Mo element during the energy storage process.

Recent Advances in Application of Graphitic Carbon Nitride-Based Catalysts for Photocatalytic Nitrogen Fixation.

Ammonia, the second most-produced chemical, is widely used in agricultural and industrial applications. However, traditional industrial ammonia production dominated by the Haber-Bosch process presents huge resource and environment issues due to the massive energy consumption and CO2 emission. The newly emerged nitrogen fixation technology, photocatalytic N2 reduction reaction (p-NRR), uses clean solar energy with zero-emission, holding great prospect to achieve sustainable ammonia synthesis. Although great efforts are made, the p-NRR catalysts still suffer from poor N2 adsorption and activation, inferior light absorption, and fast recombination of photocarriers. Due to the tunable electronic structure of the metal-free polymeric graphitic carbon nitride (g-C3 N4 ), the above-mentioned issues can be significantly alleviated, making it the most promising p-NRR photocatalyst. This review summarizes the recent development of g-C3 N4 -based catalysts for p-NRR, including the working principle of p-NRR catalysts, the challenges of developing p-NRR catalysts, and corresponding solutions. Particularly, the roles of defect engineering and heterojunction construction on g-C3 N4 to the enhancement of photocatalytic performances are emphasized. In addition, computational studies are introduced to deepen the understanding of reaction pathways. At last, perspectives are provided on the development of p-NRR catalysts.

New Analysis Method for Adsorption in Gas (H2, CO)-Solid (SnO2) Systems Based on Gas Sensing.

The chemisorption phenomenon is widely used in the explanation of catalysis, gas-solid reactions, and gas sensing mechanisms. Generally, some properties of adsorbents, such as adsorption sites and dispersion, can be predicted by traditional methods through the variation of the chemisorption capacity with the temperature, pressure, and gas-solid interaction potential. However, these methods could not capture the information of the interaction between adsorbents, the adsorption rate, and the competitive adsorption relationship between adsorbents. In this paper, metal oxide semiconductors (MOSs) are employed to study the adsorption behavior. The gas sensing responses (GSRs) of MOSs caused by the gas adsorption process are measured as a new method to capture some adsorption behaviors, which are impossible for the traditional methods to obtain. The following adsorption behaviors characterized by this new method are presented for the first time: (1) distinguishing the adsorption type using an example of two reducing gases: the adsorption type of the two gases is single-molecular layer adsorption in this work; (2) detecting the interaction between different gases: this will be a promising method to provide original characterization data in the fields of gas-solid reaction mechanisms and heterogeneous catalysis; and (3) measuring the adsorption rate based on the GSR.

A universal strategy towards high-energy aqueous multivalent-ion batteries.

Rechargeable multivalent metal (e.g., Ca, Mg or, Al) batteries are ideal candidates for large-scale electrochemical energy storage due to their intrinsic low cost. However, their practical application is hampered by the low electrochemical reversibility, dendrite growth at the metal anodes, sluggish multivalent-ion kinetics in metal oxide cathodes and, poor electrode compatibility with non-aqueous organic-based electrolytes. To circumvent these issues, here we report various aqueous multivalent-ion batteries comprising of concentrated aqueous gel electrolytes, sulfur-containing anodes and, high-voltage metal oxide cathodes as alternative systems to the non-aqueous multivalent metal batteries. This rationally designed aqueous battery chemistry enables satisfactory specific energy, favorable reversibility and improved safety. As a demonstration model, we report a room-temperature calcium-ion/sulfur| |metal oxide full cell with a specific energy of 110 Wh kg-1 and remarkable cycling stability. Molecular dynamics modeling and experimental investigations reveal that the side reactions could be significantly restrained through the suppressed water activity and formation of a protective inorganic solid electrolyte interphase. The unique redox chemistry of the multivalent-ion system is also demonstrated for aqueous magnesium-ion/sulfur||metal oxide and aluminum-ion/sulfur||metal oxide full cells.

Desulfurization through Photocatalytic Oxidation: A Critical Review.

Fuel oil, the most important strategic resource, has been widely used in industrial applications. However, the sulfur-containing compounds in fuel oil also present humanity with huge environmental issues and health concerns due to the hazardous combustion waste. To address this problem, the low vulcanization of fuel production technology has been intensively explored. Compared with traditional hydrodesulfurization technology, the newly emerged photocatalytic desulfurization has the advantages of milder operating conditions, lower energy consumption, and higher efficiency, holding great prospect to achieve deep desulfurization. Though great efforts have been made, the desulfurization catalysts still suffer from inferior light absorption, fast recombination of photocarriers, and poor structure modification. This Review summarizes recent development of photocatalytic desulfurization, including the desulfurization principle, current desulfurization challenges, and corresponding solutions. Particularly, the roles of defect engineering, hybrid coupling, and structure modifications in the enhancement of photocatalytic performance are emphasized. In addition, the photocatalytic desulfurization mechanism is also introduced with the . OH and . O2 - radicals as main active species. Finally, some perspectives on the photocatalytic desulfurization are provided, which can further optimize the desulfurization efficiency and guide future photocatalyst design.

Polyolefin-Based Janus Separator for Rechargeable Sodium Batteries.

Rechargeable sodium batteries are a promising technology for low-cost energy storage. However, the undesirable drawbacks originating from the use of glass fiber membrane separators have long been overlooked. A versatile grafting-filtering strategy was developed to controllably tune commercial polyolefin separators for sodium batteries. The as-developed Janus separators contain a single-ion-conducting polymer-grafted side and a functional low-dimensional material coated side. When employed in room-temperature sodium-sulfur batteries, the poly(1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethanesulfonyl)imide sodium)-grafted side effectively enhances the electrolyte wettability, and inhibits polysulfide diffusion and sodium dendrite growth. Moreover, a titanium-deficient nitrogen-containing MXene-coated side electrocatalytically improved the polysulfide conversion kinetics. The as-developed batteries demonstrate high capacity and extended cycling life with lean electrolyte loading.

Hot Hole Enhanced Synergistic Catalytic Oxidation on Pt-Cu Alloy Clusters.

Hot holes in Pt-Cu alloy clusters can act as catalyst to accelerate the intrinsic aerobic oxidation reactions. It is described that under visible light irradiation the synergistic alcohol catalytic oxidation on Pt-Cu alloy clusters (≈1.1 nm)/TiO2 nanobelts could be significant promoted by interband-excitation-generated long-lifetime hot holes in the clusters.

Synthesis of a novel electrode material containing phytic acid-polyaniline nanofibers for simultaneous determination of cadmium and lead ions.

The development of nanostructured conducting polymers based materials for electrochemical applications has attracted intense attention due to their environmental stability, unique reversible redox properties, abundant electron active sites, rapid electron transfer and tunable conductivity. Here, a phytic acid doped polyaniline nanofibers based nanocomposite was synthesized using a simple and green method, the properties of the resulting nanomaterial was characterized by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A glassy carbon electrode modified by the nanocomposite was evaluated as a new platform for the simultaneous detection of trace amounts of Cd2+ and Pb2+ using differential pulse anodic stripping voltammetry (DPASV). The synergistic contribution from PANI nanofibers and phytic acid enhances the accumulation efficiency and the charge transfer rate of metal ions during the DPASV analysis. Under the optimal conditions, good linear relationships were obtained for Cd2+ in a range of 0.05-60 µg L-1, with the detection limit (S/N = 3) of 0.02 µg L-1, and for Pb2+ in a range of 0.1-60 µg L-1, with the detection limit (S/N = 3) of 0.05 µg L-1. The new electrode was successfully applied to real water samples for simultaneous detection of Cd2+ and Pb2+ with good recovery rates. Therefore, the new electrode material may be a capable candidate for the detection of trace levels of heavy metal ions.

Watt-level passively Q-switched Er:Lu2O3 laser at 2.84 µm using MoS2.

Efficient diode-pumped passively Q-switched Er:Lu2O3 laser operation at 2.84 µm was realized. A few-layer MoS2 nanosheet film on a YAG substrate, was fabricated and employed as saturable absorber (SA) in a short plane-plane cavity. Under an absorbed diode laser pump power of 7.61 W, an average output power of 1.03 W was generated with a pulse duration of 335 ns and a repetition rate of 121 kHz, resulting in a pulse energy of 8.5 µJ.

Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films.

Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1-65 µM with a low detection limit of 0.01 µM (S/N=3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets.

Synthesis and anticancer activity of some novel 2-phenazinamine derivatives.

In this study, we report the synthesis and spectral characterization of a novel series of 2-phenazinamine derivatives. In vitro evaluation for their anticancer activity toward cultured K562 (human chronic myelogenous leukemia), HepG2 (human hepatocellular carcinoma), MGC803 (human gastric carcinoma), HCT116 (human colorectal carcinoma), MCF7 (human breast adenocarcinoma) cell lines, as well as 293T (epithelial cells from human embryo kidney) non-cancer cell was carried out. The compounds 4, 7, 16 and 19 showed good positive anticancer activity in vitro. In particular, compound 4, 2-chloro-N-(phenazin-2-yl)benzamide, possessed a potent anticancer effect comparable to cisplatin against both K562 and HepG2 cancer cells but was very low or had no effect against 293T non-cancer cell. Preliminary anticancer mechanism of 4 was investigated by cell apoptosis assays compared with cisplatin using flow cytometry.

A novel anticancer and antifungus phenazine derivative from a marine actinomycete BM-17.

A marine actinomycete, designated strain BM-17, was isolated from a sediment sample collected in the Arctic Ocean. The strain was identified as Nocardia dassonvillei based on morphological, cultural, physiological, biochemical characteristics, along with the cell wall analysis and 16S rDNA gene sequence analysis. A new secondary metabolite (1), N-(2-hydroxyphenyl)-2-phenazinamine (NHP), and six known antibiotics (2-7) have been isolated from the saline culture broth of the stain by sequentially purification over macroporous resin D101, silica gel, Sephadex LH-20 column chromatography and preparative HPLC after the stain was incubated in soy bean media at 28°C for 7 days. The chemical structures of the compounds were elucidated on the basis of spectroscopic analysis, including two-dimensional (2D) NMR and HR-ESI-MS data. The new compound showed significant antifungal activity against Candida albicans, with a MIC of 64 µg/ml and high cancer cell cytotoxicity against HepG2, A549, HCT-116 and COC1 cells.