1D-2D hybrids as efficient optoelectronic materials: a study on graphitic carbon nitride nanosheets wrapped with zinc oxide rods

Synergistic effect of ZnO/Ag2O@g-C3N4 based nanocomposites embedded in carrageenan matrix for dye degradation in water

This research achieved success by synthesizing innovative nanocomposite composed of zinc oxide (ZnO), graphitic carbon nitride (g-C3N4) and silver oxide (Ag2O) nanomaterials incorporated into a carrageenan matrix, thus creating an environmentally friendly and stable support structure. The synthesis process involved hydrothermal and chemical precipitation methods to create photocatalytic g-C3N4, ZnO, and Ag2O nanocomposites. The success is evident through the characterization results, which unveiled distinctive peaks corresponding to Zn-O (590-404 cm-1) and Ag-O (2072 cm-1) stretching in the Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses, conclusively confirming the successful synthesis of g-C3N4, ZnO, Ag2O, and their respective nanocomposites. Further validation through a scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDX) and elemental mapping affirmed the presence of Zn, O, Ag, C, and N. Additionally, transmission electron microscope (TEM) imaging unveiled the nanosheet morphology of g-C3N4, the nanorod structure of ZnO, and the spherical form of Ag2O nanomaterials. ZnO and Ag2O nanomaterials demonstrated a consistent 10-20 nm size range. To underscore their ability to harness visible light, the nanomaterials were excited at 380 nm, emitting visible light emission within the 400-450 nm range. The synthesized nanocomposites showcased outstanding adsorption and photocatalytic properties, achieving efficiency ranging from 80 % to 98 %, attributed to the synergistic interactions between the various components. These findings culminate in a confirmation of the research's success, validating the exceptional potential of these nanocomposites for various applications.

Progress of charge carrier dynamics and regulation strategies in 2D CxNy-based heterojunctions

Two-dimensional carbon nitrides (CxNy) have gained significant attention in various fields including hydrogen energy development, environmental remediation, optoelectronic devices, and energy storage owing to their extensive surface area, abundant raw materials, high chemical stability, and distinctive physical and chemical characteristics. One effective approach to address the challenges of limited visible light utilization and elevated carrier recombination rates is to establish heterojunctions for CxNy-based single materials (e.g. C2N3, g-C3N4, C3N4, C4N3, C2N, and C3N). The carrier generation, migration, and recombination of heterojunctions with different band alignments have been analyzed starting from the application of CxNy with metal oxides, transition metal sulfides (selenides), conductive carbon, and Cx'Ny' heterojunctions. Additionally, we have explored diverse strategies to enhance heterojunction performance from the perspective of carrier dynamics. In conclusion, we present some overarching observations and insights into the challenges and opportunities associated with the development of advanced CxNy-based heterojunctions.

A room-temperature gas sensor based on 2D Ni-Co-Zn ternary oxide nanoflakes for selective and sensitive ammonia detection

While most of the reports on NH3 gas sensors are either based on metal oxide composites with other 2D materials, polymers or noble metals or involve multi-step-based synthesis routes, this work is the first report on a pristine ternary metal oxide, 2D NiCo2ZnO4 nanoflake based room-temperature (RT) NH3 gas sensor. The 2D NiCo2ZnO4 nanoflakes were prepared by a one-step hydrothermal method. FESEM and TEM images displayed micro-flower like morphologies, containing vertically aligned interwoven porous 2D nanoflakes, whereas XPS and XRD data confirmed the successful growth of this ternary metal-oxide. This sensor revealed a good response, repeatability, linearity (R2 = 0.9976), a low detection limit of 3.024 ppb, and a response time of 74.84 s with excellent selectivity towards NH3 over six other VOCs. This improved performance of the sensor is ascribed to its large specific surface area (127.647 m2 g-1) resulting from the 2D nanoflake like structure, good electronic conductivity, variable valence states and abundant surface-active oxygen of NiCo2ZnO4. Thus, this highly selective 2D NiCo2ZnO4 based RT NH3 gas sensor can be an attractive solution for the fabrication of next-generation NH3 gas sensors.

Electrochemical Immunosensor for Detection of H. pylori Secretory Protein VacA on g-C3N4/ZnO Nanocomposite-Modified Au Electrode

A g-C₃N₄/ZnO (graphitic carbon nitride/zinc oxide) nanocomposite-decorated gold electrode was employed to design an antigen-antibody-based electrochemical biosensor to detect Helicobacter pylori specific toxin, vacuolating cytotoxin A (VacA). The thermal condensation method was used to synthesize the g-C₃N₄/ZnO nanocomposite, and the nanocomposite was deposited electrochemically on a gold electrode. The morphology as well as the structure of the synthesized nanocomposite were confirmed by scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, and Fourier transform infrared techniques. The nanocomposite efficiently increased the sensor performance by amplifying the signals. EDC-NHS chemistry was exploited for attachment of VacA antibodies covalently with the g-C₃N₄/ZnO-modified gold electrode. This modified electrode was exploited for immunosensing of H. pylori-specific VacA antigen. The immunosensor was stable for up to 30 days and exhibited good sensitivity of 0.3 μA^-1 ng mL^-1 in a linear detection range of 0.1 to 12.8 ng mL^-1. Apart from this, the fabricated sensor showed unprecedented reproducibility and remarkable selectivity toward the H. pylori toxin VacA. Thus, the highly sensitive immunosensor is a desirable platform for H. pylori detection in practical applications and clinical diagnosis.

Strategic combination of ultra violet-visible-near infrared light active materials towards maximum utilization of full solar spectrum for photocatalytic chromium reduction

Maximum utilization of the full solar spectrum has been considered as a holy grail in the field of photocatalysis and has emerged important in the recent years, as the world needs to move towards renewable energy sources and also to maintain environmental health. In the search for a sustainable solution, we have come up with a strategic combination of materials, which can be active under all the three regions, namely ultraviolet (UV), visible and near infrared (NIR) of the sunlight. Specifically, we have developed a series of nanocomposites comprising of two dimensional nanosheets of zinc oxide (ZnO) and graphitic carbon nitride (GCN), and successfully coupled them with upconversion nanoparticles (UCNP). These nanocomposites have been successfully utilized for the photocatalytic chromium (Cr(VI)) reduction. The prepared nanocomposites exhibit an excellent photocatalytic activity toward reduction of Cr(VI) under different light region. A plausible mechanism for the photocatalytic process has been proposed based on the detailed study. This work is expected to pave way for the strategic design and development of many photocatalytic systems, which can utilize sunlight to the maximum extent.

Enhancing the permeability and antifouling properties of cellulose acetate ultrafiltration membrane by incorporation of ZnO@graphitic carbon nitride nanocomposite

This study reports the modification of cellulose acetate (CA) membrane with zinc oxide (ZnO)@graphitic carbon nitride (g-C₃N₄) nanocomposite to improve the antifouling and separation performance. Different combinations of the CA-based membranes such as CA/g-C₃N₄, CA/ZnO, and CA/ZnO@g-C₃N₄ were fabricated using the non-solvent induced phase separation (NIPS) method. Membranes were analyzed for their morphology (SEM), porosity, pore size, contact angle, permeability, rejection, and antifouling properties. According to the SEM images of CA/ZnO@g-C₃N₄, the formation of pear-shaped macro voids and finger-like canals originating from the top layer was evident. Nanocomposite blended membrane with 0.25 wt.% ZnO@g-C₃N₄ achieved the largest pore radius (3.05 nm) and the lowest contact angle (67.7°). With these characteristics, 0.25 wt.% ZnO@g-C₃N₄ membrane obtained a pure water flux of 51.3 LMH, which is 2.1 times greater than the bare CA and high BSA and dye rejections with 97.20% and 93.7% respectively. Finally, the antifouling resistance of the CA membrane was greatly improved with FRR increasing from 73.7% to 94.8%, which was accompanied by a significant decrease in the fouling resistance parameters.

In situ formed zinc oxide/graphitic carbon nitride nanohybrid for the electrochemical determination of 4-nitrophenol

The electrochemical determination of 4-nitrophenol using a nanohybrid consisting of glassy carbon (GC) and zinc oxide/graphitic carbon nitride (ZnO/g-CN nanosheet), is described. The ZnO/g-CN nanohybrid was in situ synthesized by chemical method and well characterized using absorption spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopic analysis. It was observed that the nanosized ZnO particles were present inside the sheet-like g-CN nanostructure. The nanohybrid-modified electrode showed an enhanced electrocatalytic response for 4-nitrophenol reduction compared with the bare GC electrode. The assay exhibited linear ranges of 13.4-100 μM and 100-1000 μM for 4-NP determination. The limit of detection and limit of quantification were 4.0 and 13.4 μM, respectively, at the working potential of - 0.85 V. An appreciable precision was found towards the stability of the assay in the determination. It provides selectivity against inorganic and organic substances such as calcium chloride, potassium chloride, nitrobenzene, uric acid, 1-chloro,2,4-dinitrobenzene, 1-bromo,2-nitrobenzene and 1-iodo,2-nitrobenzene. The practical applicability of the assay was also checked in the analysis of real water samples and satisfactory recovery of 4-NP was found. Schematic representation of the synthesis of zinc oxide (ZnO) nanostructures incorporated graphitic carbon nitride nanosheets (g-C₃N₄ NSs) and its application in the voltammetric determination of 4-nitrophenol (4-NP) is presented. The nanohybrid assay showed selectivity among coexisting compounds and good recovery in real sample analysis.

Influence of Dy3+ co-doping on the luminescence properties of bluish-green Ba1−0.5ySr1−0.5yAl2SiO7:yEu2+ phosphors

The emission intensity of Ba_0.985Sr_0.985Al₂SiO₇:0.03Eu²⁺ is enhanced due to the incorporation of Dy³⁺. The emission intensity of Ba_0.975Sr_0.975Al₂SiO₇:0.03Eu²⁺, 0.02Dy³⁺ was about 350% that of the Ba_0.985Sr_0.985Al₂SiO₇:0.03Eu²⁺ phosphor.