A general nonaqueous sol-gel route to g-C3N4-coupling photocatalysts: the case of Z-scheme g-C3N4/TiO2 with enhanced photodegradation toward RhB under visible-light

Spatial charge separated two-dimensional/two-dimensional Cu-In2S3/CdS heterojunction for boosting photocatalytic hydrogen production

Two-dimensional (2D) beta indium sulfide (β-In2S3) shows great potential in photocatalytic hydrogen production due to its broad-spectrum response, relatively negative conduction band edge, high carrier mobility and low toxicity. However, the high charge recombination rate limits the application of In2S3. Here, we in-situ grew 2D cadmium sulfide (CdS) on the surface of In2S3 doped with copper ions (Cu2+) to construct a heterojunction photocatalyst that suppresses charge recombination. The in-situ grown method and shared sulfur composition were conducive to forming the efficient interface contact between In2S3 and CdS, promoting charge transfer and showing the high spatial charge separation rate, resulting in a hydrogen production rate of 868 µmol g-1h-1. The induced Cu2+ extended the light absorption range and stabilized the photocatalyst. By creating stable 2D/2D heterojunction photocatalysts with high charge separation efficiency, this work opens new possibilities for applying In2S3 materials in photocatalytic hydrogen production.

Altass H, Althagafi II, Ahmed SA. Fabrication of Direct Z-Scheme CoNiWO4/Ph-gC3N4 Heterocomposites: Enhanced Photodegradation of Bisphenol A and Anticancer Activity

Photocatalysis is realized by the design of a visible-light-active catalyst with robust redox capacity and broad absorption. In this study, a series of novel Z-scheme CoNiWO4/Ph-gC3N4 photocatalysts are synthesized to improve their redox property and photocatalytic activity toward broad visible light absorption. An intimate stable heterojunction is made between cobalt-nickel tungstate (CoNiWO4) and phenyl-doped graphitic carbon nitride (Ph-gC3N4), and its physicochemical properties are studied. The bifunctional properties of all of the synthesized materials were assessed by studying the decomposition of bisphenol A (BPA) and methyl orange (MO) dye as model pollutants, followed by an evaluation of their anticancer activity on human lung cancer cell lines. The photocatalyst with 20 wt % CoNiWO4 heterocomposite showed an enhanced response toward the removal of cancerous cells. The synthesized pristine CoNiWO4 and Ph-gC3N4 exhibit well-matched band structures and, hence, make it easier to create a Z-scheme heterocomposite. This may increase the lifetime of photoinduced charge carriers with a high redox power, thereby improving their photocatalytic and anticancer activity. An extensive analysis of the mechanism demonstrates that hydroxyl radicals (•OH) and superoxide radical anions (•O2-) are responsible for the degradation of organic compounds via Z-scheme charge transfer approach. These findings point toward a new route for creating effective Co-Ni tungstate-based direct Z-scheme photocatalysts for various redox processes, particularly the mineralization of resistant organic molecules.

Spinach-derived boron-doped g-C3N4/TiO2 composites for efficient photo-degradation of methylene blue dye

Green synthesis of nanoparticles can be beneficial due to their low toxicity, cost-effectiveness, and environment-friendliness. Its synthesis involves the use of eco-friendly and biodegradable materials such as plant extracts, natural products, and microorganisms to reduce the negative environmental impacts of traditional nanoparticle synthesis methods. Herein, Spinacia oleracea leaves are used as a boron source, and a visible light active photo-catalyst is produced. The effect of Co-Catalyst Boron in Graphitic carbon nitride based nanocomposites for methylene blue dye photo-degradation in water is examined. Titanium dioxide (TiO₂) was activated by changing the hydrogen potential value while utilizing a typical orange dye as a sensitizer. The graphitic carbon nitride/TiO₂ nanocomposites were synthesized through a hydrothermal technique. To improve their performance, Boron used as a co-catalyst and B-doped g-C₃N₄/TiO₂nanocomposites prepared through wet chemical co-percipitate mathod. UV-visible spectroscopy, SEM and FTIR spectroscopy were used to analyze the photocatalyst and boron-doped composites in detail. The photocatalytic performance of pristine photocatalyst CNTx (x = 2%,4%,6%,8%) and B-doped CNTx composites were examined for Methylene Blue degradation in the presence of a light source. The spectroscopy analysis showed that B-doped g-C₃N₄/TiO₂ -8% nano-composites performed better than all other synthesized pristine catalysts and composites in this research. This research has demonstrated that B-doped g-C₃N₄/TiO₂ composites can provide an ideal solution for treating polluted water using visible light as a source to activate these photocatalysts.

Microwave Synthesis of Visible-Light-Activated g-C3N4/TiO2 Photocatalysts

The preparation of visible-light-driven photocatalysts has become highly appealing for environmental remediation through simple, fast and green chemical methods. The current study reports the synthesis and characterization of graphitic carbon nitride/titanium dioxide (g-C₃N₄/TiO₂) heterostructures through a fast (1 h) and simple microwave-assisted approach. Different g-C₃N₄ amounts mixed with TiO₂ (15, 30 and 45 wt. %) were investigated for the photocatalytic degradation of a recalcitrant azo dye (methyl orange (MO)) under solar simulating light. X-ray diffraction (XRD) revealed the anatase TiO₂ phase for the pure material and all heterostructures produced. Scanning electron microscopy (SEM) showed that by increasing the amount of g-C₃N₄ in the synthesis, large TiO₂ aggregates composed of irregularly shaped particles were disintegrated and resulted in smaller ones, composing a film that covered the g-C₃N₄ nanosheets. Scanning transmission electron microscopy (STEM) analyses confirmed the existence of an effective interface between a g-C₃N₄ nanosheet and a TiO₂ nanocrystal. X-ray photoelectron spectroscopy (XPS) evidenced no chemical alterations to both g-C₃N₄ and TiO₂ at the heterostructure. The visible-light absorption shift was indicated by the red shift in the absorption onset through the ultraviolet-visible (UV-VIS) absorption spectra. The 30 wt. % of g-C₃N₄/TiO₂ heterostructure showed the best photocatalytic performance, with a MO dye degradation of 85% in 4 h, corresponding to an enhanced efficiency of almost 2 and 10 times greater than that of pure TiO₂ and g-C₃N₄ nanosheets, respectively. Superoxide radical species were found to be the most active radical species in the MO photodegradation process. The creation of a type-II heterostructure is highly suggested due to the negligible participation of hydroxyl radical species in the photodegradation process. The superior photocatalytic activity was attributed to the synergy of g-C₃N₄ and TiO₂ materials.

Enhanced photodegradation of organic contaminants using V-ZnSQDs@TiO2 photocatalyst in an aqueous medium

Vanadium-doped zinc sulfide quantum dots complexed with TiO₂ have been designed using the sol-gel technique and characterized using analytical techniques, such as X-ray diffraction analysis (XRD), UV-Vis diffuse reflectance spectra (DRS), Fourier transforms Infra Red (FTIR), Brunauer-Emmett-Teller analysis (BET), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and transmission electron microscopy (TEM). The X-ray diffraction analysis of the composite material showed sharp peaks corresponding to both TiO₂ and ZnS_QDs. The FTIR analysis exhibits a strong and broad absorption at 807 cm^-1 indicating the assimilation of vanadium metal in the ZnS_QDs lattice. The DRS spectra showed a bathochromic shift of 25 nm in the synthesized V-ZnS_QDs@TiO₂ composite compared with the pure sample. The photocatalytic performance of the synthesized composite was tested by studying the degradation of two different chromophoric organic dyes, rhodamine B (RhB), methylene blue (MB) and a drug derivative paracetamol (PCM) in aqueous suspension under UV-light illumination. Among the synthesized materials, the composite (V-ZnS_QDs@TiO₂) was established to be more active than the pure ZnS_QDs, TiO₂, and V-ZnS_QDs for the degradation of compounds under investigation. The activity of the synthesized catalyst was also tested for the mineralization of all compounds by measuring the depletion in total organic carbon (TOC) at different irradiation times. The results showed that the catalyst degrades the compounds and mineralizes them efficiently. The primary reactive species involved in the photodegradation reaction were determined by quenching studies, terephthalic acid, and NBT probe methods. A probable mechanistic pathway for the decomposition of compounds has been proposed.

Tunable band structure of synthesized carbon dots modified graphitic carbon nitride/bismuth oxychlorobromide heterojunction for photocatalytic degradation of tetracycline in water

In this study, graphitic carbon nitride (CN) decorated with carbon quantum dot (CQD) and bismuth oxychlorobromide (BiOCl_xBr_1-x) was fabricated by calcination and hydrothermal methods. The morphology characterization of the synthesized photocatalyst revealed that CQD and BiOCl_xBr_1-x solid solution were deposited on the CN surface. CQD served as the electron reservoir, which could reduce the recombination of electron-hole pairs, thus improving the overall photocatalytic performance. The synergistic effect of 1 wt% CQDs and BiOCl_0.75Br_0.25 markedly improved the interfacial charge transfer efficiency and light-harvesting capacity of the composite. The degradation rate of tetracycline (TC) over CN/CQD/BiOCl_0.75Br_0.25 was 83.4 % after 30 min and favorable stability with near-initial capacity under visible light irradiation. Meanwhile, the reaction mechanism of the photocatalytic performance was demonstrated by the analysis of the surface adsorption sites, efficient utilization of visible light, and charge carrier transfer. The degradation by-products and potential degradation pathways were also analyzed using liquid chromatography-mass spectrometry. Finally, the toxicity estimation software tool (T.E.S.T) analysis indicated that the toxicity of most intermediates was lower than TC. This work provideed a strategy for fabricating visible light (VL) photocatalyst with excellent photocatalytic activity, furnishing a new insight for interface charge transfer.

Construction of SnO2/g-C3N4 an effective nanocomposite for photocatalytic degradation of amoxicillin and pharmaceutical effluent

The current study mainly focused on the fabrication of 2D graphitic carbon nitride-supported tin oxide nanoparticles (SnO₂/g-C₃N₄) for the effective degradation of Amoxicillin (AMX). Tin oxide (SnO₂) NPs were prepared by green and easy modification technique, and then it is decorated over g-C₃N₄ nanosheets. The structural morphology and surface composition of the synthesized SnO₂/g-C₃N₄ nanocomposite were fully analysed by UV-Vis, XRD, XPS, and HR-SEM with EDAX, FT-IR, and BET analysis. The (HR-TEM) microscopy, the size of SnO₂ NPs which as a diameter is about 6.2 nm. The Raman analysis revealed that the SnO₂/g-C₃N₄ composite had a moderate graphitic structure, with a measured I_D/I_g value of 0.79. The degradation efficiency of antibiotic pollutant AMX and pharma effluent treatment was monitored by UV spectroscopy. The optical band gap of SnO₂ (2.9 eV) and g-C₃N₄ (2.8 eV) photocatalyst was measured by Tauc plots. To investigate the mechanism through the photodegradation efficiency of the catalyst was analysed by using different Scavenger EDTA-2Na holes (h⁺) has a greater contribution towards the degradation process. Under visible irradiation, SnO₂/g-C₃N₄ nanocomposite has exhibited an excellent degradation performance of 92.1% against AMX and 90.8% for pharmaceutical effluent in 80 min.

Environment Friendly g-C3N4-Based Catalysts and Their Recent Strategy in Organic Transformations

Organic molecules synthesized in an environmentally friendly manner have excellent therapeutic potential. The entire preparation technique was examined in the existence of a light source, implying that light has been replaced by heating and the usage of dangerous chemicals has decreased, resulting in less pollution of the environment. The advantages of these nanocarbon catalysts include high efficiency, environmentally friendly synthesis, eco-friendly, inexpensive, and non-corrodible. In organic transformations, solid metal base/metal-free catalysts produce better results. Here, the metal-free semiconductor g-C₃N₄ was used to demonstrate the catalytic behavior of organic conversions. g-C₃N₄ is a two-dimensional material and a p‑type semiconductor to enhance the photocatalytic activity. The excellent properties of g-C₃N₄ sheet lead to the support of metals to form metal-organic frameworks. Most of the reactions gained positive response under visible light irradiation. This review will inspire readers in widen the applications of g-C₃N₄ based catalyst in various organic transformation reactions.

Photocatalytic degradation of lignin by low content g-C3N4 modified TiO2 under visible light

TiO2/g-C3N4 photocatalysts efficiently degraded lignin to obtain small molecule aromatics, which facilitated the efficient utilization of biomass.

Tandem Photocatalysis Protocol for Hydrogen Generation/Olefin Hydrogenation Using Pd-g-C3N4-Imine/TiO2 Nanoparticles

An unprecedented visible-light-driven photocatalytic system consisting of Pd nanoparticles stabilized on g-C₃N₄-imine-functionalized TiO₂ nanoparticles was discovered for photoassisted hydrogen generation followed by olefin hydrogenation under mild conditions. The structural integrity of the as-synthesized photocatalyst was corroborated by Fourier transform infrared spectroscopy, X-ray powder diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-diffuse reflectance spectroscopy, Brunauer-Emmett-Teller measurements, and thermogravimetric analysis (TGA). Transmission electron microscopy and high-resolution scanning electron microscopy revealed the nanoscopic nature of the catalyst. The photocatalyst promoted several different transformations in a one-pot reaction sequence: hydrogen evolution through photocatalytic acceptorless formation of benzimidazoles as important therapeutic agents followed by visible-light-driven photocatalytic reduction of olefins with a high hydrogen utilization efficiency of up to 92% under mild conditions. A significant volume of H₂ was produced under blue light-emitting diode (LED) irradiation during the selective formation of benzimidazole, while the selectivity reduced significantly under a Xe lamp or in the dark. The in situ-generated H₂ could be activated by the as-prepared Pd-C₃N₄-imine/TiO₂ photocatalyst to effectively hydrogenate olefins under mild conditions at appropriate time exposed to blue LED irradiation. The light-dependent photocatalytic performance of the title catalyst was assessed using action spectra by calculating the apparent quantum efficiency (AQE), which exhibited the maximum AQEs at 410 and 550 nm, at which the highest performance for styrene hydrogenation was obtained. The improved photoredox activity of the title nanohybrid could be caused by the synergistic effects of the heterojunction of carbon nitride-Pd on TiO₂ nanoparticles evidenced by photoluminescence spectra and catalytic reactions. The catalyst proved to be air-stable, robust, recyclable, and very active in the absence of any undesirable additives and reducing agents. Thus, this work presents a new protocol for improving the photocatalytic properties of semiconducting materials for various photocatalytic applications under environmentally friendly conditions.

Titanium dioxide and graphitic carbon nitride-based nanocomposites and nanofibres for the degradation of organic pollutants in water: a review

The paper reviews graphitic carbon nitride-based nanostructured photocatalytic materials and nanofibres for applications in water purification. Titanium dioxide has shown unique features that continue to attract research and development (R&D) due to its unique properties such as availability, ultraviolet absorptivity, photocatalysis, adsorption of pollutants and solar cell engineering. Graphitic carbon nitride is an attractive photocatalyst due to its non-toxicity characteristics, good visible light absorption and good thermal and chemical stabilities. In water purification, nanofibres are currently noticed due to their distinctive properties of effective separation and sometimes elimination of organic pollutants in water. In this review, synthesis and utility of doped titanium dioxide and carbon nitride with metal nanoparticles and polymeric nanofibres from nanocomposites as effective materials for the degradation of organic contaminations from water are discussed. The history, current trends and future perspectives are highlighted.

A first report of separation calls in southern yellow-cheeked gibbons (Nomascus gabriellae) in captivity

The effects of social separation, including vocalization, have been studied for a very long time in non-human primates under laboratory conditions. As part of the long-term research on the vocal behaviour of Nomascus gibbons in zoos, this study provides the first record of calls of the southern yellow-cheeked gibbon (Nomascus gabriellae) in response to involuntary separation. Our study revealed that calls were also emitted by an infant (aged 1 year 8 months), and that the acoustic structure of the infant's calls was similar to that of older individuals' calls. Separation-induced calls seem to have a shorter developmental convergence than vocalizations with a stable pattern (which are specific for species and sex). The acoustic structure of the calls reported here comprised simple syllables, and differed from the sex- and species-specific vocal patterns of this species. Our findings demonstrate a novel paradigm in this genus, and provide evidence of the ability of gibbons to express distress when socially separated.

The role of seashell wastes in TiO2/Seashell composites: Photocatalytic degradation of methylene blue dye under sunlight

This paper proposes a sustainable and facile approach for the synthesis of photocatalysts in which shell waste is used as support material. The synthesized photocatalysts exhibited a significant performance in the mineralization of organic substances under solar irradiation or artificial lighting. Calcined abalone shell with a TiO₂ loading of 23.4% led to a significant improvement in optical absorption: the degradation efficiencies of methylene blue (MB) after 140 min under UV light, vis light, UV-vis light, and natural sunlight were 93%, 96%, 100%, and 100%, respectively. Notably, the byproducts obtained after the degradation by commercial P25 TiO₂ disappeared with the utilization of shell waste as support material. The Na, Sr, S present in the calcined abalone shell were doped into the substitutional sites of TiO₂ and were indispensable to achieve the desired band-gap narrowing and photocatalytic performance; moreover, the Ti and Zn oxides in the calcined abalone shell acted as semiconductors and improved the charge separation efficiency of TiO₂. Above all, this paper describes a green synthesis based on the use of waste seashell. This material acts as an excellent photocatalyst support for environmental pollution treatments, leading to the 'control of waste by waste' and opening up new possibilities for shell waste reutilization and sustainable chemistry.

Graphitic nitride-catalyzed advanced oxidation processes (AOPs) for landfill leachate treatment: A mini review

Landfill leachate poses significant risks to public health via the release of high-toxicity contaminants, including refractory organic compounds, ammonia-nitrogen compounds, and heavy metals. Significant efforts have been made to develop useful methods for leachate disposition and treatment. Advanced oxidation processes (AOPs) are one of the most promising methods, because they can rapidly degrade diverse pollutants and significantly improve the biodegradability of leachate. Graphitic carbon nitride (g-C₃N₄), a fascinating conjugated polymer, has become a hot topic in AOP research due to its metal-free benefits and high photosensitivity. Thus, combining AOPs with g-C₃N₄ achieves excellent degradation of refractory pollutants in leachate. Since the composition of leachate is complex in the practical conditions, the information reported by current studies of using g-C₃N₄ as a remediator is still incomplete and fragmented. Thus, in this review, the recent status of leachate treatment and approaches for its disposal has been summarized and some conclusions have been drawn. In addition, a brief introduction to g-C₃N₄ and its application in AOPs for leachate treatment have been critically discussed and with its future outlook assessed. Although the development of g-C₃N₄ in AOPs for leachate treatment is highly efficient and practical, comprehensive study about its application and technology expansion is urgently needed, based on the complex operating conditions. Perspectives on the treatment of leachate using g-C₃N₄-AOPs are also included. The information and perspectives provided in this review will provide guidance and novel understanding to accelerate the development of g-C₃N₄-based AOPs for leachate treatment.

Pt nanoparticles decorated heterostructured g-C3N4/Bi2MoO6 microplates with highly enhanced photocatalytic activities under visible light

Exploring an efficient and photostable heterostructured photocatalyst is a pivotal scientific topic for worldwide energy and environmental concerns. Herein, we reported that Pt decorated g-C₃N₄/Bi₂MoO₆ heterostructured composites with enhanced photocatalytic performance under visible light were simply synthesized by one-step hydrothermal method for methylene blue (MB) dye degradation. Results revealed that the synthetic Pt decorated g-C₃N₄/Bi₂MoO₆ composites with Bi₂MoO₆ contents of 20 wt.% (Pt@CN/20%BMO) presented the highest photocatalytic activity, exhibiting 7 and 18 times higher reactivity than the pure g-C₃N₄ and Bi₂MoO₆, respectively. Structural analyses showed that Bi₂MoO₆ microplates were anchored on the wrinkled flower-like g-C₃N₄ matrix with Pt decoration, leading to a large expansion of specific surface area from 10.79 m²/g for pure Bi₂MoO₆ to 46.09 m²/g for Pt@CN/20%BMO. In addition, the Pt@CN/20%BMO composites exhibited an improved absorption ability in the visible light region, presenting a promoted photocatalytic MB degradation. Quenching experiments were also conducted to provide solid evidences for the production of hydroxyl radicals (^•OH), electrons (e⁻), holes (h⁺) and superoxide radicals (^•O²⁻) during dye degradation. The findings in this critical work provide insights into the synthesis of heterostructured photocatalysts with the optimization of band gaps, light response and photocatalytic performance in wastewater remediation.

Highly efficient degradation of 2,4-dichlorophenol over CeO2/g-C3N4 composites under visible-light irradiation: Detailed reaction pathway and mechanism

Herein, we report for the first time the highly efficient degradation of 2,4-dichlorophenol (2,4-DCP) over CeO₂/g-C₃N₄ composites (xCeO/CN) prepared via wet-chemical solution method. It is shown that the resultant nanocomposites with a proper mass ratio percentage (15%) of CeO coupled exhibit greatly enhanced visible-light activity for 2,4-dichlorophenol (2,4-DCP) degradation compared to the bare g-C₃N₄. From photoluminescence (PL) and Fluorescence (FL) results, it is suggested that enhanced photo-degradation is attributed to the significantly improved charge separation and transfer as a result of the proper band alignments between g-C₃N₄ and CeO components. Further, from radical trapping experiments, it is confirmed that hydroxyl radicals (OH) are the predominant oxidants involved in the degradation of 2,4-DCP over CeO/CN composites. Furthermore, a possible reaction pathway and detailed photocatalytic mechanism for 2,4-DCP degradation is proposed mainly based on the detected liquid chromatography tandem mass spectrometry (LC-MS) intermediate products, that readily transform into CO₂ and H₂O. This work would help researchers to deeply understand the reaction mechanism of 2,4-DCP and would provide feasible routes to fabricate g-C₃N₄-based highly efficient photocatalysts for environmental remediation.

Immunomodulatory effect of mesenchymal stem cells: Cell origin and cell quality variations

The immunomodulatory property of mesenchymal stem cells (MSCs) has been previously reported. Still it is unclear if this property can be affected by the cell origin and cell quality. Using primary MSCs expanded from bone marrow (BM-MSCs) and adipose tissue (AD-MSCs) of mice, we investigated whether the immunomodulatory property of MSCs varied with cell origin and cell quality (early- vs. late-passaged BM-MSCs). BM-MSCs (p1) and AD-MSCs (p1) had a typical spindle shape, but morphological changes were observed in late-passaged BM-MSCs (p6). A pathway-focused array showed that the expression of chemokine/cytokine genes varied with different cell origins and qualities. By co-culturing with spleen mononuclear cells (MNC) for 3 days, the expression of CD4 was suppressed by all types of MSCs. By contrast, the expression of CD8 was suppressed by BM-MSCs and increased by AD-MSCs. The expression ratio of CD206 to CD86 was at a comparable level after co-culture with AD-MSCs and BM-MSCs, but was lower with late-passaged BM-MSCs. AD-MSCs highly induced the release of IL6, IL-10 and TGF-β in culture medium. Compared with early-passaged BM-MSCs (p1), late-passaged BM-MSCs (p6) released less TGF-β. Our data suggests that the immunomodulatory properties of MSCs vary with cell origin and cell quality and that BM-MSCs of good quality are likely the optimal source of immunomodulation.

Photocatalytic 4-nitrophenol degradation and oxygen evolution reaction in CuO/g-C3N4 composites prepared by deep eutectic solvent-assisted chlorine doping

Heterostructured Cl-CuO/g-C₃N₄ composite for OER and photocatalytic 4-nitrophenol degradation.

Phenyl-grafted carbon nitride semiconductor for photocatalytic CO2-reduction and rapid degradation of organic dyes

Molecular engineering of graphitic carbon nitride (g-C₃N₄) is achieved by the copolymerization of π-conjugated phenyl urea, melamine, and urea.

Electronic, structural, optical, and photocatalytic properties of graphitic carbon nitride

Graphitic carbon nitride (g-C₃N₄)-based materials exhibit an organized layered porous structure and a band position optimum for the development of various optoelectronic devices and photocatalysts.

Influence of g-C3N4 Precursors in g-C3N4/NiTiO3 Composites on Photocatalytic Behavior and the Interconnection between g-C3N4 and NiTiO3

In this study, composite photocatalysts were produced from NiTiO₃ and N₂-rich precursors (dicyandiamide, melamine, urea, and thiourea) under N₂ flow conditions. The goal of the study was to investigate the interaction between NiTiO₃ and the synthesized g-C₃N₄. The properties of the g-C₃N₄/NiTiO₃ (CNT) composites were different depending on the starting materials. Dicyandiamide and thiourea created strong connections with NiTiO₃ and resulted in the generation of Ti-N and Ti-O-S bonds. Urea and melamine, however, had difficulty forming g-C₃N₄ structures or interconnections with NiTiO₃. The Ti-N and Ti-O-S bridges in the composite photocatalysts led to increased photocatalytic activity as well as inhibition of the recombination rate. Additionally, the band diagrams of g-C₃N₄ prepared from dicyandiamide and thiourea exhibited positions suitable for the Z-scheme charge-transfer model with NiTiO₃, implying that the composite photocatalysts were applicable for photocatalytic degradation of organic contaminants under the visible-light irradiation. Higher reaction rate constants for the composites prepared with dicyandiamide and thiourea confirmed the significant role of the Ti-N/Ti-O-S bridge between g-C₃N₄ and NiTiO₃.

Visible-light-driven activity and synergistic mechanism of TiO2@g-C3N4 heterostructured photocatalysts fabricated through a facile and green procedure for various toxic pollutants removal

Heterostructured photocatalysts based on g-C₃N₄ and TiO₂ represent a promising kind of photocatalyst in environmental fields, but the synthesis methods are always complex and not green. In the present paper, a facile and green one-step calcination procedure at lower temperature (450 °C) with the assistance of water is developed to synthesize a visible-light-active TiO₂@g-C₃N₄ heterostructured photocatalyst, which shows higher visible-light-driven activity (k = 0.014 min^-1) than pure g-C₃N₄ (k = 0.0036 min^-1) and TiO₂ (k = 0.0067 min^-1) for methyl orange degradation. Excellent performance (over 90% conversion) was also observed for the removal of rhodamine B, phenol, and Cr(VI) under visible light. The heterostructured photocatalyst showed favorable reusability, preserving 86% of its activity after five successive cycles. A mechanism study demonstrates that the enhanced photocatalytic activity results from the efficient separation of the photo-generated charge carriers through the intimate interface between the two semiconductors based on their appropriate band structures and light-induced mechanism. The heterostructured photocatalyst will certainly find wide applications in the treatment of various toxic pollutants in wastewater using abundant solar energy. Furthermore, this facile and green procedure and the proposed synergistic mechanism will provide guidelines in designing other g-C₃N₄ based organic-inorganic composite photocatalysts for various applications.

Nanocrystalline Cellulose-Derived Doped Carbonaceous Material for Rapid Mineralization of Nitrophenols under Visible Light

Nitrophenols (NPs) and related derivatives are industrially important chemicals, used notably to synthesize pharmaceuticals, insecticides, herbicides, and pesticides. However, NPs and their metabolites are highly toxic and mutagenic. They pose a serious threat to human health and ecosystem. Current work was undertaken to develop a suitable visible-light active catalyst for the sustainable and efficient mineralization of NPs in an aqueous environment. Nanocrystalline cellulose (NCs)-based nitrogen-doped titanium dioxide and carbonaceous material (N-TiO₂/C) was synthesized by pyrolysis and sol-gel methods using NCs, polydopamine, and TiO₂. The synthesized N-TiO₂/C was characterized using different analytical techniques. Photocatalytic degradation of NPs under visible light indicated that acidic pH (3) was most suitable for the optimal degradation. 4-NP degradation followed both pseudo-first-order (R ² = 0.9985) and Langmuir-Hinshelwood adsorption kinetic models (adsorption constant, K _LH = 1.13 L mg^-1). Gas chromatography-mass spectrometry and ion chromatography analysis confirmed the total mineralization of 4-NP into smaller molecular fragments such as acids, alcohols, and nitrates. The total organic carbon showed that 67% of total carbon present in 4-NP was mineralized into CO₂ and CO. The catalyst was recycled for five consecutive cycles without losing its catalytic activities. The degradation mechanism of NPs with N-TiO₂/C was also explored.

A weak-light-responsive TiO2/g-C3N4 composite film: photocatalytic activity under low-intensity light irradiation

A TiO₂/g-C₃N₄ composite photocatalytic film was prepared by in situ synthesis method and its photocatalytic capability under weak-visible-light condition was studied. The co-precursor with different ratio of melamine and TiO₂ sol-gel precursor were treated using ultrasonic mixing, physical deposition, and co-sintering method to form the smooth, white-yellow, and compact TiO₂/g-C₃N₄ composite films. The prepared TiO₂/g-C₃N₄ materials were characterized by SEM, TEM, EDS, XRD, BET, VBXPS, and UV-vis diffuse reflectance spectra. The results of composite showed that TiO₂ and g-C₃N₄ have close interfacial connections which are favorable to charge transfer between these two semiconductors with suitable band structure, g-C₃N₄ retard the anatase-to-rutile phase transition of TiO₂ significantly, the specific surface area were increased with g-C₃N₄ ratio raised. Under weak-light irradiation, composite films photocatalytic experiments exhibited RhB removal efficiency approaching 90% after three recycles. Powders suspension degradation experiments revealed the removal efficiency of TiO₂/g-C₃N₄ (90.8%) was higher than pure TiO₂ (52.1%) and slightly lower than pure g-C₃N₄ (96.6%). By control experiment, the enhanced photocatalysis is ascribed to the combination of TiO₂ and g-C₃N₄, which not only produced thin films with greater stability but also formed heterojunctions that can be favorable to charge transfer between these two semiconductors with suitable band structure. This study presents the potential application of photocatalytic film in the wastewater treatment under weak-light situation.

Ultrasensitive detection of heparin by exploiting the silver nanoparticle-enhanced fluorescence of graphitic carbon nitride (g-C3N4) quantum dots

A composite (Ag-g-CNQDs) was prepared from graphitic carbon nitride quantum dots and silver nanoparticles by water phase synthesis. Aided by metal-enhanced fluorescence, the composite exhibits excitation-dependent red emission with a peak at 600 nm with a quantum yield of 21%. If the composite is coated with polyethylenimine (PEI) to form the Ag-g-CNQD/PEI complexe, fluorescence is strongly reduced. Upon addition of heparin, the fluorescence of the system is enhanced because PEI has a higher affinity for heparin than Ag-g-CNQDs. The effect was used to design a fluorometric  assay for heparin. The emission at 600 nm increases linearly in the 0.025 to 2.5 μM heparin concentration range, with a 8.2 nM limit of detection. Graphical abstract Schematic illustration for fabricating a composite consisting of silver nanoparticles and graphitic carbon nitride quantum dots (Ag-g-CNQDs). Its red fluorescence is weak in presence of polyethyleneimine but restored on addition of heparin. This forms the basis for a new method for heparin detection.

First Report on High Entropy Alloy Nanoparticle Decorated Graphene

This is the first report on synthesis of multimetal high entropy alloy (HEA) nanoparticle-few layer graphene composite. A two-step methodology for synthesizing multi-component HEA nanoparticle-graphene composite is provided. In the first step, high purity graphite powder was mechanically milled with metal powders (Ni, Cr, Co, Cu, Fe) to produce multimetal-graphite composite. This composite was then sonicated with sodium lauryl sulphate (SLS) for 2 hours to produce a dispersion of graphene decorated with multi-component nanoparticles with face centred cubic structure. Potentiodynamic polarization and electrochemical impedance spectroscopy methods revealed that the HEA nanoparticle graphene composite possess excellent corrosion resistance properties which was better than the corrosion resistance exhibited by milled and exfoliated graphene. The HEA nanoparticle-graphene composite can be used for corrosion resistant coating applications.

Moderate Bacterial Etching Allows Scalable and Clean Delamination of g-C3N4 with Enriched Unpaired Electrons for Highly Improved Photocatalytic Water Disinfection

Delamination treatment is crucial in promoting the activity of bulk graphitic carbon nitride (g-C₃N₄). However, most of the currently used methods of exfoliating bulk g-C₃N₄ to achieve g-C₃N₄ thin layers suffer from low yield and environmental pollution. Herein, we developed a facile bacterial etching approach for the preparation of high-quality g-C₃N₄ nanosheets by exfoliating bulk g-C₃N₄ under room temperature. Morphology and physicochemical characterizations show that the bacteria-treated g-C₃N₄ (BT-CN) samples, especially BT-CN-2d, have a lamina-like two-dimensional (2D) in-plane porous structure, a significantly enlarged specific surface area (82.61 m² g^-1), and a remarkable narrow band gap (2.11 eV). X-ray photoelectron spectroscopy and electron paramagnetic resonance spectra confirm the dramatic enrichment of unpaired electron in the BT-CN-2d g-C₃N₄ nanosheets. EIS spectra and photocurrent tests indicate the fast electron transportation. As a result, the representative BT-CN-2d g-C₃N₄ photocatalyst shows an optimal visible light-driven photocatalytic performance in water disinfection (fourfold higher than bulk g-C₃N₄), as well as good cycle stability. This moderate and clean bacterial etching process can be realized in tens of gram scale in the laboratory and should be readily extended to kilogram scale. The present work provides fundamental knowledge about the scalable production of high-quality g-C₃N₄ by bioengineering method, offering extendable availability for designing and fabricating other functional 2D materials.

Constructing a visible-light-driven photocatalytic membrane by g-C3N4 quantum dots and TiO2 nanotube array for enhanced water treatment

Photocatalytic membranes that driven by visible light are highly desired for water treatment. Here g-C₃N₄ quantum dots (QDs) assembled into TiO₂ nanotube array (TNA) membranes were fabricated for the first time as a visible-light-driven g-C₃N₄/TNA membrane. Benefiting from the synergistic effect of membrane filtration and photocatalysis, more than 60% of rhodamine B could be removed from water under visible light irradiation. Meanwhile, the g-C₃N₄/TNA membrane presented an enhanced anti-fouling ability during filtering water containing Escherichia coli under visible light irradiation, and a permeate flux of 2 times higher than that of filtration alone was obtained by integrated process. This study offers a promising strategy for the potential application of the visible-light-driven membranes in water treatment.

Photosensitization of TiO2 nanofibers by Ag2S with the synergistic effect of excess surface Ti3+ states for enhanced photocatalytic activity under simulated sunlight

TiO₂ nanofibers, with mean diameter ~200 nm, were fabricated by electrospinning and successfully photosensitized with low bandgap Ag₂S nanoparticles of 11, 17, 23 and 40 nm mean sizes, with corresponding loading of 4, 10, 18 and 29 wt.% Ag₂S, respectively. 17 nm Ag₂S@TiO₂ nanofibers exhibited optimal activity in the photodegradation of methylene blue under simulated sunlight with pseudo-first order rate constant of 0.019 min⁻¹ compared to 0.009 min⁻¹ for pure TiO₂ nanofibers. In spite of greater visible-light absorption and reduced bandgap, larger than 17 nm Ag₂S nanoparticles exhibited sluggish photodegradation kinetics probably due to less photo-induced carriers generation in TiO₂ and reduced electron injection rates from the larger sized Ag₂S into TiO₂. Furthermore, a UV-O₃ surface treatment induced excess Ti³⁺ surface states and oxygen vacancies which synergistically enhanced the photodegradation rate constant to 0.030 min⁻¹ for 17 nm Ag₂S@TiO₂ sample which is ~70% better than the previously reported for Ag₂S/TiO₂ hierarchical spheres. This was attributed to the efficient charge separation and transfer driven by increased visible-light absorption, bandgap narrowing and reduced electron-hole recombination rates. The present study demonstrate the potential utilization of Ag₂S@TiO₂ nanofibers in filtration membranes for removal of organic pollutants from wastewater.

Metallic 1T-TiS2 nanodots anchored on a 2D graphitic C3N4 nanosheet nanostructure with high electron transfer capability for enhanced photocatalytic performance

The introduction of metallic TiS₂ nanodots in 2D-C₃N₄ nanosheets improved the photocatalytic activity due to the suppression of e–h recombination.

Ionic liquid-assisted synthesis of Ag/Ag2Te nanocrystals via a hydrothermal route for enhanced photocatalytic performance

Herein, Ag₂Te and Ag/Ag₂Te nanocrystals were synthesised via a hydrothermal method using diphenyl ditelluride as a new tellurium source and 1-butyl-3-methyl imidazolium acetate (BMIA IL) as a structure controlling and conducting coating source.