Sugarcane juice derived carbon dot-graphitic carbon nitride composites for bisphenol A degradation under sunlight irradiation

A dual-mode green emissive fluorescent probe for real-time detection of doxycycline in milk using a smartphone sensing platform

Real-time quantitative analysis of tetracyclines is urgently needed to provide consumers with early warning of potential risks. Herein, we report a dual-mode green emissive fluorescent probe, which refers to the liquid mode and the solid mode of electrospun films doped with nitride-doped carbon nanosheets (NCNSs) for real-time detection of doxycycline (DOX). Highly fluorescent NCNSs were prepared by low-temperature solid treatment of urea and sodium citrate. With the addition of DOX, the green emission intensity of NCNSs at 475 nm can be obviously reduced. Method validation exhibited a good linear relationship in 0.05-150 μM between the fluorescence quenching of NCNSs and the concentration of DOX with a limit of detection (LOD) of 0.0127 μM. Furthermore, the immobilization of NCNSs in PAN carriers forming electrospun films stabilizes the green fluorescence of NCNSs. Additionally, electrospun films integrated into a smartphone were developed for real-time detection of DOX with LOD of 0.285 μM. Additionally, DOX in milk was monitored with satisfactory recoveries. Therefore, the integration of the smartphone and electrospun film provides a promising and convenient method for real-time identification of DOX in food analysis.

Potential Efficacy of Herbal Medicine-Derived Carbon Dots in the Treatment of Diseases: From Mechanism to Clinic

Carbon dots (CDs), a crucial component of nanomaterials, are zero-dimensional nanomaterials with carbon as the backbone structure and smaller than 10 nm. Due to their beneficial characteristics, they are widely used in biomedical fields such as biosensors, drug delivery, bio-imaging, and interactions with DNA. Interestingly, a novel type of carbon dot, generated by using herbal medicines as synthetic raw materials, has emerged as the most recent incomer in the family of CDs with the extensive growth in the number of materials selected for carbon dots synthesis. Herbal medicine-derived carbon dots (HM-CDs) have been employed in the biomedical industry, and are rapidly emerging as "modern nanomaterials" due to their unique structures and exceptional capabilities. Emerging trends suggest that their specific properties can be used in bleeding disorders, gastrointestinal disorders, inflammation-related diseases, and other common intractable diseases including cancer, menopausal syndrome, central nervous system disorders, and pain of various forms and causes. In addition, HM-CDs have been found to have organ-protective and antioxidant properties, as evidenced by extensive studies. This research provides a more comprehensive understanding of the biomedical applications of HM-CDs for the aforementioned disorders and investigates the intrinsic pharmacological activities and mechanisms of these HM-CDs to further advance their clinical applications.

g-C3N5-dots as fluorescence probes prepared by an alkali-assisted hydrothermal method for cell imaging

Carbon nitride materials have become one of the highly explored carbon-based nanomaterials due to their unique properties. Herein, the novel graphitic carbon nitride quantum dots (g-C₃N₅-dots) were synthesized using an alkali-assisted hydrothermal method. The proposed strategy was simple, time-saving and the entire synthetic process only takes 60 min. And the prepared g-C₃N₅-dots showed excellent dispersion and good stability in water. What is more, the g-C₃N₅-dots displayed bright blue fluorescence with a high quantum yield of 12%. It was found that the g-C₃N₅-dots exhibited peroxidase-like activity, good biocompatibility and low cytotoxicity and can be successfully applied in cell imaging. The proposed method opens a new and efficient way for the preparation of fluorescent g-C₃N₅-dots and facilitates g-C₃N₅-dots for bioimaging and related biological sensing applications.

Novel graphitic carbon nitride quantum dots (g-C₃N₅-dots) were synthesized by an alkali-assisted hydrothermal method, having great potential applications in bioimaging and biological sensing.

Synthesis of tungsten oxide/ amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO3/N-CQDs) composites for methylene blue removal

In this present study, the tungsten oxide/amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO₃/N-CQDs) composite has successfully been prepared through a simple mixing process. The WO₃ was synthesized through a precipitation method, and CQDs were amino-functionalized using ethylenedinitrilotetraacetic acid (EDTA) and ethylenediamine (EDA) through one-pot hydrothermal method. It is revealed that N-CQDs incorporation into WO₃ alters the bandgap energy, crystallinity, surface area, and photoluminescence (PL) properties. The produced composites exhibit higher monoclinic WO₃ crystallinity, larger surface area, lower bandgap energy and quenched photoluminescence intensity. The as-prepared WO₃/N-CQDs composites exhibit better adsorption and photocatalytic degradation performance of methylene blue (MB) than the pristine WO₃. It shows that the combination of N-CQDs and WO₃ enhanced visible light absorption, by lowering the bandgap energy of WO₃ from 2.175 to 1.495 eV. The best performance composite is WO₃/N-CQDs EDA 2.5% with an efficiency of 96.86%, removal rate constant of 0.02017/min, and chemical oxidation demand (COD) removal efficiency achieved 84.61%. Moreover, the WO₃/N-CQDs EDA 2.5% shows a significant photocatalytic activity even at higher MB initial concentration with 92.93% removal for 50 ppm MB. Subsequently, the composite also has good stability after a sequential 3-times cycle of degradation with 86.85% removal. The increasing photocatalytic performance is affected by the quenching effect of PL and lower bandgap energy. The lower intensity of the PL indicates the reduced charge carrier recombination resulting in increased photocatalytic activity. The combination of N-CQDs and WO₃ resulted in improved photodegradation, which shows its significant potential to be utilized for wastewater treatment.

Green synthesis of water-soluble fluorescent carbon dots from rosemary leaves: Applications in food storage capacity, fingerprint detection, and antibacterial activity

Blue fluorescent carbon dots are synthesized via a one-step hydrothermal method using rosemary leaves as a carbon source. The obtained carbon dots are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis, FTIR, and fluorescence spectrometry. The results show that carbon dots gave a maximum emission peak at 422 nm when excited at 332 nm. The average particle diameter of the synthesized spherical carbon dots is found to be 16.13 nm with a 4.6-nm standard deviation. The diameters of the produced carbon dots vary, as is evident from standard deviation heights, resulting in multicolor emission spectra. The fruit storage experiment is carried out by investigating the qualitative antioxidant ability of the produced carbon dots. The results obtained for polyvinyl alcohol–carbon dot–coated samples differ remarkably compared to polyvinyl alcohol–coated samples only. The polyvinyl alcohol–carbon dot composition is used in latent fingerprint detection applications. In analyses made on a glass surface, fingerprints cannot be monitored on the glass surface with the polyvinyl alcohol layer under ultraviolet light, while they are observed on the surface covered with the polyvinyl alcohol–carbon dot composition. Moreover, biological activity against Gram-positive, Gram-negative, and yeast strains are investigated.

Novel Carbon Quantum Dots/Silver Blended Polysulfone Membrane with Improved Properties and Enhanced Performance in Tartrazine Dye Removal

This study produced a novel polysulfone (PSF) membrane for dye removal using lemon-derived carbon quantum dots-grafted silver nanoparticles (Ag/CQDs) as membrane nanofiller. The preparation of CQDs was completed by undergoing hydrothermal treatment to carbonize the pulp-free lemon juice into CQD solution. The CQD solution was then coupled with Ag nanoparticles to form Ag/CQDs nanohybrid. The synthesized powders were characterized in terms of morphologies, functional groups and surface charges. A set of membranes was fabricated with different loadings of Ag/CQDs powder using the nonsolvent-induced phase separation (NIPS) method. The modified membranes were studied in terms of morphology, elemental composition, hydrophilicity and pore size. In addition, pure water flux, rejection test and fouling analysis of the membranes were evaluated using tartrazine dye. From the results, 0.5 wt % of Ag/CQD was identified as the optimum loading to be incorporated with the pristine PSF membrane. The modified membrane exhibited an excellent pure water permeability and dye rejection with improvements of 169% and 92%, respectively. In addition, the composite membrane also experienced lower flux decline, higher reversible fouling and lower irreversible fouling. This study has proven that the addition of CQD additives into membrane greatly improves the polymeric membrane’s properties and filtration performance.

Aqueous solution photocatalytic synthesis of p-anisaldehyde by using graphite-like carbon nitride photocatalysts obtained via the hard-templating route

Graphite-like carbon nitride (GCN)-based materials were developed via the hard-templating route, using dicyandiamide as the GCN precursor and silica templates. That resulted in urchin-like GCN (GCN-UL), 3D ordered macroporous GCN (GCN-OM) and mesoporous GCN (GCN-MP). The introduction of silica templates during GCN synthesis produced physical defects on its surface, as confirmed by SEM analysis, increasing their specific surface area. A high amount of nitrogen vacancies is present in modified catalysts (revealed by XPS measurements), which can be related to an increase in the reactive sites available to catalyse redox reactions. The textural and morphological modifications induced in GCN an enhanced light absorption capacity and reduced electron/hole recombination rate, contributing to its improved photocatalytic performance. In the photocatalytic conversion of p-anisyl alcohol to p-anisaldehyde in deoxygenated aqueous solutions under UV-LED irradiation, the GCN-UL was the best photocatalyst reaching 60% yield at 64% conversion for p-anisaldehyde production after 240 min of reaction. Under oxygenated conditions (air), the process efficiency was increased to 79% yield at 92% conversion only after 90 min reaction. The GCN-based photocatalyst kept its performance when using visible-LED radiation under air atmosphere. Trapping of photogenerated holes and radicals by selective scavengers showed that under deoxygenated conditions, holes played the primary role in the p-anisaldehyde synthesis. Under oxygenated conditions, the process is governed by the effect of reactive oxygen species, namely superoxide radicals, with a significant contribution from holes.

Solvothermal assisted phosphate functionalized graphitic carbon nitride quantum dots for optical sensing of Fe ions and its thermodynamic aspects

A facile method has been proposed for the determination of Ferrous (Fe(II)) and Ferric (Fe(III)) ions using phosphate functionalized graphitic carbon nitride quantum dots (Ph-g-CNQDs) in an aqueous medium. The easy solvothermal procedure using oleic acid as the solvent yielded the Ph-g-CNQDs in less than 30 min. The communication among the Fe(II) and Fe(III) with Ph-g-CNQDs caused quenching of the blue Ph-g-CNQDs fluorescence signals. The Ph-g-CNQDs have been successfully characterized using X-ray diffractometry (XRD), X-ray Photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), Fourier Transform Infrared (FT-IR) spectroscopy, UV-vis absorption and photoluminescence spectrophotometry. The temperature dependent behavior of the Ph-g-CNQDs was also observed and various thermodynamic parameters have also been evaluated. The Ph-g-CNQDs displayed an excellent quantum yield of 60.54% using quinine sulfate as the standard reference. The developed method has been applied to water samples collected from different sources and good recoveries were observed which entitles this method as apt for real time monitoring.

Nitrogen doped carbon quantum dots and GO modified WO3 nanosheets combination as an effective visible photo catalyst

Nitrogen doped carbon quantum dots (NCQDs) based highly efficient ternary photocatalyst are fabricated by modifying surface of GO incorporated WO₃ nano-sheets. XRD confirmed the formation of monoclinicWO₃ nano-sheets. All the characteristic peaks of WO₃, GO and NCQDs are obvious in XRD patterns of WO₃/GO/NCQDs ternary photocatalysts confirming successful fabrication of the photocatalysts. SEM images showed that WO₃ host matrix is distorted after incorporation of GO and NCQDs owing to lower interfacial tension. The surface of WO₃ nano-sheets is modified with morphological defects making more active sites available. UV-vis spectra exhibited extended visible light absorption and remarkable reduction of WO₃ band gap energy. The photoluminescence spectra confirmed the efficient charge separation in NCQDs modified ternary photocatalyst. The synthesized composites were applied for the photocatalytic degradation of harmful organic dye i.e. methyl orange (MO). The ternary composites represented the excellent photocatalytic activity as compared to binary and pure WO₃ photocatalysts. This enhanced photocatalytic activity is attributed to the availability of active sites, extended light absorption in visible region and enhanced charge separation efficiency.

An overview of photocatalytic degradation: photocatalysts, mechanisms, and development of photocatalytic membrane

Photocatalysis is an ecofriendly technique that emerged as a promising alternative for the degradation of many organic pollutants. The weaknesses of the present photocatalytic system which limit their industrial applications include low-usage of visible light, fast charge recombination, and low migration ability of the photo-generated electrons and holes. Therefore, various elements such as noble metals and transition metals as well as non-metals and metalloids (i.e., graphene, carbon nanotube, and carbon quantum dots) are doped into the photocatalyst as co-catalysts to enhance the photodegradation performance. The incorporation of the co-catalyst which alters the photocatalytic mechanism was discussed in detail. The application of photocatalysts in treating persistent organic pollutants such as pesticide, pharmaceutical compounds, oil and grease and textile in real wastewater was also discussed. Besides, a few photocatalytic reactors in pilot scale had been designed for the effort of commercializing the system. In addition, hybrid photocatalytic system integrating with membrane filtration together with their membrane fabrication methods had also been reviewed. This review outlined various types of heterogeneous photocatalysts, mechanism, synthesis methods of biomass supported photocatalyst, photocatalytic degradation of organic substances in real wastewater, and photocatalytic reactor designs and their operating parameters as well as the latest development of photocatalyst incorporated membrane.

Fluorescent N/Al Co-Doped Carbon Dots from Cellulose Biomass for Sensitive Detection of Manganese (VII)

Development of metallic and nonmetallic heteroatom doped carbon dots have gained attention due to their enhanced physicochemical and photoluminescence properties. In this study, a facile one pot hydrothermal carbonisation approach was taken to synthesise nitrogen, aluminum co-doped carbon dots (N/Al-CDs) with a photoluminescence quantum yield of 28.7%. Durian shell, a cellulose biomass waste, was used as the primary carbon source and compared to previously reported cellulose based carbon dots, this study presents one of the highest quantum yields. The structural and fluorescent properties of the synthesised N/Al-CDs were characterized through X-ray photoelectron spectroscopy (XPS), fluorescence spectra, and Fourier transform infrared spectroscopy (FTIR). The maximum emission was at 415 nm upon excitation at 345 nm. The synthesised N/Al-CDs were resistant to photobleaching and highly photostable within the pH, ionic strength and temperature variations investigated. The transmission electron microscopy (TEM) images showed particles were quasi-spherical and well dispersed with an average diameter of 10.0 nm. Further, the N/Al-CDs was developed as a fluorescence sensor for highly selective and sensitive detection of Mn (VII) ions. A linear relationship was developed over a concentration range of 0-100 μM while the limit of detection was 46.8 nM. Application of the sensor for detection of Manganese (VII) to two real water samples showed relative standard deviation was less than 3.9% and 1.3%, respectively.

Future Perspectives and Review on Organic Carbon Dots in Electronic Applications

Over the span of the past decade, carbon dots (CDs) synthesized from renewable organic resources (organic CDs) have gathered a considerable amount of attention for their photoluminescent properties. This review will focus on organic CDs synthesized using clean chemistry and conventional synthetic chemistry from organic sources and their fluorescence mechanisms, such as quantum confinement effect and surface/edge defects, before outlining their performance in electronic applications, including organic photovoltaic devices, organic light-emitting devices, biosensors, supercapacitors, and batteries. The various organic resources and methods of organic CDs synthesis are briefly covered. Many challenges remain before the adoption of CDs can become widespread; their characterization, structure, functionality, and exact photoluminescent mechanism all require additional research. This review aims to summarize the current research outcomes and highlight the area where further research is needed to fully use these materials.

Graphitic carbon nitride QDs impregnated biocompatible agarose cartridge for removal of heavy metals from contaminated water samples

Highly fluorescent, water-stable graphitic carbon nitride quantum dots (gCN QDs) synthesized by microwave assisted solvo-thermal technique and characterized via optical spectroscopy, XRD, HR-TEM, Fluorescence spectroscopy, FT-IR and Raman spectroscopy. Synthesized gCN were used for the removal of mercury ions from polluted water samples in a microcartridge format. Density functional theory (DFT) calculations revealed a possible interaction of mercury atoms, and embedment of mercury atom onto synthesized gCN surface lead to moderate structural distortion, reduced band gap and altered dielectric response. Experimentally, the excitation dependent fluorescence of QDs is highly compromised in presence of mercuric (Hg²⁺) and other ions, validating the theoretical findings, and establishing their use as metal sensor probes. Hg²⁺ binding ability with gCN QDs was further utilized in developing bioinspired micro-cartridge via covalent conjugation to Agarose microbeads. Micro-cartridge can remove heavy metal contamination from polluted water with a binding efficiency of 24.63 mg HgCl₂ for 10 mg of Agarose-gCN conjugate.

Tuning the visible-light photocatalytic degradation activity of thin nanosheets constructed porous g-C3N4 microspheres by decorating ionic liquid modified carbon dots: roles of heterojunctions and surface charges

The visible-light photocatalytic degradation activity of thin nanosheets constructed g-C₃N₄ microspheres was tuned by decorating ionic liquid modified carbon dots.

M/g-C3N4 (M=Ag, Au, and Pd) composite: synthesis via sunlight photodeposition and application towards the degradation of bisphenol A

In this work, natural sunlight successfully induced the deposition of gold (Au), silver (Ag), and palladium (Pd) nanoparticles (NPs) with 17.10, 9.07, and 12.70 wt% onto the surface of graphitic carbon nitride (g-C₃N₄). The photocatalytic evaluation was carried out by adopting Bisphenol A (BPA) as a pollutant under natural sunlight irradiation. The presence of noble metals was confirmed by EDX, HRTEM, and XPS analysis. The deposition of Ag NPs (7.9 nm) resulted in the degradation rate which was 2.15-fold higher than pure g-C₃N₄ due to its relatively small particle size, contributing to superior charge separation efficiency. Au/g-C₃N₄ unveiled inferior photoactivity because the LSPR phenomenon provided two pathways for electron transfer between Au NPs and g-C₃N₄ further diminished the performance. The improved degradation lies crucially on the particle size and Schottky barrier formation at the interface of M/g-C₃N₄ (M=Au, Ag, and Pd) but not the visible light harvesting properties. The mechanism insight revealed the holes (h⁺) and superoxide radical (^•O₂^-) radical actively involved in photocatalytic reaction for all composites.