Nitrogen and Sulfur Co-Doped Graphene Quantum Dots Anchored TiO2 Nanocomposites for Enhanced Photocatalytic Activity

Multifunctional carbon dots originated from waste garlic peel for rapid sensing of heavy metals and fluorescent imaging of 2D and 3D spheroids cultured fibroblast cells

Here, we prepared sulfur and nitrogen self-doped carbon dots derived from garlic peel extract (GPSNCDs) using a hydrothermal method. The as-synthesized GPSNCDs were confirmed using Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The analytical techniques indicate that the resulting GPSNCDs exhibit distinct emissive carbon-core with functionalities (owing to various ligands in the GPSNCDs). These functionalities are responsible for excellent hydrophilic and optical properties, including excitation-dependent emission and anti-photobleaching. Fluorescence intensities of GPSNCDs were quenched in the existence of Mn2+ and Fe3+ ions. This indicates that the GPSNCDs were sensitive to Fe3+ and Mn2+ ions with a limited range from 5 to 50 µM and showed lower recognition at ∼0.75 and 0.95 µM, respectively. In addition, the sensing results were generated in a short time (20 s). The cytotoxicity of GPSNCDs was tested to demonstrate that they are sufficiently safe to use for cellular imaging. The novel fluorescent GPSNCDs-based sensor can be used as a high-performance sensor for environmental monitoring. Further, GPSNCDs showed greater biocompatibility with normal fibroblast cells, and In Vitro fluorescent imaging of GPSNCDs revealed strong fluorescence signals in the two-dimensional (2D) and three-dimensional (3D) spheroids cultured fibroblast cells. The properties mentioned above demonstrate that the GPSNCDs can be applied to imaging normal cells without further modifications.

Facile synthesis of a GO-g-C3N4/BaTiO3 ternary nanocomposites for visible-light-driven photocatalytic degradation of rhodamine B

Photogenerated charge carriers can undergo rapid recombination in conventional photocatalyst systems, reducing their photocatalytic efficiency. To address this bottleneck, a g-C3N4/BaTiO3 (CNB) heterojunction composite was decorated with different mass ratios of graphene oxide (GO) to form a novel visible-light responsive ternary GO-g-C3N4/BaTiO3 (GOCNB) nanocomposite using a facile fabrication method. The GOCNB photocatalyst exhibited significantly higher light absorption and greater charge transfer than CNB, g-C3N4, or BaTiO3. The photodegradation performance of GOCNB was optimized with a 2% mass loading of GO, and it achieved a degradation rate constant of 14.9 × 10-3 min-1 for rhodamine B with an efficiency of 94% within 180 min. The rate constant was 8-fold and 6-fold higher than that of bare BaTiO3 and CNB, respectively. The stronger photocatalytic activity was attributed to the synergistic effect of GO, g-C3N4, and BaTiO3, with g-C3N4 and BaTiO3 promoting charge transfer within a wider visible light range and GO promoting electron mobility and the photocatalyst's adsorption capacity. In particular, the proposed system maintained the spatial separation of photogenerated electron-hole pairs, which is vital for high photocatalytic activity. This study provides new insights into semiconductor-based photocatalytic systems and suggests a route for more environmentally sustainable technologies.

Photothermal therapy using graphene quantum dots

The rapid development of powerful anti-oncology medicines have been possible because of advances in nanomedicine. Photothermal therapy (PTT) is a type of treatment wherein nanomaterials absorb the laser energy and convert it into localized heat, thereby causing apoptosis and tumor eradication. PTT is more precise, less hazardous, and easy-to-control in comparison to other interventions such as chemotherapy, photodynamic therapy, and radiation therapy. Over the past decade, various nanomaterials for PTT applications have been reviewed; however, a comprehensive study of graphene quantum dots (GQDs) has been scantly reported. GQDs have received huge attention in healthcare technologies owing to their various excellent properties, such as high water solubility, chemical stability, good biocompatibility, and low toxicity. Motivated by the fascinating scientific discoveries and promising contributions of GQDs to the field of biomedicine, we present a comprehensive overview of recent progress in GQDs for PTT. This review summarizes the properties and synthesis strategies of GQDs including top-down and bottom-up approaches followed by their applications in PTT (alone and in combination with other treatment modalities such as chemotherapy, photodynamic therapy, immunotherapy, and radiotherapy). Furthermore, we also focus on the systematic study of in vitro and in vivo toxicities of GQDs triggered by PTT. Moreover, an overview of PTT along with the synergetic application used with GQDs for tumor eradication are discussed in detail. Finally, directions, possibilities, and limitations are described to encourage more research, which will lead to new treatments and better health care and bring people closer to the peak of human well-being.

Spent Coffee Grounds Derived Carbon Loading C, N Doped TiO2 for Photocatalytic Degradation of Organic Dyes

Titanium dioxide (TiO₂) is an ideal photocatalyst candidate due to its high activity, low toxicity and cost, and high chemical stability. However, its practical application in photocatalysis is seriously hindered by the wide band gap energy of TiO₂ and the prone recombination of electron-hole pairs. In this study, C, N doped TiO₂ were supported on spent coffee grounds-derived carbon (ACG) via in situ formation, which was denoted as C, N-TiO₂@ACG. The obtained C, N-TiO₂@ACG exhibits increased light absorption efficiency with the band gap energy decreasing from 3.31 eV of TiO₂ to 2.34 eV, a higher specific surface area of 145.8 m²/g, and reduced recombination rates attributed to the synergistic effect of a spent coffee grounds-derived carbon substrate and C, N doping. Consequently, the optimal 1:1 C, N-TiO₂@ACG delivers considerable photocatalytic activity with degradation efficiencies for methylene blue (MB) reaching 96.9% within 45 min, as well as a high reaction rate of 0.06348 min^-1, approximately 4.66 times that of TiO₂ (0.01361 min^-1). Furthermore, it also demonstrated greatly enhanced photocatalytic efficiency towards methyl orange (MO) in the presence of MB compared with a single MO solution. This work provides a feasible and universal strategy of synchronous introducing nonmetal doping and biomass-derived carbon substrates to promote the photocatalytic performance of TiO₂ for the degradation of organic dyes.

Rice husk valorization into sustainable Ni@TiO2/biochar nanocomposite for highly selective Pb (II) ions removal from an aqueous media

Herein, we successfully prepared sustainable nanocomposites from agriculture waste (rice husk)-derived biochar precursor, and followed by nickel-doped, base-treated titanium dioxide nanomaterials loading for efficient lead (Pb²⁺) removal from aqueous media. By varying the loading contents of active materials, the optimized sample (Ni_0.01@Na-TiO₂/BC) possessed an efficient Pb²⁺ adsorption capability of 122.3 mg g^-1 under the under optimum adsorption parameters, which is attributable to its specific surface area (138.09 m² g^-1) and excess functional sites. Kinetic and Isothermal examination illustrated that Pb²⁺ adsorption phenomena was well followed through pseudo 2nd order and Langmuir models. In addition, superior Pb²⁺ ions adsorption selectivity was recorded by optimized sample in a multi-metallic system over other existing ion (such as Cd²⁺, Mg²⁺, Ca²⁺, Cu²⁺, and Zn²⁺). Desorption experiments has been performed by using desorbing agent that demonstrates the good regeneration ability of sample. Hence, these findings provide new insight for the biowaste management by converting them into innovative adsorbents for commercial scale environmental remediation.

Catalytic Processes for Water and Wastewater Treatment

Water and wastewater treatment still face significant challenges today [...]