Independent hydrothermal synthesis of the undoped, nitrogen, boron and sulphur doped biogenic carbon nanodots and their potential application in the catalytic chemo-reduction of Alizarine yellow R azo dye

Surface Engineering of Biochar Toward Simultaneously Generating Superamphiphilicity and Catalytic Activity for Strengthening Pickering Interfacial Catalysis

Multifunctional carbon materials have revealed distinctive features and excellent performance in the field of catalysis. However, the facile fabrication of bifunctional carbon materials with special wettability and catalytic activity remains a grand challenge in Pickering emulsion catalysis. Herein, we reported one-step construction of bifunctional biochar with superamphiphilicity and catalytic activity directly from the thermolysis of sawdust and 1-butyl-3-methylimidazolium tetrafluoroborate for enhancing the oxidation of benzyl alcohol in Pickering emulsion. Co-doping of B and F enhanced the hydrophilicity of biochar, and the oleophilicity of biochar was kept simultaneously. Conversion became 4 times using bifunctional biochar compared with blank results during the oxidation of benzyl alcohol. More interestingly, the turnover frequency (TOF) value using bifunctional biochar enhanced 61 % than that employing N-doped superamphiphilic carbon without catalytic activity. Catalytic activities of bifunctional biochar could be ascribed to the existence of different chemical bonds containing the element B. This work paves a path toward rational design of bifunctional biochar materials with special wettability and catalytic activity for greatly enhancing the liquid-liquid biphasic reaction efficiencies.

NIR-activated quercetin-based nanogels embedded with CuS nanoclusters for the treatment of drug-resistant biofilms and accelerated chronic wound healing

We have developed multifunctional nanogels with antimicrobial, antioxidant, and anti-inflammatory properties, facilitating rapid wound healing. To prepare the multifunctional nanogels, we utilized quercetin (Qu) and a mild carbonization process to form carbonized nanogels (CNGs). These CNGs possess excellent antioxidative and bacterial targeting properties. Subsequently, we utilized the Qu-CNGs as templates to prepare nanogels incorporating copper sulfide (CuS) nanoclusters, further enhancing their functionality. Notably, the CuS/Qu-CNGs nanocomposites demonstrated an exceptional minimum inhibitory concentration against tested bacteria, approximately 125-fold lower than monomeric Qu or Qu-CNGs. This enhanced antimicrobial effect was achieved by leveraging near-infrared II (NIR-II) light irradiation. Additionally, the CuS/Qu-CNGs exhibited efficient penetration into the extracellular biofilm matrix, eradicating methicillin-resistant Staphylococcus aureus-associated biofilms in diabetic mice wounds. Furthermore, the nanocomposites were found to suppress proinflammatory cytokines, such as IL-1β, at the wound sites while regulating the expression of anti-inflammatory factors, including IL-10 and TGF-β1, throughout the recovery process. The presence of CuS/Qu-CNGs promoted angiogenesis, epithelialization, and collagen synthesis, thereby accelerating wound healing. Our developed CuS/Qu-CNGs nanocomposites have great potential in addressing the challenges associated with delayed wound healing caused by microbial pathogenesis.

Green synthesis of fluorescent carbon nanodots from sage leaves for selective anticancer activity on 2D liver cancer cells and 3D multicellular tumor spheroids

Carbon nanodots, a family of carbon-based nanomaterials, have been synthesized through different methods from various resources, affecting the properties of the resulting product and their application. Herein, carbon nanodots (CNDs) were synthesized with a green and simple hydrothermal method from sage leaves at 200 °C for 6 hours. The obtained CNDs are well dispersed in water with a negative surface charge (ζ-potential = -11 mV) and an average particle size of 3.6 nm. The synthesized CNDs showed concentration-dependent anticancer activity toward liver cancer (Hep3B) cell lines and decreased the viability of the cancer cells to 23% at the highest used concentration (250 μg ml-1 of CNDs). More interestingly, the cytotoxicity of the CNDs was tested in normal liver cell lines (LX2) revealed that the CNDs at all tested concentrations didn't affect their viability including at the highest concentration showing a viability of 86.7%. The cellular uptake mechanisms of CNDs were investigated and they are thought to be through energy-dependent endocytosis and also through passive diffusion. The main mechanisms of endocytosis were lipid and caveolae-mediated endocytosis. In addition, the CNDs have hindered the formation of 3D spheroids from the Hep3B hepatocellular carcinoma cell line. Hence, it would be concluded that the synthesized CNDs from sage are more highly selective to liver cancer cells than normal ones. The CNDs' cancer-killing ability would be referred to as the production of reactive oxygen species.

Ziziphus mauritiana-derived nitrogen-doped biogenic carbon dots: Eco-friendly catalysts for dye degradation and antibacterial applications

In this study, the naturally available Ziziphus Mauritiana was used as a bioresource for the preparation of bifunctional nitrogen doped carbon dots (N-CDs). The doping of nitrogen into the graphitic carbon skeleton and the in-situ formation of N-CDs were systematically identified by the various structural and morphological studies. The green fluorescent N-CDs were used as active catalysts for the removal of Safranin-O dye and achieved 79 % removal efficiency. Furthermore, the prepared N-CDs were used to evaluate antibacterial activity with four different bacterial species, such as Shigella flexneri, Staphylococcus aureus, Streptococcus pyogenes, and Klebsiella pneumoniae. Amongst these, the highest antimicrobial activity was achieved against Klebsiella pneumonia, with a maximum zone of inhibition of 14.6 ± 1.12 at a concentration of 100 g mL-1. Thus, the obtained results demonstrate the cost efficient bifunctional application prospects of N-CDs to achieve significant catalytic and antibacterial activities.

Preparation of carbon self-doped g-C3N4 for efficient degradation of bisphenol A under visible light irradiation

In this study, visible-light-driven carbon self-doped graphitic carbon nitride photocatalyst was fabricated by a facile method with urea and ammonium citrate, and used for photodegradation of bisphenol A (BPA) in the aqueous environment. The experiments indicated that the prepared photocatalyst (C_0.02CN) showed high catalytic activity, and 96.0%, 93.2%, and 95.5% BPA could be photodegraded in 150 min under pH 3, 6, and 11, respectively. The photocatalytic degradation rate (0.018 min^-1) and mineralization (27.6%) of C_0.02CN for BPA were about 6.7 and 3.5 times higher than those of the g-C₃N₄ (0.0027 min^-1, 7.87%), respectively. C_0.02CN had high reusability with a photodegradation efficiency of 84.5% for BPA after 3 cycles. Moreover, C_0.02CN introduced additional carbon atoms, which generated C-O-C bonds in the g-C₃N₄ lattice. In contrast to g-C₃N₄, carbon doping enhanced the visible light absorption range of C_0.02CN, reduced its band gap, and improved the separation efficiency of photogenerated electron-hole pairs. Radical quenching experiment and ESR results revealed that superoxide radicals (•O₂^-) and photogenerated holes (h⁺) acted as important parts in the high photodegradation activity under visible light irradiation. This work puts forward a one-pot strategy for the preparation of carbon self-doped g-C₃N₄, displacing the high-energy consuming and complicated preparation technology with promising industrial applications.

A critical review on the environmental applications of carbon dots

The discovery of zero-dimensional carbonaceous nanostructures called carbon dots (CDs) and their unique properties associated with fluorescence, quantum confinement and size effects have intrigued researchers. There has been a substantial increase in the amount of research conducted on the lines of synthesis, characterization, modification, and enhancement of properties by doping or design of composite materials, and a diversification of their applications in sensing, catalysis, optoelectronics, photovoltaics, and imaging, among many others. CDs fulfill the need for inexpensive, simple, and continuous environmental monitoring, detection, and remediation of various contaminants such as metals, dyes, pesticides, antibiotics, and other chemicals. The principles of green chemistry have also prompted researchers to rethink novel modes of nanoparticle synthesis by incorporating naturally available carbon precursors or developing micro reactor-based techniques. Photocatalysis using CDs has introduced the possibility of utilizing light to accelerate redox chemical transformations. This comprehensive review aims to provide the reader with a broader perspective of carbon dots by encapsulating the concepts of synthesis, characterization, applications in contaminant detection and photocatalysis, demerits and research gaps, and potential areas of improvement.

Multiplex heteroatoms doped carbon nano dots with enhanced catalytic reduction of ionic dyes and QR code security label for anti-spurious applications

Herein, a simple hydrothermal approach was used to make multiplex heteroatoms doped carbon dots from Tinospora cordifolia miers plant extract. Their ability to the catalytic activity of dyes and anti-spurious applications was evaluated. The formation of NBCNDs and source of (T. cordifolia miers) study the optical properties, and functional groups are investigated using UV-Visible spectroscopy and FT-IR techniques. The synthesized NBCNDs structure and elemental compositions were examined via HR-TEM, XRD, and XPS, respectively. According to the HRTEM images, the average particle size of the NBCNDs was around 4.3± 1 nm, with d-spacing of 0.19 nm. The obtained NBCNDs were exposed under 395 nm UV light to emit bluish-green tuneable fluorescence with QY (quantum yield) of 23.7%. The prepared NBCNDs as a potential catalyst for the AYR and CV dye reduction process using freshly prepared NaBH₄, with determined rate constant values at 0.1220 and 0.1521 min^-1, respectively. Lastly, we constructed a quick response (QR) code security label for anti-spurious applications using stencil techniques. The "confidential info" was encrypted using a QR code digital system, and the decryption was read using a smartphone under 365 nm light irradiation.

Amorphous Co@TiO2 heterojunctions: A high-performance and stable catalyst for the efficient degradation of sulfamethazine via peroxymonosulfate activation

Persulfate-based advanced oxidation processes (AOPs) cannot easily achieve the efficient degradation of persistent organic pollutants (POPs) with high stability. In this study, a simple in situ precipitation method was used to prepare an amorphous Co@TiO₂ heterojunction catalyst. The deposition of Co oxide on TiO₂, which is relatively nontoxic, efficiently activated peroxymonosulfate (PMS) to degrade sulfamethazine (SMT) and reduce the leaching of Co ions (0.915%). A catalytic system prepared using 0.3 g L^-1 Co@TiO₂ and 0.5 g L^-1 PMS could degrade SMT within 30 min with a degradation rate of 95.8%. Co@TiO₂ could activate PMS over a wide pH range (5.00-9.00) to efficiently degrade other antibiotics and dyes. Radical-capture experiments and electron paramagnetic resonance analysis suggested that SMT degradation occurs through a combination of the free radical and non-radical pathways, in which singlet ¹O₂ played a major role. Owing to the novelty of the proposed composite materials, the degradation path of SMT, which was determined through liquid chromatography-mass spectrometry, differed from that reported previously. This study provides not only an advanced and renewable catalyst for SMT degradation but also a feasible strategy for designing materials for AOPs.

Biobased carbon dots production via hydrothermal conversion of microalgae Chlorella pyrenoidosa

A promising green hydrothermal process was used to produce biobased nanomaterials carbon dots (CDs) by using microalgae Chlorella pyrenoidosa (CP) and its main model compounds (i.e., glucose, glycine, and octadecanoic acid). The possible reaction pathway including hydrolysis, Amadori rearrangement, cyclization/aromatization, and polymerization was first proposed for the hydrothermal process to produce microalgae-based CDs. Interactions among carbohydrates and proteins in microalgae were vital intermediate reactions in the generation of CDs. The mass yield of CDs reached 7.2% when the CP was hydrothermally treated with 20:1 of liquid-to-solid ratio at 230 °C for 6 h. It was confirmed that nitrogen, sulfur, phosphorous, and potassium were doped onto CP-based CDs (CD-CP) successfully without additional reagents or treatments. The CD-CP yield was 4.0-24.3 times higher than that of model compound-based CDs. Regarding morphology, CD-CP was constituted by many spherical nanoparticles smaller than 20 nm. These CDs emitted blue fluorescence under ultraviolet light, and the fluorescence quantum yield of CD-CP was 4.7-9.4 times higher than that of CP model compound-based CDs. Last, CD-CP displayed broad application prospects as a sensor for Fe³⁺ detection in wastewater with high sensitivity.

Broad-Spectrum Antibacterial Activity of Synthesized Carbon Nanodots from d-Glucose

Carbon nanodots, a class of carbon nano-allotropes, have been synthesized through different routes and methods from a wide range of precursors. The selected precursor, synthetic method, and conditions can strongly alter the physicochemical properties of the resulting material and their intended applications. Herein, carbon nanodots (CNDs) have been synthesized from d-glucose by combining pyrolysis and chemical oxidation methods. The effect of the pyrolysis temperature, equivalents of oxidizing agent, and refluxing time were studied on the product and quantum yield. In the optimum conditions (pyrolysis temperature of 300 °C, 4.41 equiv of H2O2, 90 min of reflux) CNDs were obtained with 40% and 3.6% of product and quantum yields, respectively. The obtained CNDs are negatively charged (ζ-potential = -32 mV), excellently dispersed in water, with average diameter of 2.2 nm. Furthermore, ammonium hydroxide (NH4OH) was introduced as dehydrating and/or passivation agent during CNDs synthesis resulting in significant improvement of both product and quantum yields of about 1.5 and 3.76-fold, respectively. The synthesized CNDs showed a broad spectrum of antibacterial activities toward different Gram-positive and Gram-negative bacteria strains. Both synthesized CNDs caused highly colony forming unit reduction (CFU), ranging from 98% to 99.99% for most of the tested bacterial strains. However, CNDs synthesized in the absence of NH4OH, due to a negatively charged surface enriched in oxygenated groups, performed better in zone inhibition and minimum inhibitory concentration. The elevated antibacterial activity of high-oxygen-containing carbon nanodots is directly correlated to their ROS formation ability.

Ag nanozyme strengthened by folic acid: Superior peroxidase-mimicking activity and application for visual monitoring of dopamine

Dopamine (DA) is an important neurotransmitter; however, any excess or deficiency of DA will cause several diseases in humans. To monitor DA efficiently and conveniently, a Ag nanozyme strengthened by bioactive folic acid (FA@AgNPs) was developed by homogeneous redox assembly. After the microstructure and performance were characterized in detail, it was noted that the proposed FA@AgNPs possessed superior peroxidase-like activity due to the ultra-small Ag nanoparticles and multiple amino, hydroxyl, and aromatic rings in FA. FA@AgNPs accelerated the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with a low Michaelis constant (K_m) and high maximal reaction rate (V_max). Importantly, the characteristic absorbance intensity of FA@AgNPs-TMB-H₂O₂ at 652 nm (A₆₅₂) was exclusively deteriorated in the presence of trace DA, accompanied by a visual color change from blue to colorless. Under the optimized conditions (pH 4.0, 300 μL 1.5 mM TMB, 300 μL 1.0 M H₂O₂ and incubated for 30 min at room temperature), there expressed an excellent linear relationship between lgA₀/A₆₅₂ and c_DA from 1.0 ×10^-8 to 6.67×10^-6 mol/L with a low limit detection of 7.1×10^-10 mol/L (S/N=3). When applied for monitoring of DA in real fruit juice and pharmaceutical samples, the recovery was between 96.6% and 104.9%, with RSD less than 2.2%. The enhanced peroxidase-like activity of the FA@AgNP system and its selective recognition mechanism for DA are also proposed.

Metal ions mediated carbon dots nanoprobe for fluorescent turn-on sensing of N-acetyl-L-cysteine

Carbon dots (CDs) was facilely synthesized from aspartic acid through a pyrolysis method in this work. Based on their favorable fluorescence property, CDs was utilized to design a metal ions-mediated fluorescent probe for N-acetyl-L-cysteine (NAC) detection. The fluorescence intensity of CDs was firstly quenched by manganese ion (Mn²⁺ ) through static quenching effect and subsequently restored by NAC via the combination with Mn²⁺ owing to the coordination effect. Therefore, the fluorescent turn-on sensing of NAC was actuated based on the fluorescence quenching stimulated by Mn²⁺ and recovery induced by coordination. The fluorescence recovery efficiencies showed a proportional range to the concentration of NAC in the range of 0.04-5 mmol L^-1 and the detection limit was 0.03 mmol L^-1 . Further, this metal ions-mediated fluorescent nanoprobe was applied to human urine sample detection and the standard recovery rates were located in the range of 97.62-102.34 %. It was the first time that Mn²⁺ was used to construct fluorescent nanoprobe for NAC. Compared to other heavy metal ions, Mn²⁺ with good biosecurity prevented the risk of application, which made the nanoprobe green and bio-practical. The facile synthesis of CDs and novel metal ions-mediated sensing mode made it a promising method for pharmaceutical analysis.

Boron doped Fluorescent Carbon Nano Dots for reduction of ionic dyes and as Encryption and decryption QR code labels

This work discusses the synthesis of fluorescent undoped and boron-doped carbon nanodots (BDCNDs) by a simple hydrothermal approach using Tribulus terretris as carbon precursor and boric acid as boron source....