Optical Management of CQD/AgNP@SiNW Arrays with Highly Efficient Capability of Dye Degradation

Effect of Hydrothermal Conditions on Kenaf-Based Carbon Quantum Dots Properties and Photocatalytic Degradation

The development of biomass-based CQD is highly attentive to enhancing photocatalytic performance, especially in secondary or ternary heterogeneous photocatalysts by allowing for smooth electron-hole separation and migration. In this study, kenaf-based carbon quantum dots (CQD) were prepared. The main objective of the current work was to investigate temperature, precursor mass and time in hydrothermal synthesis treatment to improve the CQD properties and methylene blue photocatalytic degradation. Optimization of kenaf-based CQD for inclusion in hydrothermal treatment was analyzed. The as-prepared CQDs have been characterized in detail by Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscope (HRTEM), photoluminescence (PL) and ultraviolet–visible (UV–Vis) spectroscopy. It was found that C200-0.5-24 exhibits a higher photocatalytic activity of the methylene blue dye and optimized hydrothermal conditions of 200 °C, 0.5 g and 24 h. Therefore, novel kenaf-based CQD was synthesized for the first time and was successfully optimized in the as-mentioned conditions. During the hydrothermal treatment, precursor mass controls the size and the distribution of CQD nanoparticles formed. The C200-0.5-24 showed a clearly defined and well-distributed CQD with an optimized nanoparticle size of 8.1 ± 2.2 nm. Indeed, the C200-0.5-24 shows the removal rate of 90% of MB being removed within 120 min.

Preparation of Fluorescent Carbon Dots Composites and Their Potential Applications in Biomedicine and Drug Delivery-A Review

Carbon dots (CDs), a new member of carbon nanostructures, rely on surface modification and functionalization for their good fluorescence phosphorescence and excellent physical and chemical properties, including small size (<10 nm), high chemical stability, biocompatibility, non-toxicity, low cost, and easy synthesis. In the field of medical research on cancer (IARC), CDs, a new material with unique optical properties as a photosensitizer, are being applied to heating local apoptosis induction of cancer cells. In addition, imaging tools can also be combined with a drug to form the nanometer complex compound, the imaging guidance for multi-function dosage, so as to improve the efficiency of drug delivery, which also plays a big role in genetic diagnosis. This paper mainly includes three parts: The first part briefly introduces the synthesis and preparation of carbon dots, and summarizes the advantages and disadvantages of different preparation methods; The second part introduces the preparation methods of carbon dot composites. Finally, the application status of carbon dot composites in biomedicine, cancer theranostics, drug delivery, electrochemistry, and photocatalysis is summarized.

Visual Cu2+ Detection of Gold-Nanoparticle Probes and its Employment for Cu2+ Tracing in Circuit System

Highly sensitive, simple and reliable colorimetric probe for Cu²⁺-ion detection was visualized with the L-cysteine functionalized gold nanoparticle (LS-AuNP) probes. The pronounced sensing of Cu²⁺ with high selectivity was rapidly featured with obvious colour change that enabled to visually sense Cu²⁺ ions by naked eyes. By employing systemic investigations on crystallinities, elemental compositions, microstructures, surface features, light absorbance, zeta potentials and chemical states of LS-AuNP probes, the oxidation-triggered aggregation effect of LS-AuNP probes was envisioned. The results indicated that the mediation of Cu²⁺ oxidation coordinately caused the formation of disulfide cystine, rendering the removal of thiol group at AuNPs surfaces. These features reflected the visual colour change for the employment of tracing Cu²⁺ ions in a quantitative way.

Day-night active photocatalysts obtained through effective incorporation of Au@CuxS nanoparticles onto ZnO nanowalls

Photocatalytic degradation of organic dyes has been considered one of the promising solutions that enabled to effectively treat the demanding pollutants in wastewater. Yet, insight into the photocatalytic process under both illumination and dark conditions were hitherto missing. Herein, by virtue of incorporating the core-shell Au@Cu_xS nanoparticles to the ZnO nanowalls synthesized via all-solution synthesis, the intriguing heterostructures allowed to trigger the extraordinary capability of dye degradation either under light irradiance or dark environment. It was found that the coexistence of bi-constituted Cu₂S/CuS shells on Au nanoparticles obtained with turning the concentrations of sulfurization acted as the decisive role on day-night active degradation performance, where the degradation efficiency was more than 8.3 times beyond sole ZnO sheets. The mediation of remarkable visible-light absorption and efficient charge separation due to band alignment of heterojunctions were responsible for the improved photodegradation efficiency under visible illuminations. Moreover, at dark environment, the involving peroxidase-like activity of Cu_xS shells with the mediation of Au nanoparticles facilitated the catalytic formation of hydroxyl radicals, manifesting the oxidative degradation of MB dye. Such all-day active photocatalysts further displayed the capability for the recycling treatment of MB dye, which offered the pathways to potentially treat the organic wastewater.

Application of carbon dots and their composite materials for the detection and removal of radioactive ions: A review

Radioactive ions with high-heat release or long half-life could cause long-term influence on environment and they might enter the food chain to damage human body for their toxicity and radioactivity. It is of great importance to develop methods and materials to detect and remove radioactive ions. Carbon dots and their composite materials has been applied widely in many fields due to their plentiful raw materials, facile synthesis and functional process, unique optical property and abundant functional groups. This comprehensive review focuses on the preparation of CDs and composite materials for the detection and adsorption of radioactive ions. Firstly, the recent-developed synthetic methods for CDs were summarized briefly, including hydrothermal/solvothermal, microwave, electrochemistry, microplasma, chemical oxidation methods, focusing on the influence of CDs properties. Secondly, the synthetic methods for CDs composite materials were classified to four categories and summarized generally. Thirdly, the application of CDs for radioactive ions detection and adsorption were explored and concluded including uranium, iodine, europium, strontium, samarium et al. Finally, the detection and adsorption mechanism for radioactive ions were searched and the perspective and outlook of CDs for detection and adsorption radioactive ions have been proposed based on our understanding.

Ultrasound Assisted Synthesis of Gadolinium Oxide-Zeolitic Imidazolate Framework-8 Nanocomposites and Their Optimization for Photocatalytic Degradation of Methyl Orange Using Response Surface Methodology

An ultrasound-assisted method was used to prepare gadolinium oxide (Gd2O3)-zeolitic imidazolate framework (ZIF)-8 nanocomposites. The surface morphology, particle size, and properties of the Gd2O3-ZIF-8 nanocomposites were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy. The synthesized Gd2O3-ZIF-8 nanocomposites were used as a catalyst to degrade methyl orange (MO) under UV light irradiation at 254 nm. The color of the aqueous MO dye solution during photocatalytic degradation was examined using color spectroscopy. Response surface methodology (RSM) using a four-factor Box-Behnken design (BBD) was used to design the experiments and optimize the photocatalytic degradation of MO. The significance of the experimental factors and their interactions were determined using analysis of variance (ANOVA). The efficiency of Gd2O3-ZIF-8 nanocomposites for the photocatalytic degradation of MO reached 98.05% within 40 min under UV irradiation at 254 nm under the experimental conditions of pH 3.3, 0.4 g/L catalyst dose, 0.0630 mM MO concentration, and 431.79 mg/L H2O2 concentration. The kinetics study showed that the MO photocatalytic degradation followed a pseudo-first-order reaction rate law.

Enhanced Photocatalytic Activity of Spherical Nd3+ Substituted ZnFe2O4 Nanoparticles

In this study, nanocrystalline ZnNd_xFe_2−xO₄ ferrites with x = 0.0, 0.01, 0.03 and 0.05 were fabricated and used as a catalyst for dye removal potential. The effect of Nd³⁺ ions substitution on the structural, optical and photo-Fenton activity of ZnNd_xFe_2−xO₄ has been investigated. The addition of Nd³⁺ ions caused a decrease in the grain size of ferrites, the reduction of the optical bandgap energies and thus could be well exploited for the catalytic study. The photocatalytic activity of the ferrite samples was evaluated by the degradation of Rhodamine B (RhB) in the presence of H₂O₂ under visible light radiation. The results indicated that the ZnNd_xFe_2−xO₄ samples exhibited higher removal efficiencies than the pure ZnFe₂O₄ ferrites. The highest degradation efficiency was 98.00%, attained after 210 min using the ZnNd_0.03Fe_1.97O₄ sample. The enhanced photocatalytic activity of the ZnFe₂O₄ doped with Nd³⁺ is explained due to the efficient separation mechanism of photoinduced electron and holes. The effect of various factors (H₂O₂ oxidant concentration and catalyst loading) on the degradation of RhB dye was clarified.