Nguyen Thi Kim Phuong

This study endeavors to harness electrical energy from discarded materials. We developed a triboelectric nanogenerator (TENG) employing the waste plastic petri dish as the negative triboelectric material and the waste food packaging aluminum foil as the positive triboelectric material. By manual tapping to TENG at a frequency of 3 Hz, a short‐circuit current and open‐circuit voltage of approximately 2.5 µA and 5 V were measured, respectively. When connected to a 500 kΩ resistor, TENG achieved a peak power density of 35 nW/cm ² . To better understand the TENG mechanism, a simulation model was also applied. Notably, the direct operation of two LEDs and the display of a stopwatch via a capacitor highlight the potential of TENG to power portable electronics. This research contributed to environmental remediation and holds promise for generating renewable and sustainable energy.

Tetracycline residues in aquatic ecosystems, resulting from widespread antibiotic use, pose significant risks by fostering antibiotic resistance and threatening ecological and human health. Addressing the need for rapid, sensitive, and portable tetracycline detection, this study presents a novel device utilizing iron-coordinated carbon dots (CDs-Fe) derived from Chromolaena odorata as a peroxidase-mimic nanozyme. Synthesized via a one-step hydrothermal method, the CDs-Fe nanozyme exhibits enhanced catalytic activity, enabling a colorimetric assay with 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H₂O₂). Tetracycline detection relies on the nanozyme’s peroxidase-like activity, where tetracycline competitively inhibits TMB oxidation, reducing the absorbance at 652 nm due to surface adhesion and substrate competition. The assay achieves a detection limit of 1.34 μM and a linear range of 17 to 67 μM. A portable Arduino-based device, fabricated via 3D printing with smartphone-enabled Bluetooth data reading, was developed for on-site tetracycline monitoring in real water samples, showing recoveries of 95 to 102% and high selectivity against other antibiotics. Validated against UV–vis spectrophotometry, this green-synthesized, cost-effective system offers a sustainable and field-deployable solution for environmental water quality assessment. Graphical abstract

Dipicolinic acid (DPA) is a key biomarker of bacterial spores. In this study, we present a novel distance-based paper analytical device (d-PAD) for the fluorescence sensing of DPA. The detection mechanism relies on the complexation of ofloxacin (OFL) with Cu²⁺ ions, where Cu²⁺ quenches the fluorescence of OFL via static quenching. Upon the introduction of DPA, it interacts with the OFL-Cu²⁺ complex, resulting in an enhanced fluorescence signal from OFL. The assay demonstrated a limit of detection (LOD) of 0.08 μM over a range of 0.6–120 μM, as measured using a spectrofluorometer. The d-PAD was designed for efficient reagent transport through capillary action on paper substrates, allowing for rapid on-site DPA analysis without requiring advanced laboratory equipment. The length of the fluorescent bands on the d-PADs was proportional to the concentration of DPA, providing a simple and effective readout method. With a sensitivity of 0.6 μM, the device shows a strong response to varying DPA concentrations. This distance-based platform offers a straightforward and quantitative approach to result interpretation, making it a promising tool for detecting bacterial spores in real samples. The development and optimization of this paper-based microfluidic assay represent a significant step forward in portable diagnostic technologies.

Using a simple, low cost, and excellent efficient approach, carbon dots (CDs) were fabricated via a one-pot hydrothermal process of coffee waste. Amazingly, the combination of 2 CDs with ZnBi₂O₄ to form a new and excellent heterogeneous photocatalyst enabled the complete decomposition of 2, 4-dichlorophenoxyacetic acid (2, 4-D) into CO₂ and H₂O. The findings of this study provide a new perspective on the utilization of agricultural waste for creating products of scientific and practical significance. More than 91 of 2, 4-D (initial concentration of 30mg/L) was completely decomposed and dechlorinated using 1.0g/L of CDs (2)-ZnBi₂O₄ at pH 4.0 after 120min of exposure to visible light (with k=0.0178min⁻¹), and more than 86 of the decomposed 2, 4-D was mineralized into CO₂ and H₂O. There was no sign of catalyst deactivation after four cycles of reuse, demonstrating the durability and efficiency of CDs (2)-ZnBi₂O₄. The significant improvement in the photocatalytic efficiency of CDs (2)-ZnBi₂O₄ compared with that of bare CDs or ZnBi₂O₄ is due to the formation of defects at the interfaces of the heterojunction; therefore, the movement of photogenerated electrons at the interface between the two components is rapid. The mineralization of 2, 4-D by CDs (2)-ZnBi₂O₄ upon exposure to visible light is induced mainly by the photogenerated holes, followed by O₂^•−, and finally OH^• radicals.

In recent years, solid-state engineering has emerged as a promising method for improving the stability and potency of antibiotics and anti-inflammatory drugs. This study focuses on the design and optimization of the intercalation of levofloxacin (an antibiotic drug) and salicylic acid (an anti-inflammatory drug) into zinc-aluminium-layered double hydroxide galleries using response surface method. Release studies revealed that a burst release phenomenon was observed at the beginning of the release assay, and the pH value (in the range of 5.8-7.4) had very little influence on the levofloxacin and salicylic acid release efficiency. This indicates that zinc-aluminium-layered double hydroxide could be an effective inorganic carrier for levofloxacin and salicylic acid over a wide range of pH values. Four kinetic models were used to study the release kinetics and the drug release mechanism was also discussed. In addition, the intercalation of levofloxacin and salicylic acid into zinc-aluminium-layered double hydroxide exhibited enhanced antibacterial activity against Gram-positive Bacillus subtilis. The cell viability assay revealed non-toxic behavior of levofloxacin and salicylic acid intercalated into zinc-aluminium-layered double hydroxide against the monocyte/macrophage-like cell line.

A superior heterojunction of HC-ZnBi-LDO was synthesized in two steps, namely hydrothermal carbonization, followed by co-precipitation. The 2% HC-ZnBi-LDO heterojunction photocatalysts could degrade over 90.8% of 30 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) using 1.0 g/L of the catalyst after 135 min of visible light exposure at pH 4. The activity of 2% HC-ZnO-LDO was remarkably stable. Approximately 86.4–90.8% of 30 mg/L 2,4-D was degraded, and more than 79–86.4% of TOC was mineralized by 2% HC-ZnBi-LDO at pH 4 after 135 min of visible light exposure during four consecutive cycles. The rapid separation and migration of charge carriers at the interfaces between HC and ZnBi-LDO were achieved within 2% HC-ZnBi-LDO. Moreover, the electron acceptor characteristic of HC in 2% HC-ZnBi-LDO caused the recombination of charge carriers to decrease significantly, thus generating more reactive radicals, such as hydroxyl radicals (OH^●) and superoxide radicals (O₂^●−). These results demonstrate that the novel 2% HC-ZnBi-LDO is a superior photocatalyst for the remediation of hazardous organic pollutants.