Eco-friendly fabrication of multifunctional magnetic plasmonic photocatalyst for adsorption, SERS monitoring and photodegradation of residual fluoroquinolone antibiotics in water

Dual-function reusable SERS substrate based on Ag/Ag3PO4/MXene heterojunction: Efficient detection and photocatalytic degradation of organic pollutants

A flexible cotton-based Ag/Ag3PO4/MXene (APMX) ternary composite material was successfully synthesized, serving as a dual-function and reusable surface-enhanced Raman scattering (SERS) substrate for both sensitive detection and efficient organic dye degradation. The remarkable SERS properties of the composite can be attributed to the combined effects of electromagnetic enhancement by Ag nanoparticles (Ag NPs), charge transfer enhancement from Ag3PO4, and the chemical enhancement mechanisms associated with MXene. When employed for the detection of crystal violet (CV), the material exhibits outstanding sensitivity, achieving a limit of detection (LOD) as low as 3.82 × 10-11 M. Moreover, the synergistic effects between the localized surface plasmon resonance (LSPR) of Ag NPs and the high electrical conductivity of MXene significantly improve charge transfer on the Ag3PO4 surface, thereby enhancing photocatalytic efficiency. Under visible light irradiation, the composite achieves an 83.64 % degradation rate of CV within 90 min. By integrating the composite material onto cotton, its flexibility and practical applicability are enhanced, allowing for in-situ SERS detection and effective analysis on irregular surfaces. Additionally, the photocatalytic degradation function imparts a self-cleaning property, greatly improving its reusability and sustainability. As a high-performance, dual-function material, the APMX cotton shows great potential in environmental monitoring and pollution control by providing sensitive SERS detection and efficient wastewater pollutant degradation.

Lithium-doped ZrO2 nanoparticles for SERS-based norfloxacin drug detection

Surface-enhanced Raman scattering (SERS) spectroscopy is a highly specific and ultrasensitive analytical technique; thus, it is an ideal candidate for therapeutic drug monitoring. However, SERS measurements of drugs in a sample are inevitably affected by the environment. In this study, we synthesized ZrO2 nanoparticles (NPs) doped with the first group of elements (Li, Na, and K) in the main block and evaluated their SERS performance. The results showed that Li-ion doping could significantly enhance the SERS effect, and the degree of enhancement depended on the type and concentration of the doped ions. Compared with the highly stable ZrO2, Li ion-doped ZrO2 (Li-ZrO2) exhibited a significant increase in SERS activity. In particular, 1 % Li-ZrO2 NPs exhibited excellent SERS enhancement with an enhancement factor (EF) of 2.60 × 104, which was attributed to the decreased band gap and improved the charge transfer (CT) process after Li ion doping. The adsorption capacity of the Li-ZrO2 NPs for norfloxacin (NOR) molecules was gradually saturated with time. In addition, both acidic and alkaline conditions were unfavorable for NOR detection by the substrate. The SERS intensity exhibited a linear relationship within the NOR concentration range of 10-3-10-6 mol/L, and approximately 97.51 % of the active ingredients were detected, with a competitive detection limit of 10-6 mol/L. Furthermore, NOR detection is cost-effective and time-efficient, and the results of our study can aid in the research process and support practical applications. The proposed study provides a guidance for improving the SERS activity of semiconductors for sensing.

Surface-enhanced Raman scattering based on noble metal nanoassemblies for detecting harmful substances in food

Residues of harmful substances in food can severely damage human health. The content of these substances in food is generally low, making detection difficult. Surface-enhanced Raman scattering (SERS), based on noble metal nanomaterials, mainly gold (Au) and silver (Ag), has exhibited excellent capabilities for trace detection of various substances. Noble metal nanoassemblies, in particular, have extraordinary flexibility and tunable optical properties, which cannot be offered by single nanoparticles (NPs). These nanoassemblies, with their various morphologies synthesized using NPs through artificially induced self-assembly or template-driven preparation, can significantly enhance the local electric field and create "hot spots" due to the gaps between adjacent NPs. Consequently, the SERS properties of NPs become more prominent, leading to improved performance in the trace detection of various substances and detection limits that are considerably lower than the current relevant standards. Noble metal nanoassemblies show promising potential in ensuring food safety. This review discusses the synthesis methods and SERS properties of noble metal nanoassemblies and then concentrates on their application in detecting biotoxins, drug residues, illegal additives, and heavy metals. The study provides valuable references for further research into the application of nanoassemblies in food safety detection.

Direct Z-scheme system of UiO-66 cubes wrapped with Zn0.5Cd0.5S nanoparticles for photocatalytic hydrogen generation synchronized with organic pollutant degradation

Optimized fabrication of Z-scheme photocatalyst based on MOF materials offers sustainable energy generation and environmental improvement due to their attractive properties. The Z-scheme heterojunctions consisting of UiO-66 cubes covered with Zn0.5Cd0.5S nanoparticles were fabricated by a facile solvothermal method. Thanks to the Z-scheme carrier transport under simulated sunlight irradiation, UiO-66@Zn0.5Cd0.5S exhibited enhanced photocatalytic performance of H2 generation synchronized with organic pollutant degradation in fluoroquinolone antibiotic wastewater. Synergistically, the highest comprehensive performance was obtained in ciprofloxacin solution. The H2 yield reached 224 μmol∙ g-1∙ h-1 and simultaneously the removal efficiency was up to 83.6 %. The degradation pathways revealed that the process of piperazine ring cleavage and decarboxylation also generates H protons, further promoting the production of H2. Therefore, the effective spatial separation and transfer of the photoinduced carriers are attributed to the good band structure, large specific surface area, and cooperative reduction and oxidation reactions of UiO-66@Zn0.5Cd0.5S, resulting in significant photocatalytic activity. The toxicity assessment of antibiotics and intermediate products during the photocatalytic reaction also verifies the reduction of environmental risk. This study highlights a promising way to expand the application of the MOFs-based photocatalyst in clean energy conversion coupling with water remediation.

Efficient Sequential Detection of Two Antibiotics Using a Fiber-Optic Surface Plasmon Resonance Sensor

Antibiotic residues have become a worldwide public safety issue. It is vital to detect multiple antibiotics simultaneously using sensors. A new and efficient method is proposed for the combined detection of two antibiotics (enrofloxacin (Enro) and ciprofloxacin (Cip)) in milk using surface plasmon resonance (SPR) sensors. Based on the principle of immunosuppression, two antibiotic antigens (for Enro and Cip) were immobilized on an optical fiber surface with conjugates of bovine serum albumin using dopamine (DA) polymerization. Each single antigen was bound to its corresponding antibody to derive standard curves for Enro and Cip. The fiber-optic sensor's sensitivity was 2900 nm/RIU. Detection limits were calculated to be 1.20 ng/mL for Enro and 0.81 ng/mL for Cip. The actual system's recovery rate was obtained by testing Enro and Cip in milk samples; enrofloxacin's and ciprofloxacin's mean recoveries from the milk samples were 96.46-120.46% and 96.74-126.9%, respectively. In addition, several different regeneration solutions were tested to analyze the two target analytes' regeneration ability; NaOH and Gly-HCl solutions were found to have the best regeneration ability.