Simultaneous photocatalytic degradation and SERS detection of tetracycline with self-sustainable and recyclable ternary PI/TiO2/Ag flexible microfibers

Facile and efficient photocatalysts using sunlight, as well as fast and sensitive surface-enhanced Raman spectroscopy (SERS) substrates, are urgently needed for practical degradation of tetracycline (TC). To meet these requirements, a new paradigm for PI/TiO2/Ag organic‒inorganic ternary flexible microfibers based on semiconducting titanium dioxide (TiO2), the noble metal silver (Ag) and the conjugated polymer polyimide (PI) was developed by engineering a simple method. Under sunlight, the photocatalytic characteristics of the PI/TiO2/Ag flexible microfibers containing varying amounts of Ag quantum dots (QDs) were evaluated with photocatalytic degradation of TC in aqueous solution. The results demonstrated that the amount of Ag affected the photocatalytic activity. Among the tested samples, PI/TiO2/Ag-0.07 (93.1%) exhibited a higher photocatalytic degradation rate than PI/TiO2 (25.7%), PI/TiO2/Ag-0.05 (77.7%), and PI/TiO2/Ag-0.09 (63.3%). This observation and evaluation conducted in the present work strongly indicated a charge transfer mechanism. Moreover, the PI/TiO2/Ag-0.07 flexible microfibers exhibited highly sensitive SERS detection, as demonstrated by the observation of the Raman peaks for TC even at an extremely low concentration of 10-10 moles per liter. The excellent photocatalytic performance and SERS detection capability of the PI/TiO2/Ag flexible microfibers arose from the Schottky barrier formed between Ag and TiO2 and also from the outstanding plasmonic resonance and visible light absorptivity of Ag, along with immobilization by the PI. The successful synthesis of PI/TiO2/Ag flexible microfibers holds significant promise for sensitive detection and efficient photocatalytic degradation of antibiotics.

A novel tubular up-flow magnetic film photocatalytic system optimized by main factors control for efficient removal of chlorophenols wastewater

Chlorophenols (CPs) are still used as raw material or intermediate in some industries. Photocatalytic oxidation is free from secondary pollution, but the efficiency is restricted by some main factors. In this study, a novel high efficiency tubular up-flow magnetic film (TUMF) photocatalytic system was investigated based on the magnetic lanthanum doping core-shell Fe₃O₄@SiO₂@TiO₂ (La-FST) nanoparticles. When the dosage of La-FST was 0.4 g/L, the flow velocity was 94.2 mL/min, and the circulated irradiation of 15 W maintained 40 min, the average removal rate of 2,4-dichlorophenol (2,4-DCP) was reduced significantly from 10 mg/L to 0.0803 mg/L by TUMF system, meeting the limits of the particular items (0.093 mg/L) from national environmental quality standards for surface water, avoiding the problem of photocatalyst separation and loss. The photoinduced holes (h⁺) was the key active radical to oxidize 2,4-DCP, and the main factors of TUMF system could be well controlled to achieve satisfactory effluent quality. A prediction method of photocatalytic reaction time in a multistage series TUMF system was established to remove 2,4-DCP from 100 mg/L to 0.5 mg/L, saving 86 min. The novel high-efficiency TUMF system provides a technical selection for the photocatalytic degradation of CPs and other refractory organics.

Synthesis and evaluation of the SERS effect of Fe3O4–Ag Janus composite materials for separable, highly sensitive substrates

Fe₃O₄–Ag Janus composites were synthesized using a two-step solvothermal method. The optimal growth process was determined by investigating the relationship between the particle morphologies and reaction time. Magnetic and Raman spectroscopic measurements showed that the as-synthesized Janus composites have both good magnetic response and significant surface-enhanced Raman scattering (SERS) effects, as well as reproducibility. The calculated Raman enhancement factor reached an unprecedented magnitude of 10⁹ compared with the values of other Fe₃O₄–Ag compounds. Furthermore, the SERS effect was exhibited even at a concentration of probe molecules as low as 10⁻¹³ M. This demonstrates that the as-synthesized Fe₃O₄–Ag Janus composite particles have promise for application as separable, highly sensitive SERS substrates.

Fe₃O₄–Ag Janus composites were synthesized using a two-step solvothermal method.

NaYF4:Yb,Tm@TiO2 core@shell structures for optimal photocatalytic degradation of ciprofloxacin in the aquatic environment

The removal of antibiotic residues in the aquatic environment is still a big challenge in environmental protection. Here, we developed NaYF₄:Yb,Tm@TiO₂ as a highly efficient photocatalyst for photocatalytic degradation of ciprofloxacin (CIP), a representative antibiotic in water under simulated solar irradiation. NaYF₄:Yb,Tm@TiO₂ can efficiently utilize a broad spectrum of solar energy to improve the efficiency of ciprofloxacin removal from an aquatic environment. The optimum operation conditions of photocatalyst dosage, pH value, and initial concentrations of CIP were determined by a series of contrast experiments. The dynamic process of CIP removal was monitored by UV-vis spectrophotometry, and can be well predicted by a pseudo first order model. The optimal conditions of photocatalyst dosage, initial concentration of CIP and pH value for CIP photocatalytic degradation were 1 g L⁻¹, 10⁻⁵ M and 8, respectively. This study provides an efficient method for antibiotic removal and enables a promising strategy for other organic water pollutant treatments.

The study indicated the optimum operation conditions to effectively remove ciprofloxacin from aquatic environment by NaYF₄:Yb,Tm@TiO₂ structures.

Optimization of Malachite Green Removal from Water by TiO₂ Nanoparticles under UV Irradiation

TiO₂ nanoparticles with surface porosity were prepared by a simple and efficient method and presented for the removal of malachite green (MG), a representative organic pollutant, from aqueous solution. Photocatalytic degradation experiments were systematically conducted to investigate the influence of TiO₂ dosage, pH value, and initial concentrations of MG. The kinetics of the reaction were monitored via UV spectroscopy and the kinetic process can be well predicted by the pseudo first-order model. The rate constants of the reaction kinetics were found to decrease as the initial MG concentration increased; increased via elevated pH value at a certain amount of TiO₂ dosage. The maximum efficiency of photocatalytic degradation was obtained when the TiO₂ dosage, pH value and initial concentrations of MG were 0.6 g/L, 8 and 10⁻⁵ mol/L (M), respectively. Results from this study provide a novel optimization and an efficient strategy for water pollutant treatment.

Surface-enhanced Raman spectroscopic detection of molecular chemo- and plasmo-catalysis on noble metal nanoparticles

The in situ detection of reactions catalyzed by metal NPs is challenging because the underlying chemical transformations occur at interfaces. Surface-enhanced Raman scattering (SERS), a surface-selective, sensitive and label-free vibrational spectroscopic technique, is ideally suited for monitoring of heterogeneous catalysis with high chemical specificity. A major limitation in the past, however, was that small, catalytically active metal NPs do not exhibit the high plasmonic activity required for SERS. This feature article focuses on the design, synthesis and use of bifunctional NPs with both catalytic and plasmonic activity for in situ SERS detection of reactions catalyzed by metal NPs. We focus on model reactions induced by chemical reducing agents such as hydride or molecular hydrogen as well as on plasmon-induced photo-catalysis including both photo-oxidation and photo-reduction. Finally, we highlight the concept of photo-recycling on halide-containing silver surfaces for unprecedented multi-electron reduction chemistry.

A novel heterojunction photocatalyst, Bi2SiO5/g-C3N4: synthesis, characterization, photocatalytic activity, and mechanism

A new type of heterojunction photocatalyst, Bi₂SiO₅/g-C₃N₄, was prepared using a controlled hydrothermal method.

Synthesis of a highly dispersive sinapinic acid@graphene oxide (SA@GO) and its applications as a novel surface assisted laser desorption/ionization mass spectrometry for proteomics and pathogenic bacteria biosensing

GO-modified sinapinic acid was synthesized and characterized; it was then investigated for use in SALDI-MS for proteomics and pathogenic bacterial biosensing.