TiO2 photocatalysis: Impact of the platinum loading method on reductive and oxidative half-reactions

Synthesis of TiO2-SiO2-Ag/Fiberglass with Antibacterial Properties and Its Application for Air Cleaning

The TiO₂-SiO₂-Ag/fiberglass with antibacterial properties under UV light irradiation was synthesized. The effects of compositions of TiO₂-SiO₂-Ag/fiberglass, optical, and textural characteristics on the antibacterial activity were studied. The TiO₂-SiO₂-Ag film was coated on the surface of fiberglass carrier filaments. The temperature effect on the formation of the TiO₂-SiO₂-Ag film was established by thermal analysis, and the temperature treatment mode was selected as 300 °C for 30 min, 400 °C for 30 min, 500 °C for 30 min, and 600 °C for 30 min. The influence of silicon oxide and silver additives on the antibacterial properties of TiO₂-SiO₂-Ag films was established. Increasing the treatment temperature of the materials up to 600 °C increased the thermal stability of the titanium dioxide anatase phase, while the values of optical characteristics decreased: the film thickness decreased to 23.92 ± 1.24 nm, the refractive index decreased to 2.154 ± 0.002, the energy of the band gap width decreased to 2.8 ± 0.5, and the light absorption shifted to the visible-light regime, which is important for photocatalytic reactions. The results showed that the use of TiO₂-SiO₂-Ag/fiberglass allows significant decrease in the value of CFU microbial cells to 125 CFU m^-3.

Synergistic Effects of AgNPs and Biochar: A Potential Combination for Combating Lung Cancer and Pathogenic Bacteria

The synthesis of reliable biological nanomaterials is a crucial area of study in nanotechnology. In this study, Emericella dentata was employed for the biosynthesis of AgNPs, which were then combined with synthesized biochar, a porous structure created through biomass pyrolysis. The synergistic effects of AgNPs and biochar were evaluated through the assessment of pro-inflammatory cytokines, anti-apoptotic gene expression, and antibacterial activity. Solid biosynthesized AgNPs were evaluated by XRD and SEM, with SEM images revealing that most of the AgNPs ranged from 10 to 80 nm, with over 70% being less than 40 nm. FTIR analysis indicated the presence of stabilizing and reducing functional groups in the AgNPs. The nanoemulsion's zeta potential, hydrodynamic diameter, and particle distribution index were found to be -19.6 mV, 37.62 nm, and 0.231, respectively. Biochar, on the other hand, did not have any antibacterial effects on the tested bacterial species. However, when combined with AgNPs, its antibacterial efficacy against all bacterial species was significantly enhanced. Furthermore, the combined material significantly reduced the expression of anti-apoptotic genes and pro-inflammatory cytokines compared to individual treatments. This study suggests that low-dose AgNPs coupled with biochar could be a more effective method to combat lung cancer epithelial cells and pathogenic bacteria compared to either substance alone.

Ultrasound-Assisted Mineralization of 2,4-Dinitrotoluene in Industrial Wastewater Using Persulfate Coupled with Semiconductors

Oxidative degradation of 2,4-dinitrotoluenes in aqueous solution was executed using persulfate combined with semiconductors motivated by ultrasound (probe type, 20 kHz). Batch-mode experiments were performed to elucidate the effects of diverse operation variables on the sono-catalytic performance, including the ultrasonic power intensity, dosage of persulfate anions, and semiconductors. Owing to pronounced scavenging behaviors caused by benzene, ethanol, and methanol, the chief oxidants were presumed to be sulfate radicals which originated from persulfate anions, motivated via either the ultrasound or sono-catalysis of semiconductors. With regard to semiconductors, the increment of 2,4-dinitrotoluene removal efficiency was inversely proportional to the band gap energy of semiconductors. Based on the outcomes indicated in a gas chromatograph-mass spectrometer, it was sensibly postulated that the preliminary step for 2,4-dinitrotoluene removal was denitrated into o-mononitrotoluene or p-mononitrotoluene, followed by decarboxylation to nitrobenzene. Subsequently, nitrobenzene was decomposed to hydroxycyclohexadienyl radicals and converted into 2-nitrophenol, 3-nitrophenol, and 4-nitrophenol individually. Nitrophenol compounds with the cleavage of nitro groups synthesized phenol, which was sequentially transformed into hydroquinone and p-benzoquinone.

Fungal-Mediated Silver Nanoparticle and Biochar Synergy against Colorectal Cancer Cells and Pathogenic Bacteria

Background: Silver nanoparticles (AgNPs) are attractive substrates for new medicinal treatments. Biochar is pyrolyzed biomass. Its porous architecture allows it to hold and gather minuscule particles, through which nanoparticles can accumulate in its porous structure. This study examined AgNPs’ antibacterial and anticancer properties alone and combined with biochar. Methods: The fungus Emericella dentata was responsible for biosynthesis of AgNPs. The characterization of AgNPs using STEM images and a Zetasizer was carried out. Accordingly, the antibacterial and antiproliferation activity of AgNPs and biochar was studied using MIC and MTT assays, respectively. To evaluate the antiangiogenic and anti-inflammatory effects of AgNPs with biochar, VEGF and cytokines including TNF alpha, IL-6 and IL-beta were tested using an ELISA assay. Results: The size of the AgNPs ranged from 10 to 80 nm, with more than 70% of them being smaller than 40 nm. The combination of AgNPs and biochar enhanced the antibacterial activity against all tested bacteria. Furthermore, this combination showed antiproliferative properties against HT29 cancer cells with high selectivity to fibroblasts at low concentrations. AgNPs with biochar significantly reduced VEGF and proinflammatory cytokine expression levels. Conclusions: Biochar and AgNPs may be novel treatments for bacteria and colorectal cancer cells, according to the current findings.

One Stone Two Birds: Utilization of Solar Light for Simultaneous Selective Phenylcarbinol Oxidation and H2 Production over 0D/2D-3D Pt/In2S3 Schottky Junction

Precise regulation and control solar-light-driven charges photoexcited on photocatalysts for separation-transfer and target redox reactions is an attractive and challenging pathway toward sustainability. Herein, 0D/2D-3D Pt/In2S3 Schottky junction was fabricated for simultaneous selective phenylcarbinol conversion into value-added aldehydes and production of clean energy H2 by directly utilizing photoexcited holes and electrons in one reaction system under mild reaction conditions. In contrast to pure water splitting and pure In2S3, the reaction thermodynamics and kinetics of H2 evolution on the Pt/In2S3 were significantly enhanced. The optimized 0.3% Pt/In2S3 exhibited the highest and most stable photocatalytic activity with 22.1 mmol g−1 h−1 of H2 production rate and almost 100% selectivity of benzaldehyde production. Notably, this dual-function photocatalysis also exhibited superiority in contrast to sacrificial-agent H2 evolution reactions such as lactic acid, Na2S, methanol and triethanolamine. The turnover frequency (TOF) could reach up to ~2394 h−1. The Pt clusters anchored at the electron location and strong metal-support interactions (SMSI) between Pt and In2S3 synergistically improved the spatial charge separation and directional transportation (~90.1% of the charge transport efficiency could be achieved over the Pt/In2S3 hybrid), and thus result in significant enhancement of photocatalytic H2 evolution with simultaneous benzaldehyde production.

Al-Dalain S, Al-Dmour R, Alahmad A, Batarseh MI. Accumulation, Source Identification, and Cancer Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Different Jordanian Vegetables

The accumulation of polyaromatic hydrocarbons in plants is considered one of the most serious threats faced by mankind because of their persistence in the environment and their carcinogenic and teratogenic effect on human health. The concentrations of sixteen priority polycyclic aromatic hydrocarbons (16 PAHs) were determined in four types of edible vegetables (tomatoes, zucchini, eggplants, and cucumbers), irrigation water, and agriculture soil, where samples were collected from the Jordan Valley, Jordan. The mean total concentration of 16 PAHs (∑16PAHs) ranged from 10.649 to 21.774 µg kg−1 in vegetables, 28.72 µg kg−1 in soil, and 0.218 µg L−1 in the water samples. The tomato samples posed the highest ∑16PAH concentration level in the vegetables, whereas the zucchini samples had the lowest. Generally, the PAHs with a high molecular weight and four or more benzene rings prevailed among the studied samples. The diagnostic ratios and the principal component analysis (PCA) revealed that the PAH contamination sources in soil and vegetables mainly originated from a pyrogenic origin, traffic emission sources, and biomass combustion. The bioconcentration factors (BCF) for ∑16PAHs have been observed in the order of tomatoes > cucumbers and eggplants > zucchini. A potential cancer risk related to lifetime consumption was revealed based on calculating the incremental lifetime cancer risk of PAHs (ILCR). Therefore, sustainable agricultural practices and avoiding biomass combusting would greatly help in minimizing the potential health risk from dietary exposure to PAHs.

Property-governed performance of platinum-modified titania photocatalysts

Titania is probably the most widely investigated semiconductor photocatalyst because of various advantages, such as high activity, thermal and chemical stability, low price, abundance, and negligible toxicity. However, pristine titania is also characterized by charge carriers’ recombination, and thus lower quantum yields of photocatalytic reactions than theoretical 100%. Moreover, its wide bandgap, despite being recommended for excellent redox properties, means also inactivity under visible part of solar radiation. Accordingly, titania has been surface modified, doped and coupled with various elements/compounds. For example, platinum deposited on the surface of titania has shown to improve both UV activity and the performance under vis. Although the studies on titania modification with platinum started almost half a century ago, and huge number of papers have been published up to now, it is unclear which properties are the most crucial and recommended to obtain highly efficient photocatalyst. In the literature, the opposite findings could be found on the property-governed activities that could result from huge differences in the reaction systems, and also examined photocatalysts. Considering the platinum properties, its content, the size of nanoparticles and the oxidation state, must be examined. Obviously, the characteristics of titania also influence the resultant properties of deposited platinum, and thus the overall photocatalytic performance. Although so many reports on Pt/TiO₂ have been published, it is hardly possible to give indispensable advice on the recommended properties. However, it might be concluded that usually fine platinum NPs uniformly deposited on the titania surface result in high photocatalytic activity, and thus in the low optimal content of necessary platinum. Moreover, the aggregation of titania particles might also help in the lowering the necessary platinum amount (even to 0.2 wt%) due to the interparticle electron transfer mechanism between titania particles in one aggregate. In respect of platinum state, it is thought that it is highly substrate-specific case, and thus either positively charged or zero valent platinum is the most recommended. It might be concluded that despite huge number of papers published on platinum-modified titania, there is still a lack of comprehensive study showing the direct correlation between only one property and the resultant photocatalytic activity.

Application of EPR Spectroscopy in TiO2 and Nb2O5 Photocatalysis

The interaction of light with semiconducting materials becomes the center of a wide range of technologies, such as photocatalysis. This technology has recently attracted increasing attention due to its prospective uses in green energy and environmental remediation. The characterization of the electronic structure of the semiconductors is essential to a deep understanding of the photocatalytic process since they influence and govern the photocatalytic activity by the formation of reactive radical species. Electron paramagnetic resonance (EPR) spectroscopy is a unique analytical tool that can be employed to monitor the photoinduced phenomena occurring in the solid and liquid phases and provides precise insights into the dynamic and reactivity of the photocatalyst under different experimental conditions. This review focus on the application of EPR in the observation of paramagnetic centers formed upon irradiation of titanium dioxide and niobium oxide photocatalysts. TiO2 and Nb2O5 are very well-known semiconductors that have been widely used for photocatalytic applications. A large number of experimental results on both materials offer a reliable platform to illustrate the contribution of the EPR studies on heterogeneous photocatalysis, particularly in monitoring the photogenerated charge carriers, trap states, and surface charge transfer steps. A detailed overview of EPR-spin trapping techniques in mechanistic studies to follow the nature of the photogenerated species in suspension during the photocatalytic process is presented. The role of the electron donors or the electron acceptors and their effect on the photocatalytic process in the solid or the liquid phase are highlighted.