In the present work, we used doxycycline hyclate (DX) and tetramethylguanidine (TMG) for the synthesis of silver–silver chloride nanoparticles (DX-Ag–AgCl NPs) as a simple method for the production of nanoparticles (NPs). A new synthesis method for DX-Ag–AgCl NPs in aqueous medium, using the DX and TMG as a reducing and stabilizing agent, is reported. DX-Ag–AgCl NPs were characterized by transmission electron microscopy. The elemental composition and the crystalline nature of synthesized nanoparticles were determined by energy-dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis, respectively. From EDX, it is confirmed that synthesized NPs contain elemental silver and chloride, and their crystalline nature was confirmed by XRD. The Fourier transform infra-red spectra showed the DX present in surface of DX-Ag–AgCl NPs. Synthesized NPs analyzed for antibacterial activity by agar well method against Gram-positive and Gram-negative pathogens. Synthesized DX-Ag–AgCl NPs were spherical shaped and in the range of 10–40 nm of size was observed from TEM images. In the crystalline nature, XRD peaks indicate the presence of silver and silver chloride in produced NPs. Synthesized NPs show potential antibacterial activity on Bacillus cereus KCCM 11773, Bacillus subtilis KCCM 11316, Staphylococcus aureus KCCM 40050, Escherichia coli KCCM 11234, Klebsiella pneumoniae KCCM 11418, and Proteus vulgaris KCCM 40211.

In this work, a new metal-to-metal charge transfer (MMCT) heterogeneous catalyst (Nb–O–Mo) was synthesized by a chemical grafting method under an inert atmosphere. The activity of the covalently anchored oxo-bridged Nb–O–Mo catalyst was estimated for decolorization of Rh B, congo red, and crystal violet dyes in an aqueous solution under fluorescent light. The catalyst was characterized via X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometer, Fourier-transform infrared, and FT-Raman. The catalytic decolorization was evaluated from the UV spectra of dyes in aqueous solution by changing different factors, including dye concentration, temperature, and catalyst loading. Decolorization percentages were 83%–89%, 86%–95%, 97%–99% for Rh B, Congo Red and Crystal Violet in 1 min at 298 K, showing the best performance among other catalysts. Decolorization efficiency for 50 ppm of Rh B was improved from 92% to 98%, with a temperature increase to 318 K.

This study aims to prepare a supported catalyst based on zeolite Y doped with NaOMe (sodium methoxide) for the transesterification of waste cooking oil (WCO). The catalytic screening data showed that NaOMe/zeolite is a prominent catalyst for the transesterification of WCO prepared by a solvent-free, ball-milling process. We initially tested 5–20% of sodium methoxide loading onto zeolite Y and found that 20% is the optimum loading for the reaction. The transesterification reaction required a comparatively lower methanol-to-oil mole ratio of 16:1 with the reaction temperature as 60 °C. The ball-milled NaOMe/zeolite catalyst was characterized by BET surface area analysis, FE-SEM, TEM, FT–IR, and XRD. The BET surface analysis revealed that the surface area for zeolite Y was substantially decreased in the NaOMe/zeolite catalyst. The ball-milling process dropped the crystallinity of zeolite Y, which can be seen from the XRD and FE-SEM images of both zeolite Y and the NaOMe/zeolite catalyst. Finally, the transesterification reaction product was fully characterized by ${}^1$H-NMR and viscosity analysis for biodiesel, glycerol, and the WCO. The chemical shifts for the biodiesel and glycerol are found accordingly. This is also supported by the FT–IR characterization of biodiesel, glycerol, and WCO. It is noteworthy that a very high mass ratio of 250 g oil/g NaOMe is obtained when converting WCO to biodiesel, indicating very high catalytic activity for the aforementioned catalyst.

In this study, the synthesis of a novel catalyst WO₃/MoCl₅ was carried out by the thermal method. The method gave an entirely different product compared to previous studies that doped Mo on the surface of semiconductor metal oxides. The degradation reaction of crystal violet (CV) and rhodamine B (RB) dye were done without any energy source. The results showed an incomparably superior result for degradation, with a reaction rate constant of 1.74 s⁻¹ for 30 ppm CV, 1.08 s⁻¹ for 30 ppm RB, and a higher value than 1 s⁻¹ for both cases of 50 ppm dye solution. To the author’s knowledge, this catalyst has the highest reaction rate compared to other studies that targeted CV and RB, with an immense reaction rate increase of more than 100 times. Reusability of the three trials was verified, and the only process required was washing the catalyst after the reaction. One of the drawbacks of the advanced oxidation process (AOP), which has a degradation percent limit, has been solved, since 100% mineralization of the dye was available using this catalyst. FT-IR spectroscopy revealed that W-O-Mo linkage was successfully processed while Mo-Cl linkage has retained. ¹H-NMR spectroscopy results confirmed that the degradation product of the dye treated by simple MoCl₅ and WO₃/MoCl₅ was different. Deep inspection of specific regions of NMR fields gave necessary information about the degradation product using WO₃/MoCl₅.

In this study, we attempted to synthesize visible light active nano-sized photocatalysts using metal oxides such as zinc oxide, zirconium oxide, tungsten oxide, and strontium titanium oxide with (MoCl₅)₂ as a dopant by the simple ball-milling method. Fourier-transform infrared spectroscopy data confirmed the presence of M-O-Mo linkage (M = Zn, Zr, W, and SrTi) in all the molybdenum-doped metal oxides (MoMOs), but only MoZnO inhibited the growth of the bloom-forming Microcystis aeruginosa under visible light in a concentration-dependent manner up to 10 mg/L. Further, structural characterization of MoZnO using FESEM and XRD exhibited the formation of typical hexagonal wurtzite nanocrystals of approximately 4 nm. Hydroxyl radical (·OH), reactive oxygen species (ROS), and lipid peroxidation assays revealed ·OH generated by MoZnO under the visible light seemed to cause peroxidation of the lipid membrane of M. aeruginosa, which led to an upsurge of intracellular ROS and consequently introduced the agglomeration of cyanobacteria. These results demonstrated that nano-sized MoZnO photocatalyst can be easily synthesized in a cost-effective ball-mill method and utilized for biological applications such as the reduction of harmful algal blooms. Further, our study implies that a simple ball-milling method can provide an easy, green, and scalable route for the synthesis of visible light active doped metal oxides.