Photocatalytic Dye Degradation and Biological Activities of Cu-Doped ZnSe Nanoparticles and Their Insights

Environmental nanotechnology has received much attention owing to its implications on environmental ecosystem, and thus is promising for the elimination of toxic elements from the aquatic surface. This work focuses on Cu-doped ZnSe nanoparticles using the co-precipitation method. The synthesized Cu-doped ZnSe nanoparticles were examined for structural, optical, and morphological properties with the help of XRD, FTIR, UV/vis diffuse reflection spectroscopy (DRS), FESEM, TEM, and XPS. The synthesized Cu-doped ZnSe nanoparticles revealed the presence of Cu2+ in the ZnSe lattice, which has been shown to take a predominant role for enhanced catalysis in the Cu-doped ZnSe nanoparticles. The synthesized Cu-doped ZnSe nanoparticles were investigated for their catalytic and antibacterial activities. The 0.1 M copper-doped ZnSe nanoparticles exhibited the highest rate of degradation against the methyl orange dye, which was found to be 87%. A pseudo-first-order kinetics was followed by Cu-doped ZnSe nanoparticles with a rate constant of 0.1334 min−1. The gram-positive and gram-negative bacteria were used for investigating the anti-bacterial activity of the Cu-doped ZnSe nanoparticles. The Cu-doped ZnSe nanoparticles exhibited enhanced photocatalytic and antibacterial activity.

Structural, Optical, and Photocatalytic Properties of ZnSe Nanoparticles Influenced by the Milling Time

ZnSe nanoparticles (NPs) were prepared by combining both hydrothermal and mechanical milling methods. Transmission electron microscopy images show that fabricated ZnSe NPs with a sphere-like shape have an average size (d) in the range of 20–100 nm, affected by changing the milling time from 10 to 60 min. All the samples crystalize in zincblende-type structure without impurities, as confirmed by analyzing X-ray diffraction patterns, Raman spectra, and energy-dispersive X-ray spectroscopy. Carefully checking Raman spectra, we have observed the broadening and redshift of vibration modes as decreasing NP size, which are ascribed to extra appearance of disorder and defects. The photoluminescence study has found a blue emission at 462 nm attributed to the excitonic near-band edge and a broad defect-related emission around 520–555 nm. Increasing milling time leads to the decrease in the exciton-emission intensity, while the defect-related emissions increase gradually. Interestingly, as decreasing d, we have observed an improved photodegradation of Rhodamine B under UV irradiation, proving application potentials of ZnSe NPs in photocatalytic activity.

Synthesis and Characterization of Sr-Doped ZnSe Nanoparticles for Catalytic and Biological Activities

The development of cost-effective and ecofriendly approaches toward water purification and antibacterial activity is a hot research topic in this era. Purposely, strontium-doped zinc selenide (Sr-doped ZnSe) nanoparticles, with different molar ratios of Sr2+ cations (0.01, 0.05, and 0.1), were prepared via the co-precipitation method, in which sodium borohydride (NaBH4) and 2-mercaptoethanol were employed as reducing and stabilizing agents, respectively. The ZnSe cubic structure expanded by Sr2+ cations was indicated by X-ray diffraction (XRD) analysis. The absorption of the chemical compounds on the surface was observed via Fourier transform infrared (FT-IR) spectroscopy. The optical orientation was measured by ultraviolet–visible diffused reflectance spectroscopy (UV-DRS) analysis. The surface area, morphology, and elemental purity were analyzed using field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and energy-dispersive spectroscopy (EDS) analyses. The oxidation state and valency of the synthesized nanoparticles were analyzed using X-ray photoelectron spectroscopy (XPS). Sr-doped ZnSe nanoparticles were investigated for photocatalytic degradation of methyl orange (MO), and their antibacterial potential was investigated against different bacterial strains. The antibacterial activity examined against Staphylococcus aureus and Escherichia coli implied the excellent biological activity of the nanoparticles. Moreover, the Sr-doped ZnSe nanoparticles were evaluated by the successful degradation of methyl orange under visible light irradiation. Therefore, Sr-doped ZnSe nanoparticles have tremendous potential in biological and water remediation fields.

Structural and Optical Properties of ZnSe Nanoparticles

We successfully synthesized ZnSe nanoparticles (NPs) by using a hydrothermal method. Careful analyses of X-ray diffraction pattern and high-resolution transmission electron microscopy images showed that the synthesized ZnSe NPs with the size of ˜100 nm and sphere-like morphology crystallized in the zincblende/cubic structure (the F-43m space group). This was also confirmed based upon characteristic vibration modes recorded by using Raman scattering spectroscopy. The study on room-temperature absorption and photoluminescence (PL) spectra proved ZnSe NPs having high crystal quality with the band gap energy Eg≈2.63 eV at 300 K and excitonic emission peaked at ˜2.64 eV (469 nm). Particularly, as studying temperature-dependent PL spectra, we found the shift of the emission peak towards lower energies while the PL intensity decreased when temperature increased from 15 to 300 K. The PL spectral parameters were analyzed by using the Arrhenius and Varshni laws.