In this work, we have carried out systematic studies on the critical role of polyvinyl pyrrolidone (PVP) and citrate in the well-known chemical reduction route to synthesize silver nanodecahedra (AgND). Silver nitrate (AgNO₃) was used as silver source, which can be directly converted to metallic silver after being reduced by sodium borohydride (NaBH₄) under blue light-emitting diode (LED) irradiation (λ_max = 465 nm), and polyvinyl pyrrolidone (PVP) as a capping agent to assist the growth of AgND. The obtained products were silver nanodecahedra of excellent uniformity and stability with high efficiency and yield. The results showed that PVP acted as a capping agent to stabilize the silver nanoparticles, prolonging the initiation time required for nanodecahedra nucleation, thus inducing anisotropic growth, allowing the size and morphology of the AgND to be controlled successfully. This improved understanding allows a consistent process for the synthesis of AgND with significantly enhanced reproducibility to be developed and the formation mechanism of these nanostructures to be elucidated. This is a simple, cost-effective and easily reproducible method for creating AgND. The typical absorption maxima in the UV-vis spectroscopy of Ag seeds was λ_max ∼400 nm and that of AgND was λ_max ∼480 nm. The size of the prepared AgND was in the range of 60–80 nm. SEM images confirmed the uniform and high density of AgND when the concentration of PVP was 0.5 mM. The XRD pattern showed that the final product of AgND was highly crystallized. In addition, the prepared AgND can be used to detect methylene blue (MB) in a sensitive manner with good reproducibility and stability using Surface-Enhanced Raman Scattering (SERS) phenomenon. Out of the obtained products, the AgND prepared with 50 min blue LED light irradiation (AgND-50) displayed the strongest SERS signal. Interestingly, MB in diluted solution can be detected with a concentration as low as 10⁻⁷ M (the limit of detection, LOD) and the linear dependence between SERS intensity and the MB concentration occurred in the range from 10⁻⁷ to 10⁻⁶ M. The enhancement factor (EF) of the SERS effect was about 1.602 × 10⁶ with a MB concentration of 10⁻⁷ M using 532 nm laser excitation.

This article studies the synthesis, as well as the structural, vibrational, and optical properties of Eu³⁺-doped ZnO quantum dots (QDs) and investigates the energy transfer mechanism from the ZnO host to Eu³⁺ ions using Reisfeld's approximation. Eu³⁺-doped ZnO QDs at varying concentrations (0–7%) were successfully prepared using a wet chemical method. The successful doping of Eu³⁺ ions into the ZnO host lattice, as well as the composition and valence states of the elements present in the sample, were confirmed through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. XRD results demonstrated the crystalline nature of the ZnO QDs, revealing their wurtzite (WZ) structure with no secondary phases. XPS analysis provided further confirmation of the presence of Eu³⁺ ions within the ZnO host, with clear signals corresponding to the Zn, O, and Eu elements. The valence states of Eu were verified as trivalent (Eu³⁺), confirming the successful doping of Eu³⁺ ions, as evidenced by the characteristic Eu 3d peaks in the XPS spectra. Raman spectroscopy (RS) was employed to analyze the vibrational modes, revealing shifts in ZnO lattice vibrations due to Eu³⁺ incorporation, indicating strong coupling between Eu³⁺ ions and the ZnO host. Optical properties were studied using UV-Vis absorption, photoluminescence (PL) spectroscopy, and PL decay spectroscopy, showing a significant enhancement of red emission, attributed to the ⁵D₀ → ⁷F₂ transition of Eu³⁺ ions under UV excitation. Using Judd–Ofelt (JO) analysis, the intensity parameters (Ω₂, Ω₄, Ω₆) were derived, providing insights into the asymmetry of the Eu³⁺ ion's local environment and the radiative transition probabilities. Energy transfer processes between the ZnO host and Eu³⁺ dopants were examined, showing efficient sensitization of Eu³⁺ through excitation of the ZnO host, with an optimal Eu³⁺ doping level maximizing luminescence. Eu³⁺-doped ZnO QDs, which emit in the visible light region and are non-toxic, have great potential for applications in photonic devices, light-emitting diodes, and bioimaging.

Tunable copper doped Zn _1−x Cd _x S alloy quantum dots (QDs) were successfully synthesized by the wet chemical method.

Ag/Au nanoframes were synthesized via room temperature solution phase chemical reduction using pre-synthesized triangular Ag nanoplates as templates in the presence of appropriate amounts of HAuCl ₄ , and were applied in detecting methyl red.

The role of samarium (Sm) dopant on the structural, morphological, and optical properties of CdS QDs and CdS/ZnS core/shell QDs was methodically reported. The synthesis of Sm-doped CdS QDs and CdS/ZnS QDs was carried out via a facile wet chemical method. The structure, chemical composition, and optical properties of the synthesized QDs were investigated by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RS), and photoluminescence (PL) spectroscopy. XRD analysis showed that the synthesized CdS QDs exhibited zinc blende structure which was not affected by doping Sm³⁺ ions. The particle size of the CdS:Sm and CdS:Sm (2%)/ZnS QDs was estimated to be ∼4 nm and ∼7 nm, respectively. Transmission electron microscopy (TEM) images revealed that the incorporation of Sm dopant did not significantly affect the size and morphology of CdS QDs, while the formation of the ZnS shell increased the particle size. XPS and XRD results confirmed the successful incorporation of Sm³⁺ ions into the CdS QDs. The effect of dopant concentration on the structural and luminescent properties was studied. The emission and excitation spectra of Sm³⁺-doped CdS QDs and CdS/ZnS QDs consisted of the characteristic lines corresponding to the intra-configurational f–f transitions. The energy transfer (ET) mechanism from the host to Sm³⁺ ions and the ET process through cross-relaxation between Sm³⁺ ions have been elucidated. The effect of the ZnS shell on the optical stability of the Sm³⁺-doped CdS QDs was studied in detail and the results showed that the CdS:Sm (2%)/ZnS QDs retained their good emission characteristics after 376 days of fabrication. The luminescent properties of Sm-doped QDs ranging from violet to red and PL lifetime extending to milliseconds demonstrated that these QDs are the potential materials for applications in white LEDs, biomarkers, and photocatalysis.