All-optical Properties Research Articles

A photoluminescence and colorimetric dual-active mode of copper-modified carbon dots for quantitative sensing of histamine

Determination of the histamine in food is a crucial aspect regarding its safety issue. The present study reported the preparation of copper-doped carbon dots (Cu-CDs) through the pyrolysis method and further applied them for sensitive histamine detection via UV–vis absorption and photoluminescence (PL) techniques. Several characterizations, including X-ray diffraction, Raman, Infrared, and photoluminescence spectra, confirmed this nanomaterial’s well-formed Cu-CDs and all-optical properties. While Photoluminescence spectra perform regular degradation of Cu-CDs emission, the absorption spectra also showed increasing peaks at 270 nm following the enhancement of histamine concentration introduced to Cu-CDs. The analytical method parameters were next used to evaluate histamine detection performance, where the Cu-CDs showed good accuracy and selectivity for detecting histamine with LOD and LOQ values as low as 19.20 and 64 mg l−1, respectively. It also possessed a valuable recovery rate ranging from 89%–106%. Even though UV–vis Spectrophotometry successfully detected histamine, Cu-CDs maintained their photoluminescence properties, offering more distinct advantages, including low cost, simplicity, high sensitivity, and selectivity properties.

Profundity study on structural and optical properties of heavy oil fly ash (HOFA) doped calcium carbonate (CaCO3) nanostructures and thin films for optoelectronic applications

The present study was concerned with the synthesis of thin films and nano samples from heavy oil fly ash (HOFA) doped-calcium carbonate (CaCO3) with different contents (x = 0, 1, 2, 3, 4, and 5 wt%.). The motivation of this study was to benefit from fly ash resulting from heavy oil combustion in power plants in optoelectronic applications rather than as an environmental problem with repercussions including global warming, etc. The nano- and thin-film samples with a thickness of 200 nm were controlled and tuned by the monitor device and were prepared by the spin coating method on pre-clean glass substrates. The structural analysis was carried out using XRD and SEM techniques. Both techniques were proven on the crystallinity of the studied samples, and the structural parameters were calculated, such as grain size, which was affected by the increase in calcium carbonate. Furthermore, SEM images of thin-film surfaces revealed a more packed structure with a lower number of pores in the thin film containing nano-CaCO3. According to the optical spectra (transmittance T, reflectance, R), the optical absorption coefficient was calculated. Then, the related optical parameters (Tauc energy Eg, Urbach energy Eu), optical constants (an extinction coefficient kex., a reflective index n), and dispersion parameters (a single oscillator energy Eo, a dispersion energy Ed) were determined. It was clear that these layers have the great potential to be used as a window layer in solar cells and other optoelectronic applications due to the high energy range of the optical bandgap. In addition, all-optical properties were affected and improved by increasing the calcium carbonate content. This improvement in the optical properties along with the improvement of the structural properties makes the thin films and the nanoscaled samples very suitable for various applications.

Electronic and optical performance of Ni-doped FeS2 nanocrystals for photovoltaic applications

Systematic ab-initio investigations were used to explore whether the electronic and optical behaviors of iron pyrite can achieve by alloying with nickel. The results show a band gap increase to a value of 1.24 eV and a high-absorption coefficient of α ~ ≥7.5*105 cm−1. Ni doping improves n-type conductivity and charge carriers’ mobility is averaging (0.65 ± 0.04) Ω−1.cm−1 in the visible range. We observe that the anti-bonding S-3Pppσ* band states are at the origin of the band gap variation. Indeed, a sensitive reduction in the number of sulfur bonds in iron pyrite can have a significant effect on the absorption threshold leading, consequently, to the optical gap of 1.45 eV due to the formation of covalent S–S interaction. So that, all-optical properties were examined by the study of critical peaks contributions that were identified by partitioning the dielectric function spectra. Hence, the incorporation of Ni in FeS2 lattice improves properties of a buffer layer best matched in a heterostructure with Cu2ZnSnS4 (CZTS) or p-type crystalline silicon (c-Si) based solar cells.