Mercaptoalkanoic Acid‐Induced Band Gap Attenuation of Copper Selenide Quantum Dot

Abstract

Copper selenide quantum dot (CuSeQD) materials functionalised with mercaptoalkanoic acids {3-mercaptopropionic acid (3-MPA), 6-mercaptohexanoic acid (6-MHA) and mercaptosuccinic acid (MSA)} were synthesized by a reproducible aqueous colloidal technique at room temperature. The impact of the capping agents on the size and the crystallinity of the CuSeQD materials, were investigated by small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) spectroscopic techniques, respectively. SAXS results confirmed that 6-MHA-CuSeQD had the smallest average particle core size when dried, whereas MSA-CuSeQD had the smallest size in aqueous solution, though with a tendency to aggregate. Dynamic light scattering (DLS) measurements indicated strong bonding of the capping agents to CuSe particles, with MSA being the weakest binding agent, as confirmed by comparatively, low Zeta potential(ζ = À 31.1 mV) and high polydispersity index (0.469) values. UV-Vis absorption studies confirmed a large blue shift of the band gap for the QD compared to the bulk material, with characteristic absorption band (λ) and direct band gap (E gd ) values being (λ = 435 nm, E gd = 8.0 eV), (λ = 400 nm, E gd = 5.6 eV) and (λ = 340 nm, E gd = 4.0 eV), for 6-MHA-CuSeQD, 3-MPA-CuSeQD and MSA-CuSeQD, respectively. As supported by the formal potential values for 6-MHA-CuSeQD (E 0' � 120 mV), 3-MPA-CuSeQD (E 0' � 159 mV) and MSA-CuSeQD (E 0' � 183 mV), the smaller the particle size, the lower the potential required for the application of the quantum dots in an electron transfer process.[a] L.

Nickel Selenide Quantum dot Reactor for Electro‐oxidation of Nevirapine in Wastewater

“…For peaks (A 1 ), A 2 and A 3, the observed anodic peaks were attributed to the Ni 2+ generated from the oxidation of the QD and the interaction between the metal to ligand charge transfer (NiCl 2 ‐3‐MPA)(Figure S4C). A shift in the selenium oxidation from 0.91 V to 0.56 V in comparison to the starting material precursor (Figure S4D) was observed hence peak A 4 is characteristic of oxidation Se 0 of the QD [92] . This is similar to the results obtained by Gaponic et al [93] .…”

“…A shift in the selenium oxidation from 0.91 V to 0.56 V in comparison to the starting material precursor (Figure S4D) was observed hence peak A 4 is characteristic of oxidation Se 0 of the QD. [92] This is similar to the results obtained by Gaponic et al [93] where the anodic current peak observed around 0.62 V was attributed to Se in Au/ZnSe. The peak at 0.76 V is due to the oxidation of NiSe 2 QD.…”

Electroconductive Polyaniline–Ag-ZnO Green Nanocomposite Material

“…The PDDF analysis of AgNPs (Figure 5D, red line) and ZnONPs (Figure 5D, green line) exhibited a spherically shaped characteristic features with maximum radiuses of 70.5 nm and 76.2 nm, respectively. When the AgNPs and ZnONPs were combined to form a composite material, the Ag-ZnONPs (Figure 5D, blue line) exhibited a dumbbell shape, indicating an inhomogeneous mixture of the small ZnONPs and the larger AgNPs which is confirmed by the size distribution by intensity and volume in Figure 5E,F [84,85]. The AgNPs obtained had average particle sizes of approximately 70.4 nm and agglomerated particles appearing at 116.8 nm, while ZnONPs exhibited particle sizes ranging from 12.9 nm to 58.3 nm, and were agglomerated at 106.4 nm.…”

Facile one pot synthesis of highly photoresponsive coinage metal selenides (Cu1.8Se and Ag2Se) achieved through novel Cu and Ag pyridylselenolates as molecular precursors

“…67 It is to be noted that the theoretically calculated exciton Bohr's radii of Cu 1.8 Se and Ag 2 Se falls in the range of 6–8 nm. 68,69 Thus, to exhibit quantum confinement, the particle size of these materials should be in the range 12–16 nm. Since in the present case, the average crystallite size of both Cu 1.8 Se and Ag 2 Se nanoparticles are quite larger than this value, the presence of quantum confinement is ruled out and the blue shift in band gap values compared to bulk is attributed to either lattice distortion or surface lattice defects.…”

“…1.8 Se and Ag 2 Se falls in the range of 6-8 nm 68,69. Thus, to exhibit quantum confinement, the particle size of these materials should be in the range 12-16 nm.…”