Effect of Polymer Capping on Photonic Multi-Core–Shell Quantum Dots CdSe/CdS/ZnS: Impact of Sunlight and Antibacterial Activity

Abstract

The highly luminescent CdSe/CdS/ZnS core–multi-shell quantum dots (QDs) were prepared without a protective atmosphere through the precursor injection method (phosphine free) in paraffin liquid and oleic acid. Polymers (PEG, PVA, PVP, and PAA) were coated to CdSe/CdS/ZnS core–multi-shell quantum dots to increase stability. However, core–multi-shell structured QDs reveal enhanced emission in the range 355–410 nm by suppressing the defect sensitive cores and nonradioactive recombination in PL spectra. The cubic zinc blended quantum dots with crystallite size in the range 22–44 nm, as confirmed by XRD, were obtained. The resultant absorption spectra of all the samples showed that the samples were absorbent in the UV region over the 302–380 nm range. In the FT-IR spectrum 712, 731, and 400–700 cm–1 band values were assigned to CdSe, CdS, and ZnS band stretching, respectively. Images of CdSe, CdSe/CdS, and CdSe/CdS/ZnS quantum dots obtained from the SEM were spherical whereas QDs capped with different polymers (PEG, PVA, PVP, and PAA) showed nanofibers that were linear and homogeneous size ranged between 12 and 38 nm. These as prepared QDs were placed under visible light for 48 h. After absorbing UV light, the range of UV–vis intensity was enhanced until 389–464 nm and emission intensity enhanced until 492–509 nm, which was confirmed by UV and PL spectra. CdSe/CdS/ZnS QDs with organic ligands revealed antibacterial activity over a broad range against Klebsiella Pneumoniae and Pseudomonas aeruginosa.

CdSe Core and CdSe@ZnSe Core–Shell QDs Decorated with Human Serum Albumin: Deciphering the Antimicrobial Properties and Sensing of Mercury Ion

“…This is because of the smaller size of the biosynthesized QDs (2−3 nm) and the specific surface chemistry of the HSA protein immobilized on the QDs surface, which can penetrate the bacterial cell wall (Gram-negative) easily and enhance the bactericidal activity. The results obtained for these biosynthesized QDs are better than the reported literature 15,17,66 (Table S5), and have advantages over chemically synthesized QDs, such as easy synthesis, being aqueous and biocompatible. Moreover, the antibacterial activities of synthesized QDs were compared with the standard antibiotics lomefloxacin (against E. coli) and doxycycline (against S. aureus), as depicted in Figure S8 and ZOI values included in Table S4.…”

Lignin-Based CdS Dots as Multifunctional Platforms for Sensing and Wearable Photodynamic Coatings

“…As depicted in previous reports, the red-shift pattern has also been observed during poly(vinyl alcohol) (PVA)-capped CdS QD synthesis. 41 Following these absorption spectra of CdS and CdSe/CdS/ZnS, quantum dots have also been noticed in the region of 302−380 nm, which also reflects the QD synthesis. 42−44 Afterward, we assessed the surface charge of the L@CdS QDs, which exhibited a negative value of −28 mV.…”

Assessing the environmental effects related to quantum dot structure, function, synthesis and exposure

“…Capping agents are necessary to ensure photostability during application by minimizing the impact of surface defects on luminescent efficiency. 84,85 The surface of QDs can be modified using organic (such as tri-noctylphosphine oxide (TOPO) 85,86 ) or inorganic (such as tetraethyl orthosilicate (TEOS) 87,88 ) capping agents (Table 1).…”