Fully Flexible Organic Photoelectrochemical Transistor for the Detection of Serum Amyloid A.

Typical photoluminescent semiconductor nanoparticles, called quantum dots (QDs), have potential applications in biological labeling. When used to label stem cells, QDs may impair the differentiation capacity of the stem cells. In this study, we synthesized zinc oxide (ZnO) QDs in methanol with an average size of ∼2 nm. We then employed two different types of polyethylene glycol (PEG) molecules (SH-PEG-NH2 and NH2-PEG-NH2) to conjugate ZnO QDs and made them water-dispersible. Fourier transform infrared spectroscopy spectra indicated the attachment of PEG molecules on ZnO QDs. No obvious size alteration was observed for ZnO QDs after PEG conjugation. The water-dispersible ZnO QDs still retained the antibacterial activity and fluorescence intensity. The cytotoxicity evaluation revealed that ZnO QDs at higher concentrations decreased cell viability but were generally safe at 30 ppm or below. Cell lines of hepatocytes (HepG2), osteoblasts (MC3T3-E1) and mesenchymal stem cells (MSCs) were successfully labeled by the water-dispersible ZnO QDs at 30 ppm. The ZnO QD-labeled MSCs maintained their stemness and differentiation capacity. Therefore, we conclude that the water-dispersible ZnO QDs developed in this study have antibacterial activity, low cytotoxicity, and proper labeling efficiency, and can be used to label a variety of cells including stem cells.

Zinc oxide (ZnO) quantum dot (QD) is a promising inexpensive inorganic nanomaterials, of which potential toxic effects on biological systems and human health should be evaluated before biomedical application. In this study, the cytotoxicity of ZnO QDs was assessed using HeLa cervical cancer cell and HEK-293T human embryonic kidney cell lines. Cell viability was significantly decreased by treatment with 50 µg/ml ZnO QDs after only 6 h, and the cytotoxicity of ZnO QDs was higher in HEK-293T than in HeLa cells. ZnO QDs increased the level of reactive oxygen species and decreased the mitochondria membrane potential in a dose-dependent manner. Several gene expression involved in apoptosis was regulated by ZnO QDs, including bcl-2 gene and caspase. In HeLa cells, ZnO QDs significantly increased early and late apoptosis, but only late apoptosis was affected in HEK-293T cells. These findings will be helpful for future research and application of ZnO QDs in biomedicine.

Among the different types of metal oxides, zinc oxide (ZnO) is a most commonly used metal oxide in a broad variety of applications. In the present investigation, a modified green synthesis route was used to synthesize pure and starch-capped ZnO (ZnO/starch) quantum dots (QDs) and studied their structural and optical characteristics. In this study, hexagonal crystal structure was observed in both pure and ZnO/starch QDs using X-ray diffraction technique. A spherical-shaped surface morphology was found with the size of 5–10 nm using transmission electron microscope technique. The interaction between ZnO QDs and starch molecules was proved via Fourier infra-red spectrometer technique. On the other hand, their fluorescence behaviors were investigated using photoluminescence technique, in that the ZnO/starch QDs showed an enhanced emission behavior when compared to the pure ZnO QDs. Further, the solar photocatalytic activity of both the ZnO QDs was examined with the dye Rhodamine B (RhB) at the end of 30, 60, 90, and 120 min. In this, ZnO/starch QDs show a good and more decomposition of RhB than pure ZnO QDs. Collectively, in the present study, green synthesis route produced an efficient QDs (pure and ZnO/starch) and it will be very useful for many other QDs. The ZnO/starch QDs are suitable for decomposing the RhB and other toxic organic dyes.

We have studied the role of surface bound anionic species on zinc oxide (ZnO) quantum dots (QDs) for the antibacterial activity against Escherichia coli (E. coli) bacteria. The ZnO QDs with surface adsorbed anionic species of acetate ions and nitrate ions have been synthesized using wet chemical route. X-Ray diffraction studies reveal single-phase hexagonal wurtzite structure of as synthesized ZnO QDs. The particle size was found to be 3-5 nm for acetate adsorbed ZnO QDs and 4-7 nm for nitrate adsorbed ZnO QDs. Minimum inhibitory concentration (MIC) measurements and growth kinetics studies for E-coli show a marked difference in the antibacterial activity of ZnO QDs with both anionic species. The MIC for acetate adsorbed ZnO QDs was found to be 2.5 mM in light and 3 mM in dark. However, nitrate adsorbed ZnO QDs exhibits MIC about 6 mM in light and no significant bacterial growth inhibition was observed upto 30 mM under dark. The enhanced bacterial growth inhibition observed for acetate adsorbed ZnO QDs is attributed to the inherent ability of acetate ions to generate reactive oxygen species. The acetate adsorbed QDs having excellent antibacterial activities suggests its potential application for practical bactericidal realization.

We discuss the synthesis of zinc oxide (ZnO) and cadmium telluride (CdTe) quantum dots (QDs), the characterization of their optical properties on their own as well as combined, and their influence on the power conversion efficiency of photovoltaic structures when the QD blends were dispersed in a polymeric solution and deployed on the window surface of polycrystalline Si solar cells as down-shifting photoluminescent (PL) coatings. Upon the incorporation of increasing amounts of ZnO QDs into a colloidal solution of CdTe, the characteristic CdTe PL peak location was monotonically red-shifted from 598 nm to 611 nm. A 1:3 volumetric combination CdTe:ZnO QDs exhibited a the power conversion efficiency increase from 14.71% for an uncoated solar cell to 15.02% with the QD layer, that is, an approximate improvement of approximately 2%.

Zinc oxide (ZnO) quantum dots (QDs) stabilized/functionalized with oleic acid and core-shelled with silicon dioxide (SiO2) are presented. A colloidal route, free surfactant was followed to synthesize ZnO QDs with an average size of 5 nm. After, the ZnO QDs were stabilized with oleic acid to avoid aggregation followed by (3-aminopropyl) trimethoxysilane functionalization. The X-ray diffraction patterns and transmission electron microscopy results indicated that the ZnO QD size and morphology did not suffer any change after functionalization. In addition, the photoluminescence measurements showed a strong green emission band related to particle size and the shell formation. Moreover, the quantum yield and z potential values were determined and the results showed an enhanced for those ZnO@SiO2 samples with 10 wt% of shell precursor. In this research, we report a high relationship between the stability and photoluminescence properties with the shell precursor concentration. Furthermore, we have developed a reliable method to obtain functionalized ZnO QDs which offer a great potential for future use as photoemission devices such as photonics, photocatalytic activities, biomedicine, optoelectronic devices, and chemical sensing.

Silicon-based solar cells dominate the photovoltaic market, with commercial monocrystalline silicon cells reaching efficiencies as high as 27.3% by May 2024. An alternative to monocrystalline silicon solar cells is polycrystalline solar cells. Despite their lower efficiency (record: 23.81%), their manufacturing process is simpler and cheaper, and their energy conversion efficiency is less sensitive to temperature changes. However, limitations persist in optical and electrical losses, particularly underutilizing ultraviolet (UV) radiation due to silicon’s bandgap. To address these issues, the application of down-converting materials like zinc oxide (ZnO) quantum dots (QDs) has gained attention. ZnO QDs absorb high-energy UV light and re-emit it in the visible spectrum, optimizing the portion of solar energy usable by silicon cells. This study explores the synthesis of ZnO QDs using a sol–gel method, followed by their application on polycrystalline silicon solar cells. Experimental results indicated an increase in short-circuit current and overall efficiency, with the efficiency rising from 18.67% to a maximum of 19.05% when ZnO QDs were deposited from a 5 mg/mL solution. These findings suggest that ZnO QDs could significantly enhance solar energy conversion efficiency by utilizing portions of the solar spectrum that would otherwise be wasted.

Green synthesis, characterization and antimicrobial activity of zinc oxide quantum dots using Eclipta alba

Despite the numerous available treatments for cancer, many patients succumb to side effects and reoccurrence. Zinc oxide (ZnO) quantum dots (QDs) are inexpensive inorganic nanomaterials with potential applications in photodynamic therapy. To verify the photoluminescence of ZnO QDs and determine their inhibitory effect on tumors, we synthesized and characterized ZnO QDs modified with polyvinylpyrrolidone. The photoluminescent properties and reactive oxygen species levels of these ZnO/PVP QDs were also measured. Finally, in vitro and in vivo experiments were performed to test their photodynamic therapeutic effects in SW480 cancer cells and female nude mice. Our results indicate that the ZnO QDs had good photoluminescence and exerted an obvious inhibitory effect on SW480 tumor cells. These findings illustrate the potential applications of ZnO QDs in the fields of photoluminescence and photodynamic therapy.

In our present work, an alternative approach to synthesize Zinc oxide (ZnO) quantum dots (QDs) using simple aqueous route under ambient conditions is reported. ZnO QDs were synthesized using zinc nitrate as a precursor and different thiols as effective capping molecules. The synthesized powders were characterized by XRD and UV‐Vis optical absorption. The XRD results indicated that as synthesized ZnO QDs had pure hexagonal wurtzite structure and 2‐ME capped ZnO QDs gives smallest sized nanoparticles. All these nanoparticles emit clearly visible blue emission under UV lamp.

Quest for the quenching and binding mode of functionalized ZnO QDs with calf thymus DNA: Biophysical and in silico molecular modelling approach

The increasing number of cancer patients has cast attention on developing new anti-cancer modalities. Photodynamic therapy is a safe anti-cancer approach, which encompasses (1) local administration of a photosensitizer and (2) light irradiation. Zinc oxide (ZnO) quantum dots (QDs) are photosensitizers that can be utilized for this purpose. In the present study, to better appreciate the likely more efficient cytotoxic effect of the combination of ZnO QDs and the visible 470-nm blue light in comparison to the QDs alone, several assays were to be conducted upon breast cancer MDA-MB 231 cells. MTT assay showed that in certain groups the combination displayed higher cytotoxic effects compared to those following QD treatment alone. LDH leakage and lipid peroxidation rates by the combination were significantly higher than treatment with either the blue laser or QDs. Although the combination managed to meaningfully reduce the number of colonies and CAT activity compared to QD treatment, there were no palpable differences between them. Lastly, the combination was able to increase the apoptotic genes, including BAX, TP53, caspase 3, and caspase 9 compared to QD, while, in the case of Bcl-2, an anti-apoptotic gene, none of the groups managed to make any tangible differences on its expression levels. Our findings propose that there may be synergistic effects between the blue laser and QD that can possibly be adopted in anti-cancer therapy in the future. However, further investigations regarding this matter are of the essence.

The estrogenic property of bisphenol A (BPA) leads to potential adverse health and ecological effects. A simple, selective, and cost-effective sensor capable of detecting BPA would have a noteworthy relevance for the environmental system. The present work illustrates the synthesis and characterization of β-cyclodextrin (β-CD) functionalized zinc oxide (ZnO) quantum dots (QDs) for the selective detection of BPA. BPA has a fluorescence quenching effect on functionalized ZnO QDs, and the decrease in fluorescence intensity is associated with the BPA concentration between 2 and 10μM. Under the optimum reaction condition, a good linear correlation was obtained between relative fluorescence-quenching intensity of β-cyclodextrin-functionalized ZnO QDs and BPA concentration (R2 = 0.9891). The lower detection limit of functionalized QDs for BPA was estimated to be 0.19μM, which is lower than the toxic limits in aquatic biota. The fluorescence-based detection of BPA may be ascribed to the electron transfer mechanism, which is elucidated with scientific details from the literature.

We report on the synthesis of photo luminescent zinc oxide (ZnO) quantum dots, their deployment on the window side of photovoltaic structures and the measured influence on the power conversion efficiency. Down-shifting effects were characterized by exciting the synthesized nanostructures with photons in the 340–350 nm range, and measuring the wavelength of the emitted photons observed to be ~500 nm. The colloidal ZnO quantum dots were synthesized in an ethanol-based solution, obtaining different sized nanostructures centered at 4 nm, optically recognizable by their emission in various colors. Subsequently, different concentrations of zinc oxide quantum dots were prepared and dispersed in poly-methyl-methacrylate (PMMA) to be spin cast on the window side of previously characterized solar cells. The observations made to date indicate an improvement of ~4.8% in the PCE. In this work, we discuss the results obtained and suggest pathways to further increase the power conversion efficiency of photovoltaic devices employing quantum dots.

We report the synthesis of stable and water dispersible fluorescent zinc oxide (ZnO) quantum dots (QDs). Hydrophilic polyethyleneimine (PEI) was used to stabilize QDs in water and trisodiumcitrate was used as linker between ZnO and PEI. X-ray diffraction reveals the nanocrystalline nature and hexagonal wurtzite structure of as synthesized ZnO QDs. High-resolution transmission electron micrograph suggests nearly spherical particles of size 3-6 nm and lattice spacing of 0.28 nm corresponding to the (100) plane of zinc oxide. Water dispersed ZnO QDs exhibit efficient yellow-green fluorescence centered at 555 nm (2.23 eV) with an excitation wavelength of 360 nm, which is found to be stable for two month revealing the high stability of QDs in water.