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Microwave-assisted particle size-controlled synthesis of ZnO nanoparticles and its application in fabrication of PLED device
摘要： ZnO nanoparticles were synthesised in diethylene glycol (DEG) with different ZnO molar precursor concentration (1 mmol, 2 mmol, 4 mmol and 8 mmol) in a microwave reactor for 15 minutes up to 250 °C. Zinc acetate dihydrate was used as the precursor for ZnO nanoparticles and oleic acid as a capping agent. It was found that different mmol precursor concentration yielded in different nanoparticle sizes. The crystallinity and particle size was analysed by XRD and the optical properties of the nanoparticles were studied by UV-Vis and PL. Oleic acid forms a layer around the ZnO nanoparticle surface. This layer helps in preparing nanocomposite solution by dispersing the ZnO nanoparticles in MEH-PPV solution. Further, the nanocomposite solution is deposited as a thin-film by spin-coating and this forms the emissive layer of the fabricated PLED device. The diode characteristics were analysed by studying the I-V and EL graphs.
关键词： PLED device,ZnO nanoparticles,MEH-PPV,microwave-assisted synthesis,optoelectronic properties
更新于2025-09-23 15:19:57
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Photoluminescence and Nonlinear Optical Properties of Transition Metal (Ag, Ni, Mn) Doped ZnO Nanoparticles
摘要： ZnO nanoparticles doped with transition metal (Ag, Ni, Mn) were prepared by using co-precipitation method. Absorption spectra showed exciton peak for ZnO nanoparticles at 367 nm and for Ag, Ni, Mn doped ZnO nanoparticles at 328, 354 nm and 342 nm respectively. Photoluminescence dynamics showed shallow level-trap and deep-level emission where the intensity of deep-level trap increases with transition metal doping due to the oxygen deficiency. Nonlinear absorption measurements showed the two-photon absorption increasing with transition metal following the trend Ag > Ni > Mn when excited with 532 nm, 30 ps laser pulses. The transition metal doped and un-doped ZnO nanoparticles can be used as optical limiters.
关键词： ZnO Nanoparticles,Photoluminescence,NLO,Optical Limiters
更新于2025-09-19 17:15:36
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Optical Sensing Properties of ZnO Nanoparticles Prepared by Spray Pyrolysis
摘要： We studied the optical sensing properties of ZnO nanoparticles prepared by spray pyrolysis. To investigate their optical sensing performance, we incubated peptides on ZnO nanoparticles. The photoluminescence (PL) peak intensity of peptides on the ZnO nanoparticles was higher than that of peptides on the ZnO film or on the glass plate. This observed PL enhancement is attributed to the optical confinement of ZnO nanoparticles. The low-temperature spectra displayed a strong exciton emission peak with multiple sidebands, attributed to the bound exciton and its longitudinal optical phonon sidebands. The strong exciton emission is thought to be the combined effect of optical confinement due to the nanoparticle geometry, reduction of defect emission by thermal annealing, and reduction of non-radiative relaxation at low temperatures.
关键词： Exciton,ZnO Nanoparticles,Photoluminescence,Peptide,Optical Sensing
更新于2025-09-19 17:15:36
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Structural characterization and thermal degradation of poly(methylmethacrylate)/zinc oxide nanocomposites
摘要： This work is based on the preparation of composites of poly(methylmethacrylate) with zinc oxide nanoparticles synthesized by solution casting method. Chloroform cast poly(methylmethacrylate) films containing different amounts of ZnO nanoparticles were characterized by XRD, SEM, UV-vis spectroscopy, FTIR spectroscopy and TGA. The results show that ZnO nanoparticles with a size of 24 nm were fairly dispersed in the polymer matrix. The obtained material had UV shielding capability with optical transparency. Thermal characterization shows that, the nanocomposites were more thermally stable than pure PMMA presenting three degradation steps. Apparent kinetic parameters were determined for each degradation step using peak fitting methodology. According to activation energies, ZnO particles affect simultaneously but oppositely the kinetics of underlying degradation reactions. Thermal stability of the PMMA/ZnO nanocomposites was the result of the overall balance in favor of the inhibiting effect of ZnO.
关键词： PMMA,polymer nanocomposites,activation energy,ZnO nanoparticles,degradation kinetics,TGA
更新于2025-09-19 17:15:36
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Photo-inactivation and efflux pump inhibition of methicillin resistant Staphylococcus aureus using thiolated cobalt doped ZnO nanoparticles
摘要： Multidrug resistance (MDR) in bacteria is a major concern these days. One of the reasons is the mutation in efflux pump that prevents the retention of antibiotics and drugs in the bacterial cell. The current work is a step to overcome MDR in bacteria via inhibition of efflux pump and further photoinhibition by thiolated chitosan coated cobalt doped zinc oxide nanoparticles (Co-ZnO) in visible light. Co-ZnO were synthesized in a size range of 40–60 nm. Antibacterial activity of the Co-ZnO against methicillin resistant Staphylococcus aureus (MRSA) was found 100% at a concentration of 10 μg/ml upon activation in sunlight for 15 min. Interestingly, it was found that cobalt as a dopant was able to increase the photodynamic and photothermal activity of Co-ZnO, as in dark conditions, there was only 3–5% of inhibition at 10 μg/ml of nanoparticle concentration. Upon excitation in light, these nanoparticles were able to generate reactive oxygen species (ROS) with a quantum yield of 0.23 ± 0.034. The nanoparticles were also generating heat, Because of the magnetic nature, thus helping in more killing. Thiolated chitosan further helped in blocking the efflux pump of MRSA. The current nanoparticles were also found biocompatible on human red blood cells (LD50 = 214 μg/ml). These data suggest that the MRSA killing ability was facilitated through efflux inhibition and oxidative stress upon excitation in visible light hence, were in accordance with previous findings.
关键词： Multidrug resistant bacteria,Biocompatibility,ZnO nanoparticles,Photo-inactivation,ROS,MRSA
更新于2025-09-19 17:15:36
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Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation
摘要： Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit hybrid nanocomposite thin films based on cobalt phthalocyanine (CoPc), C60 fullerene and ZnO nanoparticles. The inorganic nanoparticles, with a size of about 20 nm, having the structural and optical properties characteristic of ZnO, were chemically synthesized by a simple precipitation method. Furthermore, ZnO nanoparticles were dispersed in a dimethyl sulfoxide solution in which CoPc and C60 had been dissolved, ready for the freezing MAPLE target. The effect of the concentration of ZnO nanoparticles on the structural, morphological, optical and electrical properties of the CoPc:C60:ZnO hybrid nanocomposite layers deposited by MAPLE was evaluated. The infrared spectra of the hybrid nanocomposite films confirm that the CoPc and C60 preserve their chemical structure during the laser deposition process. The CoPc optical signature is recognized in the ultraviolet–visible (UV–Vis) spectra of the obtained layers, these being dominated by the absorption bands associated to this organic compound while the ZnO optical fingerprint is identified in the photoluminescence spectra of the prepared layers, these disclosing the emission bands linked to this inorganic semiconductor. The hybrid nanocomposite layers exhibit globular morphology, which is typical for the thin films deposited by MAPLE. Current-voltage (J-V) characteristics of the structures developed on CoPc:C60:ZnO layers reveal that the addition of an appropriate amount of ZnO nanoparticles in the CoPc:C60 mixture leads to a more efficient charge transfer between the organic and inorganic components. Due to their photovoltaic effect, structures featuring such hybrid nanocomposite thin films deposited by MAPLE can have potential applications in the field of photovoltaic devices.
关键词： cobalt phthalocyanine,photovoltaic effect,hybrid nanocomposite films,MAPLE,ZnO nanoparticles
更新于2025-09-19 17:13:59
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Oxygen vacancy induced ferromagnetism in ball milled Zn0.97Ni0.03O: Confirmation through electron spin resonance
摘要： Among the semiconducting materials, ZnO is a versatile multifunctional candidate with a direct band gap of 3.37 eV at 300 K and large excitonic binding energy of 60 meV which can be useful for spintronics device applications. ZnO has high solubility for transition metals. The transition metals which have been used for DMS, Ni is the most efficient doping element to improve the electrical, magnetic properties of ZnO. Ni doped ZnO would be a good candidate to achieve ferromagnetic property with a high curie temperature i.e. above the room temperature. In this study, Zn1?xNixO (x = 0.03) powder sample was successfully synthesized by a ball milling technique. The X-ray diffraction analysis confirms the polycrystalline, hexagonal wurzite structure for 3% Ni doped ZnO nanoparticles. The substitution of Ni in the ZnO matrix has been confirmed by micro-Raman analysis with the observation of E2 (High) vibrational mode at 437 cm?1 which refers to the strongest mode of vibration in wurtzite crystal structure. A broadened peak observed at 570 cm?1 informs about the presence of clusters of oxygen vacancies. VSM measurement of the sample shows the ferromagnetic hysteresis loop at room temperature with saturation moment of 9 × 10?5 emu/g. The calculated ‘g’ value of 1.95 from electron spin resonance spectrum suggests that the observed ferromagnetism is due to the oxygen vacancy.
关键词： Diluted magnetic semiconductor,Electron spin resonance,Defects,Ferromagnetism,ZnO,Nanoparticles
更新于2025-09-19 17:13:59
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Biofabrication of size-controlled ZnO nanoparticles using various capping agents and their cytotoxic and antitermite activity
摘要： Herein, monodisperse Zinc oxide nanoparticles (ZnO-NPs) have been fabricated by green adeptness with and without using capping agents. The different capping agents used include Syzygium cumini leaves extract, starch and cetyl trimethyl ammonium bromide (CTAB). The UV/Vis analysis showed an exciton absorption band in the range of 370–385 nm for all NPs. The SEM analysis showed that average particle size of all ZnO NPs was consistent with that which was calculated by using the Debye-Scherrer equation also by using effective mass model approach. The XRD analysis has confirmed their crystalline nature and monodisperse size distribution. The Photoluminescence spectrum (PL) indicated the presence of surface defects on ZnO nanoparticles, which are the driving force in the efficient photocatalysis of brilliant green dye showing 89.33% degradation efficiency after 2 h. The plant-mediated ZnO NPs were an efficient antimicrobial agent against P. aeruginosa, E. coli, A.baumannii and K. pneumoniae strains; however, all including P. chrysogenum, A. niger, T. citrinoviride, A. fumigatus were resistant to ZnO NPs at all concentrations. Furthermore, they showed a strong antitermite activity against Heterotermes indicola workers and soldiers with a 100% mortality rate in 24 h.
关键词： antitermite activity,Photocatalysis,ZnO nanoparticles,cytotoxicity,capping agents
更新于2025-09-16 10:30:52
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Optimization of the electron transport in quantum dot light-emitting diodes by codoping ZnO with gallium (Ga) and magnesium (Mg)
摘要： In our study, to optimize the electron–hole balance through controlling the electron transport layer (ETL) in the QD-LEDs, four materials (ZnO, ZnGaO, ZnMgO, and ZnGaMgO NPs) were synthesized and applied to the QD-LEDs as ETLs. By doping ZnO NPs with Ga, the electrons easily inject due to the increased Fermi level of ZnO NPs, and as Mg is further doped, the valence band maximum (VBM) of ZnO NPs deepens and blocks the holes more e?ciently. Also, at the interface of QD/ETLs, Mg reduces non-radiative recombination by reducing oxygen vacancy defects on the surface of ZnO NPs. As a result, the maximum luminance (Lmax) and maximum luminance e?ciency (LEmax) of QD-LEDs based on ZnGaMgO NPs reached 43 440 cd m?2 and 15.4 cd A?1. These results increased by 34%, 10% and 27% for the Lmax and 450%, 88%, and 208% for the LEmax when compared with ZnO, ZnGaO, and ZnMgO NPs as ETLs.
关键词： electron transport layer,ZnO nanoparticles,quantum dot light-emitting diodes,Ga-Mg codoping,electron-hole balance
更新于2025-09-16 10:30:52
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Effect of Potassium Nitrate in ZnO Nanoparticle Synthesis to Study the Performance of Dye Sensitized Solar Cell
摘要： X-ray diffraction, Raman investigations, band gap energy of zinc oxide nanoparticles (ZnO NPs) along with current-voltage characteristic curves of an assembled dye-sensitized solar cell (DSSC) are presented in this article. ZnO NPs were first synthesized with and without potassium nitrate (KNO3) salt by precipitation method from precursor solutions of zinc acetate and sodium hydroxide. Then, their thin films were deposited on FTO substrates from the paste made with acetic-acid glacial, and Triton X-100 in ethanol by doctor blade method. The X-ray diffraction (XRD) pattern of ZnO NPs prepared without KNO3 annealed at 500 °C showed a hexagonal wurtzite structure with preferred orientation along (101) planes and crystallite size of 25 nm. Very similar XRD pattern was found for ZnO NPs prepared with KNO3. The crystallite size was found decreased to 17 nm for ZnO NPs made with KNO3 salt. Raman spectrum of ZnO NPs showed the presence of E2 high or E2(2) peak at 437 cm-1. The optical band gaps of the ZnO thin films prepared from ZnO NPs with and without KNO3 were measured to be of 3.16 eV and 3.26 eV, respectively. After sensitizing the above-prepared ZnO films by dye extract of Artocarpus lakoocha, the dye-sensitized solar cells were prepared, and their performance was tested by measuring I-V curves under light illumination of the power density of 1000 W/m2. The measurement showed highest Isc and Voc of 44 μA and 326 mV, respectively.
关键词： Dye-sensitized solar cell,Band gap energy,ZnO nanoparticles,X-ray diffraction,Raman spectrum
更新于2025-09-16 10:30:52