Effects of L-Cysteine on the Photoluminescence Properties of ZnO:S Quantum Dots

2020 ◽  
Vol 842 ◽  
pp. 242-250
Author(s):  
Wen Dai ◽  
Shu Wang Duo ◽  
Xiao Xia Li ◽  
Zhong Chen ◽  
Zi Chuan Zheng ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Quantum Dots ◽  
Band Gap ◽  
Visible Region ◽  
Average Crystallite Size ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Microwave Hydrothermal ◽  
Uv Emission ◽  
Zno Crystal

ZnO:S quantum dots (QDs) were synthesized by a microwave hydrothermal method. The effects of L-cysteine (L-cys) on the crystal structure, size, morphology, band gap energy and photoluminescence (PL) properties were studied by XRD, EDS, TEM, FTIR, DRS and PL spectroscopy, respectively. The XRD results showed that all samples had a wurtzite structure ZnO crystal structure and the average crystallite size was 8.4, 5.8, and 9.2 nm for ZnO, ZnO:S and L-cys capped ZnO:S (LZOS) QDs, respectively. The EDS, HRTEM and FTIR results confirmed L-cys was capped on the surface of ZnO:S QDs. It was found that the band gap energy was 3.25, 3.29 and 3.31 eV for ZnO, ZnO:S and LZOS QDs, successively. PL spectrum of ZnO QDs showed two emission peaks in the UV and visible region, respectively. When doping S into ZnO, the intensity of the UV emission reduced, while the intensity of the visible emission dramatically increased. Also, L-cys coated obviously enhanced the PL intensity of ZnO:S QDs. This work suggested that LZOS QDs could be applied in luminescent devices.

Band gap energy of PbS quantum dots in oxide glasses as a function of concentration

2006 ◽  
Vol 352 (32-35) ◽  
pp. 3633-3635 ◽  
Author(s):  
P.M. Naves ◽  
T.N. Gonzaga ◽  
A.F.G. Monte ◽  
N.O. Dantas
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Band Gap Energy ◽  
Oxide Glasses ◽  
Gap Energy ◽  
Pbs Quantum Dots

Photoelectrochemical Properties of Alkali-treated Sodium Titanate Nanorods

2015 ◽  
Vol 1784 ◽  
Author(s):  
Mingu Kim ◽  
Gwanghyo Choi ◽  
Daeheung Yoo ◽  
Kwangmin Lee
Keyword(s):  
Crystal Structure ◽  
Heat Treatment ◽  
Band Gap ◽  
Heat Treatment Temperature ◽  
Alkali Treatment ◽  
Sodium Titanate ◽  
Band Gap Energy ◽  
Treatment Temperature ◽  
Photoelectrochemical Properties ◽  
Gap Energy

ABSTRACTThe band gap energy of the TiO2 photocatalytic is high at 3.2 eV. Ultraviolet (UV) light irradiation (<388nm) is required for the photocatalytic application. The lowering the band gap energy of TiO2 and enlarging light absorbing area are effective ways to enhance the efficiency of photocatalytic activity. Furthermore, the morphology and crystal structure of nanosized TiO2 considerably influences its photocatalytic behavior.In this study, sodium titanate nanorods were formed using an alkali-treatment and were heat treated at different temperatures. The photoelectrochemical properties of sodium titanate nanorods was measured as a function of heat treatment temperature. The nanorods were prepared on the surface of Ti disk with a diameter of 15mm and a thickness of 3mm. Ti disk was immersed in 5 M NaOH aqueous solution at a temperature of 60 °C for 24 h. Morphology of sodium titanate nanorods was observed using FE-SEM. Crystal structure of sodium titanate nanorods was analyzed using X-ray diffractometer. Photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) was used to evaluate photoelectrochemical properties of sodium titanate nanorods. The thin amorphous sodium titanate layer was formed during alkali-treatment. The sodium titanate layer was changed to nanorods after heat treatment at a temperature of 700 °C. The thickness and length of sodium titanate nanorods obtained at 700 °C were around 100 nm and 1μm, respectively. The crystal structure of sodium titanate was identified with Na2Ti6O13. Above 900 °C, the morphology of nanorods changed to agglomerated shape and the thickness of nanorods increased to 1 μm. The lowest value of PL was obtained at a temperature of 700 °C, while nonalkali treated specimen showed the highest value of PL. EIS revealed that polarization resistance at interface between sodium titanate nanorods and electrolyte was increased with increasing heat treatment temperature.

scholarly journals Effect of thickness on the optical properties of Gaas thin films

2013 ◽  
Vol 37 (1) ◽  
pp. 83-91 ◽  
Author(s):  
Chitra Das ◽  
Jahanara Begum ◽  
Tahmina Begum ◽  
Shamima Choudhury
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Refractive Index ◽  
Band Gap ◽  
Optical Band Gap ◽  
Visible Region ◽  
Solar Spectrum ◽  
Band Gap Energy ◽  
Optical Parameters ◽  
Gap Energy

Effect of thickness on the optical and electrical properties of gallium arsenide (GaAs) thin films were studied. The films of different thicknesses were prepared by vacuum evaporation method (~10-4 Pa) on glass substrates at a substrate temperature of 323 K. The film thickness was measured in situ by a frequency shift of quartz crystal. The thicknesses were 250, 300 and 500 nm. Absorption spectrum of this thin film had been recorded using UV-VIS-NIR spectrophotometer in the photon wavelength range of 300 - 2500 nm. The values of some important optical parameters of the studied films (absorption coefficient, optical band gap energy and refractive index; extinction co-efficient and real and imaginary parts of dielectric constant) were determined using these spectra. Transmittance peak was observed in the visible region of the solar spectrum. Here transmittance showed better result when thicknesses were being increased. The optical band gap energy was decreased by the increase of thickness. The refractive index increased by increasing thickness while extinction co-efficient and real and imaginary part of dielectric constant decreased. DOI: http://dx.doi.org/10.3329/jbas.v37i1.15684 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 83-91, 2013

Effect of Nb doping on morphology, crystal structure, optical band gap energy of TiO2 thin films

2014 ◽  
Vol 14 (3) ◽  
pp. 421-427 ◽  
Author(s):  
Deuk Yong Lee ◽  
Ju-Hyun Park ◽  
Young-Hun Kim ◽  
Myung-Hyun Lee ◽  
Nam-Ihn Cho
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Band Gap ◽  
Optical Band Gap ◽  
Band Gap Energy ◽  
Tio2 Thin Films ◽  
Gap Energy ◽  
Nb Doping

The effect of edges and shapes on band gap energy in graphene quantum dots

2016 ◽  
Vol 175 (1) ◽  
pp. 211-219 ◽  
Author(s):  
Lanchakorn Kittiratanawasin ◽  
Supa Hannongbua
Keyword(s):  
Quantum Dots ◽  
Band Gap ◽  
Graphene Quantum Dots ◽  
Band Gap Energy ◽  
Gap Energy

scholarly journals The effect of doping variation on band gap energy and crystal structure of Biochar/TiO2 thin layer

2021 ◽  
Vol 1731 ◽  
pp. 012060
Author(s):  
H D Fahyuan ◽  
F Deswardani ◽  
N Nurhidayah ◽  
M F Afrianto ◽  
H Heriansyah ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thin Layer ◽  
Band Gap ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Effect Of Doping

Effect of 2,4-dinitrophenol dye doping on tristhioureazinc(II) sulfate single crystals: a potential nonlinear optical material

2020 ◽  
Vol 53 (4) ◽  
pp. 972-981 ◽  
Author(s):  
G. Durgababu ◽  
G. J. Nagaraju ◽  
G. Bhagavannarayana
Keyword(s):  
Crystal Structure ◽  
Band Gap ◽  
Single Crystals ◽  
Nonlinear Optical ◽  
Optical Band Gap ◽  
Band Gap Energy ◽  
Optical Range ◽  
Gap Energy ◽  
Uv Visible ◽  
Crystalline Matrix

Good quality single crystals of 2,4-dinitrophenol (DNP)-doped tristhioureazinc(II) sulfate (ZTS) were successfully grown by employing the simple and cost effective slow-evaporation solution technique. To study the effect of doping on various device properties, the grown single crystals were subjected to powder X-ray diffraction (PXRD), high-resolution XRD, thermogravimetric analysis (TGA), Vickers hardness testing, and UV–visible, photoluminescence (PL) and Fourier transform IR (FTIR) spectroscopy techniques. The crystal structure of DNP-doped ZTS bulk single crystals remained the same as the crystal structure of ZTS. However, the changes in intensities of the diffraction peaks in the PXRD spectra indicated the incorporation of dopants into the crystalline matrix. FTIR studies confirm the incorporation of dopants into the crystalline matrix, shown by the shifting of certain prominent absorption bands towards higher energy. This also indicated the induced useful strain due to doping, leading to charge transfer and the enhancement of nonlinear optical properties. The cut-off wavelength and optical band gap energy of pure ZTS and DNP-doped ZTS crystals were studied by UV–visible absorption spectroscopy, revealing a slight reduction in the optical band gap energy due to doping, which in turn revealed the enhancement of the optical range. PL studies revealed an enhanced optical range of photoluminescence in ZTS crystals. Second harmonic generation (SGH) studies carried out by the Kurtz powder technique revealed the enhancement of SHG value due to DNP doping. To ensure the thermal stability and mechanical strength of the grown crystals with doping (required from the point of view of device applications), TGA and Vicker's hardness studies were performed.

Band Gap Narrowing of MgO and Mg0.95Zn0.05O Nanostructures

2020 ◽  
Vol 307 ◽  
pp. 273-278
Author(s):  
Nor Fadilah Chayed ◽  
Nurhanna Badar ◽  
Kelimah Elong ◽  
Norlida Kamarulzaman
Keyword(s):  
Band Gap ◽  
Crystallite Size ◽  
Average Crystallite Size ◽  
Combustion Method ◽  
Band Gap Energy ◽  
Synthesis Condition ◽  
Gap Energy ◽  
Band Gap Narrowing ◽  
Effect Of Doping

Preparation of MgO and Mg0.95Zn0.05O nanomaterials using self-propagating combustion method are done to investigate the effect of doping on the band gap energy. The synthesis condition has been optimized to obtain pure MgO and Mg0.95Zn0.05O materials which confirmed by XRD. FESEM results shows agglomeration of crystallite with average crystallite size of samples between 30 nm to 125 nm. The band gap obtained from the measurement of UV-Vis NIR spectrophotometer for MgO nanostructure is 6.36 eV which is lower than bulk MgO of 7.8 eV. The presence of Zn in Mg0.95Zn0.05O sample causes the narrowing of band gap to 5.33 eV.

scholarly journals Enhancement of Optical Activity and Properties of Barium Titanium Oxides to Be Active in Sunlight through Using Hollandite Phase Instead of Perovskite Phase

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 550
Author(s):  
Adil Alshoaibi ◽  
Osama Saber ◽  
Faheem Ahmed
Keyword(s):  
Optical Properties ◽  
Barium Titanate ◽  
Band Gap ◽  
Perovskite Phase ◽  
Visible Region ◽  
Band Gap Energy ◽  
Titanium Oxides ◽  
Gap Energy ◽  
Optical Applications ◽  
Barium Titanium

The present study aims to enhance the optical properties of barium titanate through narrowing its band gap energy to be effective for photocatalytic reactions in sunlight and be useful for solar cells. This target was achieved through growth of the hollandite phase instead of the perovskite phase inside the barium titanate crystals. By using solvent thermal reactions and thermal treatment at different temperatures (250 °C, 600 °C, and 900 °C), the hollandite phase of barium titanate was successfully obtained and confirmed through X-ray diffraction (XRD), Raman spectra and scanning electron microscopy techniques. XRD patterns showed a clear hollandite phase of barium titanium oxides for the sample calcined at 900 °C (BT1-900); however, the samples at 600 °C showed the presence of mixed phases. The mean crystallite size of the BT1-900 sample was found to be 38 nm. Morphological images revealed that the hollandite phase of barium titanate consisted of a mixed morphology of spheres and sheet-like features. The optical properties of barium titanate showed that its absorption edge shifted to the visible region and indicated band gap energy tuning ranging from 1.75 eV to 2.3 eV. Photocatalytic studies showed the complete and fast decolorization and mineralization of green pollutants (naphthol green B; NGB) in the prepared barium titanate with hollandite phase after illumination in sunlight for ten minutes. Finally, it can be concluded that the low band gap energy of barium titanate having the hollandite phase introduces beneficial structures for optical applications in sunlight.

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