Keywords : ZnO


Thermoelectric Properties of ZrxInxZn1-xO1-δ Thin Films

Prasoon Prasannan; N.K. Deepak; P. Jayaram

Advanced Materials Letters, 2021, Volume 12, Issue 1, Pages 1-4
DOI: 10.5185/amlett.2021.011596

The variation of thermoelectric properties of Zr2O3-In2O3-ZnO film system is reported here. The films are fabricated in a chemical composition satisfies the relation ZrxInxZn1-xO1-δ, (0.01≥ x ≥ 0.04), through spray pyrolysis technique. XRD analysis shows a switching of preferred crystal growth orientation from (002) to (100) and (101) planes as x increases.  The quasi spherical surface morphology was improved on the addition of the cations. A maximum Seebeck coefficient of -159 µV/K was obtained for x=0.01 at 400K. The decrease in the Seebeck coefficient for higher x values is explained with simplified broadband model. At elevated temperature power factor increased considerably up to 2.33 X 10 -4 Wm -1 K -2 for x=0.03 which was attributed to decrease in sheet resistance at high temperature.

Photocatalytic ZnO based PES Membranes for AOP Water Treatments under UV and Sunlight

Giulia Ognibene; Gianluca Cicala;Maria Elena Fragalà

Advanced Materials Letters, 2019, Volume 10, Issue 11, Pages 793-796
DOI: 10.5185/amlett.2019.2093

ZnO nanorods (ZnO) are grown by Chemical Bath Deposition on microfiltration polyetheresulphone (PES) water membranes in order to combine photocatalytic properties of zinc oxide to adsorption properties of membranes. Degradation of a model dye (methylene blue, MB) dispersed in water is promoted by exposition of multifunctional ZnO/PES membranes to UV and solar light: in fact, ZnO decorated membrane ensures generation of reactive oxygen species (ROS) that degrade the organic pollutants dispersed in water. ZnO degradation promoted by UV irradiation is detectable by anionic meso-tetrakis(4-sulfonatophenyl) porphyrin (H2TPPS 4- ) that is used as effective molecular probe to sense the presence of Zn 2+ ions due to photocatalytic leaching. Copyright © VBRI Press.

Development of anti-bio deteriorate sustainable geopolymer by SiO2 NPs decorated ZnO NRs 

Manas Sarkar; Moumita Maiti; Muhammad Akbar Malik; Shilang Xu

Advanced Materials Letters, 2019, Volume 10, Issue 2, Pages 128-131
DOI: 10.5185/amlett.2019.2166

In concrete industry, geopolymer acts as an alternative building material of ordinary cement and possess similar/greater mechanical strength and durability, fashioned by industrial by-product; fly ash with alkaline activator. Accompanied by the chemical corrosion, biogenic corrosion is a foremost obstruction in sewer systems, bridge piers, pipelines and offshore platforms. The present works has been given an effort to introduce an anti-bio deteriorate sustainable geopolymer (GMZnO–Si) through the decoration of spherical nano silica (Si) on zinc oxide Nano-rods (ZnO NRs) surface. XRD, Zeta potential, FESEM, EDS and XPS were hired for the characterization of ZnO-SiO2 nanohybrid system and applicability of GMZnO–Si mortar was investigated against microbial species (E. coli, S. aureus, A. niger). MIC/MBC/MFC values, agar plating, Inner permeability assay and ROS generation results exhibited excellent mechanistic approaches, by showing its ability to resist the biogenic degradation. The mechanical and durability activities of the GMZnO–Si are found considerably higher in respect to conventional control samples. The experimental outcomes propose a promising way to inclusion of ZnO-SiO2 modified geopolymer for biodeterioration-resistant structure with significant mechanical properties in near future. 

Low temperature processed efficient and stable perovskite solar cell

Ashraf Uddin; Md Arafat Mahmud; Naveen Kumar Elumalai; Mushfika Baishakhi Upama; Dian Wang; Faiazul Haque; Cheng Xu

Advanced Materials Letters, 2019, Volume 10, Issue 2, Pages 98-106
DOI: 10.5185/amlett.2019.2050

MA0.6FA0.4PbI3 material based efficient and stable perovskite solar cells (PSCs) are fabricated by electron transport layer (ETL) interfacial modification. The highest power conversion efficiency (PCE) of device was ~ 17%. Cesium acetate and cesium carbonate were used with low temperature processed sol-gel ZnO ETL for interface modifications. Low leakage current and enhanced dark injection current are observed from dark current-voltage measurement. From the electrochemical impedance spectroscopy (EIS) measurement higher recombination resistance and lower interfacial contact resistance are observed in the PSC devices. Mott-Schottky analysis also shows the higher flat-band potential and enhanced device performance with cesium acetate ETL. Cesium acetate related ZnO ETL has large grain size which leads to reduce the device series resistance and contact resistance in PSC compared to cesium carbonate ETL related device. Perovskite film on cesium acetate ETL has better surface morphology, topography and hydrophobicity characterization compared to perovskite film grown on cesium carbonate ETL film. The material work function and electron injection barrier are also investigated by X-Ray photoelectron spectroscopy (XPS) measurement and ultraviolet photoelectron spectroscopy (UPS). From electrochemical impedance spectroscopy measurements the charge transport behaviour and trap-assisted carrier recombination are estimated. Fabricated PSCs device stability has been measured for a month-long degradation study. The PSC device stability is observed four times higher with cesium acetate PSCs compared to cesium carbonate ETL related PSCs. The overall device PCE is around 82% higher with cesium acetate compared to cesium carbonate devices. 

Synthesis and study of optical properties of microstructure flower-shaped ZnO 

Rajat K. Saha; Eeshankur Saikia;Mrinal K. Debanath

Advanced Materials Letters, 2018, Volume 9, Issue 7, Pages 494-498
DOI: 10.5185/amlett.2018.2066

In this study, we report the synthesis and optical properties of flower-shaped ZnO which is fabricated successfully using polyvinylpyrrolidone (PVP) as capping agent by wet chemical method at temperature 60 0 C. The structures and morphologies of flower-shaped ZnO is characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) for nonlinear dynamical study of the system of particles. The studies of SEM and TEM have confirmed flower-shaped structure of the ZnO. The UV-vis absorption spectroscopy of the synthesized sample indicates the presence of blue shift. FTIR analysis shows the characteristic absorption of the Zn-O bond. It has been observed in room temperature photoluminescence (PL) spectroscopy of the sample exhibits emission peaks at near band edge (NBE) along with a weak blue emission peak. It is found from the present study that the phenomenon of flower-like microstructure is based on the size and shape of the particles as well as their aggregated forms. Moreover, their optical properties predict the factors responsible in inhibiting microorganisms for which it may lead to some biological applications. 

Assembly and characterization of ZnO nanoparticles for Grätzel's solar cells  

Glécia V. S. Luz; Wang. S. Hui; Renata C. Roncoleta; Pedro H. O. Nogueira; Lourdes M. Brasil; Pilar Hidalgo

Advanced Materials Letters, 2018, Volume 9, Issue 4, Pages 284-290
DOI: 10.5185/amlett.2018.1599

This research aimed to build hybrid solar cells, based on Grätzel method. We used the Polyethylene Terephthalate (PET) polymer as a substrate containing a layer of Indium Tin Oxide (ITO). Films of ZnO nanoparticles (ZnO NPs) synthesized by Pechini Method, and four different dyes were tested: Congo Red (CR), Bromocresol Green (BG), Acridine Orange (AO) and a Ruthenium Complex (RC). ZnO NPs were analyzed by XRD, which generated peaks corresponding to hexagonal wurtzite crystalline structure. We also conducted analysis by UV–Vis. Spectroscopy and Transmission Electron Microscope (TEM). Rietveld analysis determined the crystal size of 115.23 ± 28.16 nm. The deposition of ZnO and dye thin films were made through spin-coating. The electrical properties of the formed films were characterized with Van der Pawn method. Efficiency in converting light in electricity under an OSRAM 20W light bulb was tested after the devices were built. The smaller sheet resistance results were obtained for material containing: PET/ITO/ZnO/CR and PET/ITO/ZnO/AO. As expected, the best open-circuit voltage (Voc) results reached were 64 and 73 mV to CR and AO, respectively. Therefore, the results demonstrated satisfactory interaction between the ZnO-Dye-Electrolyte layers.

Optical and structural characteristics of ZnO nanopowders for different preparation methods

Advanced Materials Letters, 2017, Volume 8, Issue 12, Pages 1193-1198
DOI: 10.5185/amlett.2017.1581

Zinc oxide (ZnO) nanoparticles (NPs) were synthesized by different methods known as Pechini and Sol-Gel. It was observed during the experiments significant differences comparing these methods as: particle size, time applied, crystallinity and chemical residues generated by-products. The NPs were analysed by X-ray diffraction (XRD), ultraviolet-visible (UV-Vis.) absorption and Raman spectroscopy techniques. X-Ray Difractograms showed peaks corresponding to hexagonal wurtzite crystalline structure. It was observed that NPs obtained by the Pechini showed better homogeneity and crystallinity; these presented average size of 115 nm. The NPs produced by Sol-Gel method showed crystallites with smaller average size of 8 nm. The band gap energy (Eg) obtained using UV-Vis for ZnO NPs synthesized by Pechini was 3.39 eV. Still, the results for Sol-Gel method with 5 and 10 hours of reactions were 3.53 eV and 3.55 eV respectively. Raman data obtained by Pechini and Sol-Gel Methods showed characteristics peaks. The obtained data confirmed the ZnO phase samples and the proportional relationship to the enlargement with the intensity of peaks E2 High ˜ 438 cm -1 , as evidenced by literature. These results lead to the applicability of both NPs in optoelectronic and fluorescent applications. 

Synthesis and characterization of sputtered nanostructured ZnO films: Effect of deposition time and pressure on contact angle behavior of ethylene glycol and water

Kartik H. Patel; Sushant K. Rawal

Advanced Materials Letters, 2017, Volume 8, Issue 2, Pages 101-106
DOI: 10.5185/amlett.2017.6472

This paper is aimed to explore structural, optical and wettability aspects of zinc oxide (ZnO) nanostructured thin films prepared by radio frequency (RF) magnetron sputtering from a zinc target using gas mixtures of helium and oxygen. The increase of deposition time from 40 to 110 minutes improves evolution of (100), (002) and (110) peaks for ZnO films whereas its (101) peak is evident at deposition time of 110 minutes. At sputtering pressure of 0.5Pa only (100) and (110) peaks are observed. The crystallinity of ZnO films decreases as the sputtering pressure is increased from 0.5 to 8.0Pa. The average crystallite size of films increases from 14nm to 18nm when deposition time is increased from 40 to 110 minutes and from 11nm to 17nm when deposition pressure is raised from 0.5Pa to 8.0Pa. We have studied wettability of water and ethylene glycol for deposited nanostructured ZnO films. The maximum value of contact angle; transmission and energy band gap were 106˚, 87% and 3.27eV respectively for deposited nanostructured thin films.

Nano-textured Pb (Zr0.52Ti0.48)O3/ZnO Hetero-structure On Silicon Substrate   

Govind N. Sharma; Shankar Dutta; Ratnamala Chatterjee; Sushil Kumar Singh

Advanced Materials Letters, 2016, Volume 7, Issue 12, Pages 951-956
DOI: 10.5185/amlett.2016.6509

Metal oxide based hetero-structures (like Pb (ZrxTi1-x) O3 – ZnO) can be used for wide variety of future sensors and electronic devices. This paper presents growth and electrical properties of nano-textured (110) Pb (Zr0.52Ti0.48) O3/ (001) ZnO hetrostructure on oxidized silicon substrate by RF sputtering technique. The grain sizes of ZnO and PZT films are found to be around 30 nm and 80 nm respectively. Resistivity of the ZnO layer is found to be 1x10 9 ?-cm. The electrical properties of the film are studied by creating in-plane electrodes on top of the PZT/ZnO hetrostructure film. The remnant polarization of the film is found ~ 47 µC/ cm 2 at 200 kV/ cm 2 . Dielectric constant of the film is found to be 300 at 1 kHz. The film also showed a low leakage current density of ~ 10 -5 A/cm 2 at 200 kV/ cm applied electric field. The nano-textured (110) Pb (Zr0.52Ti0.48) O3/ (100) ZnO hetrostructure integrated with inter-digital-transducers and microelectronic is well suitable for low-cost, robust, programmable passive micro sensors for military structure and systems such as aircraft, missiles.

Effect Of Tb3+ Ions On The ZnO Nanoparticles Synthesized By Chemical Bath Deposition Method 

Lehlohonolo F. Koao; Birhanu F. Dejene; Hendrik C. Swart; Setumo V. Motloung; Tshwafo E. Motaung; Shanganyane P. Hlangothi

Advanced Materials Letters, 2016, Volume 7, Issue 7, Pages 529-535
DOI: 10.5185/amlett.2016.6128

Tb3 + doped ZnO nanoparticles were synthesized using the chemical bath deposition (CBD) method at 80 ºC. All the samples were annealed at 700 ºC to remove the hydroxyl groups confirmed by the thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA). The thermal analysis, structure, morphology and optical properties were characterized. The TGA and DTGA showed that the final yield decreases with an increase in the amount of molar concentration of Tb3 + ions. The X-ray diffraction (XRD) spectra of the ZnO: Tb3 + nanoparticles correspond to the various planes of hexagonal ZnO phase for the lower and higher Tb concentration samples. The estimated average grain sizes calculated using the XRD spectra were found to be in the order of 44 ±2 nm. The grain size was found to increase with an increase in the amount of Tb3+ ions. Scanning electron microscopy (SEM) micrographs showed nanoparticles are obtained for undoped ZnO and emergence of pyramids shape for higher molar concentration of Tb3 + ions. The reflectance spectra depict a red shift with an increase in Tb3 + molar concentration. Photoluminescence (PL) results showed that the luminescence intensity increased with an increase in the amount of Tb3 + ions.

Synthesis Of C/ZnO/CdS Nanocomposite With Enhanced Visible Light Photocatalytic Activity  

Yuvraj S. Malghe; Atul B. Lavand

Advanced Materials Letters, 2016, Volume 7, Issue 3, Pages 239-245
DOI: 10.5185/amlett.2016.6130

C/ZnO/CdS nanocomposite was synthesized using microemulsion method. Thermal stability of precursor was studied with TG and DTA techniques. Structural and optical properties of composite were studied using various characterization techniques like X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM) and  UV-visible absorption spectroscopy  and photoluminescence spectroscopy. XRD study indicates that ZnO and CdS are having wurtzite and cubic phase in the composite sample. SEM and TEM study indicates formation of CdS nanospheres on ZnO nanorods. C doping and CdS coupling are responsible for red shift and shifting of absorption edge of ZnO from UV to visible region. C/ZnO/CdS nanocomposite exhibits better visible light photocatalytic activity for degradation of methylene blue (MB). Stability of photocatalyst was studied using recovered photocatalyst up to third cycle and it was found that photocatalyst prepared in the present work is stable and reusable.   

Effects Of Solvent On Structural, Optical And Photocatalytic Properties Of ZnO Nanostructures

Sini Kuriakose; Biswarup Satpati; Satyabrata Mohapatra

Advanced Materials Letters, 2015, Volume 6, Issue 12, Pages 1104-1110
DOI: 10.5185/amlett.2015.6088

ZnO nanostructures were synthesized by a facile wet chemical method using water, ethanol and propanol as solvents. X-ray diffraction, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) have been used to study the structural properties of the synthesized ZnO nanostructures, while their optical properties have been studied using UV-visible absorption spectroscopy and Raman spectroscopy. The photocatalytic activities of the as-synthesized ZnO nanostructures were evaluated by monitoring sunlight driven photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes in water and it was observed that ZnO nanostructures prepared using propanol as a solvent exhibit highly enhanced photocatalytic activity as compared to those prepared using other solvents. The mechanism underlying the photocatalytic activity of ZnO nanostructures towards photocatalytic degradation of dyes is proposed. We attribute the highly enhanced photocatalytic activity of ZnO nanostructures prepared in propanol to the high surface area of nanosheets-like structures formed, which lead to enhanced adsorption of dye molecules resulting in efficient photocatalytic degradation of dyes upon sunlight irradiation.

Native Defects And Optical Properties Of Ar Ion Irradiated ZnO

S. Pal; A. Sarkar; D. Sanyal; T. Rakshit; D. Kanjilal; P. Kumar; S. K. Ray; D. Jana

Advanced Materials Letters, 2015, Volume 6, Issue 4, Pages 365-369
DOI: 10.5185/amlett.2015.5730

1.2 MeV Argon (Ar) ion irradiation turns white coloured ZnO to yellowish (fluence 1 × 10 14 ions/cm 2 ) and then reddish brown (1 × 10 14  ions/cm 2 ). At the same time the material becomes much more conducting and purely blue luminescent for the highest fluence of irradiation. To get insight on the defects in the irradiated samples Ultraviolet-visible (UV-vis) absorption, Raman, and photoluminescence (PL) spectroscopy and Glancing Angle X-Ray Diffraction (GAXRD) measurements have been carried out. Enhancement of overall disorder in the irradiated samples is reflected from the GAXRD peak broadening. UV-vis absorption spectra of the samples shows new absorption bands due to irradiation. Complete absorption in the blue region of the spectrum and partial absorption in the green and red region changes the sample colour from white to reddish brown. The Raman peak representing wurtzite structure of the ZnO material (~ 437 cm -1 ) has decreased monotonically with the increase of irradiation fluence. At the same time, evolution of the 575 cm -1 Raman mode in the irradiated samples shows the increase of oxygen deficient disorder like zinc interstitials (IZn) and/or oxygen vacancies (VO) in ZnO. PL spectrum of the yellow coloured sample shows large reduction of overall luminescence compared to the unirradiated one. Further increase of fluence causes an increase of luminescence in the blue region of the spectrum. The blue-violet emission can be associated with the interstitial Zn (IZn) related optical transition. The results altogether indicates IZn type defects in the highest fluence irradiated sample. Large changes in the electrical resistance and luminescent features of ZnO using Ar ion beam provides a purposeful way to tune the optoelectronic properties of ZnO based devices.

Effect Of Swift Heavy Ion On Structural And Optical Properties Of Undoped And Doped Nanocrystalline Zinc Oxide Films

Vinod Kumar; L. P. Purohit;Fouran Singh; R. G. Singh

Advanced Materials Letters, 2013, Volume 4, Issue 6, Pages 423-427
DOI: 10.5185/amlett.2012.ib.107

Swift heavy ion (SHI) induced modification in structural and optical properties of undoped and doped nanocrystalline (nc) ZnO films deposited by sol-gel method are investigated. These nanocrystalline films were irradiated by MeV ions of Au, Ag and Ni at various ion fluences. The structural properties were studied using X-ray diffraction and it shows that the average crystallite size of ZnO films is observed to increase by the irradiation. The atomic force microscopy (AFM) study of films shows that the roughness of the films varies with increase in the fluence. A maximum transmittance is observed to be 85% in the visible region for doped films. It is also shown that the bandgap of undoped and doped ZnO films is varied using SHI irradiation. The modifications of structural and optical properties are explained in terms of thermal spikes induced by SHIs.

Influence Of Zn Concentration On The Size And Optical Properties Of ZnO nanocrystals In Silica Matrix Grown By RF Co-sputter Deposition

V. V. Siva Kumar; Sunil Ojha;D. Kanjilal; F. Singh

Advanced Materials Letters, 2013, Volume 4, Issue 5, Pages 343-346
DOI: 10.5185/amlett.2012.10437

In the present study we report the influence of variation in amount of Zn on growth and optical properties of thin films of ZnO nanocrystals in silica matrix deposited by rf magnetron co-sputtering with substrate heating at 200 o C. RBS studies indicate change in the concentration of Zn in the films while Raman spectroscopy measurements indicate presence of excess zinc with different concentration. The XRD spectra of the thin films shows the formation of strong ZnO phase nanocrystals with different sizes in different films while the UV-VIS spectra shows variation in the band edge energy of the ZnO nanocrystals for these films. FT-IR spectra of the films show the Zn-O, Zn-O-Si and Si-O-Si vibrational features related to ZnO, Zn2SiO4 and SiOx phases in the films. The results suggest growth of stable ZnO nanocrystals in silica matrix having better phase and optical quality with increase in the Zn concentration in the thin films, which may be useful in optical applications of ZnO.

Influence Of ZnO Buffer Layer On Growth Of Sb Doped ZnO Nano Wires Using Nano Particle Assisted Pulsed Laser Deposition (NAPLD) Using Sb As Catalyst

I.A. Palani; D. Nakamura; K. Okazaki; T. Shimogaki; M. Higashihata; T. Okada

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 66-70
DOI: 10.5185/amlett.2012.1302

Influence of ZnO buffer layer thickness on the structural and optical properties of the Sb catalyzed/doped ZnO nanowires synthesized using NAPLD has been investigated. Buffer layer with a thickness of 100 nm, 800 nm and 1600 nm coated with Sb are used as a substrate and pure ZnO was used as a target to synthesize Sb doped ZnO nanowires. Introduction of the buffer layer lead to the growth of vertically aligned along with horizontally grown ZnO nano wires. With the increase in buffer layer thickness, the core diameter of the vertically grown ZnO nano wires was subsequently increased. Nano wires synthesized with a buffer layer thickness of 1600 nm showed a significant change in the lattice constants, resulting in measurable lower angle of about 0.06º from XRD, widening of lattice fringe spacing of 0.54 nm from TEM and Suppression of A1T and E1(L0) modes in Raman Spectroscopic. In addition a strong UV emission with absence of visible emission was observed from the room temperature PL. This confirms the generation of Sb doped ZnO nano wire with high crystal quality.

Photoluminescence and ultraviolet photoresponse in ZnO nanophorsphors prepared by thermal decomposition of zinc acetate

Sheo K. Mishra; Smriti Srivastava; Rajneesh K. Srivastava; A.C. Panday; S.G. Prakash

Advanced Materials Letters, 2011, Volume 2, Issue 4, Pages 298-302
DOI: 10.5185/amlett.indias.210

In the present work, simple, low-cost, and direct route is used for the UV- photodetection and photoluminescent zinc-oxide nanoparticles (NPs) by decomposing zinc acetate in air at 400 0 C for 12 hrs. The X-ray diffraction (XRD) result indicates that the synthesized ZnO NPs is pure and single crystalline structure with wurtzite type. The crystallite size of the ZnO nanoparticles is in the range of 20–50 nm and average crystallite size of synthesized nanoparticles is found to be ~33 nm. The synthesized ZnO NPs exhibits several photoluminescence peaks centered at 396 nm, 418 nm, 441 nm, 481 nm and 522 nm. The time-resolved rise and decay of photocurrent spectrum shows initial significant increase in photocurrent and, subsequently falls gradually under UV-illumination. The photocurrent abruptly falls when illumination is turned off. The variation of photo and dark-current with applied field is found to follow power-law i.e I α V. At low voltage the behavior is sub-linear which becomes super-linear at high voltages. The ZnO NPs is found to have double traps of 0.59 eV and 0.67 eV.

Growth and characterization of ZnO nanorods by microwave-assisted route: green chemistry approach

Faheem Ahmed; Shalendra Kumar; Nishat Arshi; Ram Prakash

Advanced Materials Letters, 2011, Volume 2, Issue 3, Pages 183-187
DOI: 10.5185/amlett.2011.1213

ZnO nanorods with diameter 90-100 nm range (tip diameter~15 nm) and length of about 2 μm have been prepared using microwave irradiation technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicate that the nanorods have single phase nature with wurtzite structure and preferentially grow along [0001] direction. Raman spectrum shows the mode E2 high at 439 cm −1 that is related to the vibration of oxygen atoms in wurtzite ZnO. Room-temperature ultraviolet-visible (UV-vis) absorption spectrum shows the absorption band at around 399 nm (red-shifted as compared to bulk). This novel nanostructure would be a promising candidate for a variety of future applications.