Nanocrystallinity Enhancement of TiO2 Nanotubes by Post-Hydrothermal Treatment

2011 ◽  
Vol 277 ◽  
pp. 90-99 ◽  
Author(s):  
Akhmad Herman Yuwono ◽  
Nofrijon Sofyan ◽  
Indriana Kartini ◽  
Alfian Ferdiansyah ◽  
Tego Hadi Pujianto
Keyword(s):  
Hydrothermal Treatment ◽  
Optical Characteristic ◽  
Hydrothermal Process ◽  
Sodium Titanate ◽  
Xrd Analysis ◽  
Band Gap Energy ◽  
Crystallite Growth ◽  
Hydrothermal Temperature ◽  
Gap Energy ◽  
Vis Spectroscopy

In the present research, a modified post-hydrothermal treatment with different temperature of 80-150°C has been applied on as-annealed TiO2 nanotubes derived from conventional hydrothermal process. The treatment has two-fold objectives, i.e. enhancing the nanocrystallinity of anatase TiO2, and at the same time maintaining the integrity of nanotube structures. The resulting TiO2 nanotubes were characterized by using XRD and UV-Vis spectroscopy. The XRD analysis revealed that the as dried TiO2 nanotubes contain combined crystalline structures of sodium-titanate and anatase. It was also found that by increasing the post-hydrothermal temperature from 80 to 150°C, the nanocrystallinity of nanotubes enhances as indicated by increasing the crystallite size of anatase TiO2 from 6.93 to 7.81 nm. The anatase crystallite growth affected the optical characteristic of nanotubes, as represented with the reduction of the band gap energy, Eg from 3.75 to 3.67 eV by using Kubelka-Munk analysis for the obtained UV-Vis reflectance spectra. TEM observation confirms that the integrity of nanotubes structure can be well-maintained upon post-hydrothermal treatment.

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

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.

Effect of vacuum annealing on the properties of one step thermally evaporated Sb2S3 thin films for photovoltaic applications

2021 ◽  
Author(s):  
Emna Gnenna ◽  
Naoufel Khemiri ◽  
Minghua Kong ◽  
Maria Isabel Alonso ◽  
Mounir Kanzari
Keyword(s):  
Thin Films ◽  
Annealing Temperature ◽  
Vacuum Annealing ◽  
Xrd Analysis ◽  
Band Gap Energy ◽  
Chemical Compositions ◽  
Optical Parameters ◽  
X Ray ◽  
Vis Spectroscopy ◽  
One Step

Sb2S3 powder was successfully synthesized by solid state reaction technique using high-purity elemental antimony and sulfur. Sb2S3 thin films were deposited on unheated glass substrates by one step thermal evaporation and annealed under vacuum atmosphere for 2 hours at different temperatures 150, 200 and 250 °C. Different characterization techniques were used to better understand the behavior of the Sb2S3 material. X-ray diffraction (XRD) and Raman spectroscopy confirmed the formation of pure Sb2S3 powder with lattice parameters a = 11.07 Å, b = 11.08 Å and c = 3.81 Å. The effect of vacuum annealing temperature on the properties of the films was studied. XRD analysis revealed that as-deposited and annealed films at 150ºC were amorphous in nature whereas those annealed at T ≥ 200°C were polycrystalline with a preferred orientation along (201) plane. The crystallite size of the polycrystalline films showed a decrease from 75.8 to 62.9 nm with the increase of the annealing temperature from 200 to 250 °C. The Raman analysis showed several peaks corresponding to the stibnite Sb2S3 phase. The surface morphology of the films was examined by atomic force microscopy (AFM). The surface roughness decreases slightly as the transformation from the amorphous to the crystalline phase occurs. The chemical compositions of Sb2S3 films were analyzed by energy dispersive X-ray spectroscopy (EDS), revealing that all films were Sb-rich. The optical parameters were estimated from the transmittance and reflectance spectra recorded by UV-Vis spectroscopy. A reduction in the direct band gap energy from 2.12 to 1.70 eV with the increase of annealing temperature was also found.

Dressing of Mwcnts with TiO2 Nanoparticles Using Modified Microwave Method

2011 ◽  
Vol 364 ◽  
pp. 228-231 ◽  
Author(s):  
Mohammad Hafizuddin Haji Jumali ◽  
K. Mohamad Al Asfoor Firas ◽  
Shahidan Radiman ◽  
Akrajas Ali Umar
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Absorption Spectra ◽  
Band Gap Energy ◽  
Microwave Method ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Significant Change ◽  
Strong Attachment ◽  
Absorption Wavelength

Optical properties of TiO2 dressed on the surface of MWCNTs have been investigated. The samples were prepared using modified microwave method and characterized using TEM, XRD and UV-Vis spectroscopy. A clear interface between MWCNT and TiO2 indicated strong attachment between these two nanostructures. Significant change in absorption spectra proved the absorption wavelength and band gap energy of TiO2 nanostructures can be controlled via dressing of MWCNT.

Photocatalytic Degradation of Rhodamine B Using MnO2 and ZnO Nanoparticles

2013 ◽  
Vol 756 ◽  
pp. 167-174 ◽  
Author(s):  
Yim Leng Chan ◽  
Swee Yong Pung ◽  
Nur Syafiqah Hussain ◽  
Srimala Sreekantan ◽  
Fei Yee Yeoh
Keyword(s):  
Rate Constant ◽  
Zno Nanoparticles ◽  
Uv Light ◽  
Xrd Analysis ◽  
Band Gap Energy ◽  
Oxide Semiconductor ◽  
Manganese Sulfate ◽  
Gap Energy ◽  
Oxidizing Power ◽  
Sulfate Hydrate

The oxide semiconductor with different band gap energy i.e. manganese dioxide (MnO2) (Eg: 1.30eV) and zinc oxide (ZnO) (Eg: 3.37 eV) nanoparticles were used to degrade RhodamineB (RhB) under irradiation of UV light (254 nm).The MnO2nanoparticles were synthesized by hydrothermal method (160 °C, 4 h) using analytical grade manganese sulfate hydrate and potassium permanganate (VII) as precursors. The XRD analysis reveals that the nanoparticles were d-MnO2.The photocatalytic study shows that degradation of RhB solution by ZnO nanoparticles (rate constant: 0.02749 min-1) was approximately four times faster than the d-MnO2nanoparticles (rate constant:0.0067 min-1). This observation could be attributed to the higher reducing and oxidizing power of ZnO in producing free radicals for photodegradation of RhB solution.

The Role of Acid Concentration on Band Gap Shrinkage in Cellulose Nanocrystals Fabricated from Water Hyacinth

2022 ◽  
pp. 1-3
Author(s):  
Jack A Adem ◽  
◽  
John O Agumba ◽  
Godfrey O Barasa ◽  
Angeline A Ochung ◽  
...  
Keyword(s):  
Band Gap ◽  
Acid Concentration ◽  
Cellulose Nanocrystals ◽  
Optical Band Gap ◽  
Impurity Band ◽  
Band Gap Energy ◽  
Phase Identification ◽  
Hydrolysis Time ◽  
Gap Energy ◽  
Vis Spectroscopy

In this study, the fingerprint of the acid concentration during the hydrolysis process on the optical band gap of cellulose nanocrystals (CNCs) has been systematically studied. The CNCs have been prepared using hydrochloric acid at a hydrolysis temperature of 50°C and at a constant hydrolysis time of 4 hours but with varying hydrochloric cid concentrations of 5%, 10% and 15%. The crystalline structure and phase identification of the CNCs have been studied using XRD technique. UV-Vis Spectroscopy has been done and the optical band gap energy calculated by performing the Tauc’s plot. From the study, the grain size has been found to decrease with acid concentration while the band gap energy has been found to increase with increasing acid concentration. Further, the optical band gaps of the CNCs have been found to decrease with the increase in crystallite size. This shrinkage of the band gap has been attributed to the increased impurity concentration leading to the narrowing of the band gap due to the emerging of the impurity band formed by the overlapped impurity states

Band Gap Narrowed P Doped 1T@2H MoS2 Nanosheets Towards Synergistically Enhanced Visible Light Photochemical Property

2020 ◽  
Vol 15 (2) ◽  
pp. 257-263 ◽  
Author(s):  
Yipin Wang ◽  
Rongfang Zhang ◽  
Genliang Han ◽  
Xiaoping Gao
Keyword(s):  
Catalytic Activity ◽  
Visible Light ◽  
Band Gap ◽  
Surface Area ◽  
Hydrothermal Process ◽  
Band Gap Energy ◽  
Commercial Application ◽  
Photochemical Property ◽  
Mos2 Nanosheets ◽  
Gap Energy

The weak transport charge efficiency and great band gap energy of layered MoS2 hamper its further commercial application. To overcome these deficiencies, we report a simple, controlled and handy hydrothermal process for realizing 2H MoS2 to 1T MoS2 transition with P source. Due to the more conductive ability and larger surface area, P-doped 1T@2H MoS2 nanosheets show an outstanding catalytic activity. Noticeably, P-doped 1T@2H MoS2 nanosheets with narrowed bandgap exhibits a remarkable optical photochemical performance. It fully eliminates 50 ml of 20 mg L–1 RhB in 70 minutes with outstanding recycling and structural stability by using 10 mg catalyst.

scholarly journals Band-Gap Energies of Choline Chloride and Triphenylmethylphosphoniumbromide-Based Systems

Molecules ◽  
2020 ◽  
Vol 25 (7) ◽  
pp. 1495 ◽  
Author(s):  
Alberto Mannu ◽  
Maria Enrica Di Pietro ◽  
Andrea Mele
Keyword(s):  
Hydrogen Bond ◽  
Ethylene Glycol ◽  
Band Gap ◽  
Lewis Acids ◽  
Choline Chloride ◽  
Band Gap Energy ◽  
Hydrogen Bond Acceptor ◽  
Gap Energy ◽  
Tauc Plot ◽  
Vis Spectroscopy

UV–VIS spectroscopy analysis of six mixtures containing choline chloride or triphenylmethylphosphonium bromide as the hydrogen bond acceptor (HBA) and different hydrogen bond donors (HBDs, nickel sulphate, imidazole, d-glucose, ethylene glycol, and glycerol) allowed to determine the indirect and direct band-gap energies through the Tauc plot method. Band-gap energies were compared to those relative to known choline chloride-containing deep band-gap systems. The measurements reported here confirmed the tendency of alcohols or Lewis acids to increment band-gap energy when employed as HBDs. Indirect band-gap energy of 3.74 eV was obtained in the case of the triphenylmethylphosphonium bromide/ethylene glycol system, which represents the smallest transition energy ever reported to date for such kind of systems.

scholarly journals Synthesis of Nanostructured Cobalt Oxides using Cobalt(II) Fumarate Hydrate as Metal-Organic Precursor

2020 ◽  
Vol 32 (12) ◽  
pp. 3144-3150
Author(s):  
M. Gogoi ◽  
B.K. Das
Keyword(s):  
Polyethylene Glycol ◽  
Ethylene Glycol ◽  
Band Gap Energy ◽  
Cobalt Oxides ◽  
Particle Sizes ◽  
Tem Analysis ◽  
Organic Precursor ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Metal Organic

A series of nanostructured cobalt oxides have been prepared from a metal-organic precursor viz. [Co(fum)(H2O)4]·H2O (fum = fumarate) by using capping agents, ethylene glycol and polyethylene glycol via thermal and solvothermal decomposition in ethanol and also by doping with RuCl3·xH2O via solvothermal route. The nano oxides were characterized by IR, UV-vis spectroscopy, powder XRD, SEM and TEM analysis. The nano oxides exhibit varied morphologies and particle sizes. The TEM images reveal homogeneously distributed particles for all the oxides. The band gap energy values the Ru-doped cobalt oxide was found to be lower than the generally accepted values.

Effect of the ZnO Rods Growth Time to the Conductivity of ZnO Thin Film Combined with N3 Dye

2011 ◽  
Vol 383-390 ◽  
pp. 3286-3290
Author(s):  
Engku Abd Engku Ali Ghapur ◽  
W.A. Dhafina ◽  
S. Hasiah ◽  
N.A.N. Ali
Keyword(s):  
Thin Film ◽  
Aspect Ratio ◽  
Band Gap ◽  
Zno Nanorods ◽  
Hydrothermal Process ◽  
Hydrothermal Solution ◽  
Band Gap Energy ◽  
Growth Time ◽  
Gap Energy ◽  
Zno Rods

In this work, ZnO nanorod has been grown by hydrothermal solution method. The samples were prepared by two stages. The first stage was seeding process where the ZnO nanoparticles are spin-casted onto ITO coated glasses and the second stage was hydrothermal process. The morphology of nanorods were investigated by using scanning electron microscope (SEM) and different of length and diameter of nanorods with different growth durations have been observed. The differences of diameters and aspect ratio of nanorods have affected the optical and electrical properties of the ZnO-coated thin film with dye due to its surface area and morphologies of growth rod. Aspect ratio of ZnO nanorods increases by increasing the reaction time (growth time). From the band gap energy study, the thin film with the longest ZnO nanorods growth time has the lowest band gap energy (3.55 eV). The higher aspect ratio of the nanorod affected the conductivity, by increasing the conductivity when combined with N3 dye.

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