scholarly journals Influence of mild Cr3+ doping on the structural, optical, photochromic, and thermochromic reversibility of nano-titania systems

2019 ◽  
Vol 97 (4) ◽  
pp. 347-354 ◽  
Author(s):  
Rizwin Khanam ◽  
Dambarudhar Mohanta
Keyword(s):  
Band Gap ◽  
Anatase Phase ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Incident Radiation ◽  
Optical Absorption Spectroscopy ◽  
Smart Windows ◽  
Cell Parameters ◽  
Doped Titania ◽  
Reversible Thermochromism

We report on the effect of chromium doping on the band gap lowering of nano-titania (TiO2) and subsequent implications as regards coloration characteristics mediated via photochromism and thermochromism processes. As can be found in the X-ray diffractograms, the sol-gel derived, Cr3+-doped nano-TiO2 systems have exhibited an anatase phase with the evidence of peak shifting towards a lower diffraction angle. The average crystallite size decreases, whereas lattice unit cell parameters and, consequently, cell volume, tend to increase with the inclusion of Cr3+ into the titania host. To be specific, 1% Cr-doped titania system showed nearly 5.8% cell expansion as compared to its un-doped counterpart. As revealed from the optical absorption spectroscopy, a narrowing of band gap is observed for the Cr doped nano-titania system: 3.18 eV for the un-doped system, and 2.61 and 2.41 eV for 0.3% and 1% Cr doping cases, respectively, considering direct band-to-band transitions. Moreover, doping led noticeable lowering of the exponent (n value), from its normal value, which suggests inclusion of adequate non-parabolicity feature to the energy band scheme. The photochromic feature, for a given incident radiation, demonstrates a lowered transmission response with increasing Cr content. A reversible thermochromism response has also been demonstrated for doped nano-titania systems subjected to heating with temperature varying between 0–55 °C. The Cr3+ doped nano-titania and similar systems would find scope in smart windows, display components, photocatalysis, etc., when a select coloration is desired.

scholarly journals Preparation, characterization and enhanced photocatalytic activity of Ni2+ doped titania under solar light

2010 ◽  
Vol 8 (1) ◽  
pp. 142-148 ◽  
Author(s):  
L. Gomathi Devi ◽  
Nagaraju Kottam ◽  
S. Girish Kumar ◽  
K. Eraiah Rajashekhar
Keyword(s):  
Band Gap ◽  
Anatase Phase ◽  
Sol Gel ◽  
Visible Region ◽  
Analytical Techniques ◽  
Red Shift ◽  
Solar Light ◽  
Spectral Studies ◽  
Doped Titania ◽  
Charge Carrier Trapping

AbstractAnatase TiO2 was prepared by sol-gel method through the hydrolysis of TiCl4. Ni2+ was doped into the TiO2 matrix in the concentration range of 0.02 to 0.1 at.% and characterized by various analytical techniques. Powder X-ray diffraction revealed only anatase phase for all the samples, while diffuse reflectance spectral studies indicated a red shift in the band gap absorption to the visible region. The photocatalytic activities of these photocatalysts were probed for the degradation of methyl orange under natural solar light. The photocatalyst with optimum doping of 0.08 at.% Ni2+, showed enhanced activity, which is attributed to: (i) effective separation of charge carriers and (ii) large red shift in the band gap to visible region. The influence of crystallite size and dopant concentration on the charge carrier trapping — recombination dynamics is investigated.

On the Sol-gel Synthesis and Characterization of Titanium Oxide Nanoparticles

2011 ◽  
Vol 1352 ◽  
Author(s):  
Varun Chaudhary ◽  
Amit K. Srivastava ◽  
Jitendra Kumar
Keyword(s):  
Band Gap ◽  
Crystallite Size ◽  
Anatase Phase ◽  
Sol Gel ◽  
Finite Size ◽  
Average Crystallite Size ◽  
Photo Luminescence ◽  
Titanium Isopropoxide ◽  
Rutile Phase ◽  
Excitation Wavelength

ABSTRACTTiO2 nanoparticles have been prepared by sol-gel process using titanium isopropoxide as a precursor with ethanol and water as solvents. The synthesis involves gel formation, digestion for 24h, drying at 100oC for 10h, and calcination in air at 500-800oC for 2h. The resulting powder has been studied with respect to phase(s), morphology, optical absorption and photo -luminescence (PL) behaviour. The calcination of dried sol-gel product at 500oC for 2h leads to formation of anatase phase that possesses a tetragonal structure (a = 3.785 Å, c = 9.514 Å, Z = 4), average crystallite size ~ 11 nm and band gap of 3.34 eV. Further, increasing the time (t) of calcination causes crystallite growth that follows the relation d = α – β exp (-t/τ), α = 18.1 nm, β = 9.6 nm and τ = 6.9h. However, calcination of sol-gel product at 800oC for 2h gives rise to a rutile phase (tetragonal a = 4.593Å, c = 2.959Å, Z = 2), average crystallite size ~ 25 nm and band gap of 3.02 eV. The anatase phase exhibits strong PL emission peaks (excitation wavelength 405 nm) at 2.06 and 1.99 eV due to defect levels within the energy band gap. This observation has been attributed to finite size effects occurring in nanoparticles.

The effect of the withdrawal speed on properties of nickel oxide thin films

2019 ◽  
Vol 234 (10) ◽  
pp. 647-655
Author(s):  
Zohra Nazir Kayani ◽  
Atiqa Aslam ◽  
Rabia Ishaque ◽  
Syeda Nosheen Zahra ◽  
Hifza Hanif ◽  
...  
Keyword(s):  
Thin Films ◽  
Nickel Oxide ◽  
Band Gap ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Dip Coating ◽  
Oxide Thin Films ◽  
Withdrawal Speed ◽  
Sem Micrograph ◽  
Nickel Oxide Thin Films

Abstract Nickel oxide thin films have been prepared by sol-gel dip-coating technique on glass substrate. It is shown that nickel oxide thin films have poly crystalline nature. Nickel oxide thin films exhibit high transmission (39–85%) in the wavelength range of 400–900 nm, strong absorption between 300 and 400 nm wavelengths and decrease of band gap values are in the range 3.69–3.27 eV with increase of withdrawal speed. High band gap at low withdrawal speed is because of the small average crystallite size, which decreases with increase in withdrawal speed. The SEM micrograph shows cubic crystallites and surface of thin films become dense, smooth and homogeneous with an increase in withdrawal speed. Assessment of nickel oxide deposition conditions provides gateway for effective and cheap solar cells.

Aqueous colloidal sol–gel route to synthesize nanosized ceria-doped titania having high surface area and increased anatase phase stability

2007 ◽  
Vol 43 (3) ◽  
pp. 299-304 ◽  
Author(s):  
Pradeepan Periyat ◽  
K. V. Baiju ◽  
P. Mukundan ◽  
P. Krishna Pillai ◽  
K. G. K. Warrier
Keyword(s):  
Surface Area ◽  
Phase Stability ◽  
Anatase Phase ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Doped Titania

Structural and Optical Characterization of Synthesized TiO2 Nanopowder Using Sol–Gel Technique

2016 ◽  
Vol 15 (01n02) ◽  
pp. 1650002 ◽  
Author(s):  
S. Lourduraj ◽  
R. Victor Williams
Keyword(s):  
Anatase Phase ◽  
Sol Gel ◽  
Visible Spectrum ◽  
Average Crystallite Size ◽  
Xrd Analysis ◽  
Force Microscopy ◽  
Morphological Studies ◽  
Atomic Force ◽  
Gel Technique

The nanocrystalline TiO2 powder was synthesized by sol–gel method. The XRD analysis reveals that TiO2 powder was highly crystalline (anatase phase) and nanostructured with tetragonal system. The average crystallite size after calcined at 673[Formula: see text]K is found to be 7.7[Formula: see text]nm. The surface morphological studies using scanning electron microscopy (SEM) exhibit that the formation of nanosized TiO2 particles with less densification nature. Atomic force microscopy (AFM) topography exhibits the uniform distribution of spherical-shaped particles. The energy dispersive X-ray spectroscopy (EDX) confirms the presence of Titanium and Oxygen in synthesized TiO2 nanopowder. The value of optical bandgap of TiO2 nanopowder calculated from UV-Visible spectrum is 3.45[Formula: see text]eV. The presence of TiO2 particles is confirmed from the dominant fourier transform infrared (FTIR) peaks at 621[Formula: see text]cm[Formula: see text] and 412[Formula: see text]cm[Formula: see text].

RAMAN STUDY OF VANADIUM-DOPED TITANIA NANOPOWDERS SYNTHESIZED BY SOL-GEL METHOD

2010 ◽  
Vol 24 (06n07) ◽  
pp. 667-675 ◽  
Author(s):  
M. ŠĆEPANOVIĆ ◽  
S. AŠKRABIĆ ◽  
M. GRUJIĆ-BROJČIN ◽  
A. GOLUBOVIĆ ◽  
Z. DOHČEVIĆ-MITROVIĆ ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Structural Characteristics ◽  
Anatase Phase ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Synthesis Conditions ◽  
Raman Modes ◽  
Doped Titania

Pure titania ( TiO 2) nanopowders and TiO 2 doped with 10 mol % of vanadium ions ( V 3+) are synthesized by sol-gel method. The dependence of structural characteristics of nanopowders on synthesis conditions is investigated by X-ray diffraction and Raman spectroscopy. Very intensive modes observed in Raman spectra of all nanopowders are assigned to anatase phase of TiO 2. Additional Raman modes of extremely low intensity which can be related to the presence of small amount of brookite amorphous phase are observed in pure TiO 2 nanopowders. In V -doped nanopowders anatase was the only TiO 2 phase detected. The variations in duration and heating rate of calcination influence slightly the Raman spectra of pure TiO 2, but have a great impact on Raman modes of anatase, as well as the additional Raman modes related to the presence of vanadium oxides in V -doped samples.

scholarly journals Comparative study on antimicrobial activities of green synthesized TiO2 nanoparticles of Tephrosia purpurea leaves with its crude extracts

2020 ◽  
Vol 9 (2) ◽  
pp. 1022-1028
Keyword(s):  
Tio2 Nanoparticles ◽  
Spherical Surface ◽  
Anatase Phase ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Antimicrobial Activities ◽  
Wound Infections ◽  
Antimicrobial Potential ◽  
Tephrosia Purpurea ◽  
Crude Extracts

The present study deals with the enhancement of antimicrobial potential of Tephrosia purpurea crude extracts by making their composite with TiO2 nanoparticles against ubiquitous pathogens which may cause skin and wound infections. The synthesis was accomplished by the sol-gel method using precursor Titanium isopropoxide. The nanoparticles characterized by XRD, FESEM and FTIR techniques. XRD results showed that particles were in anatase phase with average crystallite size 12- 24 nm. FESEM reveals the spherical surface morphology of the nanoparticles. FTIR spectra gave the idea about associated functional groups with the synthesized particles. The antimicrobial potential of chemically synthesized TiO2 nanoparticles, green synthesized TiO2 nanoparticles and the crude extracts tested against Escherichia coli MTCC 40, Pseudomonas aeruginosa MTCC 2474 and Streptococcus pyogenes MTCC 442 which are actively involved in skin and wound infections. Results showed that green synthesized TiO2 nanoparticles gave better results in comparison with chemically synthesized TiO2 nanoparticles and crude extracts.

scholarly journals Synthesis of Fe- and Co-Doped TiO2 with Improved Photocatalytic Activity Under Visible Irradiation Toward Carbamazepine Degradation

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3874 ◽  
Author(s):  
Abderrahim El Mragui ◽  
Yuliya Logvina ◽  
Luís Pinto da Silva ◽  
Omar Zegaoui ◽  
Joaquim C.G. Esteves da Silva
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Diffuse Reflectance Spectroscopy ◽  
Anatase Phase ◽  
Aqueous Suspension ◽  
Sol Gel ◽  
Pure Tio2 ◽  
Doped Tio2 ◽  
Doped Titania ◽  
Co Doped

Pure TiO2 and Fe- and Co-doped TiO2 nanoparticles (NPs) as photocatalysts were synthesized using wet chemical methods (sol-gel + precipitation). Their crystalline structure and optical properties were analyzed using X-ray diffraction (XRD), Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible light (UV-Vis) diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The photocatalytic activity of the synthesized nanoparticles was evaluated through degradation of carbamazepine (CBZ) under UV-A and visible-light irradiations. The XRD and Raman analyses revealed that all synthesized nanomaterials showed only the anatase phase. The DRS results showed that the absorption edge was blue-shifted for Fe-doped TiO2 NPs. The decrease in charge recombination was evidenced from the PL investigation for both Co-doped and Fe-doped TiO2 nanomaterials. An enhancement in photocatalytic degradation of carbamazepine in aqueous suspension under both UV-A light and visible-light irradiations was observed for Fe-doped Titania NPs by comparison with pure TiO2. These results suggest that the doping cations could suppress the electron/hole recombination. Therefore, the photocatalytic activity of TiO2-based nanomaterials was enhanced.

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