Nanocrystallisation of TiO2 induced by dense electronic excitation

Thakurdesai, Madhavi; Mahadkar, Ajit; Kanjilal, D.; Bhattacharyya, Varsha

doi:10.1016/j.vacuum.2007.10.002

Cited by 12 publications

(6 citation statements)

References 23 publications

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“…12 that with the increase of Au concentration, and after annealing at 400 ˚C the extinction coefficient (k) decreases, it can be notes that (k) decrease at the absorption edge region(see Table 5), in general the extinction coefficient of annealing samples is smaller than that prepared before annealing. The Extinction coefficient (k) is calculated using the relation [25]: k = (6)…”

Section: -4 Extinction Coefficientmentioning

confidence: 99%

The effect of gold nanoparticles on WO3 thin film

Ibrahim¹

2018

IJP

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Chemical spray pyrolysis technique was used at substrate temperature 250 ˚C with annealing temperature at 400 ˚C (for 1hour) to deposition tungsten oxide thin film with different doping concentration of Au nanoparticle (0, 10, 20, 30 and 40)% wt. on glass substrate with thickness about 100 nm. The structural, optical properties were investigated. The X-ray diffraction shows that the films at substrate temperature (250 ˚C) was amorphous while at annealing temperature have a polycrystalline structure with the preferred orientation of (200), all the samples have a hexagonal structure for WO3 and Au gold nanoparticles have a cubic structure. Atomic force microscopy (AFM) was used to characterize the morphology of the films. The optical properties of the films were studied using UV-Vis spectrophotometer within the wavelength in the range (300-1100) nm. The optical energy gap of the films was (2.80) eV for WO3 and it decreased at annealing temperature (400 ˚C) equal to (2.65) eV. And finally the optical constants such as refractive index, real and imaginary dielectrics, absorption coefficient, absorption, transmission, and extinction coefficient were investigated.

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Section: -4 Extinction Coefficientmentioning

confidence: 99%

The effect of gold nanoparticles on WO3 thin film

Ibrahim¹

2018

IJP

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“…The tuning of size-dependent parameters, such as specific surface area and quantum confinement, is required in photocatalytic (Byrne et al, 2002;Schumacher et al, 2003), solar cell (O'Regan & Grä tzel, 1991;Koo et al, 2008), gas sensor (Ferroni et al, 1996;Ruiz et al, 2004) and photovoltaic (Barbé et al, 1997) applications, where morphology and composition are controlled at near-unit-cell scales. Nanotitania is commonly prepared as (i) thin films using chemical/ physical vapour deposition (Szymanowski et al, 2007;Thakurdesai et al, 2008) and molecular beam epitaxy (Shao et al, 2007); (ii) crystalline aggregates by sol-gel routes (Koo et al, 2008;Mohammadi et al, 2008); and (iii) fine powders via mechanochemical milling (Bilik et al, 2007). To enhance visible light photocatalysis, a large surface area is beneficial but by itself is insufficient to maximize quantum yield, because the relatively wide band gap of titania ($3.0-3.2 eV depending on polymorph) inhibits exciton production and the excited states that do form are rapidly annihilated.…”

Section: Introductionmentioning

confidence: 99%

X-ray absorption spectroscopy studies of phase transformations and amorphicity in nanotitania powder and silica–titania core–shell photocatalysts

Lim¹,

Phonthammachai²,

Liu³

et al. 2008

J Appl Cryst

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The local environment of titanium in nanocrystalline sol‐gel synthesized titania, cobaltiferous titania and silica–titania core–shell photocatalysts was investigated using X‐ray absorption spectroscopy (XAS). Anatase reconstructively transforms to rutile via a persistent amorphous phase that is retained, in part, up to 1273 K. In nanotitania, temperature‐dependent trends in Ti order correlation observed by XAS parallel the development of amorphous content extracted from powder X‐ray diffraction patterns, such that amorphicity shows a transient maximum at ∼873 K with the onset of rutile crystallization. Cobaltiferous and core–shell materials behaved similarly, but with anatase retained to 973 and 1273 K, respectively. In the former, cobalt redox reactions may stabilize anatase to higher temperatures by ready charge‐balancing during the loss of hydroxyl and the formation of oxygen vacancies. In the core–shell architecture, higher Ti coordination and interatomic distance variance in the first‐ and second‐nearest‐neighbour shells are maintained to 1273 K by interaction of a substantially aperiodic TiO6 network with the glassy silica substrate, which inhibits crystallization of rutile from the amorphous intermediate. Comparisons are also drawn with the commercial P25 catalyst. The overall transformation mechanism can be summarized as gel → non‐stoichiometric anatase → amorphous titania → rutile. Smaller anatase crystals and a higher average Ti—Ti coordination environment in the core–shell structure may enhance photocatalytic activity directly, by creating larger specific surface areas and hosting reactive defects, or indirectly, by inhibiting exciton annihilation in aperiodic titania and delaying the crystallization of less photoactive rutile.

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“…This kind of a controlled surface modification can explore the possibilities of novel applications. SHI-induced nanocrystallization in amorphous thin films of TiO 2 deposited on a fused silica substrate is studied by us in detail [15,17]. In this report, the role of the substrate in the SHI-induced process of nanocrystallization is discussed.…”

Section: Introductionmentioning

confidence: 91%

“…This eliminates the final calcination step required in chemical synthesis [8]. The particle size is confined to ion track dimensions and the periphery of the ion track restricts further growth of the particles [14,15]. In this process, an ion beam is rastered over the selected area and nanostructures can be formed in a desired region of the surface [16].…”

Section: Introductionmentioning

confidence: 99%

Substrate dependence in the formation of TiO₂nanophases by dense electronic excitation

Thakurdesai¹,

Kanjilal²,

Bhattacharyya³

2009

Semicond. Sci. Technol.

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Irradiation by swift heavy ion (SHI) is an excellent tool for the nanostructuring of thin films. During SHI irradiation, the energy of the projectile is transferred to the target mainly via electronic energy loss (S e ). If the value of S e is more than a threshold value S eth, then latent tracks are formed in the target and a large amount of deposited energy gets confined in narrow dimensions. This leads the system to a non-equilibrium state and it then relaxes dynamically by inducing nucleation of nanocrystallites along the latent tracks. In the present investigation, amorphous thin films of TiO 2 are deposited on substrates of fused silica and that of single crystal sapphire. The films are then irradiated by a 100 MeV Au ion beam. Atomic force microscopy is employed for the surface study. The structural phase change induced by SHI irradiation is identified by glancing angle x-ray diffraction. Optical characterization is carried out by UV-vis absorption spectroscopy. Defects created during irradiation are studied by electron spin resonance spectroscopy studies. The role of a substrate in the SHI-induced nanocrystallization process is studied.

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Nanocrystallisation of TiO2 induced by dense electronic excitation

Cited by 12 publications

References 23 publications

The effect of gold nanoparticles on WO3 thin film

The effect of gold nanoparticles on WO3 thin film

X-ray absorption spectroscopy studies of phase transformations and amorphicity in nanotitania powder and silica–titania core–shell photocatalysts

Substrate dependence in the formation of TiO₂nanophases by dense electronic excitation

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Nanocrystallisation of TiO2 induced by dense electronic excitation

Cited by 12 publications

References 23 publications

The effect of gold nanoparticles on WO3 thin film

The effect of gold nanoparticles on WO3 thin film

X-ray absorption spectroscopy studies of phase transformations and amorphicity in nanotitania powder and silica–titania core–shell photocatalysts

Substrate dependence in the formation of TiO2nanophases by dense electronic excitation

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Substrate dependence in the formation of TiO₂nanophases by dense electronic excitation