Study of nonlinear optical properties of TiO₂ – polystyrene nanocomposite films

Abstract

We consider an ex-situ prepared TiO2 − polystyrene (TiO2 − PS) nanocomposite, with different concentration of TiO2 nanoparticles (NPs), deposited by the spin-coating method on quartz substrates. Nonlinear optical properties of the TiO2 − PS nanocomposite films are studied using the Z-scan technique. Structural properties of the films are investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The optical band gap energy of the TiO2 − PS films are determined from the optical absorption spectra. The relation between the optical nonlinearities and the bandgap energy, as a microscopic electronic property of the semiconductor nanocomposite, is established. It is shown that an increase in the content of TiO2 NPs in the nanocomposite films results in bandgap narrowing and concomitant enhancement of optical nonlinearities. It is proposed that bandgap narrowing and enhancement of optical nonlinearities can be ascribed to the introduction of mid-gap states as a result of the formation of surface defects in TiO2 NPs. The results of this work indicate that incorporation of TiO2 NPs in the PS polymeric matrix can be a new way for bandgap narrowing of TiO2 NPs toward the visible light region, which is of great interest for their application in this part of the spectrum. Furthermore, enhancement of the optical nonlinearities of the spin-coated TiO2 − PS films by increasing the TiO2 NP content can open up new avenues for their use as nonlinear optical films in photonics applications.

Black Titanium-Oxo Clusters with Ultralow Band Gaps and Enhanced Nonlinear Optical Performance

“…Upon analyzing these work regarding band gaps, it is interesting to note that the TOCs decorated with aromatic O-donor ligands featuring C­(sp 2 )–O – (e.g., Cat-based ligands) display a narrowed band gap compared to TOCs without such functional groups (Figures S59, S60, and Table S5). Such band gap reduction might be due to the CT effect from Cat to the high valence TOCs, which is in agreement with previous studies. ,, Additionally, with the exception of sensitizing ligands, most structures in TOC band gap studies contain alkoxide ligands (Table S5), while compounds PTC-272 to PTC-277 are totally modified with carboxylate groups (HPA, HIBA, or HNBA). Meanwhile, previously reported TOCs that are largely covered with carboxylates, but lacking catechol, are generally found to be colorless (Figure S7).…”

“…Such band gap reduction might be due to the CT effect from Cat to the high valence TOCs, which is in agreement with previous studies. 24,35,36 Additionally, with the exception of sensitizing ligands, most structures in TOC band gap studies contain alkoxide ligands (Table S5), while compounds PTC-272 to PTC-277 are totally modified with carboxylate groups (HPA, HIBA, or HNBA). Meanwhile, previously reported TOCs that are largely covered with carboxylates, but lacking catechol, are generally found to be colorless (Figure S7).…”

“…37,38 As was already reported, black TiO 2 materials show better NLO responses than ordinary TiO 2 , and the optical nonlinearities of TiO 2 NPs improved as the band gap reduced. 3,36 Therefore, the low band gaps of the obtained TOCs encouraged us to study their NLO performance. We investigated the third-order NLO performance using solid samples palletized with KBr through open-aperture (OA) Zscan techniques with an Nd:YAG laser at 532 nm.…”

Large Optical Nonlinearity of the Activated Carbon Nanoparticles Prepared by Laser Ablation

“…Figure 9 shows the results of open- and closed-aperture Z-scan measurements. The next equation was used for fitting the open-aperture data and finding the value of [ 71 , 72 ]: …”

Inclined Substrate Deposition of Nanostructured TiO2 Thin Films for DSSC Application

“…Titanium dioxide has been used in a wide range of applications because of its useful electrical and optical properties, such as high dielectric constant, high electrical resistivity, high refractive index, excellent optical transmittance in the visible range, non-toxicity, low cost and large band gap [ 1 , 2 , 3 , 4 , 5 ]. TiO 2 film with a nanoporous structure is needed for applications in the solar cell and catalyst areas [ 6 , 7 , 8 , 9 ].…”