Optical Properties of Ag-TiO(2) Nanocermet Films Prepared by Cosputtering and Multilayer Deposition Techniques

Insight into the molecular mechanism, cytotoxic, and anticancer activities of phyto-reduced silver nanoparticles in MCF-7 breast cancer cell lines

This contribution insight on the cytotoxic and anticancer activities and molecular mechanism of phyto-reduced silver nanoparticles (AgNPs) in MCF-7 breast cancer cell lines. A simple, entirely green synthesis process was optimized for the phyto-reduction of AgNP (~12.7 nm) using aqueous leaf extracts of Indigofera heterantha. The structural and vibrational properties of biosynthesized AgNPs were extensively characterized using UV-Vis spectrophotometer, x-ray diffraction (XRD), dynamic light scattering (DLS), and Fourier transform Infrared spectroscopy (FTIR), while their shape and morphology was studied through scanning electron microscopy (SEM). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay indicates concentration dependent inhibition with IC50, 27.93 ± 2.10 μg/mL against MCF-7 cells and 294.38 ± 3.87 μg/mL against L929 cells. The manifested anticancer mechanism in MCF-7 cells was extensively studied using Acridine orange/ethidium bromide (AO/EB), 4',6-diamidino-2-phenylindole (DAPI) and Annexin-V/propedium iodide fluorescence microscopic assays. The level of reactive oxygen species (ROS) was measured using DCFH-DA fluorescent spectroscopy. Overall, the results show that AgNPs exhibit cytotoxic and apoptotic effect on breast cancer MCF-7 cells by damaging membrane integrity and nuclear fragmentation due to oxidative stress generated by elevated level of ROS. RESEARCH HIGHLIGHTS: Biomimetic synthesis of nano dimension size silver nanoparticles (AgNPs). Characterization of AgNPs through UV-Vis, DLS, XRD, FTIR, and SEM. Cytotoxic and anticancer effects of the biosynthesized AgNPs in L929 fibroblast cells and MCF7 breast cancer respectively. Determination of morphological, and nuclear changes triggered by AgNPs in MCF 7 breast cancer cells using fluorescent microscopy and flow cytometry. Apoptosis induction by AgNPs in cancer cells through oxidative stress generated by reactive oxygen species (ROS).

Effective Inclusion of Sizable Amounts of Mo within TiO2 Nanoparticles Can Be Obtained by Reverse Micelle Sol-Gel Synthesis

Six Mo/TiO2 samples (with 0, 1.0, 2.5, 5.0, 7.5, and 10 wt % Mo nominal contents) were obtained by reverse micelle sol-gel synthesis, followed by calcination at 500 °C. The samples were characterized by means of powder X-ray Diffraction (PXRD), quantitative phase analysis as obtained by Rietveld refinement, field-emission scanning electron microscopy (FE-SEM) coupled with energy-dispersive X-ray analysis, N2 adsorption/desorption at -196 °C, X-ray photoelectron spectroscopy, and diffuse reflectance (DR) UV-vis spectroscopy. As a whole, the adopted characterization techniques showed the inclusion of a sizeable Mo amount, without the segregation of any MoO x phase. Specifically, PXRD showed the occurrence of anatase and brookite with all the studied samples; notwithstanding the mild calcination temperature, the formation of rutile occurred at Mo wt % ≥2.5 likely due to the presence of brookite favoring, in turn, anatase to rutile transition. DR UV-vis and XP spectroscopies allowed determining the samples' band gap energy (E g) and valence band energy, respectively, from which the conduction band energy was calculated; and the observed E g value increase at 10 wt % Mo was ascribed to the Moss-Burstein effect.

VO2-based active tunable emittance thermochromic flexible coatings

This contribution reports, for what we believe is the first time, on VO₂-based thin-film coatings on flexible Al substrates exhibiting a tunable positive emittance-switching Δε=(ε_H-ε_L)>0. More precisely, a layered stack of a-Si:H/SiO₂/VO₂ on flexible Al sheets presents minimum and maximum values of emissivity of about 0.18 and 0.57 at 40ºC and 83ºC, respectively, and hence allows an emittance-switching Δε of 0.39 and a relative variation Δε/ε_Λ of ∼217%. Such variations fit with the potential applications of such coatings as smart radiation devices in small satellites and spacecraft.

Ferromagnetic-like behavior of Co doped TiO2 flexible thin films fabricated via co-sputtering for spintronic applications

TiO₂:Co thin films on ITO (Indium-tin-oxide)/PET (Poly Ethylene Terephthalate) flexible and glass substrates were fabricated via DC magnetron co-sputtering at room temperature. The samples deposited on glass substrates were subjected to annealing processes at 473 K for 2 h to improve the crystallization of the material. Both TiO₂:Co/ITO/PET and TiO₂:Co/glass thin films exhibited excellent optical properties with more than 80% transmission in the visible region. An increase on ITO/PET surface temperature was detected during the synthesis of the samples; this variation in the ITO substrate (∼ 2 K) was associated to impact energetic of ion or atoms bombarded during the deposition process. X-ray diffraction measurements evidenced local phases to growth on the flexible substrate; the random distributions of Cobalt crystals into the rutile and anatase phases were associated to a crystalline lattice embedded with magnetic ions. A configuration of small grains and absence of cluster formation on the surface of thin films was observed through SEM and AFM measurements. From this topographic study and MFM measurements evidenced that surface grains were not constituted magnetic domains formation in the thin films. The ferromagnetic-like behavior was observed in a magnetization as function of field measurement by PPMS. M vs H curves at room temperature for TiO₂:Co/ITO/PET thin films, showed the hysteresis loop. The dipolar interaction between Cobalt ions without formation of domains were correlated to the magnetic behavior in the material, as the doping concentration is lower than 12%.

Zinc(ii) and cadmium(ii) complexes, [M(iPr2P(X)NC(Y)NC5H10-κ2-X,Y)2] (X and Y = O, S), as single source precursors for metal sulfide thin films

Structural, morphological and optical studies of zinc and cadmium sulfide thin films with different contents of phosphorus.

Photoinduced electron transfer in novel CdSe-Cu2Se type II core-shell quantum dots

Herein we report the synthesis, characterisation and electron transfer studies of CdSe–Cu₂Se QDs, a novel type II core–shell system. The synthesis was achieved by a high temperature organometallic method with oleylamine as ligand. Structural and optical properties of the nanostructures were investigated using X-ray diffraction, high resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy, inductive coupled plasma optical emission spectroscopy, cyclic voltammetry, X-ray photoelectron spectroscopy and absorption spectroscopy. The electron transfer dynamics were investigated by observing the variations in steady state and time resolved emission spectra in the presence of an electron acceptor-methyl viologen. Localization of electrons in the shells was evident from the studies performed indicating efficient charge separation.

Herein we report the synthesis, characterisation and electron transfer studies of CdSe–Cu₂Se QDs, a novel type II core–shell system.

Nonlinear optical properties of metal nanoparticles: a review

Metal nanoparticles (MNPs) hold great technological promise because of the possibility of engineering their electronic and optical properties through material design.

Effect of B2O3addition on optical and structural properties of TiO2as a new blocking layer for multiple dye sensitive solar cell application (DSSC)

TiO₂–B₂O₃sol–gel thin films were prepared using titanium(iv) isopropoxide as a Ti source and boric acid (H₃BO₃) as B precursor.

Surface segregation in TiO2-based nanocomposite thin films

The morphology of nanocomposites plays a pivotal role in understanding their functionality and determines their capabilities for applications. The use of nanocomposite coatings requires a study of the size effects on their functional properties. Noble metal nanoparticles are promising candidates for nanocomposite thin film applications due to their antibacterial, plasmonic and photocatalytic properties. In this contribution, the morphology of Ag-TiO(2) and Au-TiO(2) nanocomposite thin films has been investigated experimentally using electron tomography in transmission electron microscopy in combination with UV/vis spectroscopy. Based on the additional 3D information obtained from tomography, we propose a two-step model towards the observed bimodal particle size in these nanocomposite thin films prepared by co-sputtering from two different sources. Furthermore, we show that the optical properties exhibit a well-defined relation with the morphology of the nanocomposite thin films. The present investigations demonstrate the potential of electron tomography for revealing the complex structure and formation processes of functional nanocomposites.

Fluorescence hydrogen peroxide probe based on a microstructured polymer optical fiber modified with a titanium dioxide film

A highly sensitive microstructured polymer optical fiber (MPOF) probe for hydrogen peroxide was made by forming a rhodamine 6G-doped titanium dioxide film on the side walls of array holes in an MPOF. It was found that hydrogen peroxide only has a response to the MPOF probe in a certain concentration of potassium iodide in sulfuric acid solution. The calibration graph of fluorescence intensity versus hydrogen peroxide concentration is linear in the range of 1.6 x 10(-7) mol/L to 9.6 x 10(-5) mol/L. The method, with high sensitivity and a wide linear range, has been applied to the determination of trace amounts of hydrogen peroxide in a few real samples, such as rain water and contact lens disinfectant, with satisfactory results.

Interferometric sensing platform with dielectric nanostructured thin films

A new interferometer-based optical sensing platform with nanostructured thin films of ZrO2 or TiO2 as sensing environment has been developed. With the application of an IC compatible Si(3)N(4) waveguide technology, Mach-Zehnder interferometer devices have been fabricated. The application of the glancing angle deposition technique allowed fabrication of nanostructured thin films as the optical sensing environment. Sensing ability of fabricated devices has been demonstrated through the refractive index measurement of a known gas. The transmission spectra and time response measurements have demonstrated a maximum phase shift of Delta phi=pi/10 and a |Delta P(out)|=0.65 dBm. Devices with TiO2 film on the sensing region performed much better than devices with ZrO2, with sensitivity twice as high.

Quantitative modelling of the surface plasmon resonances of metal nanoclusters sandwiched between dielectric layers: the influence of nanocluster size, shape and organization

The effects of size, shape and organization on the surface plasmon resonances of Ag nanoclusters sandwiched between Si(3)N(4) layers are studied by transmission electron microscopy and anisotropic spectroscopic ellipsometry. We present an easy-to-handle model that quantitatively links the nanostructure and optical response of the films, which are considered as dielectric/metal:dielectric/dielectric trilayers, with the central nanocomposite layer being an effective medium whose optical properties are described by an anisotropic dielectric tensor. The components of this tensor are calculated using a generalization of the Yamaguchi theory taking into account the real organization, size and shape distributions of ellipsoidal nanoclusters, whose electronic properties are assumed to reflect shape-dependent finite size effects. Using this model, it is shown that the optical response of the films in the visible range is dominated by the excitation of the surface plasmon resonance of the clusters along their in-plane long axis, while no surface plasmon resonance resulting from an excitation along their in-plane short axis can be observed due to damping effects. Moreover, the spectral position of this resonance appears to be mainly affected by the average shape of the clusters, and weakly by their size, their shape distribution and the electromagnetic interaction between them.

Properties of titanium dioxide films prepared by reactive electron-beam evaporation from various starting materials

There is a wide choice of starting materials for the production of titanium dioxide films by reactive electron-beam evaporation. We have investigated the specific merits of these materials in terms of refractive index, stress, and abrasion resistance of the resultant titanium dioxide films. The suboxides TiO, Ti2O3, and Ti3O5 as well as titanium dioxide and titanium metal were reactively evaporated, and titanium dioxide films free of absorption were obtained on substrates at 25 and 250 degrees C. On unheated substrates the refractive index, which varies from 2.06 to 2.22, the stress, and the abrasion resistance all depend on the starting material used. On substrates heated to 250 degrees C the refractive indices of all films lie closely about 2.4, and all films show high tensile stress and good abrasion resistance.