Decrease In Optical Gap Research Articles

Development and characterization of HPMC/NaAlg-CuO bio-nanocomposites: Enhanced optical, electrical, and antibacterial properties for sustainable packaging applications

Copper oxide nanoparticles (CuO NP) were incorporated into a hydroxypropyl cellulose (HPMC) and sodium alginate (NaAlg) matrix through a casting method to create bio-nanocomposite films. XRD analysis confirmed the semi-crystalline nature of the HPMC/NaAlg matrix, with a broad peak at 2θ = 21.22°, which decreased in intensity as CuO concentration increased, indicating a shift towards an amorphous structure. FT-IR analysis demonstrated changes in band intensity, which can be attributed to the reduced volume fraction of the polymer blend in the presence of the CuO nanofiller. SEM images showed homogeneity at low CuO NP concentrations, but at 0.9 wt% CuO, nanoparticle aggregation became evident. The UV–visible spectra indicated a redshift from 212 nm to 246 nm and a decrease in optical energy gap from 4.78 eV for the pure blend to 2.99 eV at 0.9 wt% CuO, associated with increased localized defect states. AC electrical conductivity and dielectric properties improved with CuO dispersion, enhancing the bio-nanocomposite's suitability for electrochemical and optoelectronic applications. The bio-nanocomposites demonstrated significant antibacterial activity, with films containing 0.4 and 0.7 wt% CuO achieving the largest inhibition zones against B. subtilis, S. aureus, P. aeruginosa, and E. coli. Overall, these findings suggest that HPMC/NaAlg-CuO bio-nanocomposites are promising candidates for use in antibacterial packaging and optoelectronics.

Impact of annealing temperature on optical, morphological, and surface characteristics of PC/PBT blend exposed to alpha particles

The induced modifications of the optical and surface characteristics in the annealed α-irradiated polycarbonate/polybutylene terephthalate (PC/PBT) blend have been studied in the temperature annealing range from 100 to 200 °C for 15 min. Several techniques have been used to study the changes in chemical composition, optical-electronic transitions, photoemission, contact angle, surface roughness, and hardness of annealed samples comparable to the pristine one. The FTIR spectra exhibit aggregate changes in the band intensities after annealing, indicating the scission and cross-linking of the polymer chains. The intensity of the peaks reduced with α-irradiation but began to increase with increasing annealing temperature. The trend of the function groups found in the annealed samples with the rise in annealing temperature supports the crosslinking mechanism. The UV/Vis spectra revealed that the absorption edges of annealed samples were shifted toward lower photon energy (red shift), reflecting the decrease of optical energy gap from 4 eV to 3.6 eV for direct transition and from 3.8 eV to 3.5 eV for indirect transition at the highest temperature. Further, the number of carbon atoms and the number of carbon clusters increases with the increase in the annealing temperature. The refractive index of the samples decreases from 1.5479 for the pristine sample to 1.4008 for the sample at the highest temperature. Moreover, the dielectric parameters and optical conductivity of the annealed samples were modified after thermal annealing. The PL emission yields are decreased with the increase in annealing temperatures that indicating an enhancement in the non-radiative recombination rate relative to the radiative recombination, which may be due to the increasing in the surface density states. The α-irradiated samples showed a notable increase in contact angle and a notable decrease in surface tension values with increasing the annealing temperatures. The side chain induction, which readily bundles and recombines the annealed parts by raising temperatures, also causes the surface roughness of annealed samples to decrease from 1.099 μm for the pristine sample to 0.696 μm for the annealed sample at the highest temperature. It is noteworthy that there is an increase in the hardness from 10.49 ΜPa for the pristine sample to 41.98 ΜPa for the annealed sample at the highest temperature. This is related to the results of changes in the polymer chains due to the active sites or branching points created by scission, which can lead to cross-linking.

Synthesis and Characterization of (PVA-CoO-ZrO2) Nanostructures for Nanooptoelectronic Fields

Nanocomposites have a wide range of applications, including optical integrated circuits, sensors, coatings, and medical devices. As a result, the purpose of this paper is to prepare a new type of nanocomposites made of polyvinyl alcohol (PVA) with different concentrations (0, 1, 2 and 3) wt% of cobalt oxide and zirconium dioxide (CoO-ZrO2) nanoparticles by using casting method. Microscopic photographs demonstrate the fact that the additive distribution amount of NPs in the polymer was uniform, and (CoO-ZrO2) NPs formed a continuous network within the polymer when the concentration reached 3wt.%. The outcomes of optical properties indicate that the absorbance of nanocomposites improves as the concentrations of cobalt oxide and zirconium dioxide nanoparticles increase while transmittance and the optical energy gap decrease. On the other hand, optical constants of nanocomposites (refractive index, absorption coefficient, extinction coefficient, real and imaginary the dielectric constants) and optical conductivity are increase with increases in the weight percentages of (CoO-ZrO2) nanoparticles. These outcomes demonstrate the (PVA-CoO -ZrO2) NCs use for various optical devices.

Characterization of oxyfluoride glasses doped with rare-earth ions through structural, thermal, and optical application thereof

Novel transparent glasses and glass-ceramics were fabricated by using melt-quenching technique with the following composition: TeO2–WO3–Nb2O5–KF–La2O3 doped with Tm2O3. Different properties and physical parameters of these glasses were investigated. As the concentration of Tm3+ ions increases, the linear refractive index increases while the optical energy gap decreases. With high Tm3+ ion concentration creates nucleation in the glass matrix this was investigated by x-ray diffraction. The Judd-Ofelt parameters used to calculate the electric and magnetic dipole transition probabilities, branching ratios, and radiative lifetimes of various excited states of Tm3+-doped parent glass. The emission cross section values for the 3F4→3H6 transition computed by using the McCumber hypothesis. The stimulated emission cross section σeFL(λ) and gain values of fabricated glass increase with Tm3+ ions. The spectroscopic quality and figure of merit (FOM) gain (σeFL(λ)×τR) factors were evaluated for the prepared transparent glass. Furthermore, the produced glasses were demonstrated to have low OH content and they have high fluoride ion content. These important properties of the glasses and glass-ceramics make them suitable for use in photonic applications.

Structural correlations for increased FOM in Pb doped Zn2SnO4 nanostructured films for applications as transparent electrode

This work reports the detailed analysis of the structure and optoelectronic properties of spin coated Zn2−xPbxSnO4 nanostructured films. XRD studies reveal the polycrystalline cubic inverse spinel structure while Raman spectra show the dominance of T2 g(3) mode and decrease in intensity of A1 g mode with Pb doped ZTO films. X-ray photoelectron spectroscopy substantiates the dominance of atom in multiple charge states and their possible substitutions in the host lattice. The maximum average transparency of 87% in 400–650 nm spectral region for x = 0.08 sample while the decrease in optical gap from 4.32 to 4.14 eV with minimal value of 4.04 eV for x = 0.04 is found. The refractive index at 500 nm is calculated using Swanepoel’s method and found to decrease from 1.72 for ZTO and 1.59 for x = 0.08 sample. The carrier concentration increases from 1018 cm−3 for ZTO to 1020 cm−3 for x = 0.08 sample. The minimal value of electrical resistivity of 2.17 × 10−3 Ω-cm and maximal Haacke’s Figure of merit (FOM) of 1.1 × 10−3/ Ω is obtained for x = 0.08. These results are significant advancement to the development of ZTO based transparent conductors for highly efficient futuristic optoelectronics and photovoltaic devices.

Structural, optical, morphological and mechanical studies of polyethylene oxide/sodium alginate blend containing multi-walled carbon nanotubes

Multi-walled carbon nanotubes were added to mixture of polyethylene oxide (PEO)/sodium alginate (SA) (70/30 wt.%) films via the casting way. X-ray diffraction exhibited the amorphous behavior of the polymer samples, also showed a decrease in the crystalline ratio after the addition of Multi-walled carbon nanotubes (MWCNTs). Fourier Transform Infrared (FTIR) spectroscopy exhibited changes in intensity of some peaks after embedding of MWCNTs, these changes were related to the interaction between PEO/SA blend and MWCNTs. The optical properties of samples were investigated by ultraviolet and visible (UV/vis) spectroscopy and showed decrease in optical energy gap as the concentration of MWCNTs increased. Scanning electron microscopy (SEM) exhibited a homogeneous growth mechanism which denotes the partial compatibility between the nanocomposite components. The mechanical behavior measurements of the prepared samples showed improvement of the modulus of elasticity and tensile strength after adding MWCNTs. This may be due to interaction and adhesion between MWCNTs and polymeric samples. Present results confirm the advantage of selecting MWCNTs as a nanofiller to improve the optical and mechanical properties of polymeric films.

Role of energy loss-range profile of heavy ions in tailoring the optical properties of polycarbonate

Polycarbonate (PC) samples have been implanted with 115 keV N+, Ar+ and Kr+ at fluences ranging from 5x1014 to 1x1016 ions/cm2 to be employed for optical studies. A Decrease in optical energy gap, enhancement in reflectivity and reduction in transmittance, particularly in UV-region, is observed for all implanted samples. The change in optical properties of PC, first, by keeping energy deposited/cm2 constant (i.e. keeping energy*fluence constant) and then by keeping same depth of penetration for different ions have been analysed in detail. The changes are found to be more prominent for N+ compared to Ar+ and Kr+ when the fluence/energy deposited/cm2 by the ions is same. Further, the energy for N+ is reduced to 46 keV, while for Kr+ it is increased to 200 keV to ensure the same penetration depth for N+, Ar+ and Kr+ in PC. Finally, the results are explained on the basis of energy loss-range profiles of these ions in polycarbonate and through Raman spectroscopy. This study convincingly demonstrates that not only the types of ion species, their energies and fluences, but the total energy deposited by ions and their depth of penetration also plays an important role in tailoring the optical properties of polymeric materials.

Improved photodetector performance of high-k dielectric material (La) doped V2O5 thin films as an interfacial layer in Schottky barrier diodes

In this work, high-k dielectric material of lanthanum (La) doped vanadium pentoxide (V2O5) thin films is deposited on glass substrate using spin coating route and annealed at 500 °C. The Cu/La-V2O5/n-Si Schottky barrier diodes with different La concentrations have fabricated. X-Ray Diffraction (XRD) characterization exposed the tetragonal crystal structure of La-V2O5 films. Field Emission Scanning Electron Microscopy (FE-SEM) morphology shows nanorod grain on La-V2O5 films. The decrease of optical gap (Eg) from 3.37 to 3.1 eV has been observed in UV-vis spectroscopy. The dc electrical conductivity is increased owing to the high-k-dielectric material influence of doping. Notably, La 4% doping exhibits high photo responsivity of 33.39 (mA/W) during fast switch response (ONOFF).

Optical Properties and Conductivity of PVA–H3PO4 (Polyvinyl Alcohol–Phosphoric Acid) Film Blend Irradiated by γ-Rays

This study assesses the optical properties and conductivity of PVA–H3PO4 (polyvinyl alcohol–phosphoric acid) polymer film blend irradiated by gamma (γ) rays. The PVA–H3PO4 polymer film blend was prepared by the solvent-casting method at H3PO4 concentrations of 75 v% and 85 v%, and then irradiated up to 25 kGy using γ-rays from the Cobalt-60 isotope source. The optical absorption spectrum was measured using an ultraviolet–visible spectrophotometer over a wavelength range of 200 to 700 nm. It was found that the absorption peaks are in three regions, namely two peaks in the ultraviolet region (310 and 350 nm) and one peak in the visible region (550 nm). The presence of an absorption peak after being exposed to hυ energy indicates a transition of electrons from HOMO to LUMO within the polymer chain. The study of optical absorption shows that the energy band gap (energy gap) depends on the radiation dose and the concentration of H3PO4 in the polymer film blend. The optical absorption, absorption edge, and energy gap decrease with increasing H3PO4 concentration and radiation dose. The interaction between PVA and H3PO4 blend led to an increase in the conductivity of the resulting polymer blend film.

Effect of Germanium Content on the Optical Constants of GexS1-x Thin Films

In this study the alloys Ge xS1-x with different Ge content (x=0, 0.1,0.2 and 0.3) wt.% have been successfully prepared by evacuated quartz tube under vacuum pressure (10−2Torr), whereas Ge xS1-x thin films were prepared by thermal evaporation technique under vacuum (10−5Torr) with (x=0,0.1,0.2 and 0.3). The optical properties measurements shows that the optical energy gap decrease from (3.4 to 3 eV) with the increase of x content, the optical constants declare significant variation with x content variation.

Influence of phase transformation on structure–property relationship in quaternary In10Sb10Ag10Se70 chalcogenide films

This work reports the effect of thermal annealing (353–413 K) on structure and physical properties of thermally evaporated In10Ag10Sb10Se70 chalcogenide films. The samples were characterized by X-ray diffraction, transmission electron microscopy, TEM, Raman spectroscopy, optical absorption and photoconductivity measurements. Thermal annealing favours amorphous to polycrystalline structure transition with the growth of Se, AgInSe2 and AgSbSe2 phases. A significant change in position/shape of Raman bands upon annealing has been observed. The indirect optical gap decreases from 1.44 to 0.68 eV while tailing parameter increases with annealing. Photosensitivity decreases from 29.3 to 14.2 with annealing temperature. The decay of photocurrents is well fitted to stretched exponential function; the value of decay time constant increases while local minimum value of dispersion parameter at 353 K has been observed. These results are explained on the basis of amorphous crystalline phase transformation in chalcogenides and are important for developing new materials for emerging technologies.

Enhancement of Mn2+ contributions on improvement of electrical characteristics for sol–gel deposited Zn2−xMnxSnO4 nanostructured films

The study of transition metal impurity in transparent metal oxides has gained much attention in scientific community for developing high efficiency optoelectronic and photovoltaic devices. Here, we report the role of Mn dopant on structure and optoelectronic properties of zinc stannate (ZTO) films deposited by spin coating technique using acetylacetone as sol–gel precursor solvent. X-ray diffraction and Raman studies validate the preferential growth along (311) plane and characteristic vibrational modes at 552 and 667 cm−1, respectively for inverse spinel ZTO system. The scanning electron microscopy reveals the change in morphology with Mn content in ZTO films. Chemical structure investigations also confirm an upsurge in Mn2+ state with Mn content. The optical transparency at 550 nm was found to decline from 80.2 to 25.4% along with a decrease in optical gap from 4.32 to 3.40 eV with Mn content. An increase in defect dominated emission spectra with dopant content was observed in ZTO films. An enhancement in carrier concentration and drastic decrement in carrier mobility to favour decreased electrical resistivity with Mn dopant in ZTO films. These results are incredible stimulus to optoelectronic properties of ZTO for developing next generation of transparent conductors for optoelectronic devices.

Surface charge doping induced carrier type reversal in spin coated CdS/rGO layered nanohybrid films

The growth of reduced graphene oxide (rGO) based semiconductor nanohybrids through simple, scalable, additive-free and cost-effective route has fascinated significant attention of researchers for both fundamental research areas and its commercial applications. In the present work, cadmium sulphide/reduced graphene oxide (CdS/rGO) films were sequentially or layer-by-layer (LBL) deposited by spin coating method. The samples were characterized by using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-visible spectroscopy, Raman spectra and Hall measurements. The cubic phase of the CdS and formation of rGO was confirmed by XRD measurements. The FESEM micrographs elucidate a change in morphological features with rGO content in CdS/rGO nanohybrid films. The Raman spectra indicate the characteristic features for nanostructured CdS and rGO in these samples. Optical transmission is found to increase along with a decrease in optical gap with rGO content. Hall measurements showed the change in the majority carrier concentration with rGO content or the observation of surface charge transfer doping (SCTD) in these nanocomposites. The change in dispersion of refractive index with rGO content for CdS/rGO nanocomposites in terahertz (THz) spectral region has been observed. These results are very important for the development of new functionality of nanohybrid materials for emerging technologies.

Effect of gamma radiation on the structure and optical properties of polycarbonate-polybutylene terephthalate/silver nanocomposite films

Samples from the PC-PBT/Ag nanocomposite have been exposed to gamma radiation with doses between 2 and 25 kGy. The resultant effect of gamma radiation on the structure and optical properties of PC-PBT/Ag nanocomposite has been investigated using TEM, XRD, FTIR and UV spectroscopy. The gamma irradiation with doses 5–25 kGy causes proper spreading of Ag nanoparticles in the PC-PBT matrix, resulted in an increase in the amorphous phase associated with a decrease in optical energy gap from 3.80 to 2.94 eV. Further, the nanocomposite has a response to color change as the color intensity increases from 0.64 to 4.94.

Influence of ZnO/Ag nanoparticles doping on the structural, thermal, optical and electrical properties of PAM/PEO composite

Zinc oxide nanoparticles (ZnO NPs) had been synthesized via sol-gel and the silver nanoparticles (Ag NPs) had been synthesized via chemical synthesis. The XRD and TEM confirmed the formation of ZnO and Ag nanoparticles. A series of polyacrylamide and polyethylene oxide (PAM/PEO) blend films doped with ZnO NPs and various concentrations of Ag NPs were prepared by the solution casting method. The FTIR spectra and XRD studies indicate the structural changes taking place in the nanocomposites which confirmed the compatibility between ZnO/Ag NPs and pure blend. The optical energy gap decreases by the addition of ZnO and Ag nanoparticles. The TGA data showed that the stability of thermal of the all films enhanced after adding the ZnO and Ag nanoparticles. The dielectric and conductivity of the samples has been carried out by an impedance analyzer in the frequency range of 1.0 Hz–10.0 MHz at RT. It has been viewed that the conductivity raised with addition of the ZnO/Ag NPs due to an increase in the number of charges carrier. The dielectric constant reduces with a raise in the frequency for the samples prepared. These properties illustrate ZnO and Ag NPs doped PAM/PEO nanocomposites samples are a prominent material for potential applications.

Vibronic Effects in the Ultrafast Interfacial Electron Transfer of Perylene-Sensitized TiO2 Surfaces

We combine ultrafast transient absorption (TA) spectroscopy and nonadiabatic quantum dynamics simulations to describe the real-time unfold of vibronic effects on the photoabsorption of TiO2 anatase sensitized with the (perylen-9-yl)carboxylate dye (Pe-COOH/TiO2). The excited state is mapped in time and frequency by ultrafast broadband spectroscopy while atomistic quantum dynamics is used to simulate the self-consistent vibronic effects. The TA map shows the lifetime of the electronic population generated in the S1 state of the dye and the rise of the absorption D0–D1 of the cation. The theoretical analysis reveals that the electron transfer from perylene into TiO2 is complete within 20 fs, in agreement with the 12 fs experimental measurement. Because of the structural relaxation produced by the photoinduced electron transfer, the optical gap decreases by 390 meV, in agreement with the D0–D1 transition band. Furthermore, the reorganization energy estimated to be around 220 meV is mostly due to the energy s...

Structural, optical, mechanical and dielectric properties of titanium dioxide doped PVA/PVP nanocomposite

We report preparation of Titanium dioxide (TiO2) nanoparticles doped PVA/PVP polymer nanocomposites by solvent casting technique. FTIR spectra and XRD studies signify the structural modifications taking place in the nanocomposites. The optical energy gap decreases by the addition of TiO2 nanoparticles. The mechanical properties such as tensile strength and Young’s modulus are enhanced by the addition of Titanium dioxide (TiO2) nanoparticles. The Fluorescence studies indicate that photoluminescence intensity is maximum for 4 wt% doping concentration of TiO2. The AFM analysis provides information about the surface roughness of the polymer film. The dielectric plot shows that the dielectric constant increases up to 12 wt% doping of TiO2, a further increase in the doping concentration results in the reduction of dielectric constant. The dielectric constant decreases with an increase in the frequency for all the films. The above properties show TiO2 doped PVA/PVP nanocomposite films are a prominent material for potential applications.

Physical and optical properties of CdO B2O3 Bi2O3 TeO2 glass system

The physical and optical properties of xCdO (35-x) B2O3 60Bi2O3 5TeO2 glass system (where, x=10, 20, 30) has been investigated. Thermal stability , density , optical transmittance and the refractive index of these glasses have been studied. It was found that the values of density increase but the values of molar volume and oxygen packing density decrease by increasing CdO content. Also, the thermal stability of all the studied samples increase by increasing CdO content. However, it was found that the values of optical energy gap decrease by increasing CdO content for all the studied samples. While as the values of refractive index, molar polarizability, oxide ion polarizability, optical basicity increase by increasing CdO content. Also, all the studied samples exhibit insulating behavior and become more basic and more polarized by increasing CdO content. The high values of third order nonlinear optical susceptibility for all the studied samples, were found to be in the range (1.408-2.307)x 10-12esu, which is larger than that of pure silica glass. Finally, it has been suggested that all the studied samples are promising materials for nonlinear optical requests.

Effect of nanocrystals concentration on optical and luminescent properties of PVK:ZnSe nanocomposites

Abstract This work presents a systematic study of the effect of ZnSe nanocrystals (NCs) concentration on the optical and luminescent properties of poly N-vinylcarbazole (PVK) polymer nanocomposites. The ZnSe nanocrystals were synthesized by a simple coprecipitation chemical route, while PVK:ZnSe nanocomposite films were fabricated using the spin coating technique. The samples were characterized by XRD, TEM, SEM, UV-Vis and fluorescence techniques. The X-ray diffraction and TEM studies confirmed the particle size, microstructure and spherical shape of the synthesized nanocrystals. The ZnSe nanocrystals in PVK caused a decrease in optical gap with increasing concentration of nanocrystals. The emission spectra exhibited augmentation in intensity up to 70 wt.% of nanoparticles while further addition resulted in a decrease in luminescence. The structure-property relationships obtained for the present system are important for developing low cost illumination devices.

Ion irradiation induced effects on the optical properties of polymers: a possible correlation with the energy loss profile

In the present study, the samples of CR-39 (monomer composition C12H18O7) have been implanted with 100keV Ar+ and Kr+ ions to different fluencies ranging from 5x1014 to 1x1016 ions/cm2. Further, these samples were subjected to UV-Visible, FTIR and Raman spectroscopic techniques to reveal the change in the optical behaviour of the samples in terms of induced structural changes in the polymer as a result of ion irradiation. The observed decrease in optical energy gap and increase in refractive index of the material under study after irradiation to Ar+ and Kr+ ions at the same energy have been tried to explain in terms of the energy loss profile along the trajectory of the respective ions. These studies are quite important towards the development of new materials with desired properties besides their fundamental importance.