Intensities Of Vibrational Modes Research Articles

Mos2 2D nanoparticles as inducers of changes in liposomes formation and their spectroscopic properties

Liposomes, due to their biocompatible and flexible lipid bilayer, serve as ideal model structures to study the biophysical properties and physiological functions of cell membranes. To investigate the impact of 2D nanoparticles on liposomes formation, methods of dynamic light scattering, optical and SEM microscopy were used to determine the size of liposomes, along with Raman, IR spectroscopy and quantum-chemistry calculations for structural study. Optical microscopy study confirmed feasibility of the preparation method and liposomes size redistribution, depending on the nanoparticles. SEM data and EDS analysis provided insides on the morphological structures of the nanopowder, nanoplatelets, liposomes, and its elemental composition. Sizes of the liposomes increase up to 12% with addition of 2D MoS2 nanoparticles. Analysis of IR spectra showed a change in the spectral properties of liposomes with particles in comparison with unloaded liposomes in the region of stretching C = O and CH vibration, bending OH. Changes in H-bonds redistribution, contribution from = C–H stretching ring vibrations at 3035 cm–1 and disappearance of the band at 3006 cm–1 in IR spectrum together with the virtual disappearance of Raman bands of liposomes seems to be a marker for particle entry into the liposome. Quenching of luminescence in Raman spectra is observed in liposomes with nanoparticles compared to unloaded liposomes which is weaker in the case of liposome preparation together with nanoparticles. Enhancement of intensity of vibration modes in IR spectra for nanoparticles introduced after liposome preparation from 34% (powder) to 52% (platelets) and covered the liposome surface is observed and could be liposome particle coating marker.

Vibronic Structure of the UV/Visible Absorption Spectra of Phenol and Phenolate: A Hybrid Density Functional Theory─Doktorov's Quantum Algorithm Approach.

The Doktorov's quantum algorithm has been enacted in combination with time-dependent density functional theory (TD-DFT) to simulate the vibronic structure of the UV/visible absorption spectra of the phenol and phenolate molecules. On the one hand, DFT and TD-DFT are employed with classical algorithms to calculate the ground and excited-state electronic structures as well as their vibrational frequencies and normal modes, whereas, on the other hand, quantum algorithms are employed for evaluating the vibrational transition intensities. In comparison to a previous study, J. Phys. Chem. A 2024, 128, 4369-4377, which demonstrated Doktorov's quantum algorithm as a proof of concept to predict the vibronic structure of ionization spectra, it is applied here to medium-size molecules with more than 30 vibrational normal modes, without accounting for Duschinsky rotations due to software limitations. This application to simulate the vibronic structures of the spectra of phenol and phenolate also enables assessing the impact of the differences in vibrational frequencies between the ground and excited electronic states.

Influence of LaMnO3 Nanocrystallite Size on its Optical and Raman Spectra

: In the current study, nanocrystalline LaMnO3 perovskite was prepared by combustion method and annealed at different annealing temperatures. The X-ray diffraction (XRD) patterns provided evidence that the structure formed has a Rhombohedral structure with R3 ̅c space group. The remarkable growth in the crystallite size, reduction in microstrain, and dislocation density were observed with annealing temperature. Ultraviolet-visible spectroscopy was used to determine the optical band gap by the Tauc-plot method. The optical band gap was found to be 3.5 ± 0.4eV and 2.9 ± 0.5eV for 600°C and 1200°C annealed samples, respectively. The observed results were influenced by crystallite size. Raman spectra of the LaMnO3 nanocrystallites revealed five Raman-active modes, like out-of-phase rotation modes and bending mode of MnO6 octahedra. Moreover, the intensity of vibrational modes also varied significantly with annealing temperature.

Rovibrational analysis of AlCO3, OAlO2, and HOAlO2 for possible atmospheric detection.

The lack of observational data for the AlO molecule in the mesosphere/lower thermosphere may be due to ablated aluminum reacting quickly to form other species. Previously proposed reaction pathways show that aluminum could be ablated in the atmosphere from meteoritic activity, but there currently exist very limited spectroscopic data on the intermediates in these reactions, limiting the possible detection of said molecules. As such, rovibrational spectroscopic data are computed herein using quartic force field methodology at four different levels of theory for the neutral intermediates AlCO3, OAlO2, and HOAlO2. Each molecule exhibits multiple vibrational modes with large vibrational transition intensities. For instance, the C-O stretch (ν1) in AlCO3 has a harmonic intensity of 536 km mol-1, the Al-O stretch (ν2) in OAlO2 has an intensity of 678 km mol-1, and the out-of-plane torsion (ν9) in HOAlO2 has an intensity of 158 km mol-1. All three molecules have exceptionally large dipole moments of 6.27, 4.21, and 5.04D, respectively. These properties indicate that all three molecules are good candidates for potential atmospheric observation utilizing vibrational and/or rotational spectroscopic techniques.

Influence of the octahedral cation on the evolution of lattice phonons in metal halide double perovskites: Raman spectroscopic investigation of Cs2B′B″Cl6 ( B′=Ag1−xNax ; B″=Bi1−xInx )

Vibrational dynamics in halide double perovskites govern several key aspects including carrier recombination and transport properties. Here, we present comprehensive vibrational studies investigated through micro-Raman spectroscopy to understand how octahedral cation substitution in a wide range of metal halide double perovskites ${\mathrm{Cs}}_{2}{B}^{\ensuremath{'}}{B}^{\ensuremath{''}}{\mathrm{Cl}}_{6}$ (${B}^{\ensuremath{'}}={\mathrm{Ag}}_{1\ensuremath{-}x}{\mathrm{Na}}_{x}$; ${B}^{\ensuremath{''}}={\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{In}}_{x}$) influence lattice vibrations. A significant enhancement in ${F}_{2g}$ mode intensity---a key factor in determining the cation ordering---is observed with ${\mathrm{Na}}^{+}$ substitution. In contrast to a generally observed trend, despite similar ionic sizes of ${\mathrm{Na}}^{+}$ and ${\mathrm{Bi}}^{3+}$, an increase in cationic ordering is observed as ${\mathrm{Na}}^{+}$ substitutes at ${\mathrm{Ag}}^{+}$ site in ${\mathrm{Cs}}_{2}{\mathrm{Ag}}_{1\ensuremath{-}x}{\mathrm{Na}}_{x}\mathrm{Bi}{\mathrm{Cl}}_{6}$ and ${\mathrm{Cs}}_{2}{\mathrm{Ag}}_{1\ensuremath{-}x}{\mathrm{Na}}_{x}\mathrm{In}{\mathrm{Cl}}_{6}$. The ${F}_{2g}$ mode intensity depends on ${B}^{\ensuremath{'}}$-site cationic ordering (${\mathrm{Ag}}^{+}$ or ${\mathrm{Na}}^{+}$), while its vibrational energy is governed by the ${B}^{\ensuremath{''}}$-site cations (${\mathrm{Bi}}^{3+}$ or ${\mathrm{In}}^{3+}$). The symmetric stretching vibrations depicted by ${A}_{1g}$ mode are mainly influenced by $[{B}^{3+}\text{\ensuremath{-}}{X}_{6}]$ octahedra. The reduction in the linewidth of symmetric-stretching LO phonon mode (${A}_{1g}$) and the disappearance/diminishing of asymmetric-stretching vibrations (${E}_{\mathrm{g}}$) further substantiates the improved cationic ordering. The changes in the vibrational mode intensities with ${B}^{\ensuremath{'}}$-site substitution (${\mathrm{Ag}}^{+}, {\mathrm{Na}}^{+}$) and the appearance of distinct octahedral modes with ${B}^{\ensuremath{''}}$-site substitution (${\mathrm{Bi}}^{3+}, {\mathrm{In}}^{3+}$) allow us to disseminate different octahedral contributions to the vibrational dynamics in the lattice. Further, the vibrational analyses on double perovskites with different choices of ${B}^{\ensuremath{'}}$ and ${B}^{\ensuremath{''}}$ cations and $X$ anion reveal the origin of asymmetric stretching (${E}_{\mathrm{g}}$). This mode mainly prevails when sublattice distortions in the lattice exist. Thus, asymmetric-stretching mode can be a measure of sublattice distortion in the double perovskite, and a highly ordered system would exhibit very minimal or no asymmetric vibrations.

Thermally activated transformations of the dielectric response function of mono- and disaccharides in the THz range

The variety of physical and chemical properties of saccharides is determined, in particular, by their isomerism and the variability of their hydrogen bond parameters. We studied the transformation of the vibrational spectra of mono- and disaccharides using pulsed terahertz spectroscopy in a wide temperature range. The stability ranges of saccharides were determined from the temperature dependences of the vibrational spectra and resonance parameters. The revealed difference in frequencies and intensities of vibrational modes of the hydroxyl groups in different saccharides correlate with the parameters of hydrogen bonds. Based on the data over a wide temperature range, it was found that the anharmonicity of vibrational modes appears in the form of coupling between resonances and the formation of wide asymmetric bands. Temperature square dependence of the resonance eigenfrequencies in the disaccharides has been revealed.

Label-free DNA detection using silver nanoprism decorated silicon nanoparticles: Effect of silicon nanoparticle size and doping levels

In the present work, we have fabricated silver nanoprism (AgNPrs)/silicon nanoparticle (SiNPs) hybrid arrays for highly sensitive detection of biomolecules via surface-enhanced Raman spectroscopy (SERS) technique. SiNPs having 7 to 37 nm in size and with phosphorous doping varying from 1 × 1019 to 1 × 1020 cm−3 were synthesized in nonthermal plasma synthesis. SiNPs were further immobilized on glass substrates using spin-coating, followed by deposition of AgNPrs using the drop-casting method. SERS studies showed that AgNPrs/SiNPs hybrid arrays exhibit substantial amplification of fingerprint bands of rhodamine 6G (R6G) compared to bare silicon as the reference. Raman signal intensity was found to be dependent on the size of SiNPs, with the largest nanoparticles exhibiting the highest SERS enhancement. In addition, an increase in phosphorous doping concentration was found to reduce R6G peak intensities. AgNPrs/SiNPs hybrid arrays showed excellent stability over time and high spot-to-spot reproducibility as well. Moreover, hybrid arrays enabled DNA detection through intense vibrational modes of human genomic DNA, with a lower detection limit of 1.5 pg/µL; indicating that AgNPrs/SiNPs sensors can serve as a reliable and cost-effective biosensing platform for rapid and label-free analysis of biomolecules.

Fingerprints of carbon defects in vibrational spectra of GaN considering the isotope effect

In this paper, we examine the carbon defects associated with peaks of infrared (IR) absorption and Raman scattering appearing in GaN crystals at carbon ($^{12}\mathrm{C}$) doping in the range of concentrations from $3.2\ifmmode\times\else\texttimes\fi{}{10}^{17}$ to $3.5\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}3}$. Here, 14 unique vibrational modes of defects are observed in GaN samples grown by HVPE (hydride vapor phase epitaxy) and then compared with defect properties predicted from first-principles calculations. The vibrational frequency shift in two $^{13}\mathrm{C}$-enriched samples related to the effect of the isotope mass indicates six distinct configurations of the carbon-containing point defects. The effect of the isotope replacement is well reproduced by the density functional theory (DFT) calculations. Specific attention is paid to the most pronounced defects, namely, tricarbon complexes (${\mathrm{C}}_{\mathrm{N}}=\mathrm{C}={\mathrm{C}}_{\mathrm{N}}$) and carbon substituting for nitrogen (${\mathrm{C}}_{\mathrm{N}}$). The position of the transition level $(+/0)$ in the bandgap found for ${\mathrm{C}}_{\mathrm{N}}=\mathrm{C}={\mathrm{C}}_{\mathrm{N}}$ defects by DFT at 1.1 eV above the valence band maximum suggests that ${({\mathrm{C}}_{\mathrm{N}}=\mathrm{C}={\mathrm{C}}_{\mathrm{N}})}^{+}$ provides compensation of ${\mathrm{C}}_{\mathrm{N}}^{\ensuremath{-}}$. Here, ${\mathrm{C}}_{\mathrm{N}}=\mathrm{C}={\mathrm{C}}_{\mathrm{N}}$ defects are observed to be prominent yet have high formation energies in DFT calculations. Regarding ${\mathrm{C}}_{\mathrm{N}}$ defects, it is shown that the host Ga and N atoms are involved in the delocalized vibrations of the defect and significantly affect the isotopic frequency shift. Much more faint vibrational modes are found from di-atomic carbon-carbon and carbon-hydrogen (C--H) complexes. Also, we note changes of vibrational mode intensities of ${\mathrm{C}}_{\mathrm{N}}, {\mathrm{C}}_{\mathrm{N}}=\mathrm{C}={\mathrm{C}}_{\mathrm{N}}$, C--H, and ${\mathrm{C}}_{\mathrm{N}}--{\mathrm{C}}_{i}$ defects in the IR absorption spectra upon irradiation in the defect-related ultraviolet/visible absorption range. Finally, it is demonstrated that the resonant enhancement of the Raman process in the range of defect absorption $>2.5\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ enables the detection of defects at carbon doping concentrations as low as $3.2\ifmmode\times\else\texttimes\fi{}{10}^{17}\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}3}$.

Infrared Spectra of Hydrogen-Bonded Molecular Complexes Under Spatial Confinement.

Infrared (IR) spectroscopy is commonly used in chemical laboratories to study the geometrical structure of molecules and molecular complexes. The analysis of experimental IR spectra can nowadays be reliably supported by the results of quantum-chemical computations as vibrational frequencies and corresponding vibrational transition intensities are routinely calculated using harmonic approximation by virtually all quantum chemistry packages. In the present study we combine the methodology of computing vibrational spectra using high-level electron correlation treatments with an analytical potential-based approach to take into account spatial confinement effects. Using this approach, we perform a pioneering analysis of the impact of the spatial confinement caused by a cylindrical harmonic oscillator potential on the harmonic vibrational transition intensities and frequencies of two hydrogen-bonded complexes: HCN…HCN and HCN…HNC. The emphasis is put on the largest-intensity bands, which correspond to the stretching vibrations. The obtained results demonstrate that embedding the molecular complexes in an external confining potential causes significant changes of transition intensities and vibrational frequencies.

Effect of Er3+ ion doping on structural, ferroelectric and up/down conversion luminescence in BaBi2Nb2O9 ceramic

Lead-free ferroelectric ceramic with formula BaBi2−xNb2ErxO9 (x = 0.00, 0.005) were prepared by solid-state method. The X-ray diffraction study revealed the synthesized ceramic has orthorhombic geometry, and the absence of a secondary phase indicates the effective incorporation of Er3+ ion into the host material. Raman spectroscopy showed various intense modes positioned at 74, 161, 226, 568, and 863 cm−1, along with some less intense vibrational modes. The ferroelectric measurements showed a decrease in Pr from 3.5434 to 3.4083 µF/cm2 and an increase in Ec from 46.1994 to 46.4428 kV/cm for Er3+ doped BBN. The strong green emission spectra were spotted at 527 nm and 550 nm for both up and down-conversion luminescence through transitions 2H11/2 to 4I15/2 and 4S3/2 to 4I15/2.

Characterization of liquid deproteinized natural rubber prepared via oxidative degradation

AbstractIn the present work, liquid deproteinized natural rubber (LDPNR) was prepared by oxidative depolymerization of deproteinized natural rubber using hydrogen peroxide (H2O2) and sodium nitrite (NaNO2) as oxidizing reagents. Structural characterization of LDPNRs was performed using FT‐IR, 1H‐NMR, 13C‐NMR, and Heteronuclear Multiple Quantum Coherence (HMQC) spectroscopy. After degradation, the intensity of vibration mode at 1660 cm‐1 (νC=C) decreased, indicating the decrease in the number of C=C bonds in the NR chain. 1H‐NMR signals at 1.6 ppm and 13C‐NMR signals at 40.0 ppm appeared in the NMR spectra of LDPNR prepared in acidic condition suggesting the occurrence of isomerization from cis‐1,4‐isoprene units to trans‐1,4‐isoprene units. Epoxidation also occurred during degradation of DPNR as a side reaction. End groups of LDPNRs were found to depend on pH of reacted latex. LDPNR prepared in pH 5‐6 contains aldehyde end group, while LDPNR prepared at pH 8‐9 has a hydroxyl end group. The gel content of LDPNRs was found to reduce compared to that of DPNR, significantly. GPC was employed to determine molecular weight of LDPNRs. The results show that the degradation in acidic medium behaves more effectively in comparison to in alkaline medium.

Structural evolution, optical properties, and photocatalytic performance of copper and tungsten heterostructure materials

Several studies reported that modifying CuO with CuWO4 can increase its photoactivity. In this study, copper and tungsten heterostructure materials were synthesized via a simple sol-gel method using ammonium paratungstate. The temperature’s influence (300, 500, 700, and 900 °C) was analyzed in the structural, morphological, microstructural, and optical properties of Cu and W materials using X-ray diffraction, infrared spectroscopy, field emission-scanning electron microcopy, transmission electron microscopy, diffuse reflectance spectroscopy, and dynamic light-scattering studies. The CuO diffraction patterns exhibited a tenorite phase formation, and the copper-tungsten materials diffractograms demonstrated the formation of CuO/CuWO4 at 300 and 500 °C and CuO/CuWO4/Cu2WO4/WO3 materials at 700 and 900 °C with crystallite sizes from 25 to 56 nm. Intense vibrational modes obtained at 300 °C for the CuWO4 phase decreased at 500 °C. Therefore, 500 °C is not a temperature that promotes CuO/CuWO4 heterostructure formation. Analyses conducted using microscopy techniques demonstrated the morphology of the CuO/CuWO4 heterostructure obtained at 300 °C, where CuWO4 nanoparticles covered the CuO polyhedral; microstructural analysis verified the heterostructure’s formation. The synthesized materials at 300 °C had an optical band gap of 2.66 eV (direct gap) and 1.35 eV and 2.11 eV (indirect gap), which were lower values than those of the CuO and CuWO4. The temperature at 300 °C proved to be optimal for the formation of the CuO/CuWO4 heterostructure. Only the material obtained at 300 °C exhibited a photocatalytic response in the rhodamine B degradation due to a possible interfacial charge transfer between the CuWO4 and CuO. The synthesis process used to obtain the CuO/CuWO4 heterostructure was novel, with a short processing time, low energy consumption and cost, and environmentally friendly properties.

Distinguishing Mesoscale Polar Order (Unidirectional vs Bidirectional) of Cellulose Microfibrils in Plant Cell Walls Using Sum Frequency Generation Spectroscopy.

Cellulose in plant cell walls are synthesized as crystalline microfibrils with diameters of 3-4 nm and lengths of around 1-10 μm. These microfibrils are known to be the backbone of cell walls, and their multiscale three-dimensional organization plays a critical role in cell wall functions including plant growth and recalcitrance to degradation. The mesoscale organization of microfibrils over a 1-100 nm range in cell walls is challenging to resolve because most characterization techniques investigating this length scale suffer from low spatial resolution, sample preparation artifacts, or inaccessibility of specific cell types. Here, we report a sum frequency generation (SFG) study determining the mesoscale polarity of cellulose microfibrils in intact plant cell walls. SFG is a nonlinear optical spectroscopy technique sensitive to the molecular-to-mesoscale order of noncentrosymmetric domains in amorphous matrices. However, the quantitative theoretical model to unravel the effect of polarity in packing of noncentrosymmetric domains on SFG spectral features has remained unresolved. In this work, we show how the phase synchronization principle of the SFG process is used to predict the relative intensities of vibrational modes with different polar angles from the noncentrosymmetric domain axis. Applying this model calculation for the first time and employing SFG microscopy, we found that cellulose microfibrils in certain xylem cell walls are deposited unidirectionally (or biased in one direction) instead of the bidirectional polarity which was believed to be dominant in plant cell walls from volume-averaged characterizations of macroscopic samples. With this advancement in SFG analysis, one can now determine the relative polarity of noncentrosymmetric domains such as crystalline biopolymers interspersed in amorphous polymer matrices, which will open opportunities to study new questions that have not been conceived in the past.

An APT charge based descriptor for atomic level description of chemical Raman enhancement by adsorption of 4-Mercaptopyridine on semiconducting nanaoclusters: A theoretical study

Density functional theory (DFT) based calculations are carried out to study effect of molecular charge on both the binding energy as well as chemical Raman enhancement of deprotonated 4-Mercaptopyridine (ligand) bound to the semiconducting nanocluster, Zn3Se3 and metal substituted nanoclusters, Zn2MSe3 (M: Ag, Cu). Change of molecular charge from 0 to −1 increases binding energy of the ligand for Zn3Se3 cluster and decreases Raman activity of vibrational modes. On the other hand, the ligand bound to the metal substituted nanoclusters, Zn2MSe3 shows minimal decrease in binding energy and a noteworthy enhancement in Raman activity of the vibrational modes, on varying the molecular charge from 0 to −1. Static Raman activities of vibrational modes are analyzed using change of molecular polarizability components with normal coordinates of the modes. An APT (Atomic Polar Tensor) charge based descriptor is used for characterization of the chemical Raman enhancement. The descriptor measures substrate induced charge concentration per unit displacement of an atom involved in a mode of vibration. We also show that significantly enhanced intensity of vibrational modes is associated with atoms of relatively greater magnitudes of the APT charge based descriptor.

Luminescence behaviour of Eu3+ in hot-compressed silicate glasses

Abstract This paper aims to explore density-driven effects on the luminescence of Eu3+ doped silicate glasses. For this, mildly densified samples were fabricated by quasi-isostatic hot compression at up to 2 GPa from melt-quenched precursor materials. As a result of compression, both density and glass transition temperature of the blank (Eu free) and doped compositions increase. Raman spectroscopy indicates a slight increase in the intensity of vibrational modes assigned to small silicate rings and Si-O-Si bridges. Photoluminescence experiments reveal the creation of new paths of de-excitation, reducing the relative intensity of the transitions in the excitation spectra and the lifetime of the 5D0 → 7F2 emission line. Meanwhile, the luminescence intensity remains unchanged due to enhanced oscillator strength and refractive index at uniform electron-phonon coupling strength. Luminescence spectra also show a slight expansion of some of the energy levels of Eu3+, together with an increase of the bandwidth of the 5D0 → 7F2 emission line due to the crystal-field influence and growing electron population of the lower Stark sub-levels. Finally, increasing symmetry of Eu3+ sites was detected with increasing degree of compaction, resulting in a reduction of the intensity of the forced electric dipole transition of 5D0 → 7F2 relative to the magnetic dipole transition of 5D0 → 7F1.

Chemical bonding mechanism in SERS effect of pyridine by CuO nanoparticles

AbstractThis article reports the theoretical and experimental study of nonresonant mechanisms (CHEM) of surface‐enhanced Raman spectroscopy (SERS) of pyridine (Py). An improvement in the Raman dispersion intensity of Py is determined after the chemical absorption on CuO nanoparticles synthesized in NaCl. The density functional theory predicts the formation of new electronic states as result of the chemical bond (CB) established between the Py molecule and the (CuO)n clusters. This study is focused on the study of the most intense vibrational modes of Py before and after chemical adsorption. The CHEM by CB mechanisms is found as responsible for the SERS effect in Py.

Influence of mono energetic gamma radiation on structural and electrical properties of TiO2 thin film coated on p-type porous silicon

Titanium dioxide thin film was coated on p-type porous silicon by sol–gel spin coating method. The prepared samples were irradiated by the mono-energetic gamma radiation at Auto-irradiation facility with the Cesium-137 for the Gamma dose range from 100 to 1000 mSv. Gamma irradiated samples revealed that the physical changes of titanium oxide/porous silicon layer found to be varying with increasing gamma dose. The irradiated titanium oxide/porous silicon layer were investigated by scanning electron microscopy, X-ray diffraction, Fourier transform infra-red, Photoluminescence and I–V characteristics studies. The surface morphology of the irradiated titanium oxide/porous silicon layer has shown deformation with increasing gamma dose. The X-ray diffraction patterns of titanium oxide/porous silicon layer after irradiation revealed changes in crystallite size, dislocation density, strain and phase content. These changes in anatase (004) are linear with gamma dose than the rutile (310) of TiO2-PSi. Fourier transform infra-red spectrums of the irradiated samples showed an increase in intensity of vibration modes with the increase of the radiation dose. Photoluminescence peaks are found to be in the range of 330 to 360 nm for all the irradiated samples and the intensity of Photoluminescence peak increased for the irradiated samples with increasing gamma dose. I–V Characteristics revealed that the electrical conductivity of irradiated samples increased linearly with gamma dose. The linear changes in electrical property of titanium oxide/porous silicon under the influence of mono-energetic gamma photons gives a positive indication that it can be further studied for the development of radiation sensor for applications in nuclear field.

Thermally induced plasmonic resonance of Cu nanoparticles in fullerene C70 matrix

Nanocomposite of fullerene C70 embedded with Cu nanoparticles is synthesized using thermal co-deposition method. The temperature dependency of SPR and size of Cu nanoparticles are assessed by thermal annealing in inert atmosphere up to a temperature of 350 °C. Rutherford backscattering spectroscopy is performed to assess the thickness of the film and the atomic fraction of Cu metal. The UV-visible absorption spectra on as-deposited and annealed samples reveal that the SPR peak of Cu nanoparticles appears at 300 °C and its evolution with further rise in temperature takes place with a red shift and broadening of the peak at 350 °C. The thermal induced growth of Cu nanoparticles at higher temperature is responsible for the red shift. Raman spectra show the decrease in the intensity of vibrational modes of fullerene C70 with temperature due to breaking of bonds among carbon atoms in fullerene molecules. Transmission electron microscopy confirms the evolution of Cu nanoparticles with bi-modal distribution at 350 °C. Atomic force microscopy is performed to observe the variation in the morphology and roughness of nanocomposite film with temperature. The evolution of Cu nanoparticles and excitation of SPR with temperature makes it an interesting nanocomposite for SPR sensing applications.

A detailed research for determination of Bi/Ga partial substitution effect in Bi-2212 superconducting matrix on crucial characteristic features

This multidisciplinary study paves way to investigate the crucial of fundamental characteristic properties including the bulk density, electrical, superconducting, flux pinning mechanism, crystal structure quality and strength quality of interaction between the superconducting grains in the Bi2.1Sr2.0Ca1.1Cu2.0Oy (Bi-2212) superconducting materials with the partial replacement of gallium foreign impurity by bismuth nanoparticles in the crystal structure. Characterizations of polycrystalline ceramic materials prepared by standard ceramic route in the atmospheric air are performed by means of conventional experimental measurement methods such as powder X-ray diffraction, Archimedes water displacement, dc electrical resistivity versus temperature and critical current density examinations. All the bulk Bi-site Ga partial replaced materials exhibit the Bi-2212 superconducting phase within the different fraction levels (%73.1–94.8), moderate self-field critical current densities 54–96 A/cm2 and wide-ranging offset and onset critical transition temperature range of 45.65 K–84.52 K and 70.06 K-85.00 K. As for the experimental findings of bulk density and related degrees of granularity (porosity) parameters, the bulk density parameter is found to be between 5.76 g/cm3 and 6.12 g/cm3 when the corresponding residual porosity value is also obtained to be in a range of 8.57 %–2.86%. Moreover, the mobile hole carrier concentrations in the short-range-ordered antiferromagnetic CuO2 layers are found to be in the range from 0.085 until 0.152. Additionally, the role of Ga/Bi partial substitution in the crystal lattice on the normal state resistivity, residual resistivity, residual resistivity ratio, vibrational mode intensities, texturing, superconducting volume fractions, mobile hole carrier concentrations, average crystallite sizes, Lotgering indices and cell parameters are discussed in details. All the experimental results and theoretical approaches show that the characteristic properties tend to improve regularly with the increment in the Ga foreign impurity level until x = 0.05 due to the increment in the crystal structure quality and interaction between the superconducting grains. After the critical Ga/Bi substitution level of x = 0.05, every feature degrades considerably.

Role of Bi/Tm substitution in Bi-2212 system on crystal structure quality, pair wave function and polaronic states

This comprehensive study finds strongly out the crucial variations in the dc electrical resistivity, superconducting, crystal structural and flux pinning mechanisms with the partial replacement of homovalent Tm+3 inclusions by Bi+3 impurity in the active layers of Bi-2212 superconducting material. Materials of type Bi2.1-xTmxSr2.0Ca1.1Cu2.0Oy with molar ratio changes of 0.00 ≤ x ≤ 0.30 are prepared by conventional solid-state reaction route in atmospheric pressure and the characterizations are exerted by the bulk density, dc electrical resistivity (ρ-T), powder X-ray diffraction (XRD), critical current density (Jc), scanning electron microscopy (SEM) and electron dispersive X-ray (EDX) experimental measurements. The combination of experimental results evaluated from the bulk density, dc electrical resistivity, XRD and EDX measurements points out that the Tm foreign impurities mostly incorporate successfully into the Bi-2212 crystal lattice. In fact, the EDX investigations verify that the thulium impurities may mostly be substituted for the bismuth sites in the crystal structure. All the experimental results declare that the characteristic features improve regularly with the increment in the Tm impurity level up to x = 0.07 beyond which the properties degrade dramatically. In this respect, the sample with x = 0.07 exhibits highest electrical conductive/metallic characteristics as a consequence of the refinement in the crystal structure quality and connectivity between the superconducting grains, being favored by bulk density and related relative degrees of granularity surveys. Likewise, the material presents the maximum offset-onset critical transition temperature values of 85.61 K–85.85 K due to the increment in the formation of effective and strong electron-phonon coupling probabilities and optimization of mobile hole carrier concentrations in the Cu-O2 consecutively stacked layers. In other words, the optimum content level leading to transit inherently over-doped nature into optimally doped state strengthens the amplitude of pair wave function for the Bi-2212 material. In more sophisticated interpretations, the presence of optimum dopant in the crystal structure changes the vibrational mode intensities of O (1)CuA1g, B1g phonons and O (2)SrA1g phonon so that the formation possibility of bipolaron out of two polarons increases strongly in a polarizable lattice (polaronic effect). Additionally, the highest self-field Jc of 95 A/cm2 confirms the fact that the optimum dopant augments the effective nucleation centers along the intragrain and inter-grain boundaries in the crystal system. Similarly, the material prepared with x = 0.07 presents the smoothest, densest, largest average crystalline distribution, lowest porosity and most uniform surface appearance with the finest connection between the superconducting grains. The XRD results (the increased high phase, c-axis length and average grain size but decreased a-axis length) also show the optimum dopant level of x = 0.07 for Bi-2212 crystal system. All in all, the paper developing a strong methodology about why the characteristic properties improve with the presence of Tm impurity in the Bi-2212 system may be a pioneering research to construct newly, novel and feasible market areas for the Bi-2212 superconducting ceramics in the universe economy.