Search

Phthalocyanines (Pcs) bearing phosphonic acid groups at the periphery exhibit a potential photodynamic effect to induce phototoxicity on human bladder cancer epithelial cells (UM-UC-3). In vitro photophysical and biological studies show high intrinsic ability to inhibit the activity of urokinase plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP-9). [ABSTRACT FROM AUTHOR]

The aim of this work was the development of a family of novel water soluble Zinc(ii) phthalocyanines (Pc) for the photodynamic inactivation of Gram-negative bacteria. Pc derivatives 1a, 2a and 3a containing trimethylammonium groups with varied number and nature of the groups at peripheral positions were synthesized by cyclotetramerization of dimethyl amino substituted phthalonitriles in the presence of zinc powder, using 1-chloronaphthalene as a solvent, followed by cationization using dimethyl sulfate. The solubility, singlet oxygen generation (1O2) and stability/photostability of each Pc were evaluated as well as the affinity to bacterial cells and their photosensitizing potential against a recombinant bioluminescent Escherichia coli strain, used as a biological model for Gram negative bacteria. The efficiency of photodynamic inactivation was assessed under white and red light at an irradiance of 150 mW cm−2. All Pc were soluble in phosphate buffer saline and in dimethyl sulfoxide and demonstrated good stability/photostability. The photochemical parameters reveal that Pc 2a and 3a are more efficient singlet oxygen producers than Pc 1a, for which singlet oxygen generation could not be demonstrated. Pc 2a and 3a caused photosensitization in E. coli. The inactivation factors attained with red light were, however, generally higher than those with white light. Under red light Pc 3a and 2a caused, respectively, 5.6 and 4.9 log reduction in the bioluminescence of the E. coli while, with white light, the corresponding inactivation factors were 2.5 and 0.5 log. The order of the PDI efficiency (3a ＞ 2a⫸1a) was determined by the combined effect of solubility, singlet oxygen generation ability and affinity to bacterial cells. Ammonium phthalocyanines with eight charges or containing halogen atoms such as chlorine, when irradiated with red light can, therefore, be regarded as promising photosensitizers for the inactivation of Gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Fluorescent molecular probes based on phospho-nate-functionalized porphyrin derivatives have been designed for selective detection of nitroaromatics. It is shown that molecular recognition is based on cooperative hydrogen bonding and π-π stacking interactions with electron-deficient molecules (nitro-aromatic compounds, NACs), displaying superior detection toward trinitrotoluene (TNT). The P=0 functional groups decrease the lowest unoccupied molecular orbital (l.UMO) energy level of the porphyrins and, consequently, facilitate the electron inoculation to TNT through a photoinduced electron transfer (PET) process. The hydroxyl groups of the phosphonates and pyrrole -NH protons are further engaged in donor-acceptor interactions with TNT by strong intermolecular hydrogen bonding interactions (as evidenced by single crystal X-ray, NMR, and density functional theory (DFT) showing turn off fluorescence behavior. The nonplanarity of the porphyrins induced by protonation at the central core of the porphyrin H4TPPA2+ undergoes additional interactions, furnishing an anomalous increase in the selectivity of TNT at nanomolar levels in solution (limit of detection, LOD ~ 5 nM) Porphyrin-doped hybrid PMMA [poly(methyl methacrylate)] polymer films demonstrate the reversibility of the fluorescence behavior and exhibit high photostability. The formation of discrete molecular aggregates on the surface of hybrid films and efficient diffusion of TNT vapors (10 ppb) displayed high selectivity in the solid state. The hybrid films are further used to demonstrate the detection of NACs in the aqueous medium, ultimately providing a platform for a practical strategy and implementation for the detection of toxic NACs. [ABSTRACT FROM AUTHOR]

A new class of dual fluorescent chemosensors for nitroaromatic compounds (NACs) based on phosphonated pyrene derivatives is reported, showing high selectivity towards trinitrotoluene (TNT). The strong intermolecular interactions (π- π stacking and hydrogen bonding) allow high fluorescence quenching with visual detection in short response times. [ABSTRACT FROM AUTHOR]

Nonlinear optical transmission of graphene oxide–(Cu, Zn, Sn, H2) porphyrin composites was investigated using the Z-scan technique at 532 nm with picosecond (ps) and 800 nm with femtosecond laser pulses. Pure porphyrins show saturable absorption (SA) in reverse saturable absorption (RSA) behaviour and graphene oxide shows complete RSA behaviour, observed in an open aperture Z-scan curve. Interestingly, composites have shown a switch-over from reverse RSA to SA and back to RSA behaviour, observed with variation of intensity towards the focus, due to strong two-photon absorption as well as excited state absorption in the ps regime. This switching behaviour was interpreted as due to long lifetimes and saturation of the excited states. This may find application in optical switching. [ABSTRACT FROM AUTHOR]

We report herein, a novel method for the formation of highly stable BF3-induced J-aggregates by interaction between meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) and BF3O(C2H5)2. The aggregates were characterized by NMR (1H, 11B and 19F), optical absorption, cyclic voltammetry, FT-IR and fluorescence spectroscopic techniques. TPPS4 readily forms a 1 : 2 adduct with BF3 which further converts into BF3-induced TPPS4 aggregates whose spectroscopic properties strongly depend on the concentration of BF3. The optical absorption spectrum shows the formation of J-type aggregates with an apparent association constant (logKapp) of 4.2 ± 0.1. The steady state emission shows formation of 1 : 2 (TPPS4–BF3) adducts at ∼685 nm and J-aggregates exhibit emission at 732 nm with a red shift of ∼17 nm in comparison to J-aggregates of TPPS4 with TFA. The fluorescence lifetime of TPPS4 : BF3 (1 : 2) adducts exhibits ∼3.68 ns and aggregates show a lifetime of 4.32 ± 0.2 ns with major abundance. NMR study reveals that proton transfer occurs from pyrrole N–H to the SO3− groups and J-aggregates were stabilized by strong intermolecular hydrogen bonding interaction between N2–BF2 and SO3H. Cyclic voltammetry shows a decrease in the reduction peak current along with a change in the peak potentials for the aggregates. The PXRD pattern of the aggregates exhibits orthorhombic structure with interplanar distance of 4.87 Å. The variations in unusual stability, photophysical, electrochemical properties and nature of the aggregates were rationalized with aggregates of TPPS4 dication. [ABSTRACT FROM AUTHOR]

Herein we report a novel fluoranthene-based fluorescent fluorophore 7,10-bis(4-bromophenyl)-8,9-bis[4-(hexyloxy)phenyl]fluoranthene ( S3) and its remarkable properties in applications of explosive detection. The sensitivity towards the detection of nitroaromatics (NACs) was evaluated through fluorescence quenching in solution, vapor, and contact mode approaches. The contact mode approach using thin-layer silica chromatograp- hic plates exhibited a femtogram (1.15 fg cm−2) detection limit for trinitrotoluene (TNT) and picric acid (PA), whereas the solution-phase quenching showed PA detection at the 2-20 ppb level. Fluorescence lifetime measurements revealed that the quenching is static in nature and the quenching process is fully reversible. Binding energies between model binding sites of the S3 and analyte compounds reveal that analyte molecules enter into the cavity created by substituted phenyl rings of fluoranthene and are stabilized by strong intermolecular interactions with alkyl chains. It is anticipated that the sensor S3 could be a promising material for the construction of portable optical devices for the detection of onsite explosive nitroaromatics. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, we report our results on Sn(IV)TPP and its derivatives doped hybrid borate glasses. The photophysical and structure of Sn(IV)Porphyrins in borate glass matrix was studied through micro-Raman, optical absorption, steady state and time resolved fluorescence emission techniques. The optical absorption spectrum shows red shift in Soret band and change in the intensity of Q-bands. Upon exposure to UV light at 260nm, the glass samples exhibit strong blue emission and red emission at 365nm. Steady state fluorescence emission spectrum of hybrid glasses exhibits dual emission bands originating from the S2 →S0 and S1 →S0 states. The appearance of large stokes shift (Δυ), enhanced S2 →S0 emission at ∼482nm and excitation dependent of S1 →S0 emission indicates that the structure of Sn(IV)Porphyrins were inherently modified in the borate glass matrix. Time resolved fluorescence of S2 →S0 emission was found to be in the range of 0.23–0.36ns, S1 →S0 emission shows 1.23–1.57ns and 9.12–9.63ns, respectively. The results obtained in glass matrix were correlated with solution medium and the possible structures were investigated. [Copyright &y& Elsevier]

Abstract: The glasses of the composition 19Na2SO4–20MO–60P2O5: 1.0Ho2O3/1.0Er2O3 (M=Mg, Ca, and Ba) have been synthesized. Optical absorption and fluorescence spectra (in the spectral range 350–2100nm were studied at ambient temperature. The spectra were characterized using Judd–Ofelt theory. From the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for blue (B), green (G) and red (R) emission levels of these glasses have been evaluated. The energy transfer between the two rare earth ions (Ho3+ and Er3+) in co-doped Na2SO4–MO–P2O5 glass systems in the visible and NIR regions has also been investigated. Highest intensity, the highest quantum efficiency and maximum energy transfer with low phonon losses of B, G, and R lines has been observed in BaO mixed glasses. The reasons for such higher values of these parameters have been discussed in the light of varying field strengths at the rare earths ion site due to replacement of one modifier oxide with the other. The enhanced intensity of NIR emission (at 2.0μm) has also been discussed in terms of cross relaxation of Er3+ ions from 4I13/2 level to 5I7 of Ho3+ ions. [Copyright &y& Elsevier]

Abstract: Hybrid borate glasses containing a series of Al(III)Porphyrins were prepared by rapid melt quench technique at 230°C. The hybrid glass samples were characterized by X-ray diffraction, optical absorption, steady state and time resolved fluorescence emission. Upon exposure to UV light at 260nm, the glass samples exhibit strong blue emission and red emission at 365nm. The appearance of large stokes shift (Δυ) and enhanced S 2 → S 0 emission at ∼495nm indicates that structure of Al(III)Porphyrins were inherently modified in glass matrix. Time resolved fluorescence of the hybrid glasses shows three exponential decay with τ 1 =0.11–0.59ns, τ 2 =3.13–3.95ns and τ 3 =8.13–9.56ns. In the present study, we investigate the influence of glassy environment on the photophysical properties and the structure of Al(III)Porphyrins in borate glass was modeled through DFT calculations. [Copyright &y& Elsevier]

Abstract: Hybrid borate glasses containing various hydroxy phenyl derivatives of porphyrin were prepared by melt quenching technique. The effect of hydroxy functional groups on the photophysical properties was investigated by means of optical absorption, steady-state fluorescence and time resolved fluorescence spectroscopy. The optical absorption spectra show red shift in Soret and Q-band with increase in the number of –OH groups on the phenyl ring of the porphyrin. The steady-state emission spectrum shows strong S2→S0 emission around 498–540nm and red shifted S1→S0 emission around 669–803nm. Time resolved fluorescence shows three exponential decay with τ 1 =11±2ps (64.56%), τ 2 =0.16±0.1ns (24.54%), and τ 3 =2.94±0.1ns (10.9%) for 2mg of H2OHP doped glass. The appearance of strong S2→S0 emission indicates that the structure of porphyrin inherently modified in the glass matrix. The boron ions of the borate network interact at the central core of the porphyrin and also form oxy bridge at the periphery. The effect of porphyrin concentration on photophysical properties and the possible structures of porphyrin in the borate glass matrix were investigated. [Copyright &y& Elsevier]

Abstract: Freebase tetra phenyl porphyrin (H2TPP) and its derivatives in different concentration ranges (0.5–2.0mg per 12g of boric acid) were incorporated into borate glass matrix by melt quenching technique at 230°C. The formed glasses were stable and in green colour. The optical absorption and emission properties are different from that observed in solutions. The absorption spectrum shows a two line pattern Soret band at 435–454nm and Q-band at 665–701nm. The emission spectrum shows strong S2 →S0 emission at 490–520nm region and S1 →S0 emission at 725–810nm. The time resolved fluorescence decay of S1 →S0 emission shows three exponential decay. For example, in the case of 2mg of H2THP doped glass the lifetimes were found to be τ 1 =0.511ns (26.7%), τ 2 =10ps (64.68%) and τ 3 =3.965ns (8.62%). These unusual photophysical properties were found to arise from different structural motifs of porphyrin in the glass. These structures were further modeled through reactions of porphyrin with BF3O(C2H5) in solution and DFT calculations. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid borate glasses containing different concentrations of meso-tetrakis(p-sulfonatophenyl) porphyrin sodium salt (TPPS4) were prepared. The obtained glass samples were found to be transparent and homogeneous. Formation of TPPS4-J-aggregates in borate glass was investigated by means of optical absorption, steady state and time resolved fluorescence spectroscopy. The hybrid glasses exhibit a strong S2→S0 emission at ∼473nm and J-aggregates show emission at ∼733nm. Time resolved fluorescence show two exponential decay with lifetime of τ 1 =65±10ps (∼80%) and τ 2 =3.87±0.1ns (∼20%) respectively. Dielectric properties such as dielectric constant (ɛ′), dielectric loss (tan δ) and ac conductivity (σ ac) over a range of frequency and temperature of these glasses were studied. The ac conductivity was found to be proportional to ω s (where s <1). The observed change in dielectric parameters due to different concentrations of TPPS4 has been analyzed in light of different polarization mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid borate glasses containing different concentrations (0.5–2.0mg in 12g of boric acid) of Mesoporphyrin(IX)dimethylester, Protoporphyrin(IX)dimethylester and Hematoporphyrin(IX)dimethylester were prepared by rapid melt quench technique at 230°C. The hybrid glass samples were characterized by X-ray diffraction, optical absorption, steady state and time-resolved fluorescence emission. The optical absorption spectrum shows red-shift in Soret band along with change in Q-band pattern. The intensity of Q-band was found to increase with increase in the concentration of porphyrin in the glass. Steady state emission spectrum shows strong S2→S0 emission in the range 462–495nm and blue shift in S1→S0 emission. Time-resolved fluorescence emission and fluorescence excitation spectra showed that different structures of porphyrins were exist in the glass samples. The variation in the spectral behaviour in the glass was correlated with those in solution medium and possible structures of porphyrin in borate glass were explored. [ABSTRACT FROM AUTHOR]

Abstract: ZnF2–As2O3–TeO2 glasses mixed with different concentrations of V2O5 (ranging from 0 to 0.6mol%) were synthesized. The amorphous nature of these glasses was checked by X-ray diffraction and scanning electron microscopy techniques. A variety of properties, i.e. optical absorption, photoluminescence, infrared, ESR spectra and dielectric properties (constant ε′, loss tan δ, ac conductivity σ ac over a wide range of frequency and temperature) of these glasses have been explored. The optical absorption, electron spin resonance studies together indicated vanadium ions coexist in V4+ with V5+state in these samples. The IR spectra of these samples have exhibited bands due to ν s-TeO2ax and AsO3 structural groups; these results indicated the most structural disorder in the network as the concentration of V2O5 is increased. Luminescent emission spectra recorded at room temperature of these glasses excited at 640nm have exhibited a broad emission band in the spectral wavelength range of 750–850nm. The luminescence efficiency is found to be the highest for the sample doped with 0.6mol%. The dielectric parameters viz., ε′, tan δ and σ a.c are found to increase and the activation energy for ac conduction is found to decrease with the increase in the concentration of V2O5 up to 0.6mol%, reflecting an increase in the concentration of V4+ ions that take part modifying positions in the glass network. The ac conduction in these glasses could satisfactorily be explained by both classical activation energy and the tunneling phenomena. [Copyright &y& Elsevier]

Abstract: PbO–As2O3 glasses mixed with different concentrations of Fe2O3 (ranging from 0 to 2.0mol%) were crystallized. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques. Studies were extended to optical absorption, IR, ESR and magnetic susceptibility on these glass ceramic samples. The X-ray diffraction and scanning electron microscopic studies reveal the presence of PbFe4(As5O11)2, Fe2PbAs2O6 crystal phases. The optical absorption studies together with ESR and magnetic susceptibility measurements indicated the dominant presence of iron ions in the trivalent state when the concentration of nucleating agent Fe2O3 is less than 0.3mol%. The analysis of the IR spectra indicated a gradual transformation of iron ions from tetrahedral sites to octahedral sites as the concentration of Fe2O3 is increased beyond 0.3mol%. [Copyright &y& Elsevier]

A series of Sr (1-x) Al 2 O 4 :xTb3+ (SAOTx; 0 ≤ x ≤ 10.0 mol%) nanophosphors were prepared by solid state reaction technique for various photonic applications. The sintering temperature was estimated to be 1050 °C to crystallize SAOT phosphors into monoclinic structure. The powder X-ray diffraction profiles were well consistent with JCPDS No. 34–0379. Upon 375 nm excitation, the SAOT phosphors displayed two groups of emission bands corresponding to 5D 3 → 7F J and 5D 4 → 7F J transitions. A quenching in luminescence was noticed beyond 5.0 mol% of Tb3+ concentration due to the transfer of energy at higher concentrations. The emission spectra of SAOTx phosphors showed an intense green luminescence through 5D 4 → 7F 5 (546 nm) transition. The colour purity of SAOTx phosphors was analyzed by evaluating the chromaticity coordinates. The SAOT5 phosphor could be the best choice for various photonic applications. [ABSTRACT FROM AUTHOR]

The main objective of this study is to achieve Ce substituted hydroxy apatite (HAp) deposition on the surface of the bio-active glasses which is more affective in antibacterial activity. Calcium oxy fluoro borophosphate glasses (with BaO as modifier) doped with different concentrations of Ce 2 O 3 were prepared by melt quenching techniques. In vitro bioactivity studies were performed by soaking the samples in simulated body fluid (SBF) for about 30 days. The XRD and SEM studies have revealed the deposition of cerium substituted crystalline HAp coating on the surface of the post immersed glasses. The formation of HAp layer is further confirmed by IR and Raman spectral studies. The possible site preference of cerium ions in the HAp layer has been discussed using the results of above mentioned studies. The information regarding dependence of the magnitude of HAp layer developed on the concentration of Ce 2 O 3 dopant is obtained by degradation studies viz., weight loss of the samples and the variation of pH of the residual solutions. The analysis of the results of degradability together with X-ray diffraction (XRD), Infrared (IR), Raman and optical absorption spectra indicated the increasing magnitude of Ce-HAp with the concentration of Ce 2 O 3 . Some of the characterization studies have also pointed out the co-presence of Ce ions in Ce 4+ oxidation state along with Ce 3+ state in the glass samples. The simultaneous presence of cerium ions in these two states in the crystalline HAp layer is predicted to be more useful in promoting the antibacterial activity of the glasses. [ABSTRACT FROM AUTHOR]

Zinc selenium phosphate glasses added with the traces of Au2O3 were prepared and heat-treated. XRD, TEM, DSC, FT-IR and optical absorption (OA) spectroscopy methods were used for the structural assessment of these samples. Later, different dielectric parameters viz., dielectric constant (ε′), electric moduli (M), impedance (Z) and a.c. conductivity (σac) were measured over wide regions of frequency (ω) and temperature (T) as functions of Au2O3 concentration. Dielectric breakdown strength (DBS) of these samples was also measured at ambient conditions. The characterization studies indicated that multiple crystal grains were entrenched in the residual amorphous phase of the samples. The X-ray diffraction studies revealed that the bulk glasses consisted of Au2(SeO3)3 crystal phase and Au0 metallic particles (MPs). As Au2O3 content was raised, the intensity of the XRD peak related to Au3+ crystal phase indicated a growing trend, whereas that of Au0 MPs showed a decreasing trend. The results of XPS studies revealed similar inferences. The FT-IR results pointed out an improved degree of augmentation of the glass network as the content of Au2O3 was increased. Optical absorption (OA) - spectra of the glasses indicated a broad absorption band in the spectral range of 500–600 nm due to the surface plasmon resonance (SPR) of Au0 MPs. The intensity of the band was observed to decrease as Au2O3 content was increased and indicated decreasing proportion of Au0 metallic particles in the samples. The dielectric parameters exhibited a decreasing trend, whereas the dielectric breakdown strength (DBS) and electrical impedance indicated a substantial hike due to the increasing concentration of Au2O3. Overall, the presence of Au2O3 caused a significant improvement in the insulating strength of the ZnO added SeO2-P2O5 glasses and hence such glasses may be considered as insulating layers in the display panel devices. [ABSTRACT FROM AUTHOR]

Third-order nonlinear optical properties of tetra-phenyl porphyrin (HTPP) derivatives viz., HTPP(OH) and Zn(II)TPP doped in boric acid glass thin films were measured using single beam Z-scan and forward degenerate four-wave mixing (DFWM) techniques. Excited state lifetimes and absorption cross-sections were estimated from these experiments. Thickness of the porphyrin doped sandwich glass films were determined using DFWM technique for the first time. The values of nonlinear refractive index () obtained for these systems are are found to be sensitive to the nature of substituents in porphyrin molecule. These results are interpreted in terms of delocalized electrons contributing to the third-order optical nonlinearity. [ABSTRACT FROM AUTHOR]

This study investigates the enhancement of the sharp 311 nm UVB emission from Gd3+ ions in antimony silicate glass system doped with a fixed concentration of Gd 2 O 3 (1.0 mol%) and varying amounts of red lead (40–10 mol%). The emission spectra revealed an intense sharp UVB band at 311 nm, originating from the 6P 7/2 → 8S 7/2 transition of gadolinium ions upon excitation at 273 nm. Interestingly, the intensity of this band nearly doubles as the Pb 3 O 4 content decreases from 40 to 10 mol%. Such improvement was attributed to the decomposition of Pb 3 O 4 into various phases that include α-PbO 2 , β-PbO 2 polymorphs, and PbO. Out of these decomposition products, PbO acted as modifiers, reduced phonon losses and consequently enhanced the emission intensity. The decrease in Pb 3 O 4 content is also hypothesized to promote de-clustering of Gd3+ ions within the glass matrix. This de-clustering reduced cross-relaxation losses, further contributed to the observed emission enhancement. In summary, this study demonstrated a successful strategy for boosting the UVB emission from Gd3+ ions in antimony silicate glasses by manipulating the content of Pb 3 O 4. UVB 311 emission band of Gd3+ ions in Sb 2 O 3 –SiO 2 glass mixed with different concentrations of Pb 3 O 4. [Display omitted] • ▸UVB 311 nm emission from Gd3+ ions in Sb 2 O 3 –SiO 2 –Pb 3 O 4 glass system is explored. • ▸Intensity of UVB band nearly doubled as Pb 3 O 4 content decreased from 40 to 10 mol%. • ▸Increment was ascribed to decomposition of Pb3O4 into α-PbO2, β-PbO2 and PbO phases. • ▸Study contains a successful strategy for boosting UVB emission from Gd3+ ions in this glass. • ▸This study proposed a strategy to enhance UVB emission from Gd3+ ions in this glass. [ABSTRACT FROM AUTHOR]

Abstract: Li2O–CaF2–P2O5 glasses mixed with different concentrations of Cr2O3 (ranging from 0 to 1.0mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS), differential thermal analysis and conventional spectroscopic techniques. The X-ray diffraction and scanning electron microscopic studies reveal the presence of lithium phosphate, calcium phosphate and chromium phosphate (complexes of Cr3+, Cr5+ and Cr6+ ions) crystal phases. The study on DTA suggests that the crystallization is predominantly due to the surface crystallization when the concentration of nucleating agent Cr2O3 is around 0.8mol%. The IR and Raman spectral studies of these samples indicate that the sample crystallized with 0.8mol% Cr2O3 is more compact and possesses high rigidity due to the presence of chromium ions largely in tetrahedral positions. [Copyright &y& Elsevier]

Abstract: Li2O–CaF2–P2O5 glasses mixed with different concentrations of TiO2 (ranging from 0 to 0.8mol%) were crystallized at 500°C. The samples are characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. Spectroscopic properties (IR and Raman) and elastic properties (viz., Young''s modulus E, shear modulus G and micro-hardness H) at room temperature are studied. The X-ray diffraction and the scanning electron microscopic studies revealed the presence of lithium phosphate, lithium titanium phosphate and titanium phosphate crystal phases. The differential thermal analysis traces of these samples exhibit three crystalline temperatures. The IR and Raman spectra of these samples have exhibited bands due to TiO4 and TiO6 structural units in addition to the conventional bands due to various phosphate structural groups. The analysis of these results indicated that the sample crystallized with 0.6mol% of TiO2 possesses the highest density, high mechanical strength and more compact network. [Copyright &y& Elsevier]

Abstract: The results of various physical properties namely, dielectric properties (dielectric constant, loss tan δ, ac conductivity σ, over a wide range of frequency and temperature and dielectric breakdown strength in air medium at room temperature), optical absorption, electron spin resonance (ESR) at liquid nitrogen temperature and magnetic susceptibility at room temperature of Li2O–CaF2–P2O5:TiO2 glass-ceramics have been reported. The optical absorption and magnetic susceptibility studies indicated that the titanium ions exist in Ti3+ state in addition to Ti4+ state in these samples. However, the reduction seems to be the lowest in the sample containing 0.6mol% of TiO2. The dielectric constant and loss variation with the concentration of TiO2 have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analyzed by a pseudo Cole–Cole plot method and the spreading of dielectric relaxation has been observed. The ac conductivity in the high temperature region seems to be related both with electronic and ionic movements. The low temperature (or the nearly temperature independent) part of conductivity could be explained on the basis of quantum mechanical tunneling model. The studies on dielectric breakdown strength indicated the highest insulating strength for the sample containing 0.6mol% of TiO2. [Copyright &y& Elsevier]

This study consists of comprehensive investigations on dielectric permittivity (ε′), electric moduli (M′, M″), impedance (Z), and conductivity (σac) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe2O3. The observed increase in dielectric permittivity with the content of Fe2O3 is attributed to the increasing presence of iron ions in octahedral positions. Electric moduli plots with frequency (ω) and temperature (T) exhibit dipolar effects. These effects are quantitatively analyzed by Cole–Cole plots; the analysis indicates the distribution of relaxation times. Probable dipoles for these effects are identified and discussed. AC conductivity (σac) shows a rising trend with an increase in Fe2O3 beyond 0.2 mol%, and this increase is attributed to the polaron exchange among Fe2+ and Fe3+ ions. The conduction mechanism is well explained using a polaron tunneling model in the middle‐frequency and high‐temperature regions. [ABSTRACT FROM AUTHOR]

The nonlinear optical (NLO) and optical limiting (OL) properties of covalently linked graphene-porphyrin composite materials were investigated using Z-scan technique in nanosecond regime. We observed enhanced NLO and OL properties of graphene-porphyrin composites in comparison to the individual graphene and porphyrins. The improved OL property of composites is attributed to energy transfer between porphyrin and graphene, which improved excited state absorption and nonlinear scattering. Nonlinear optical susceptibilities χ(3) of graphene and graphene-porphyrin composites were, in the order of 10-12 esu, measured using degenerate four wave mixing technique in nanosecond regime. High values of excited state absorption and two-photon absorption were observed for the composites. [ABSTRACT FROM AUTHOR]

This study is aimed to identify the role of Fe2O3 in enhancing the efficiency of THG beam of Nd:YAG laser in lead zirconium silicate glass ceramics. The PbO–ZrO2–SiO2:Fe2O3 glass ceramics were synthesized by heat-treating the glasses for a prolonged time. XRD and SEM studies were performed to identify different crystalline phases in the samples. The SEM pictures have shown the presence of multiple crystallites of size in the range 0.1–0.6 µm, while characterization by XRD technique indicated the glass ceramic samples consist of perovskite Pb2FeIII2O5, FeII2SiO4, crystal phases. These studies have also demonstrated that there is an enhancement in the concentration of Fe3+ (Oh) crystalline phases with increasing quantity of Fe2O3 in the samples. Spectroscopic investigations (viz., IR and optical absorption) have further reinforced the above result and additionally indicated an increased degree of internal chaos in the material. The intensity of third harmonic generation (THG) beam of Nd:YAG laser (λ = 1064 nm) measured in the reflected regime after the pre-photopolarization of the samples indicated the largest intensity for the samples containing the highest concentration of Fe2O3. Thorough analysis of these results indicated that the tilted glass samples heat-treated with 0.5 mol% of Fe2O3 have significant chaotic internal structure and paved the way for obtaining intense THG signal with minimal phonon losses. Hence, such glass ceramics are predicted to be useful materials in the design of different optoelectronic devices. [ABSTRACT FROM AUTHOR]

The rationale of the current study was to assess the suitability of BF-2 cell line as a model to assess nanotoxicity in the caudal fin cells of bluegill sunfish in vitro. The current study investigates the potential toxicity, morphological changes and oxidative stress of nickel nanoparticles (Ni NPs) in bluegill sunfish cells (BF-2) using mitochondrial, neutral red uptake and lactate dehydrogenase assays. Results indicated a concentration dependent cytotoxic effect after 24 h in mitochondrial, lysosomal and lactate dehydrogenase activities. BF-2 cells morphology was altered when exposed to 30 μg ml−1 concentrations of Ni NPs for 24 h. Dose dependent increase of oxidative stress was evidenced in BF-2 cells when exposed to Ni NPs, showed significant escalation in peroxidation of lipids (LPO), protein carbonyl (PC), glutathione sulfo-transferase (GST) and glutathione peroxidase (GPX) as compared to their experimental controls. However, the catalase (CAT) and total glutathione content (TGSH) was found to decrease dose dependently in BF-2 cells exposed to Ni NPs. The current study demonstrated that BF-2 cells may serve as a sensitive indicator for aquatic contaminant evaluations in toxicological research. Unlabelled Image • This study highlights the role of Ni NPs cytotoxicity on Bluegill sunfish cells. • Morphology of BF-2 cells was altered when exposed to Ni NPs. • Ni NPs caused induction of LPO and PC in BF-2 cells. • Ni NPs enhanced the levels of GST and GPX. • NPs of Ni were found to be cytotoxic and induce oxidative stress in BF-2 cells. [ABSTRACT FROM AUTHOR]

The objective of this work is to explore the Ag ion concentration dependence on structural and dielectric characteristics of Na 2 O Sb 2 O 3 : Ag 2 O glass ceramics. The prepared glass ceramics were characterized by XRD, XPS, SEM, TEM, EDS and DSC techniques. These studies have revealed that the samples are composed of multiple crystal grains entrenched in the remnant amorphous phase. The IR and Raman spectroscopic studies indicated increasing degree of polymerization of the glass network with increase of Ag 2 O concentration up to 0.1 mol%. This is attributed to increasing concentration of tetrahedral Sb5+ ions that take part in the glass network forming. Optical absorption spectra have exhibited surface plasmon resonance (SPR) band in the wavelength region 400–450 nm. Quantitative studies on dielectric properties were performed over wide ranges of frequency and temperature and the variations of these properties with the concentration of Ag 2 O are discussed in the light of various polarization processes. Dipolar orientational effects exhibited by electric moduli spectra suggested multiple relaxation times for electric dipoles. The observed decrease of A.C. conductivity (that contains both ionic and polaronic components) with increase of Ag 2 O content up to 0.1 mol% is attributed to the increasing degree of polymerization of the glass network that hinders the migration of charge carriers. The polaronic conduction is understood due to exchange of polarons between Sb3+ ‒ Sb5+ and Ag0 Ag+ ions, while ionic conductivity is predicted due to transport of monovalent silver and Na+ ions. A changeover of polaronic to ionic conductivity seemed to take place at about 0.1 mol% Ag 2 O. Impedance plot for sodium antimonate glass crystallized with 0.1 mol% of Ag 2 O. Image 1 • Structural and dielectric properties of Na2O Sb2O3: Ag2O glass ceramics investigated. • Structural studies indicated samples contain Sb3+, Sb5+, Ag+, Ag0 crystal phases. • Samples with >0.1 Ag mol% exhibit larger ionic conductivity. • Polaronic component of a.c. conductivity is prevailed up to 0.1 mol% of Ag 2 O. [ABSTRACT FROM AUTHOR]

• As 2 O 3 glass ceramics mixed with SeO 2 and TeO 2 and doped with Ag 2 O were prepared. • Characterization indicated entrenchment of Ag 3 AsO 4 phase and Ag0 MPs in the samples. • ε′, σ ac exhibited increase with Ag 2 O beyond 0.5 mol% due to increase of Ag0 MPs. • σ ac variation with Ag 2 O content was analyzed using different conduction mechanisms. • Samples with > 0.5 mol% of Ag 2 O are preferable to achieve high ionic conductivity. In this work, As 2 O 3 glasses mixed with two chalcogenide oxides (SeO 2 and TeO 2) and doped with varied contents of Ag 2 O were prepared and heat-treated. Characterized by various techniques suggested that these glasses were embedded with Ag 3 AsO 4 crystal phases and Ag0 metallic particles (MPs). Later, different dielectric parameters viz., dielectric constant (ε′), electric modulus (M), electrical impedance (Z). conductivity a.c. conductivity a.c. conductivity and σ ac were measured over broad frequency (ω) and temperature (T) regions. Observed decrement in ε′, σ ac with Ag 2 O up to 0.5 mol% was understood due to the increased fraction of As5+ ions that occupy network-forming positions with AsO 4 units. The observed increase of these parameters with Ag 2 O beyond 0.5 mol% was attributed to the growing fraction of Ag0 MPs that acted as modifiers. The variation of σ ac with Ag 2 O content was analyzed using different conduction mechanisms. Overall, it is predicted that greater than 0.5 mol% of silver oxide is preferable for achieving better ionic conductivity in these glasses [ABSTRACT FROM AUTHOR]

This study is mainly focused on electrical characteristics of PbO−ZrO 2 −SiO 2 : TiO 2 glass ceramics embedded with Pb 2 Ti 2 O 6 cubic pyrochlore crystal phases. The samples were synthesized by usual melt quenching technique and subsequent heat treating at crystallization temperature for prolonged times. The samples were characterized by XRD, SEM and DSC, IR, EPR and optical absorption spectroscopy techniques. Later, dielectric properties viz ., dielectric constant, loss tangent, electric moduli, electrical impedance and a.c. conductivity over wide ranges of frequency and temperature, have been measured as a function of TiO 2 content. The results of characterization techniques viz., XRD, SEM and DSC, indicated that the samples are embedded with multiple crystal grains (with sizes varying from 0.1 to 1 μm) cemented with residual glass phase. The volume fraction of the crystal grains is found to increase with increase of TiO 2 content. The XRD studies on PbO−ZrO 2 −SiO 2 :TiO 2 glass ceramics revealed that Pb 2 Ti 2 O 6 cubic pyrochlore crystal phase is the principal phase present in the bulk samples. The studies have also confirmed that a small part of Pb(Zr 0.5 Ti 0.5 )O 3 and Ti 2 O 3 crystal grains are also present in the titled glass ceramics. The results of IR spectral studies have indicated that there is an increasing degree of polymerization of glass network with increasing TiO 2 content up to 0.6 mol%. This is attributed to the presence of Ti ions predominantly in Ti 4+ state (in this concentration range of TiO 2 ) that take part in the network forming positions with TiO 4 and also substitutionally positioned octahedral sites. The results of optical absorption and EPR spectral studies have pointed out that a part of the Ti ions were reduced to Ti 3+ state and such ions were predicted to act as modifiers. These studies have also indicated that the concentration of Ti 3+ ions is higher in the samples crystallized with 0.8 and 1.0 mol%. The values of dielectric parameters are decreased with increasing of crystallizing agent. The decrease is attributed to the participation of Ti ions in the formation of Pb 2 Ti 2 O 6 cubic pyrochlore crystalline phases with TiO 4 structural units. Quantitative analysis of the dielectric properties of PbO−ZrO 2 −SiO 2 :TiO 2 glass ceramics together with the results of spectroscopic studies indicated that the electrical insulating strength is the highest for the glass crystallized with 0.6 mol% of TiO 2 . [ABSTRACT FROM AUTHOR]

• Li2O-HfO2-SiO2 glasses with fixed Sm2O3 and varied content of Au2O3 were prepared. • OA spectra exhibited a broad band in the visible region due to SPR of Au0 particles. • PL spectra of the glasses containing Au0 MPs showed a wide (sp → d) emission band. • PL spectra of Sm3+ doped glasses revealed bright orange and red emission bands. • Role of Au0 particles on improving red emission efficiency of Sm3+ ions was discussed. In this study, Li 2 O-HfO 2 -SiO 2 -Sm 2 O 3 -Au 2 O 3 glasses (doped with fixed concentration of Sm 2 O 3 and varied contents of Au 2 O 3) were synthesized and characterized. The role of Au0 particles on improvisation of red emission of Sm3+ ions was investigated. Optical absorption (OA) spectra of these glasses indicated a number of bands excited from 6H 5/2 of Sm3+ ions. A broad band in the greenish-yellow spectral region due to surface plasmon resonance (SPR) of Au0 nanoparticles was also detected in these spectra. Photoluminescence (PL) spectra of (Sm free glasses) embedded with Au0 metallic particles (MPs) showed a wide band in the visible region ascribed to the transition of electrons from sp → d energy bands. Luminescence spectra of Sm3+ doped glasses revealed bright orange and red emission bands with substantial increased intensities with increased concentration of Au 2 O 3. Effect of Au0 MPs on the red emission efficiency of Sm3+ ions was emphasized with kinetic rate equations. [ABSTRACT FROM AUTHOR]

• Pb 3 O 4 mixed lithium silicate glasses doped with variable content of Ag 2 O were prepared • Structural studies revealed increased polymerization of the glass network with Ag 2 O • Dielectric parameters and ac conductivity were measured as a function of Ag 2 O content • Plots of electric modulus vs w and T indicated a relaxator like character • Conduction was explained with polaron tunneling model in the middle w and high T ranges Glasses of the composition (40- x)Li 2 O-10Pb 3 O 4 -50SiO 2 doped with different contents of Ag 2 O were fabricated and were subsequently subjected to heat-treatment. The quantitative analysis of the results of different characterization techniques indicated increasing magnitude of internal connectivity of the glass network with increasing Ag 2 O content. Several dielectric parameters viz., ε ′, M, Z and σ ac in the frequency (ω) region 0.01 Hz – 1 MHz and in the region of temperature (T) 30 –250 °C of these glasses were measured as functions of Ag 2 O content. ε ′ showed a decreasing tendency with Ag 2 O content which may be attributed to the decrease in the space charge polarization (scp) due to the increasing order of augmentation of glass network. Such a decrease of scp was attributed to the growing presence of PbO 4 units and also Ag0 particles in these samples. The plots of electric modulus vs ω and T indicated relaxation character. Such relaxation phenomena were discussed in detail with the help of Cole-Cole diagrams. Probable dipoles responsible for such effects were recognized and analyzed. σ ac (conductivity) exhibited a decreasing trend with Ag 2 O content. The mechanism of conduction was analyzed using polaronic tunneling effect in the intermediate ω and high T ranges, whereas in the low T range it is predicted to follow QMT model. These conclusions were observed to follow the results of various spectroscopic studies. In conclusion, presence of red lead seemed to be an obstruction for the conductivity in the fast ion conducting glasses. [ABSTRACT FROM AUTHOR]

• PbO-B 2 O 3 -SeO 2 :Er 2 O 3 glass ceramics added with traces of Au 2 O 3 were synthesized. • Characterization studies indicated increasing fraction of defects with Au 2 O 3 content. • Dielectric parameters ε′ , M , Z and σ ac are measured in broad ω temperature T ranges. • ε′ is observed to increase with Au 2 O 3 content due to the space charge polarization. • Mechanism of conduction is analyzed using polaronic tunneling model middle ω region. The variations of M′ and M″ with frequency and temperature of glass ceramic sample EA 75. [Display omitted] The glass ceramics of the composition PbO-B 2 O 3 -SeO 2 :Er 2 O 3 (PBSE) doped with small concentrations of Au 2 O 3 were synthesized. The results of detailed studies on various characterization techniques and also different spectroscopic investigations suggested that these glass ceramics are entrenched with Au 2 (SeO 3) 3 crystal phases and Au0 metallic particles (MPs). These studies further revealed increasing concentration of [SeO 3 ]2- groups and Au0 metallic particles with the increase of Au 2 O 3 content upto 0.075 mol%. Such [SeO 3 ]2- groups are predicted to induce structural imperfections in the glass ceramic. Optical absorption (OA) and photoluminescence (PL) spectral studies also indicated increasing concentration of imperfections with increase of Au 2 O 3 content. The dielectric viz, dielectric permittivity (ε′), electrical modulus (M) , electrical impedance (Z) and a.c. conductivity (σ ac) spectra in the frequency (ω) region 4 Hz to 8 MHz and in the temperature (T) region 303–633 K of these glass ceramic samples were measured as functions of Au 2 O 3 concentration. The dielectric permittivity (ε′) exhibited an increasing trend with Au 2 O 3 concentration and it is ascribed to the increase in the magnitude of the space charge polarization (scp) due to the increase in the concentration of structural defects induced by [SeO 3 ]2- units and Au0 metallic particles. The plots of electric modulus (M) with frequency and temperature exhibited dipolar relaxation phenomena. Such effects were analyzed further using Cole-Cole diagrams and the possible dipoles responsible for these effects were identified. A.C. conductivity (σ ac) exhibited increasing trend with the concentration of Au 2 O 3 (up to 0.075 mol%) and such increase is attributed to the polaronic exchange between different structural groups of selenium oxide. The conduction mechanism is analyzed using polaronic tunneling effect in the middle frequency and high temperature regions, whereas in the lower temperature region QMT model seems to be applicable. Conclusions drawn from dielectric properties were found to be well in accordance with the results of spectroscopic properties. [ABSTRACT FROM AUTHOR]

• With sound velocities elastic constants of Au 2 O 3 : PBSE glass-ceramics are estimated. • These coefficients observed to be decreasing with the concentration of Au 2 O 3. • Such decrease is attributed to the increasing concentration of Au0 MPs. • The results are found to be consistent with spectroscopic and PAL studies. Various elastic coefficients of Au 2 O 3 doped PbO-B 2 O 3 -SeO 2 :Er 2 O 3 (PBSE) glass ceramics were evaluated as functions of Au 2 O 3 content using ultrasonic velocity measurements. The elastic coefficients and micro-hardness showed a decreasing tendency with the concentration of Au 2 O 3. Such decrease is attributed to the increasing concentration of gold metallic particles and [SeO 3 ]2− groups that acted as modifiers and induced imperfections in these samples. Obtained results were observed to be consistent with the conclusions drawn from spectroscopic studies that include X-ray photoelectron spectroscopy (XPS), infrared (IR), photoluminescence (PL) and positron annihilation (PAL) spectroscopy studies. Overall, these studies have revealed that even though, the presence of gold metallic particles is preferable for achieving superior luminescence and electrical properties, presence of such particles caused to decrease the elastic coefficients and micro-hardness of these glass ceramics. However, when the concentration of Au 2 O 3 is increased beyond 0.075 mol%, we have observed a slight increase of elastic coefficients and micro-hardness. [ABSTRACT FROM AUTHOR]

Abstract: A new thieno[3,2-b]thiophenediketopyrrolopyrrole-benzo[1,2-b:4,5-b′]dithiophene based narrow optical gap co-polymer (PTTDPP-BDT) has been synthesized and characterized for field-effect transistors and solar cells. In field-effect transistors the polymer exhibited ambipolar charge transport behaviour with maximum hole and electron mobilities of 10−3 cm2 V−1 s−1 and 10−5 cm2 V−1 s−1, respectively. The respectable charge transporting properties of the polymer were consistent with X-ray diffraction measurements that showed close molecular packing in the solid state. The difference in hole and electron mobilities was explained by density functional theory calculations, which showed that the highest occupied molecular orbital was delocalized along the polymer backbone with the lowest unoccupied molecular orbital localized on the bis(thieno[3,2-b]thiophene)diketopyrrolopyrrole units. Bulk heterojunction photovoltaic devices with the fullerene acceptor PC70BM were fabricated and delivered a maximum conversion efficiency of 3.3% under AM1.5G illumination. [Copyright &y& Elsevier]

Abstract: Li2O–ZrO2–SiO2: Ho3+ glasses mixed with three interesting d-block elemental oxides, viz., Nb2O5, Ta2O5 and La2O3, were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The luminescence spectra of Nb2O5 and Ta2O5 mixed Li2O–ZrO2–SiO2 glasses (free of Ho3+ ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Ta5+ and Nb5+ ions in the glass network. The Judd–Ofelt theory was successfully applied to characterize Ho3+ spectra of all the three glasses. From this theory various radiative properties, like transition probability A, branching ratio β r and the radiative lifetime τ r, for 5S2 emission levels in the spectra of these glasses have been evaluated. The radiative lifetime for 5S2 level of Ho3+ ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied the La2O3 mixed glass exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Ho3+ ions. [Copyright &y& Elsevier]

Abstract: Li2O–Nb2O5–ZrO2–SiO2 glasses mixed with different concentrations of V2O5 were crystallized. The samples were characterized by XRD, SEM and DTA techniques. The SEM pictures indicated that the samples contain well defined and randomly distributed crystal grains. The X-ray diffraction studies have revealed the presence of several crystalline phases in these samples. Optical absorption, ESR and photoluminescence spectral studies on these samples have indicated that a considerable proportion of vanadium ions do exist in V4+ state in addition to V5+ state and the redox ratio seems to be increasing with increase in the concentration of crystallizing agent V2O5. The infrared spectral studies have pointed out the existence of conventional SiO4, ZrO4, NbO6, VO structural units in the glass ceramic network. The study of dielectric properties suggested a decrease in the insulating character of the glass ceramics with increase in the crystallizing agent. A.C. conductivity in the high temperature region seems to be connected mainly with the polarons involved in the process of transfer from V4+↔V5+ ions. [ABSTRACT FROM AUTHOR]

PbO-As2O3 glasses mixed with different concentrations of TiO2 (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy (EDS) techniques. Studies were extended to optical absorption, IR, ESR, luminescence and magnetic susceptibility on these samples. The X-ray diffraction studies reveal the presence of Pb3O4, Ti(As2O7), Pb(As2O6), Pb3(AsO4)2 PbTi3O7 and Ti2O3 crystal phases. The optical absorption studies together with ESR and magnetic susceptibility measurements indicated that the titanium ions exist in both Ti3+ and Ti4+ states in all the samples and there is an increase in titanium ions in the trivalent state with increasing concentration of nucleating agent TiO2. The quantitative analysis of these results indicated that there is a growing degree of disorder in the glass network with increasing concentration of the crystallizing agent. The luminescence studies indicated that the samples crystallized with low concentrations of TiO2 show high luminescence efficiency in the visible region. [ABSTRACT FROM AUTHOR]

• Role of Au0 particles on improving PL of Ho3+ ions in a SeO 2 glass ceramic is explored. • Characterization indicated that the samples consist of [SeO 3 ]2− & [SeO 4 ]2− units. • Samples comprising of Au0 particles exhibited sp → d electronic transitional emission. • PL spectra of Au0-Ho3+ codoped samples exhibited intense bands in visible region. • Sensitization by Au0 particles on luminescence output is quantitatively discussed. This study is devoted to investigate the role of Au0 particles on the improvement of luminescence efficiency of Ho3+ ions in a non-conventional lead boroselenate glass ceramic. Characterization by different spectroscopic techniques indicated that the samples consist of [SeO 3 ]2− and [SeO 4 ]2− structural groups. Among them, the fraction of [SeO 3 ]2− groups exhibited an increasing trend with increase of Au 2 O 3 content. These studies have further revealed that a part of Au3+ ions reduced in to gold nano particles during ceramicization process. Optical absorption (OA) spectra of these samples exhibited a wide absorption band with gradual growth with the Au 2 O 3 concentration. This band is attributed to the surface plasmon resonance (SPR) of gold nanoparticles. Additionally, the OA spectra exhibited several characteristic bands of Ho3+ ions in the spectral region of 450–2000 nm. Photoluminescence (PL) spectra of (Ho free samples) containing gold particles exhibited a broad band in the green to red spectral region, identified due to the transition of electrons from sp → d energy bands of gold nanoparticles. PL spectra of co-doped samples exhibited the emission bands in the green, orange and red regions with enhanced intensities as Au 2 O 3 content is increased. OA and PL spectra were characterized using Judd-Ofelt theory and various radiative parameters were estimated. The impact of Au0 particles on the PL efficiency of holmium ions is comprehensively discussed using kinetic rate equations. The crucial role of gold particles as sensitizers in enhancing the luminescence efficiency especially the green emission is quantitatively explained. [ABSTRACT FROM AUTHOR]

Abstract: For the characterization of sediments, Computer Controlled Scanning Electron Microscopy (CCSEM) is a powerful method in obtaining chemical data on individual mineral grains and modal analysis of the heavy mineral fraction of sediment samples. Here we show how the CCSEM method can be used to evaluate ilmenite ore grade as well as a tool to investigate the source of heavy mineral deposits. The heavy mineral rich deposits in beach sands around the town of Chavara in SW India are characterized by ilmenite with elevated TiO2 contents, often exceeding 60 wt.%. In order to determine the origin of these high-TiO2 ilmenite deposits, we collected a series of beach sediment samples (22) from a c. 800 km long stretch of coastline from northern Kerala state to well within the Tamil Nadu state. A set (7) of river sediments was also taken, roughly covering the catchment area to the beach samples. The data show that the sediments in the Chavara high-Ti ilmenite deposit are distinguished by minor elements in ilmenite, garnet chemistry and heavy mineral assemblage: Chavara ilmenite has high MgO and low MnO contents; garnets have low grossular components and the heavy mineral assemblage is dominated by sillimanite–kyanite in addition to ilmenite. These features correlate with basement geology in the hinterland, and with sediments from rivers, draining the basement. Based on these observations we conclude that high-Ti ilmenite from Chavara beaches originates in the khondalite belt of high-grade metasediments. Our study demonstrates rapid mineral analyses in sediments by CCSEM to be efficient in the characterization of mineral compositions and assemblages in sediments, in the identification of possible source regions and thus ultimately in exploration for industrial mineral resources. [Copyright &y& Elsevier]

SeO 2 based glasses of the composition 39 PbO–(60- x) B 2 O 3 – x SeO 2 :1.0 Yb 2 O 3 (with 10 ≤ x ≤ 50) was synthesized. Analysis of the results of structural studies of the samples revealed that the glass network consists of [SeO 4 ]2− and [SeO 3 ]2− units; the studies further indicated an increasing fraction of [SeO 3 ]2− units and decreasing concentration of [SeO 4 ]2− groups with increase of SeO 2 content. Optical Absorption (OA) and photoluminescence (PL) spectra have exhibited bands due to 2F 7/2 → 2F 5/2 and 2F 5/2 → 2F 7/2 transitions, respectively. Evaluated absorption and emission cross-sections and lifetime of the excited state of Yb3+ ions exhibited an increase with increase of SeO 2 content. Results of PL studies indicated nearly fourfold increase of PL output with increase of SeO 2 content up to 50%. Such increase is attributed to the increased concentration of isolated [SeO 3 ]2- pyramidal groups. Overall, the rise of SeO 2 content in Yb3+ doped PbO–B 2 O 3 –SeO 2 glass system facilitated the increase of PL emission of Yb3+ ions largely. [ABSTRACT FROM AUTHOR]

• SeO 2 based glasses of composition 39PbO-(60- x)B 2 O 3 - x SeO 2 :1.0 Er 2 O 3 were synthesized. • IR/Raman spectra suggested growth of [SeO 3 ]2−/[SeO 4 ]2− units' ratio with SeO 2 content. • Analysis of OA spectra indicated J-O parameters to follow the order: Ω 2 > Ω 6 > Ω 4. • Green and NIR PL emission bands exhibited significant growth with SeO 2 content. • PL spectra quantitatively analysed using kinetic rate equations. • Gain co-efficient G(λ) of 4I 13/2 →4I 15/2 transition indicated its lasing behaviour. In this work we have studied impact of SeO 2 concentration on luminescence properties of 39PbO-(60- x)B 2 O 3 - x SeO 2 :1.0 Er 2 O 3 (10 ≤ x ≤ 50) glass system. The structural analysis of the samples carried out by XRD, SEM indicated that the prepared samples are in amorphous phase. IR, Raman and XPS studies revealed increasing presence of isolated selenite [SeO 3 ]2−groups and decreasing concentration of [SeO 4 ]2−(selenate) groups with increasing content of SeO 2 in the glass network. Optical absorption (OA) spectra revealed absorption bands due to 4I 15/2 → 4F 7/2 , 9/2 , 2H 11/2 , 4S 3/2 , 4I 9/2 , 11/2 , 13/2 transitions of Er3+ ions. Using J-O theory, the spectra were characterized and the evaluated Ω λ parameters are found to be in the order: Ω 2 > Ω 4 > Ω 6. The PL spectra recorded at λ exc = 378 nm exhibited the emission bands due to 2H 11/2 →4I 15/2 (B), S 3/2 →4I 15/2 (G), 4F 9/2 →4I 15/2 (O) and 4I 13/2 →4I 15/2 (NIR) transitionsof Er3+ ions. With the gradual increase SeO 2 content, the PL emission bands (especially green and NIR bands) have exhibited significant growth. The spectra were quantitatively analysed using kinetic rate equations and the causes for enhancement of PL emission were recognised and discussed. From the gain co-efficient G(λ) of the 4I 13/2 →4I 15/2 transition, its lasing behaviour is detected for a population inversion of nearly 50%. [ABSTRACT FROM AUTHOR]

This work is focused on the amplification of green (G), orange (O) and NIR (1.5 μm) emissions of Er3+ ions by co-doping with varying contents (traces ≤ 0.1 mol%) of Au 2 O 3 in an exotic PbO-B 2 O 3 -SeO 2 glasses ceramic. The glasses were synthesized by conventional melt quenching method and were crystallized by heat-treating them at crystallization temperature for a period of 24 h. Initial characterization of the samples by means of SEM, XRD, XPS, IR and Raman studies suggested that the post-heated samples are entrenched with poly-crystal grains (with sizes varying from 100 to 500 nm). These studies have also revealed that the concentration of such nano-crystallites is increased with increased content of Au 2 O 3 up to 0.075 mol%. The XRD studies, in particular, have indicated that the glass ceramics are composed of Au 2 (SeO 3) 2 (SeO 4) (crystal phase containing Se ions of mixed valence states) and Au0 nano particles. The XPS studies have also indicated the presence of Se and gold ions in different valence states in these samples. IR and Raman spectra have suggested increased degree of internal chaos in the glass ceramic with increasing concentration of Au 2 O 3. Optical absorption (OA) spectra of Au 2 O 3 doped glass ceramic samples (without Er3+ ions) exhibited a broad band in the visible region identified as surface plasmon resonance (SPR) band of gold metallic particles. The photoluminescence (PL) spectra of these samples exhibited an emission peak due to inter-band transition from sp to d energy bands of Au0 metallic particles. This emission is identified to play a crucial role in enhancing PL emission of Er3+ ions in the visible and NIR regions. Finally, we have recorded optical absorption, photoluminescence spectra and decay profiles of the Er3+ doped (with Au 2 O 3 as co-dopant) glass ceramics. The spectra were characterized using J–O theory and different radiative parameters (viz., transition probabilities, branching ratios, radiative lifetime) of green, orange and NIR emission transitions of Er3+ ions were evaluated. The results indicated a significant reinforcement of green (4S 3/2 → 4I 15/2), orange (4F 9/2 → 4I 15/2) and NIR (4I 13/2 → 4I 15/2) emissions of Er3+ ions due to co-doping with Au 2 O 3. Quantitative analysis of the results of PL emission indicated that 0.075 mol% of Au 2 O 3 is the optimal concentration for achieving the highest quantum yield of these three emissions in this glass ceramic. Additional population of 4S 3/2 , 4F 9/2 and 4I 13/2 energy levels of Er3+ ions from the excited state of Au0 metallic particles is found to be the reason for such enhancement of quantum efficiency. PL spectra of Au metallic particles in PbO-B 2 O 3 -SeO 2 -Er 2 O 3 glass ceramics mixed with different concentrations of Au 2 O 3 along with energy scheme of gold particles. Image 1 • Exotic PbO-SeO 2 -Er 2 O 3 : Au 2 O 3 glass ceramics were synthesized. • Amplification of G, O and NIR emission emissions of Er3+ ions is investigated. • PL results suggested that EA 75 sample exhibited the highest efficiency. • Energy transfer from Au0 particles is found to be the reason for such enhancement. [ABSTRACT FROM AUTHOR]

In this study, we have reported results of the investigation related to the influence of nickel ions on in vitro bio-activity of CaF 2 –CaO–B 2 O 3 –BaO–P 2 O 5 glasses. The studies carried out are, degradation studies of the glass samples in SBF for a long time (for about a month), XRD, SEM and spectroscopic properties performed before and after immersion in simulated fluid suggested a thin coating of HAp crystalline grains on the surface of the glasses. IR and Raman spectral studies have further confirmed the formation of HAp layer. Magnitude of fraction of the samples that are degraded in the fluid is evaluated by weight loss and pH of remaining fluid. Degradation results along with characterization studies as a function of concentration of NiO indicated an increasing quantity of HAp deposited on the samples with the rise of NiO quantity up to 0.6 mol%. Spectroscopic investigations have further indicated the nickel ions occupied O h and T d positions in the glass network. The studies have also suggested O h occupancy of these ions is dominant in the glass doped with 0.6 mol% of nickel oxide while the fraction of tetrahedral nickel ions is minimal in this glass. The scrutiny of the degradation study results in combination with spectroscopy studies indicated that higher concentration of octahedral nickel ions are preferable for achieving higher quantity of crystalline HAp layer on the surface of the samples while the tetrahedral nickel ions are hindrance in promoting the growth of HAp layer. • In vitro degradation of NiO doped calcium oxy fluoroboro phosphate glasses is studied. • Bioactivity ability of the glasses is evaluated as function of NiO concentration. • Thin coating of crystalline Ca-HAp is observed on the surface due to immersion in SBF. • 0.6 mol% of NiO is optimal concentration for the deposition of high magnitude of HAp. [ABSTRACT FROM AUTHOR]