Search

• Niobium-containing phosphate glasses prepared by melt quenching technique. • Nb 2 O 5 content influences the speciation of aluminum. • Eu3+ doping causes red light emission. • Er3+/Yb3+ co-doping causes infrared emission due to energy transfer. • 93Nb NMR indicates three distinct niobium environments. Luminescent Rare Earth (RE3+) doped phosphate glasses with molar composition (1-x)(60P 2 O 5 – 15ZnO – 5Al 2 O 3 – 10BaO – 10PbO)- x Nb 2 O 5 (x = 0, 10, 20 and 30 wt%) doped with 1.0, 1.2 and 0.3 wt% of Eu 2 O 3 , Yb 2 O 3 and Er 2 O 3 , respectively, were prepared by conventional melt cooling. The glasses were characterized by optical reflectance, Raman scattering, and multinuclear (31P, 27Al, and 93Nb) solid-state NMR spectroscopy. Monotonic 31P chemical shift changes as a function of Nb 2 O 5 content are consistent with the successive formation of Nb-O-P linkages. Aluminum is found in four-, five-, and six-coordination, with a successive decrease in average coordination number with increasing niobium content, while 93Nb NMR indicates three distinct niobium environments in these glasses. Incorporation of Nb 2 O 5 has the expected effects on refractive index values, optical basicity, optical electronegativity, Urbach Energy, and the indirect bandgap, while RE3+ emission properties are only slightly modified. Under UV excitation, narrow emission bands are observed arising from 5D 0 →7F J (J = 0, 1, 2, 3, and 4) transitions of Eu3+. At least two distinct Eu3+ lifetime values are observed, suggesting a spread of different ionic environments within the glass structure. Co-doping with Er3+/Yb3+ promotes emission in the infrared region, with a emission band maximum near 1535 nm and a width of 30.65 nm under excitation at 980 nm. Based on the results, these glasses may be potential candidates for energy conversion from infrared or UV region to the visible region and also infrared solid-state emitters. [ABSTRACT FROM AUTHOR]

Ultrasmall CdTe quantum dots (USQDs) were successfully grown in a silicate glass matrix by fusion and after thermal annealing. Growth control of USQDs was investigated by optical absorption (OA), atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL). A redshift of OA band with increasing thermal annealing time provided evidence of CdTe USQD growth. This increase of average size of the CdTe USQDs was determined by OA spectra, AFM and TEM images. In addition, PL spectra showed that longer thermal annealing times decreased deep levels luminescent intensity from cadmium vacancies ( V Cd ) in the CdTe USQDs. This phenomenon occurred because V Cd diffused to the USQDs’ surface with longer thermal annealing times. Therefore, we control the growth of CdTe USQDs as well as the luminescent intensity from surface defects and V Cd as a function of thermal annealing time. [ABSTRACT FROM AUTHOR]

Abstract: Samples of 40SiO2·30Na2O·1Al2O3·(29 − x)B2O3·xFe2O3 (mol%), with 0.0 ≤ x ≤ 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe3+ ion complexes (g = 4.27 and g = 6.4) and Fe3+-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe3+-based clusters built in from two sources of isolated ions, namely Fe2+ and Fe3+; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe2+ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed 5Eg–5T2g transition in an octahedral coordination with oxygen. Additionally, Mössbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe2+ and Fe3+ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO4 complex resulting from replacing silicon in non-bridging oxygen (SiO3O−) sites whereas ferric ions are incorporated as FeO4 complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO4). [Copyright &y& Elsevier]

Abstract: The structural properties of the glass matrix 40SiO2·30Na2O·1Al2O3·(29− x)B2O3·xFe2O3 (mol%), 0.0≤ x ≤29.0 were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman and infrared spectroscopy (FT-IR). XRD demonstrated Fe3O4 crystal formation for Fe2O3 concentrations of 29.0mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe2O3 concentration and that these alterations were related to structural change in the glass system. Interesting aspects of Raman and FT-IR spectra were found, and this gives information about of the structure changes in Si–O–Si units of these glasses as a function of Fe2O3 concentration. [Copyright &y& Elsevier]

• Er3+/Yb3+/Eu3+ triply doped PANK glass with different amount of Nb 2 O 5 ; • Uv conversion to visible and infrared region; • 'PANK glass accommodate higher Nb 2 O 5 concetration; • Band gap properties change as a function of Nb 2 O 5 concentration. This work reports on the preparation and photoluminescence properties of the phosphate glass matrix based on P 2 O 5 -Al 2 O 5 -Na 2 O-K 2 O (PANK) doped with Yb3+, Eu3+ and Er3+ with different amount of Nb 2 O 5 prepared by the conventional melting process. The Raman bands assigned to the Nb 2 O 5 indicating the insertion of this oxide in the glass. Under UV excitation, the emission spectra presented narrow bands assigned to the Eu3+, arising from the 5D0→7FJ (J = 0, 1, 2, 3 and 4). It was observed that the materials have at least two lifetimes values of the Eu3+ ion. In all materials, it was observed that the amount of Nb 2 O 5 does not influence the photo-luminescent properties of the Eu3+ ion, providing potential applications in energy conversion. The optical properties like refractive index, optical basicity, optical electronegativity, Urbach Energy, direct and indirect band-gap, Judd-Ofelt parameters were calculated and the covalence bonding of Eu3+ with the neighbors ligands was evaluated as a function of Nb 2 O 5 concentration. Co-doping with Er3+/Yb3+ promotes the emission in the infrared region, with a maximum around 1535 nm and bandwidth of 28 nm under 980 nm pumping. [ABSTRACT FROM AUTHOR]

Sb 2-x Cr x Te 3 quantum dots (QDs) were synthesized in a host glass matrix through fusion and heat treatment methods. The results revealed the specific effects inherent to the doping of Cr3+ ions in diluted magnetic semiconductors (DMS) (Sb 2-x Cr x Te 3 QDs embedded in glass matrix). Differential Thermal Analysis shows evidence of changes in glass transition and the host glass's crystallization temperatures with the presence of Sb 2-x Cr x Te 3 QDs. Transmission electron microscopy (TEM) images and energy dispersive X-ray analysis evidenced the formation, size, and composition of these DMS QDs. The interplanar distances d hkl measured in TEM and the pattern observed in electron diffraction from the selected area reinforces the Sb 2 Te 3 crystalline nature. Structural analyses of x-ray diffraction patterns confirm that all Sb 2-x Cr x Te 3 QDs crystallize in the rhombohedral R 3 _ m − D 3 d 5 structure and that Cr3+-ions had replaced Sb3+-ions. Electronic paramagnetic resonance (EPR) spectra exhibit resonance signals confirming Cr3+ ion incorporation into the Sb 2 Te 3 crystal lattice. Moreover, EPR shows that the sp-d exchange interactions become less pronounced with the formation of Cr3+ ─ Cr3+ pairs. Raman scattering spectroscopy confirmed the formation of Sb2-xCrxTe3 QDs. The red and blue shifts of the normal Raman- and IR-active vibrational modes characteristic of Sb 2 Te 3 give strong evidence of the Cr3+ ion incorporation in QDs. Interestingly, the study results revealed better structural and magnetic properties. We believe that these Sb2-xCrxTe3 QDs in SNAB glass, with appropriate dopant concentration and chemical composition, are potentially efficient for thermoelectric, topological insulators, photovoltaic devices, solar cells, magnetic devices and spintronic applications. [ABSTRACT FROM AUTHOR]

Nanostructured materials have exhibited great potential applications in the field of (bio)sensing. In particular, the capacitive electrolyte-insulator-semiconductor (EIS) sensor is a suitable field-effect device for integration of film-based nanostructures as sensing units. In this study, the fabrication of a hybrid nanostructured film using the layer-by-layer (LbL) technique combining cobalt ferrite (CoFe2O4) nanocrystals complexed with poly(vinylpyrrolidone) (PVP) and embedded with a poly(amido- amine) (PAMAM) dendrimer is investigated. LbL films containing a PAMAM/PVP- CoFe2O4 architecture with different bilayers are fabricated onto EIS chips of Al/p- Si/SiO2. The morphology of the films is characterized by atomic force microscopy (AFM) and the sensing properties toward H2O2 detection are evaluated by capacitance-voltage (C/V) and constant capacitance (ConCap) measurements. By correlating the electrochemical and morphological properties of the films, the findings lead to an optimized system, in which the best performance is observed for a 3-bilayer EIS-(PAMAM/PVP-CoFe2O4) sensor, exhibiting a sensitivity of ca. 26.5 mV decade 1 and limit of detection of ca. 157×10-6 M toward H2O2. The set-up presents for the first time a field-effect sensor for H2O2 detection as an alternative to conventional amperometric H2O2 sensors. [ABSTRACT FROM AUTHOR]

Abstract The effect of ion concentration on the saturation intensity, I s , was investigated and its effect on the evaluation of nonlinear optical properties was discussed. The suggested experimental approach points out a more accurate way to obtain I s. The value of I s in the limit of low concentration and low incident intensity was obtained as (266 ± 14) KW/cm2 at 514 nm. Through time resolved Z-scan the nonlinear refractive index, n 2 , of Nd-doped phosphate glass could be evaluated for different Nd concentrations. Finally, the n 2 and I s values were used to determine the polarizability difference between ground and excited states as Δα = (2.6 ± 0.2) × 10−26 cm3, for Nd3+ ions in this glass matrix. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

• Influence of the niobium pentoxide on the structural and luminescent properties. • Nb 2 O 5 reduces phonon energy from ∼1060 to 900 cm-1. • Increased asymmetric ratio of Eu3+ ions from ∼5 to 8. • Nd3+ ion lifetime reduces from 337 to 282 μs as the Nb 2 O 5 content increase. Niobium pentoxide (Nb 2 O 5) in glasses doped with RE3+ ions has garnered significant interest in developing luminescent materials for optical devices. This study explores a phosphate glass nanostructured with CdS and doped with Nd3+ and Eu3+ ions, focusing on the impact of Nb 2 O 5 addition. Using optical absorption, photoluminescence (PL), time–resolved photoluminescence, and Raman Scattering, the structural and luminescent properties were characterized. Nb 2 O 5 was found to significantly influence the matrix, acting as a network–forming agent, and reducing phonon energy from ∼1060 to 900 cm-1. Structural changes were also evidenced by an increase in the asymmetric ratio of Eu3+ ions from ∼5 to 8. PL decay curves indicated Nd3+ ions distributed across sites with different symmetries, with Nb 2 O 5 reducing the lifetime of the 4F 3/2 level from 337 to 282 μs. The findings demonstrate that Nb 2 O 5 can modulate the structural and luminescent properties of phosphate glass, making it a promising for advanced photoluminescent materials. [ABSTRACT FROM AUTHOR]

The effects of substitution of Al 2 O 3 by K 2 O in the raw materials for preparing phosphate glasses have been investigated using interferometer and thermal lens techniques. When the K 2 O content reaches ∼9 wt%, both techniques present an athermal behavior, with a temperature coefficient of the optical path ds/dT equal to zero. From the interferometer measurements, a linear shift of the long period in the interference fringe from 77 K to room temperature was observed, whose athermal temperature is described by the linear function A T = 145 + 246 ⋅ X. Furthermore, when applying thermal lens measurements at room temperature, it was found that there is a range of K 2 O concentration within the P 2 O 5 –Al 2 O 3 –Na 2 O–K 2 O glass system that becomes athermal. It was also observed that two glasses of the set exhibit athermality three times greater compared to the commercial athermal glass Q98, in terms of the parameter C TL (proportional do ds/dT) obtained from the thermal Lens. [ABSTRACT FROM AUTHOR]

Glyphosate detection and quantification is still a challenge. After an extensive review of the literature, we observed that Fourier transform infrared spectroscopy (FTIR) had practically not yet been used for detection or quantification. The interaction between zinc oxide (ZnO), silver oxide (Ag2O), and Ag-doped ZnO nanocrystals (NCs), as well as that between nanocomposite (Ag-doped ZnO/AgO) and glyphosate was analyzed with FTIR to determine whether nanomaterials could be used as signal enhancers for glyphosates. The results were further supported with the use of atomic force microscopy (AFM) imaging. The glyphosate commercial solutions were intensified 10,000 times when incorporated the ZnO NCs. However, strong chemical interactions between Ag and glyphosate may suppress signaling, making FTIR identification difficult. In short, we have shown for the first time that ZnO NCs are exciting tools with the potential to be used as signal amplifiers of glyphosate, the use of which may be explored in terms of the detection of other molecules based on nanocrystal affinity. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the properties of BioGlass, with and without doping with europium and silver, with a specific focus on its potential application in thermoluminescent (TL) and optically stimulated luminescent (OSL) dosimetry. The structural and optical characteristics of the samples were also analyzed using techniques such as X-ray diffraction (XRD), optical absorption (OA), and fluorescence spectroscopy (FL). An XRD analysis confirmed the amorphous phase of the BioGlass. OA and FL spectra were obtained at room temperature, and characteristic bands of dopant ions were observed which confirmed the incorporation of the Eu3+ ions and silver nanoparticles Ag(NP) ion into the BioGlass. The OSL decay curves exhibited a characteristic exponential behavior, with a notable presence of fast and medium decay components; this suggests that the charge traps within the BioGlass samples possess a high photoionization cross section when exposed to blue LEDs, which are commonly used as the light source in OSL readers. Different TL glow peaks with varying shapes of the glow curve were observed when the dopant, the co-dopant, and the concentration of silver were altered in the samples. The TL kinetic parameters were determined, such as the order value, activation energy, and frequency factor, and the OSL parameters for the compound were also analyzed, including an exponential fit to the curves. Based on these initial results, we conclude that BioGlass has the potential for use in radiation dosimetry. • BioGlass undoped and doped with europium and silver ions were evaluated. • The samples were characterized by XRD, OA and FL. • Dosimetric properties were investigated using TL and OSL techniques. • The BioGlass have promising characteristics for dosimetry. [ABSTRACT FROM AUTHOR]

In the current study, we work to acquire quantum dots from manganese-doped tin telluride (SnTe). Diluted Magnetic Semiconductor Sn 1-x Mn x Te QDs were successfully synthesized embedded in a glass matrix. Fusion and heat treatment time methods were used to form and grow the QDs. Transmission electron microscopy images showed that quantum dots with an average diameter of 5 nm formed in the glass matrix. The interplanar distances d hkl measured in TEM and the pattern observed in electron diffraction from the selected area confirms the SnTe semiconductor crystalline nature. Electron paramagnetic resonance spectra reveal six hyperfine lines for electronic transition +½ ↔ -½ resulting from Mn2+ ions in the crystal field. EPR spectra indicated Mn2+ ion incorporation in the core and surface of Sn 1-x Mn x Te QDs. The observed A 1 and E TO phonon modes and the blueshift/cm−1 in the Raman spectrum provide strong evidence for symmetry breaking and net polarizability established with xMn2+ ion doping in Sn 1-x Mn x Te QDs. • Formation of Sn1-xMnxTe QDs with size 5nm in glass matrix. • Substitutional MnSb doping at Oh crystal sites of the SnTe semiconductor. • Mn2+ ion incorporation in the core and surface of Sn1-xMnxTe QDs. • Symmetry breaking and net polarizability established in Sn1-xMnxTe QDs. • DMS Sn1-xMnxTe QDs designing new eco-friendly materials. [ABSTRACT FROM AUTHOR]

This study analyzed the optically simulated luminescence (OSL) of borate glasses containing lithium carbonate and potassium carbonate. Borate glasses present desirable characteristics for dosimetry and have been extensively analyzed in relation to thermoluminescence (TL). Five formulations containing 20% of Li 2 CO 3 and different amounts of B 2 O 3 and K 2 CO 3 were produced. Their OSL signal was analyzed following exposure to beta particles. The decay pattern typical of continuous wave stimulation (CW-OSL) was observed for all compositions. Depending on the parameter chosen to normalize the dose-response curve, the sensitivity range changed. If the initial OSL intensity was chosen as reference, the composition containing 65% B 2 O 3 and 15% K 2 CO 3 (named L15KB) presented the most intense signal. However, if the total area below the curve was considered, the composition containing 70% B 2 O 3 and 10% K 2 CO 3 (named L10KB) was the most sensitive. A comparison of the OSL decay for the two quoted compositions, after pre-heating to 200 °C for 10 s prior to the OSL readout, showed a slight change in the decay pattern compared to the absence of pre-heating. The pre-heating treatments also showed the correlation between the shallow traps and the fast component of the OSL decay for L15KB. For all compositions, an increase in dose implied an increase in emitted signal, and no saturation was observed between 0.1 Gy and 7 Gy. [ABSTRACT FROM AUTHOR]

This paper reports on the optical, morphological, structural and magnetic properties of Zn 1- x Cu x Te nanocrystals, doped with Cu ( x varying from 0.000 to 0.100) and grown by thermal annealing at 500 °C in a P 2 O 5 –ZnO–Al 2 O 3 –BaO–PbO glass system that had been synthesized by fusion. At higher levels of Cu-doping, optical absorption (OA) showed that Cu 2+ ions were incorporated within and dispersed throughout the lattice of the ZnTe semiconductor. The OA spectra also showed that the growth kinetics of these NCs were influenced by the Cu 2+ magnetic ions. Transmission electron microscopy (TEM) images revealed that the lattice parameter of the nanocrystals was not affected by the incorporation of Cu 2+ ions. Finally, electron paramagnetic resonance (EPR) spectra of the Cu 2+ ions showed asymmetrical hyperfine lines as well as proved a substitutive incorporation of Cu 2+ in ZnTe NCs. [ABSTRACT FROM AUTHOR]

CdS quantum dots (QDs) embedded in a phosphate glass matrix were investigated. The timeresolved Z-scan technique was used to determine the nonlinear refraction and absorption for different concentrations of CdS QDs. The results indicate that the nonlinear absorption presents a reverse saturable character, which is a desirable feature in the design of optical limiting devices. In addition, strong experimental evidence that the main contribution onto the refractive index variation is not of thermal origin was found. The observed variation presents a character similar to an electronic-like effect. These evidences are supported by numerical simulations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amoxicillin detection using electrochemical sensor modified with TiO 2 -1Co. • Drop casting approach over the carbon electrode for surface modification. • Simple strategy for the detection of the amoxicillin using an economical platform. • Voltammetric sensor was used to analysis of Amoxicillin in pharmaceutical samples. In this study, we propose the combination of stencil-printed carbon electrodes (SPCE) and a new nanocomposite based on titanium dioxide-cobalt (1.0 w/w %) (TiO 2 -1%Co) for the analysis of Amoxicillin (AMX) in pharmaceutical samples. The modification process by drop casting approach of the SPCE was performed with TiO 2 -1%Co and provided an increase in analytical sensitivity. Detailed morphological, structural, and electrochemical characterizations of the electrodes surface were investigated. The results obtained from characterization showed that the TiO 2 -1%Co nanocrystals were distributed on the surface of the carbon electrode. The detection of AMX (pH 7.0) was performed with square wave voltammetry using optimized conditions and resulted in a satisfactory linear response (R2 = 0.99) in the range of 20 to 150 μmol L−1, and the estimated limits of detection and quantification were 5.8 μmol L−1 and 19.5 μmol L−1, respectively. Repeatability studies (intra-day and inter-day) of modified electrodes revealed relative standard deviation values ranging from 5.8 to 8.1%. The selectivity of the proposed sensor indicated an acceptable interference (lower than 5%). Additionally, the results obtained with TiO 2 -1%Co/SPCE for real pharmaceutical samples were compared with UV–Vis Spectroscopy, and was possible to infer that the analytical responses were adequate concerning the labeled values, there are no statistical differences between the reference analysis and the proposed electrochemical method with a confidence level of 95%. The modified electrode offered some advantages such as a disposable sensor, low cost, low sample volume, high repeatability, and reproducibility. The proposed combination of SPCE modified with novel TiO 2 -1%Co nanocrystals is an attractive strategy for AMX analysis. [ABSTRACT FROM AUTHOR]

• Discrimination between thermal and populations effects. • Nonlinear optical properties of Nd/CdS phosphate glass matrix. • Third and fifth order optical nonlinearity. • Energy transfer between nd and CdS nanocrystals. In this work the nonlinear optical properties of a phosphate glass matrix doped with Nd3+and codoped with CdS nanocrystals have been investigated by the time-resolved Z-scan technique. Analyzing the transient signal, it was possible to discriminate the thermal effect from the populational effects on the nonlinear refraction and absorption, allowing the determination of the parameters n 2 ', n 2 " and n 4 '. The dependence of these parameters on the relative concentration of Nd and CdS was also investigated, and a linear increase of these parameters with the CdS absorption was observed. Evidence of energy transfer between Nd and CdS nanocrystals was investigated by the determination of the non-radiative decay rate through lifetime measurements monitoring the emission at 1064 nm referring to the transition 4F 3/2 ⟶ 4I 11/2 of the Nd3+. [ABSTRACT FROM AUTHOR]

Iron-doped bismuth sulphide (Bi2-xFexS3) nanocrystals have been successfully synthesized in a glass matrix using the fusion method. Transmission electron microscopy images and energy dispersive spectroscopy data clearly show that nanocrystals are formed with an average diameter of 7-9 nm, depending on the thermic treatment time, and contain Fe in their chemical composition. Magnetic force microscopy measurements show magnetic phase contrast patterns, providing further evidence of Fe incorporation in the nanocrystal structure. The electron paramagnetic resonance spectra displayed Fe3+ typical characteristics, with spin of 5/2 in the 3d5 electronic state, thereby confirming the expected trivalent state of Fe ions in the Bi2S3 host structure. Results from the spin polarized density functional theory simulations, for the bulk Fe-doped Bi2S3 counterpart, corroborate the experimental fact that the volume of the unit cell decreases with Fe substitutionally doping at Bi1 and Bi2 sites. The Bader charge analysis indicated a pseudo valency charge of 1.322|e| on FeBi1 and 1.306|e| on FeBi2 ions, and a spin contribution for the magnetic moment of 5.0 μB per unit cell containing one Fe atom. Electronic band structures showed that the (indirect) band gap changes from 1.17 eV for Bi2S3 bulk to 0.71 eV (0.74 eV) for Bi2S3:FeBi1 (Bi2S3:FeBi2). These results are compatible with the 3d5 high-spin state of Fe3+, and are in agreement with the experimental results, within the density functional theory accuracy. [ABSTRACT FROM AUTHOR]

P 2 O 5 – ZnO – Al 2 O 3 – BaO – PbO phosphate glass system, doped with Zn 1- x Mn x Te nanocrystals (NCs) and with Eu 2 O 3 (1 wt %) were successfully prepared. All samples were characterized with transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), optical absorption (OA), photoluminescence (PL) and lifetime. TEM images confirm the formation of Zn 1- x Mn x Te NCs and EPR spectra confirm the substitutional incorporation of Mn2+ ions in these NCs. The overlap between the Mn2+ ion emission band (4T 1 [4G] → 6A 1 [6S] transition) and the Eu3+ ion absorption bands (7F 0 → 5D 0,1) suggests energy transfer (ET) from Mn2+ to Eu3+ ions. This ET phenomenon has been confirmed by PL spectra and decay curves, since the doping with Eu 2 O 3 cause the decay of Mn2+ emission intensity when comparing with the emission of the Zn 0·99 Mn 0·01 Te sample, as well as of the 4T 1 (4G) state lifetime. These results indicate that the said glass system can be potential candidates for use in various technological applications. [Display omitted] • Growth of Mn2+ ion-doped ZnTe NCs (Zn 1- x Mn x Te samples) in a phosphate glass system using the fusion-nucleation method. • Energy transfer between Mn2+ and Eu3+ ions. • Influence of Mn concentration on the energy transfer process. • Nanostructures for technological applications. [ABSTRACT FROM AUTHOR]

Anthocyanins are the most important natural dye structure, which are contained in the orange-red-blue colors of several plants, fruits, vegetables and roots. Anthocyanins derived from ornamental plants have shown a higher degree of acylation that corresponds to a greater chemical stability. This work presents the absorption and fluorescence spectroscopic characterizations of a natural dye in the unpurified crude extracts from leaves of Tradescantia pallida purpurea. Anthocyanin dye extraction from the leaves was performed using different solvents (water, alcohol and acetone) and concentrations without further purification. The thermo-optical parameters, such as the thermal diffusivity ( D ), fractional thermal load ( φ ) and quantum yield ( η ), were determined. The η results in aqueous solutions were compared to those obtained for other dyes. [ABSTRACT FROM AUTHOR]

In this work was investigated the luminescence quantum efficiency, η , of Nd-doped phosphate glasses, as a function of temperature (298–438 K), using the normalized lifetime thermal lens technique. This system presents high quantum efficiency at low Nd 3+ concentration and at ambient temperature, 98%. In the temperature interval from 298 to 313 K, η , presents a decrease and then becomes constant until 393 K. Above this temperature it decrease again. This thermal quenching process was ascribed to thermally activated low energy phonons, associated to rocking motions of the corner-shared PO 4 tetrahedron cluster (order–disorder phase transformation), inducing changing on non-radiative transition that leave to a reduction of luminescence quantum efficiency at 298 and 393 K. From 313 to 393 K occurs a constant window of luminescence quantum efficiency in the PANK+ x Nd 3+ system. This assumption is supported by Differential Scanning Calorimetry and Raman measurements. [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) magic-sized quantum dots (MSQDs) are semiconductor nanocrystals with stable luminescence that are feasible for biomedical applications, especially for in vivo and in vitro imaging of tumor cells. In this work, we investigated the specific interaction of CdSe MSQDs with tumorigenic and non-tumorigenic cells using Langmuir monolayers and Langmuir–Blodgett (LB) films of lipids as membrane models for diagnosis of cancerous cells. Surface pressure-area isotherms and polarization modulation reflection-absorption spectroscopy (PM-IRRAS) showed an intrinsic interaction between the quantum dots, inserted in the aqueous subphase, and Langmuir monolayers constituted either of selected lipids or of tumorigenic and non-tumorigenic cell extracts. The films were transferred to solid supports to obtain microscopic images, providing information on their morphology. Similarity between films with different compositions representing cell membranes, with or without the quantum dots, was evaluated by atomic force microscopy (AFM) and confocal microscopy. This study demonstrates that the affinity of quantum dots for models representing cancer cells permits the use of these systems as devices for cancer diagnosis. [ABSTRACT FROM AUTHOR]

In this work measurements of photoluminescence quantum efficiency (η) in CdS nanocrystals embedded in phosphate glass matrix was performed using the thermal lens technique. The study was performed, using two different excitation wavelengths, in three samples with average sizes of 5.1, 6.3 and 6.7 nm and emission around 980 nm. The emission was strongly dominated by surface trap states. The photoluminescence quantum efficiency obtained was up to 60% for the smallest nanocrystals. It was also observed that η is independent of the excitation wavelength for each nanocrystal. • Study of photoluminescent properties of CdS NCs in a phosphate glass matrix. • An emission around 980 nm due to surface defects was observed on CdS NCs. • A Photoluminescence quantum efficiency of 60% was calculated for Cds NCs emission. • The Photoluminescence quantum efficiency value decreases with the size of the CdS NCs. [ABSTRACT FROM AUTHOR]

This work reports on the synthesis and characterization of Zn 1−x Mn x Te nanocrystals (NCs) with Mn doping concentration x varying from 0.000 to 0.800. Physical properties of samples were studied by transmission electron microscopy, magnetic force microscopy, vibrating sample magnetometry and electron paramagnetic resonance spectroscopy. Room temperature experiments revealed the size of NCs, the growth of magnetization and non-linear dependence of magnetic susceptibility on the concentration of Mn 2+ ions; samples with low concentrations revealed the presence of ions in the interior and near the surface of the NCs. The results obtained confirm the paramagnetic behavior of Zn 1−x Mn x Te NCs at room temperature. [ABSTRACT FROM AUTHOR]

The present work reports the spectroscopic and thermo-optical properties of CdSe/ZnS and CdSe/CdS core–shell quantum dots (QDs) embedded in synthetic saliva. Spectroscopy studies were performed applying nonfunctionalized CdSe/ZnS QDs (3.4, 3.9 and 5.1 nm cores) and hydroxyl group-functionalized ultrasmall CdSe/CdS core–shell quantum dots (1.6 nm core) suspended in artificial saliva at different potential of hydrogen (pH) values. Saliva was chosen because it is important in a variety of functions such as protecting teeth through the buffering capacity of the formed biofilm, hydration, and dental remineralization. Thermo-optical characterizations using the thermal lens (TL) technique were performed in QD-biofluids for different QD sizes and pH values (3.9–8.3) of the synthetic oral fluids. Transient TL measurements were applied to determine the fluorescence quantum efficiency ( η ) in QD-biomaterial systems. High η value was obtained for ultrasmall CdSe/CdS QDs. Fluorescence spectral measurements of the biomaterials support the TL results. In addition, for nonfunctionalized (3.4 and 5.1 nm) and hydroxyl group-functionalized QDs, the temporal behavior of the fluorescence spectra was accomplished about approximately 1200 h at two different biofluid pH values (3.9 and 8.3). The temporal fluorescence intensity result is dependent on the pH of the saliva in which the QDs were embedded, QD functionalization and QD sizes. The time for an approximately 50% decrease in the peak intensity fluorescence of CdSe/ZnS QDs (3.4 nm core) and ultrasmall CdSe/CdS QDs is respectively 25 h and 312 h at pH 3.9 and 48 h and 360 h at pH 8.3. [ABSTRACT FROM AUTHOR]

• Eu-doped Li 2 O - B 2 O 3 −Al 2 O 3 glasses and glass ceramic were synthesized. • The calculated Judd-Ofelt intensity parameters of these media were ~ 10−20 cm−1. • The glass ceramic showed greater emission intensity than the precursor glass. • They are efficient probes for optical thermometry using peak-valley ratio method. • Nearly constant relative sensitivity was obtained over a wide temperature range. [Display omitted] In this work, lithium-boron-aluminum (LBA) glasses doped with Eu3+ were produced by the traditional melting method. These precursor glasses (PG) were heat treated at 400 and 450 °C for 6 h to produce glass-ceramics (GC). The X-ray diffraction measurements showed the formation of a crystalline phase. In the LBA GCs, crystal growth is nucleated at the surface and an increase in the emission intensity of the heat-treated glasses compared with the PG was observed. Spectral analysis of the luminescence indicated that Eu3+ occupies low-symmetry site (asymmetry ratio ≈ 4) and without an inversion center. The emission spectra were analyzed using Judd-Ofelt theory and the intensity parameters Ω 2 , Ω 4 and Ω 6 were calculated. The values of these parameters were not significantly affected by the heat treatment process. The application of these materials as optical temperature sensors using the valley-peak intensity ratio (VPIR) was investigated using the multi-peak spectral profile of the 5D 0 → 7F J luminescence bands of Eu3+. We estimated the relative sensitivity, the figure-of-merit of the thermometer, to be as high as 0.40 ± 0.02% K−1. Interestingly, some VPIR that were explored presented a constant value for the relative sensitivity across the temperature interval used in our experiment (between 312 and 393 K), which is advantageous for sensor operation over a broad temperature range. [ABSTRACT FROM AUTHOR]

Highlights: [•] ZnTe NCs were successfully grown in a host glass matrix synthesized by fusion. [•] Three groups of different-sized NCs (QD1, QD2 and bulk-like NCs). [•] Dynamics in the excitonic states (QDs) and the conduction band (bulk-like NCs). [•] Desirable properties for applications in opto-electronic devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] CdSe/CdS magic-sized quantum dots were synthesized in aqueous solutions. [•] Quantum dots were functionalized with carboxyl or hydroxyl groups. [•] AFM and FTIR techniques were applied for quantum dots characterization. [•] Thermo-optical characterizations were performed in magic-sized quantum dots. [•] High radiative quantum efficiency values for the quantum dots were obtained. [Copyright &y& Elsevier]

The structural and optical properties of the TiO 2 nanocrystals (NCs) samples pure and doped with Nd3+ ions were studied as a function of temperature. These properties were studied by using the Raman spectroscopy, steady-state and time-resolved photoluminescence. A structural transformation is observed by a systematic study as a function of the temperature from room temperature. The results show that the introduction of Nd3+ ions and the increase of temperature induces a phase transformation from anatase to brookite. As a result, the intrinsic defects states of TiO 2 NCs decrease and consequently the PL intensity of the 4F 3/2 level of Nd3+ ions increases. The photoluminescence decay kinetics also shows that Nd3+ ions are located in two different environments of TiO 2 NCs: the brookite and anatase phase. • Effect of Nd on the structural and optical properties of TiO 2 NCs. • The temperature and Nd addition change the TiO 2 phase from anatase to brookite. • Raman spectroscopy shows an increase of brookite phase on the Nd:TiO 2 NCs. • Photoluminescence dynamics confirms that the Nd ions are in two environments in the sample. [ABSTRACT FROM AUTHOR]

The thermal and structural properties of a Li 2 O ⋅ B 2 O 3 ⋅ Al 2 O 3 glass matrix with the addition CaF 2 or LiF were investigated by XRD and DTA. The results showed that the samples are glasses. The thermal analysis also showed a trend of the glass transition temperature shifting to lower temperatures, and the shift or new peaks of crystallization is observed as the LiF and CaF 2 content goes up. The glass-forming tendency (GFT), thermal stability (TS) and the Reduced glass transition temperature (T gR) are discussed as a function of composition and results indicate that this parameters are highly sensitive to different compositions. • XRD measurements show that all samples are amorphous. • The thermal analysis shows the shift of the glass transition as a function of added fluoride. • ΔT is maximum for the samples LBA + 15LiF and LBA + 30CaF 2. • K H is maximum for the samples LBA + 15LiF and LBA + 20CaF 2. [ABSTRACT FROM AUTHOR]

Zinc Oxide (ZnO) and simonkolleite (SM) have been extensively studied separately in several technological applications. However, the cytotoxicity of SM has not yet been investigated, nor has the synergism between SM and ZnO. In this work, we investigated both the synergism of SM with ZnO in the physico-chemical properties and cytotoxicity in breast cancer cells. The physical characterization confirmed that with the increase of the annealing temperature, the transformation of SM into ZnO occurs and further investigated how photocatalytic performance and cytotoxicity were changed. The photocatalytic performance of ZnO was the highest (80%) in contrast to SM and the SM/ZnO nanocomposite (NCT), had no photocatalytic activity. Cytotoxicity was investigated using the MCF-10A, MCF-7, and MDA-MB-231 tumor cell lines. SM resulted in a high incidence of cell death at a high concentration and induced the production of reactive oxygen species at a low concentration. ZnO and NCT were observed to have the expected effect regarding cytotoxicity, and the induction of reactive oxygen species was much higher than with SM. The biological ROS results were in excellent agreement with the photocatalytic performance, demonstrating that the mechanism of the antitumor effect of SM does not occur predominantly via ROS. Therefore, in this work, we demonstrate how the physico-chemical and biological properties are changed due to the synergism of SM and ZnO. [Display omitted] • Transformation of simonkolleite into zinc oxide occurs with thermal annealing. • Physico-chemical properties and cytotoxicity in breast cancer cells were investigated. • Photocatalytic performance of ZnO was the highest (80%), but SM and nanocomposite had no. • Higher cytotoxicity in the MCF-7 cell line by simonkolleite was observed. • Mechanism of the antitumor effect of simonkolleite does not occur predominantly via ROS. [ABSTRACT FROM AUTHOR]

In this work, a study of the optical and structural properties of a phosphate glass (P 2 O 5 -Al 2 O 3 -Na 2 O-K 2 O) doped with cadmium sulfide (CdS) nanocrystals and co-doped with Nd3+ ions produced by the fusion method was carried out. This study was conducted by analyzing the Optical absorption, Photoluminescence (PL) spectra, Time-resolved PL decay curves, and Raman spectroscopy measurements. The growth of the CdS nanocrystal was confirmed by the optical absorption spectra, Transmission Electron Microscopy, and Raman spectroscopy, which also indicates the presence of surface defect states. After Nd doping, PL spectra show an energy transfer process between the CdS nanocrystal and the Nd3+ ions. This process decreases with the nanocrystal size and can be eliminated by tuning the excitation wavelength. In addition, the influence of the CdS nanocrystal size on the Nd emission lifetime and luminescence quantum efficiency was studied in two different excitations (405 and 532 nm). This kind of system has the potential to work as optoelectronic devices, such as laser active media, optical amplifiers, and planar waveguides due to near-infrared emission of the Nd3+ ions. ga1 • Study of the optical and structural properties of PANK glass system with Nd and CdS NC. • The NC size affects the energy transfer between CdS NCs and Nd3+ ions. • The luminescence dynamics confirms that the Nd ions are into the glass and NC sites. • By indirect excitation, the luminescence quantum efficiency of Nd ion change with CdS NC size. [ABSTRACT FROM AUTHOR]

In this work, we synthesized the phosphate glass pure and doped with erbium ions (Er3+) and investigated the effect of the controlled atmosphere and fluoride incorporation on the optical properties of Er3+ ions using the Judd-Ofelt theory. The PAN and PANK glass matrices with nominal compositions 60P 2 0 5 - 10Al 2 O 3 - 30Na 2 O (mol%) and 40P 2 O 5 - 20Al 2 O 3 - 35Na 2 O - 5K 2 O (mol%), pure and doped with Er 2 O 3 and co-doped with LiF and CaF 2 , were synthesized by the fusion method in atmosphere in the air (NA) and controlled atmosphere (CA). The optical properties were investigated by optical absorption (AO), photoluminescence (PL) and temporal resolution photoluminescence (TRPL). The Judd-Ofelt theory was applied to determine the spectroscopic properties of Er3+ ions. The lifetime and quantum efficiency of the transition 4I 13/2 → 4I 15/2 were analyzed as a function of the atmosphere and addition of fluorides. The hydroxyl density (OH−) is determinant to the spectroscopic parameters of Er3+ inserted in the PAN and PANK glass matrices, and that it can be reduced both synthesized in CA and when adding LiF or CaF 2. We found that the quantum efficiency of the transition4I 13/2 → 4I 15/2 was higher using the LiF doping methodology, and highest using together with CA, around 94%. Thus, the glass matrices synthesized with LiF and CA showed the best results. However, due to the high cost of synthesis using CA, we recommend only the use of fluorides in the matrices, since it presented close results. Interestingly, the PAN:Er matrix, which presented the worst optical results, with the incorporation of LiF and CA presented a quantum efficiency of 88% relatively high compared to other works in the literature. • The hydroxyl density (OH) can be reduced both synthesized in controlled atmosphere and when adding LiF or CaF 2. • Quantum efficiency of 94% using the LiF together with AC. • The Judd-Ofelt intensity parameters are changed with co-doped fluorides and controlled atmosphere. [ABSTRACT FROM AUTHOR]

• Growth of Ni2+ ion-doped ZnTe NCs (Zn 1- x Ni x Te samples) in a glass system using the fusion-nucleation method. • Effect of Ni concentration on the ZnTe NCs local crystalline field. • Nanostructures for technological applications. • Simultaneous use of spin, electronic and optical properties. In this work, we report the study of Zn 1- x Ni x Te nanocrystals in a glass matrix, synthesized by a new protocol based on the fusion-nucleation method. Optical absorption spectra, analyzed based on the crystalline field theory, confirm the substitutional incorporation of Ni2+ ions in the ZnTe semiconductor lattice with tetrahedral symmetry. Transmission electron microscopy images show invariance in the lattice parameter of these nanocrystals, with the incorporation of Ni2+ ions. Electron paramagnetic resonance spectra display resonance lines that confirm the substitutional incorporation (g = 2.0991) and also the presence of Ni2+ ions at Zn vacancy sites (g ≈ 2.0023) of the ZnTe lattice. [ABSTRACT FROM AUTHOR]

Semimagnetic chalcogeneide Pb 1-x Mn x S nanocrystals were grown in borosilicate glass host and their optical, structural and magnetic properties were investigated. Transmission electron microscopy images confirms the growth of the Pb 1-x Mn x S nanocrystals. Uv–Vis-Nir spectroscopy measurements of these nanocrystals revealed band-gap shifting from 0.94 eV (1307 nm) to 1.12 eV (1111 nm), which was attributed to the incorporation content (x) of Mn2+ ions in the typical PbS rock salt crystal structure. EPR data shows the six hyperfine lines assigned to the Mn2+ ions incorporated into the host crystal structure of PbS nanocrystals. The Photoluminescence obtained at 20k was analyzed and shows an anomalous increase in emission efficiency considering carrier transfer for Pb 1-x Mn x S nanocrystals with different sizes. • Mn2+-doped PbS nanocrystal were growth in glass matrix by fusion and thermal annealing. • Physical properties of nanocrystals with different sizes and dispersions. • sp-d exchange interaction of according to the annealing time and Mn concentration. [ABSTRACT FROM AUTHOR]

• Cr3+-doped Bi 2 S 3 nanocrystals were growth in borosilicate host glass. • Optical and structural properties of Bi 2−x Cr x S 3 are investigated for x = 0, 3 and 8%. • Unit cell's volume decreases with Cr doping at the Bi1 and Bi2 sites. • Band gap changes from Bi 2 S 3 bulk for Bi 2 S 3 :Cr Bi1 (Bi 2 S 3 :Cr Bi2). • Exchange interaction sp-d between Bi 2 S 3 and Cr3+-ions. The optical and structural properties of Cr-doped Bi 2 S 3 nanocrystals embedded in host glass were investigated. Transmission electron microscopy images and energy dispersive X-ray spectroscopy confirm the formation of the Bi 2−x Cr x S 3 nanocrystals and the presence of the Bi, S and Cr elements. Raman spectroscopy reveal changes of structural crystalline in function of x Cr -concentration in Bi 2−x Cr x S 3 nanocrystals. Ultraviolet and visible spectra reveal the effects of quantum confinement with the change in size of nanocrystals. Optical properties of Cr-doped Bi 2 S 3 nanocrystals are different in relation non-doped Bi 2 S 3 nanocrystals. Density functional theory simulations were carried out for bulk undoped and Cr-doped Bi 2 S 3. The unit cell volume reduces with Cr-doping, and the indirect band gap decreases from 1.17 eV (Bi 2 S 3 undoped) to 0.67 eV for Bi 2 S 3 :Cr Bi1 and 0.43 eV for Bi 2 S 3 :Cr Bi2. For both Cr-doped structures, a spin contribution to the magnetic moment of 3.0 µ B per unit cell containing one Cr atom were obtained. Within the density functional theory accuracy, these results are in agreement with the experimental results for the 3d3 high-spin state of Cr3+. [ABSTRACT FROM AUTHOR]

P 2 O 5 –Al 2 O 3 –Na 2 O–K 2 O phosphate glasses with various K 2 O/Al 2 O 3 ratios were synthesized using the melt quenching technique. Raman and absorption spectra were measured to investigate the effects of these ratios on the structures and spectroscopic properties of the glasses. As the K 2 O/Al 2 O 3 ratio increases, the Raman spectra show shifts of some of the scattering bands to lower wavenumbers, the broadening of some bands and the tendency of decreasing the overlap between them, especially in the regions 400-700 cm−1 and 850-1300 cm−1. On the other hand, the absorption spectra of these phosphate glasses showed no marked changes in the optical band gap energy. Also, optical and thermal properties were measured to evaluate their potential for athermalization. As the ratio K 2 O/Al 2 O 3 increases, the refractive index and glass transition temperature decrease, while the thermal expansion coefficient (α) increases. The existence of a negative thermo-optic coefficient (d n /dT) is important to obtain the temperature coefficient of the optical path (ds/dT) equal to −0.06·10−6/K for PAN10K glass. The results showed that increasing the K 2 O/Al 2 O 3 ratio in phosphate glasses can control the value of ds/dT to achieve the athermalization. • Fabry-Perót and Mach-Zehnder interferometers were used to measure α and d n /dT. • α and d n /dT were obtained for the phosphate glasses system changing the K 2 O/Al 2 O 3 ratio. • An athermal behavior in the glass system was observed changing the K 2 O/Al 2 O 3 ratio. [ABSTRACT FROM AUTHOR]

The effect of Cr co-doping on the optical properties of Mn-doped ZnTe nanocrystals (NCs) embedded in a glass matrix is studied in this paper. The substitutional incorporation of Cr2+ ions into these semiconducting NCs was strongly evidenced by optical absorption and crystal field theory analyses, which showed the characteristic transitions of Cr2+ and Cr3+ ions. Transmission electron microscopy images revealed the NC size and invariance lattice parameter, with the incorporation of Mn2+ and Cr2+ ions. PL spectra showed that co-doping with Cr favors a competition between Mn2+ and Cr2+ ions, resulting in a decrease in the rate of Mn2+ substitution, zinc vacancy filling (VZn) in Zn1−x−yMnxCryTe NCs, and the formation of interstitial Cr3+ ions in the host glass system. [ABSTRACT FROM AUTHOR]