Luminescence characterization of BioGlass undoped and doped with europium and silver ions.

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.

Obtaining the spectroscopic quality factor through the luminescent thermometry in 50Li2O · 45B2O3 · 5Al2O3 glasses doped with Nd3+ and fluorides.

Lithium-boron-aluminum (LBA) glasses doped with N d 3+ and fluorides were produced. From the absorption spectra, their Judd-Ofelt intensity parameters, Ω 2,4,6, and spectroscopic quality factors were calculated. Exploiting their near infrared temperature dependent luminescence, we investigated their potential for optical thermometry based on the luminescence intensity ratio (LIR) methodology. Three LIR schemes were proposed, and relative sensitivity values up to 3.57±0.06% K -1 were obtained. From the temperature dependent luminescence, we alternatively calculated their corresponding spectroscopic quality factors. The results indicated that N d 3+-doped LBA glasses are promising systems for optical thermometry and as gain mediums for solid-state lasers.

Zn[Formula: see text]Ni[Formula: see text]Te semiconductor nanocrystals in transparent glass for optoelectronic device applications.

Doping glass with semiconductors, particularly with nanostructured semiconductors, has attracted attention due to the large optical absorption cross-sections of the latter. Based on this property, Ni[Formula: see text] (5 wt%) doped phosphate glass and Zn[Formula: see text]Ni[Formula: see text]Te (x = 0.5, 1.0, 5.0 and 10.0 wt% of Ni[Formula: see text]) nanocrystals (NCs) doped phosphate glasses (GCs) were prepared by fusion method and subsequent heat treatment. Influence of Ni[Formula: see text] on structural, thermo-optical and third-order nonlinear optical properties have been analysed through various spectroscopic characterizations. The XRD pattern of the glass (G) exhibits the amorphous nature of the host material while GCs exhibit not only amorphous halo but also the presence of quantum dots (QDs) or nanocrystals (NCs) phases. TEM analysis of the studied GCs samples confirm the presence of quantum dots (QDs) and bulk NCs with an average diameter of approximately 4.2 [Formula: see text] 0.3 nm and 13.4 [Formula: see text] 0.2 nm, respectively. Several phosphate groups were observed and reported from Raman and FTIR-ATR spectra. The absorption band positions confirmed that Ni[Formula: see text] ions resemble to the octahedral symmetry. The intensity of absorption band around 1352 nm ([Formula: see text]T[Formula: see text](F) [Formula: see text] [Formula: see text]A[Formula: see text](F)) increased with the increase of Ni[Formula: see text] in GCs which is an indicative of the [Formula: see text]Ni[Formula: see text] coordination. The emission properties such as emission cross-sections ([Formula: see text]) full width at half maxima (FWHM) for the [Formula: see text]T[Formula: see text](D) [Formula: see text] [Formula: see text]T[Formula: see text](F) (visible) and [Formula: see text]A[Formula: see text](F) [Formula: see text] [Formula: see text]T[Formula: see text](F) (near-infrared) emission transitions were reported. Among the glass-containing semiconductor nanocrystals (GCs), the emission cross-sections in GC4 sample (x = 10% of Ni[Formula: see text]) are the largest for both the visible (11.88 [Formula: see text] 10[Formula: see text] cm[Formula: see text]) and infrared (0.98 [Formula: see text] 10[Formula: see text] cm[Formula: see text]) transitions. Thermal diffusivity (D), thermal conductivity (K) and temperature dependent optical path length change (ds/dT) were obtained through time-resolved thermal lens (TL) and thermal relaxation (TR) methods. The D and K parameters do not change significantly with increase of Ni[Formula: see text] ions (0.5-5%) in GCs. Nonlinear-refractive index and nonlinear absorption of the studied samples were also obtained using femtosecond Z-scan technique. The increase of nonlinear absorption coefficient ([Formula: see text]) is observed from GC2 (2.53 [Formula: see text] 10[Formula: see text] cm/W) to GC4 (7.98 [Formula: see text] 10[Formula: see text] cm/W). The GC4, sample with 10 wt% of Ni[Formula: see text], showed the lowest ds/dT (1.22 [Formula: see text] 10[Formula: see text] K[Formula: see text]) with good lasing (FOM and emission cross-sections) and nonlinear absorption properties suggesting that it can be a good candidate for visible-red emission light conversion in LED technology.

TiO2 Nanocrystals and Annona crassiflora Polyphenols Used Alone or Mixed Impact Differently on Wound Repair.

Wounds treated with TiO2 nanoparticles (TiO2-NPs) show an improvement in healing time. However, little is known about the parameters that can contribute to this result. On the other hand, the treatment of wounds with polyphenols is widely known. These compounds are found in the peel of Annona crassiflora fruit and have antioxidant, analgesic and anti-inflammatory properties. In this study, we evaluated the healing effect of TiO2 nanocrystals (TiO2-NCs), polyphenolic fractions obtained from ethanolic extract of A. crassiflora fruit peel (PFAC) and mix (PFAC + TiO2-NCs) on the parameters of wound closure, inflammation, collagen deposition, metalloproteinase activity (MMPs) and angiogenesis. TiO2-NCs and PFAC have activity for wound healing, showed anti-inflammatory action and a shorter wound closure time. These treatments also contributed to increased collagen deposition, while only treatment with TiO2-NCs increased MMP-2 activity, parameters essential for the migration of keratinocytes and for complete restoration of the injured tissue. The combination of PFAC + TiO2-NCs reduced the effectiveness of individual treatments by intensifying the inflammatory process, in addition to delaying wound closure. We conclude that the interaction between the hydroxyl groups of PFAC polyphenols with TiO2-NCs may have contributed to difference in the healing activity of skin wounds.

Application of ZnO Nanocrystals as a Surface-Enhancer FTIR for Glyphosate Detection.

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.

Development of an Electrochemical Immunosensor for Specific Detection of Visceral Leishmaniasis Using Gold-Modified Screen-Printed Carbon Electrodes.

Visceral leishmaniasis is a reemerging neglected tropical disease with limitations for its diagnosis, including low concentration of antibodies in the serum of asymptomatic patients and cross-reactions. In this context, this work proposes an electrochemical immunosensor for the diagnosis of visceral leishmaniasis in a more sensitive way that is capable of avoiding cross-reaction with Chagas disease (CD). Crude Leishmania infantum antigens tested in the enzyme-linked immunosorbent assay (ELISA) were methodologically standardized to best engage to the sensor. The antibodies anti-Trypanosoma cruzi and anti-Leishmania sp. Present in serum from patients with diverse types of CD or leishmaniasis were chosen. A screen-printed carbon electrode modified with gold nanoparticles was the best platform to guarantee effective adsorption of all antigens so that the epitope of specific recognition for leishmaniasis occurred efficiently and without cross-reaction with the evaluated CD. The current peaks reduced linearly after the recognition, and still were able to notice the discrimination between different kinds of diseases (digestive, cardiac, undetermined Chagas/acute and visceral chronic leishmaniasis). Comparative analyses with ELISA were performed with the same groups, and a low specificity (44%) was verified due to cross-reactions (high number of false positives) on ELISA tests, while the proposed immunosensor presented high selectivity and specificity (100%) without any false positives or false negatives for the serum samples from isolated patients with different types of CD and visceral leishmaniasis. Furthermore, the biosensor was stable for 5 days and presented a detection limit of 200 ng mL-1.

In vitro tracking of phospholipase A2 from snake venom conjugated with magic-sized quantum dots.

Phospholipases A2 represent a family of enzymes with important application in medicine. However, direct tracking is difficult due to the absence of a stable, effective and specific marker for these enzymes. Magic-sized quantum dots (MSQDs) are inorganic semiconducting nanocrystals with unique physical properties. They have the ability to conjugate to proteins, making them excellent markers for biological systems. In this work, we labelled phospholipase A2 from Bothrops alternatus snake venom with Cadmium selenide (CdSe)/cadmium sulphate (CdS) MSQDs-a biocompatible and luminescent probe-. Bioconjugation was confirmed using infrared spectra and fluorescence microscopy, which demonstrated that the CdSe/CdS MSQDs interact with phospholipase A2 without interfering with its activity. This probe may be an important tool for the elucidation of many biological mechanisms, because it allows the pathway of phospholipase A2 to be tracked from its entry through the plasma membrane until its incorporation into the nucleus of myoblasts.

Synthesis and Study of Fe-Doped Bi2S3 Semimagnetic Nanocrystals Embedded in a Glass Matrix.

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.

Effect of Co co-doping on the optical properties of ZnTe:Mn nanocrystals.

We study the effect of Co co-doping on the optical properties of Mn-doped ZnTe nanocrystals (NCs) embedded in a glass matrix. Optical absorption (OA) and crystal field theory strongly indicated the substitutional incorporation of Co2+ ions into these semiconducting NCs as well as the characteristic transitions of these ions in the visible and near infrared spectral region. Transmission electron microscopy (TEM) images revealed an invariant NC lattice parameter with the incorporation of Mn2+ and Co2+ ions. The same was confirmed by X-ray diffraction (XRD). The photoluminescence (PL) spectra showed that the characteristic emission bands of Co2+ ions (E1Co2+ and E2Co2+) are intense and evident at low temperatures. Indeed, Raman spectra showed that the dependence of luminescence intensity on temperature is due to the electron-phonon interaction that arises from multiphonon relaxation processes. The redshifts in the PL spectra from green to orange with the incorporation of Mn2+ ions into ZnTe NCs, and in the near infrared with increasing Co-concentration, result from sp-d exchange interactions associated with the increase in Mn2+ and Co2+ ions in tetrahedral sites of ZnTe NCs, which may be very interesting for applications in luminescent devices. These observations provide strong evidence that higher Co-concentrations inhibit the incorporation of Mn2+ into ZnTe NCs, suggesting that there may be competition between Co2+ and Mn2+ ions substituting Zn2+ ions and, furthermore, that these ions replace zinc vacancies (VZn) in these NCs.

Tunable dual emission in visible and near-infrared spectra using Co(2+)-doped PbSe nanocrystals embedded in a chalcogenide glass matrix.

Semimagnetic Pb1-xCoxSe nanocrystals were synthesized by a fusion protocol in a glass matrix and characterized by optical absorption (OA), transmission electron microscopy (TEM), and photoluminescence (PL) techniques. OA spectra and TEM images strongly indicated the formation of Pb1-xCoxSe magnetic phases in the glass system and the quantum dot size was manipulated by tuning the annealing time. The OA spectra together with crystal field theory indicate that Co(2+) is located in the tetrahedral site (Td) and the PL of the Pb1-xCoxSe nanocrystals presents characteristic recombination in the visible (∼700 nm) and near-IR (1300-1600 nm) electromagnetic spectral range. With temperature decreasing, the PL spectra, in the visible spectral range, indicate an excited-state crossover yielding PL changes from (4)T1(P) → (4)A2(F) broadband emission to (2)E(G) → (4)A2(F) narrow-line emission. This phenomenon was explained on the basis of a configurational energy model. The OA and PL spectra of PbSe:Co(2+) indicate that the localized energy transition of Co(2+) ((4)A2(F) ↔ (4)T1((4)F)) can be tuned from the band-gap energy to the conduction-band energy of PbSe NCs by changing the NC size by increasing the thermal annealing time. In the near-IR spectral range, the temperature-dependent PL spectra show that the process of thermal activation of localized electrons in Co(2+) states can be transferred to the conduction band of the NCs. This process depends on the energy distance between extended and localized states, which can be controlled by the sample annealing time.

CdSe magic-sized quantum dots incorporated in biomembrane models at the air-water interface composed of components of tumorigenic and non-tumorigenic cells.

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.

Mn concentration-dependent tuning of Mn(2+) d emission of Zn1-xMnxTe nanocrystals grown in a glass system.

We studied the effect of Mn concentration on the optical, morphological and magnetic properties of Zn1-xMnxTe NCs grown in a glass matrix produced by the fusion method. The physical properties of these materials were determined by optical absorption (OA), transmission electron microscopy (TEM), atomic/magnetic force microscopy (AFM/MFM) and photoluminescence (PL). An analysis of the OA spectra, based on the crystal field theory (CFT), showed strong evidence that Mn(2+) ions were substitutionally incorporated into the Zn1-xMnxTe NCs until reaching the solubility limit (concentration, x = 0.100). Above this nominal concentration, TEM showed the onset of Mn-related phases, such as MnO and α-MnO2, in the PZABP glass system. AFM images showed that NC density on the surface of the glass matrix decreased as x-content increased. It is probable that MnO and MnO2 NCs would outnumber Zn1-xMnxTe NCs at higher concentrations - a conclusion that was corroborated by the OA spectra and TEM images. MFM images revealed that samples with Mn(2+) ions responded to magnetization from an MFM probe. This implied that Mn(2+) ions were incorporated within the Zn1-xMnxTe NCs and gave rise to the diluted magnetic semiconductor (DMS) structure. The PL spectra not only confirmed the evidence obtained by OA, CFT, TEM and AFM/MFM, but also showed that Mn(2+) concentration could be used to tune (4)T1((4)G) → (6)A1((6)S) emission energy.

Optical characterization of core-shell quantum dots embedded in synthetic saliva: Temporal dynamics.

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.

Shell thickness modulation in ultrasmall CdSe/CdS(x)Se(1-x)/CdS core/shell quantum dots via 1-thioglycerol.

In this study, we report on the synthesis of CdSe/CdS core-shell ultrasmall quantum dots (CS-USQDs) using an aqueous-based wet chemistry protocol. The proposed chemical route uses increasing concentration of 1-thioglycerol to grow the CdS shell on top of the as-precipitated CdSe core in a controllable way. We found that lower concentration of 1-thioglycerol (3 mmol) added into the reaction medium limits the growth of the CdSe core, and higher and increasing concentration (5-11 mmol) of 1-thioglycerol promotes the growth of CdS shell on top of the CdSe core in a very controllable way, with an increase from 0.50 to 1.25 nm in shell thickness. The growth of CS-USQDs of CdSe/CdS was confirmed by using different experimental techniques, such as optical absorption (OA) spectroscopy, fluorescence spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Data collected from OA were used to obtain the average values of the CdSe core diameter, whereas Raman data were used to assess the average values of the CdSe core diameter and CdS shell thicknesses.

Evidence of phase transition in Nd3+ doped phosphate glass determined by thermal lens spectrometry.

Thermal lens spectroscopy (TLS), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) techniques were applied to the thermo-optical property analysis of a new phosphate glass matrix PANK with nominal composition 40P2O5·20Al2O3·35Na2O·5K2O (mol%), doped with different Nd(3+) compositions. This glass system, synthesized by the fusion protocol, presents high transparency from UV to the near infrared, excellent thermo-optical properties at room temperature and high fluorescence quantum efficiency. Thermal lens phase shift parameters, thermal diffusivity and the DSC signal present pronounced changes at about 61 °C for the PANK glass system. This anomalous behavior was associated with a phase transition in the nanostructured glass materials. The FTIR signal confirms the presence of isolated PO4 tetrahedron groups connected to different cations in PANK glass. As a main result, our experimental data suggest that these tetrahedron groups present a structural phase transition, paraelectric-ferroelectric phase transition, similar to that in potassium dihydrogen phosphate, KH2PO4, nanocrystals and which TLS technique can be used as a sensitive method to investigate changes in the structural level of nanostructured materials.

Dendrimer-carbon nanotube layer-by-layer film as an efficient host matrix for electrogeneration of PtCo electrocatalysts.

In this paper we demonstrate that layer-by-layer (LbL) films of polyamidoamine (PAMAM) dendrimers and single-walled carbon nanotubes (SWCNTs) are efficient for controlling the morphology of electrogenerated cobalt (Co) and the platinum-cobalt (PtCo) alloy. While Co grew to the micrometer scale and poorly covered the ITO substrate, with the LbL matrix it was kept in the nanoscale regime and provided full substrate coverage. Pt-decorated Co nanoparticles were then generated by applying a single potential pulse in a solution containing simultaneously Co and Pt ions. Segregation of Pt and Co deposits was observed in field emission gun (FEG) images, but the PtCo alloy was probably formed to some extent according to X-ray diffraction analysis. The PtCo-LbL hybrid exhibited superior catalytic activity toward H2O2 reduction compared to the Pt-modified LbL film, which opens new prospects for applications in biosensing and fuel cells.

Electrogeneration of platinum nanoparticles in a matrix of dendrimer-carbon nanotubes.

Hybrid materials with enhanced properties can now be obtained by combining nanomaterials such as carbon nanotubes and metallic nanoparticles, where the main challenge is to control fabrication conditions. In this study, we demonstrate that platinum nanoparticles (PtNps) can be electrogenerated within layer-by-layer (LbL) films of polyamidoamine (PAMAM) dendrimers and single-walled carbon nanotubes (SWCNTs), which serve as stabilizing matrices. The advantages of the possible control through electrogeneration were demonstrated with a homogeneous distribution of PtNps over the entire surface of the PAMAM/SWCNT LbL films, whose electroactive sites could be mapped using magnetic force microscopy. The Pt-containing films were used as catalysts for hydrogen peroxide reduction, with a decrease in the reduction potential of 60 mV compared to a Pt film deposited onto bare ITO. By analyzing the mechanisms responsible for hydrogen peroxide reduction, we ascribed the enhanced catalytic activity to synergistic effects between platinum and carbon in the LbL films, which are promising for sensing and fuel cell applications.

Electrodeposition of catalytic and magnetic gold nanoparticles on dendrimer-carbon nanotube layer-by-layer films.

Magnetic and catalytic gold nanoparticles were electrodeposited through potential pulse on dendrimer-carbon nanotube layer-by-layer (LbL) films. A plasmon absorption band at about 550 nm revealed the presence of nanoscale gold in the film. The location of the Au nanoparticles in the film was clearly observed by selecting the magnetic force microscopy mode. To our knowledge, this is the first report on the electrochemical synthesis of magnetic Au nanoparticles. In addition to the magnetic properties, the Au nanoparticles also exhibited high catalytic activity towards ethanol and glycerol oxidation in alkaline medium.

Growth kinetic on the optical properties of the Pb(1-x)Mn(x)Se nanocrystals embedded in a glass matrix: thermal annealing and Mn2+ concentration.

Semimagnetic Pb(1-x)Mn(x)Se nanocrystals were synthesized by a fusion method in a glass matrix and characterized by optical absorption (OA), atomic/magnetic force microscopy (AFM/MFM), and photoluminescence techniques. MFM images strongly indicated the formation of Pb(1-x)Mn(x)Se magnetic phases in the glass system. Quantum dot size was manipulated by tuning annealing time. It was shown that Mn(2+) impurity affects nucleation, where Mn(2+)-doped samples present a redshift of the OA peak after a short annealing time and a blueshift after long annealing time compared to undoped PbSe NCs. This behavior was linked to the dependence of band-gap energy and the absorption selection rule on Mn(2+) concentration. Photoluminescence in the Pb(1-x)Mn(x)Se nanocrystals increases as the temperature rises up to a point and then decreases at higher temperatures. Anomalous increases in emission efficiency were analyzed by considering temperature induced carrier-transfer in semimagnetic Pb(1-x)Mn(x)Se quantum dots nanocrystals of different sizes.

Thermal activated energy transfer between luminescent states of Mn2+-doped ZnTe nanoparticles embedded in a glass matrix.

Zn(1-x)Mn(x)Te nanocrystals (NCs), at various concentrations x, were successfully grown in a host glass matrix by the fusion method after appropriate annealing. Growth of these NCs was evidenced by optical absorption (OA), X-Ray Diffraction (XRD), magnetic force microscopy (MFM) and photoluminescence (PL) measurements. From the room temperature OA spectra, it was possible to observe the formation of two well defined, different sized groups of NCs, one attributed to quantum dots (QDs) and the other to bulk-like nanocrystals (NCs). XRD results have confirmed that the cubic zincblend structure of nanoparticles is not altered by the substitutional incorporation of Mn(2+) ions into the ZnTe NCs. MFM images supported the OA spectra results and thus provided additional confirmation of the formation of Zn(1-x)Mn(x)Te magnetic nanoparticles in the host glass matrix. The two groups of NCs were also observed in the PL spectra as well as deep defects attributed to the presence of oxygen centers in the electronic structure of the Zn(1-x)Mn(x)Te NCs. Strong agreement between the fitting model, based on rate equation, and experimental PL intensity data at different temperatures demonstrates that this model adequately describes the energy transfer processes between the NCs and the defects of the Zn(1-x)Mn(x)Te system at different temperatures.