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In this work, the impact of the doping process on the photoluminescence emission of CaWO4 as a function of the concentration of Eu3+ cation (0.01 mol%, 0.02 mol%, 0.04 mol%, 0.06 mol%, 0.08 mol%, and 0.10 mol%) is discussed in detail. Ca1−xWO4:xEu3+ samples were successfully synthesized by a simple co-precipitation method followed by microwave irradiation. The blue shift in the absorption edge confirmed the quantum confinement effect and the band gap energy cover the range from 3.91 to 4.18 eV, as the amount of Eu3+ cations increases. The experimental results are sustained by first-principles calculations, at the density functional theory level, to decipher the geometry and electronic properties, thereby enabling a more accurate and direct comparison between theory and experiment for the Ca1−xWO4:xEu3+ structure. Funding for open access charge: CRUE-Universitat Jaume I

Inorganic metal-halide perovskites hold a lot of promise for solar cells, light-emitting diodes, and lasers. A thorough investigation of their optoelectronic properties is ongoing. In this study, the accurate modified Becke Johnson generalized gradient approximation (mBJ-GGA) method without/with spin orbital coupling (SOC) implemented in the WIEN2k code was used to investigate the effect of mixed I/Br and Br/Cl on the electronic and optical properties of orthorhombic CsPb(I1-x Br x )3 and CsPb(Br1-x Cl x )3 perovskites, while the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) method was used to investigate their structural properties. The calculated band gap (Eg) using the mBJ-GGA method was in good agreement with the experimental values reported, and it increased clearly from 1.983 eV for CsPbI3 to 2.420 and 3.325 eV for CsPbBr3 and CsPbCl3, respectively. The corrected mBJ + SOC Eg value is 1.850 eV for CsPbI3, which increased to 2.480 and 3.130 eV for CsPbBr3 and CsPbCl3, respectively. The calculated photoabsorption coefficients show a blue shift in absorption, indicating that these perovskites are suitable for optical and optoelectronic devices.

We have investigated the structural, optical and magnetic properties of Zn0.90Co0.10O, synthesized by the method of two electrode electrodeposition. X-ray diffraction measurement confirms the evolution of a single-phase polycrystalline hcp Wurtzite structure. Co-2p core-level XPS confirms that Co is present in mixed 2+ and 3+ states. The Fourier Transform Infrared (FTIR) spectrum findings substantiate the fact that a single-phase Hexagonal Wurtzite ZnO Crystal Structure has evolved. The SEM micrograph of the sample reveals smooth and dispersed morphology consisting of fine particles. The U-V visible NIR and PL spectroscopy measurements substantiate the fact that Co2+ has substituted Zn2+ in the matrix of ZnO which agrees with XRD findings. The sample shows good optical property and reveals a blue shift. It seems that the material is a potential candidate to be used as UV sensors. Room Temperature Intrinsic Ferromagnetism has been confirmed by VSM measurement.

The nanocrystalline Al-doped CdS semiconductors were produced accurately by the sol-gel calcination process. The aluminum was added with different percent’s (0, 1, 5, 10, 15, and 20 wt%) to the synthesized CdS. Both FT-Raman analysis and UV–VIS-NIR absorption measurements were utilized to characterize the studied semiconductors' structural and optical characteristics. The detected X-ray diffraction (XRD) patterns of the prepared CdS present a polycrystalline structure, and Al-doping does not significantly impact this range. Optical bandgaps were determined for undoped and Al-doped CdS, showing a significant change with the percentage of Al-dopants. With increasing Al-doping up to (20 percent), the optical bandgap for CdS (2.38 eV) grows to reach (2.47 eV) and the allowed transitions were found to be direct for the investigated samples. The blue shift may be the reason for the optical bandgap variations. Scanning Electron Microscope (SEM) micrographs were performed to establish the Al-doped CdS nanostructure to identify the morphological characteristics.

Biogenic amines (BAs) are known as substantial indicators of the quality and safety of food. Developing rapid and visual detection methods capable of simultaneously monitoring BAs is highly desired due to their harmful effects on human health. In the present study, we have designed a multicolor sensor array consisting of two types of gold nanostructures (i.e., gold nanorods (AuNRs) and gold nanospheres (AuNSs)) for the discrimination and determination of critical BAs (i.e., spermine (SM), tryptamine (TT), ethylenediamine (EA), tyramine (TR), spermidine (SD), and histamine (HT)). The design principle of the probe was based on the metallization of silver ions on the surface of AuNRs and AuNSs in the presence of BAs, forming Au@Ag core-shell nanoparticles. Changes in the surface composition, size, and aspect ratio of AuNSs and AuNRs induced a blue shift in the plasmonic band, which was accompanied by sharp and rainbowlike color variations in the solution. The collected data were visually assessed and statistically analyzed by various data visualization and pattern recognition methods. Namely, linear discriminant analysis (LDA) and partial least squares (PLS) regression were employed for the qualitative and quantitative determination of BAs. The responses were linearly correlated to the concentrations of BAs in a wide range of 10-800, 20-800, 40-800, 40-800, 60-800, and 80-800 μmol L-1 with the limit of detections of 2.46, 4.79, 8.58, 14.26, 10.03, and 27.29 μmol L-1 for SD, SM, TT, HT, EA, and TR, respectively. Finally, the practical applicability of the sensor array was investigated by the determination of BAs in meat and fish samples by which the potential of the probe for on-site determination of food freshness/spoilage was successfully verified.

ZnO:Eu thin film fabricated by pulsed laser deposition was treated by pulsed UV laser. The effect of laser fluence from 70 to 125 mJ cm−2 on film properties was investigated. The results showed that the surface morphology was clearly modified and the film treated at laser fluence of 70 mJ cm−2 was more densified compared to the other annealed films. Laser treatment led to a reduction of carbon content and to a stoichiometric ZnO:Eu composition on the surface. Refractive index significantly decreased and extinction coefficient was blue shifted for higher laser fluences. Strong characteristic Eu3+ transitions were obtained using excitation at 266 nm. The highest photoluminescence intensity was observed for the annealed film at a laser fluence of 70 mJ cm−2. The influence of ambient composition (N2 and O2) and temperature (room temperature and 150 °C) to photoluminescence response was examined for optical gas sensor application. The laser-untreated film showed higher sensitivity to the presence of oxygen at both temperatures compared to the treated film. The stability of photoluminescence intensity at elevated temperature was improved for laser-treated areas.

To investigate the effect of Gd x SrO: CdO (x = 0.1, 0.3, 0.4) nanostructures (NS), in the present work an attempt has been made to synthesize Gdx SrO:CdO NS by co precipitation method. Structural properties were investigated by XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), UV-Visible, XPS (X-ray photoelectron spectroscopy). XRD indicates having mixed phase of tetragonal crystal structure and SEM images indicate spherical shaped nanoparticles (NPs) of Gd x SrO:CdO with average size laying in between ~100 nm to ~130 nm. FTIR spectra of Gd x SrO: CdO NS show stretching and bending peaks of Gd-O-Gd, Cd-O-Cd and Sr-OH at ~1311 cm −1, ~1486 cm −1, ~ 3300 cm −1 and UV-visible optical absorptivity of Gd x SrO:CdO show absorption maxima shift from 330 nm to 324 nm (blue shift) and edges at 352.4 nm, 348 nm and 346.3 nm respectively for Gd concentration varying between 0.1, 0.3 and 0.4. binding energies of the Gd 3d 3/2, Sr 3d 3/2 and Cd 3d 3/2, O1s and C1s observed at 150.8 eV, 141.6 eV, 410.1 eV, 529.6 eV and 282.4 eV respectively which confirms the chemical composition of NS. Photoluminescence (PL) spectrum of Gd 0.4 Sr 0.5 O Cd 0.1O NS exhibit broad peaks from 338 nm to 397 nm centred around 369 nm with various Gd, O, Sr and Cd related native defects. Emission band observed at UV- Visible region for Gd 0.3 Sr 0.5 O Cd 0.2 O NS PL emission spectra has two emission peaks at 369 nm (UV region) and 550 nm (Visible region). The transitions can be ascertained with shielding of 4f shells of Gd+3 ions by 6 s, 5d shells by the interaction of the other Gd+3 ions.

High-pressure ice polymorphs are important for our understanding of hydrogen bonding and exist in the interior of the earth and icy moons. Nonetheless, spectroscopic information about them is scarce, where no information about their optical properties in the near-infrared (NIR) region is available at all. We here report NIR spectra of six ice polymorphs differing in terms of their density and O-atom topology, namely, ices II, IV, V, VI, IX, and XII, in comparison with the known spectra of ice Ih. By contrast to earlier work, we do not use mulling agents or transmission of thin films but use diffuse reflectance on powdered samples in liquid nitrogen. The first overtone of the OH-stretching mode is identified as the marker band most suitable to distinguish between these ices. There is a clear blue shift of this band that increases with increasing topological density in addition to a significant narrowing of the band.

MoS2 nanosheets were developed by undertaking the liquid-phase exfoliation of bulk counterparts. In order to enhance its photocatalytic properties, the host material was doped with p-type transition metals (i.e., Ag, Co, Bi, and Zr). The hydrothermal technique was used to produce samples doped with 7.5 wt% transition metals (TM). X-ray diffraction detected the existence of 2H-phase by mirroring its reflection at 2θ ∼ 14°, while the peak distribution revealed the degree of exfoliation in samples. Low PL intensities indicated a lower recombination of electron-hole pairs, as corroborated by a high degree of photocatalytic action. Raman analysis was undertaken to identify molecular vibrations. The A1g mode in Raman spectra consistently showed a blueshift in all samples and the E12g mode was only slightly affected, which is evidence of the p-type doping in the MoS2 nanosheets. In the XPS spectrum, two characteristic peaks of Mo 3d appeared at 229.87 and 233.03 eV assigned to Mo-3d5/2 and Mo-3d3/2, respectively. Furthermore, a microstructural examination with HR-TEM and FESEM divulged a thin-layered structure of MoS2 consisting of flat, gently curved or twisted nanosheets. Diverse morphologies were observed with a non-uniform distribution of the dopant. Photocatalytic action of the TM-doped products effectively degraded methylene blue (MB) concentrations of up to 94 percent (for Ag-MoS2). The synergistic effect of doped MoS2 nanosheets against S. aureus in comparison to E. coli bacteria was also evaluated. The efficacy % age improved from (0-31.7%) and (23.5-55.2%) against E. coli, and (0-34.2%) and (8.3-69.23%) against S. aureus. Moreover, results from first principles calculations indicate that substitutional doping of TM atoms is indeed advantageous. Theoretical calculations confirmed that doping with Ag, Co, Bi, and Zr leads to a decrease in the band gap to a certain degree, in which the conduction band edge shifts toward lower energy, while the valence band shifts closer to the high energy end. It can be concluded that Ag, Co, and Bi impurities can lead to beneficial p-type doping in MoS2 monolayered structures. With regards to doping with Zr, the acceptor levels are formed above the edge of the valence band, revealing an introduction of the p-type character.

CuSe have been synthesized through chemical route at 0.5 M, 0.05 M and 0.005 M molar concentration using the polyvinylpyrrolidone (PVP) as a capping agent. The structural and optical characterization are done by XRD, UV–Vis, PL spectroscopy. XRD result confirms the formation of mixed type structure comprising hexagonal wurtzite phase, cubic along with some oxide traces. The UV–Vis spectra shows blue shift from bulk CuSe which clearly implies the quantum confinement of the as synthesized nanoparticle. The direct and indirect band gaps of CuSe are found to be enhanced upto 3.7 eV and 2.0 eV respectively on lowering the molar concentration. After ageing for 45 days the band gaps are found to decrease which is attributed to incorporation of defects that makes the agglomeration of particles. PL emission spectra of all the samples show band gap emission near UV-blue region. The band emission also shows a clear blue shift and varying from 418 nm to 397 nm in accordance with a decrease of molarity. The PL intensity is found to be enhanced for CuSe prepared at low concentration. Pl peaks are flattened covering more wavelength in near UV to blue-yellow region after ageing. Also the PL intensity enhanced along with a red shift of band emission.

A microfluidic nanopaper-based analytical device (µNPAD) has been prepared for the determination of cholesterol by using triangular silver nanoprisms (T-AgNPrs). We have developed a simple enzyme-based biosensor that can detect cholesterol by a colorimetric reaction based on the etching of T-AgNPrs. In the presence of cholesterol and cholesterol oxidase (ChOx), H2O2 was produced which etched the T-AgNPrs. As a result, after the etching process, a blue shift occurred and a color change from blue to light orange was observed. Based on this phenomenon, the amount of cholesterol was obtained by UV-Vis spectroscopy and µNPAD. A linear calibration curve in the range of 0.10-4.0 mM was obtained with a detection limit of 0.065 mM and a correlation coefficient (R2) of 0.993 using UV–Visible spectrophotometer. In the case of µNPAD, cholesterol concentration from 0.20-3.0 mM can be used with a detection limit of 0.14 mM and correlation coefficient (R2) of 0.985. T-AgNPrs detection system showed high selectivity to cholesterol and no color change was observed in the presence of other interferences. The proposed µNPAD based on T-AgNPrs can be used in the applications of point-of-care diagnostics

ZnO nanoparticles co-doped simultaneously with Ni and Cu at concentrations varying between 0 and 10% were synthesized by wet chemical method. The resulting nanoparticles were less than ~ 60 nm. At 5% Ni + 5% Cu co-doping, enhanced visible luminescence between 380 nm – 460 nm is seen. Coupled with a low bandgap of 3.4 eV, they result in conducive optical properties for application of this material as UV Photodetector. Marginal changes in bond length (~ 0.003 A) and c/a ratio (~ 0.002 A), along with absence of impurity phases reflect its microstructural superiority. Morphological studies indicate marginal reduction of interplanar spacing due to doping, thus, forming uniform crystalline nanoparticles. The nominal composition of Zn, O, Ni and Cu without any impurity phases remains intact. An overall blue shift in absorption peak for all samples than bulk ZnO is observed, emerging due to size effects. However, at doping concentrations higher than 5%, Cu (111) and Ni (200) phases are seen due to clustering. Electrical studies under UV exposure are in agreement with the characterization studies on the sample, showing highest responsivity, current gain and high quantum efficiency values of 10.003 mA, 1.0421 and 3.146% respectively. These properties enable 5% Ni + 5% Cu co-doped ZnO nanoparticles to be explored for use as a material for optoelectronic devices like UV Photodetector.

A new fluorescent probe, 3-(benzo[d]thiazol-2-yl)-5-bromosalicylaldehyde-4N-phenyl thiosemicarbazone (BTT), for ratiometric sensing of Zn2+ ions in methanol/HEPES buffer solution (3 : 2, pH = 7.4) is reported in this paper. The presence of Zn2+ ions yields a significant blue shift in the maximum emission of BTT from 570 nm to 488 nm, accompanied by a clear color change from orange to green. This emission change of BTT upon binding to Zn2+ in a 1 : 1 ratio may be due to the block of excited state intramolecular proton transfer (ESIPT) as well as chelation enhanced fluorescence (CHEF) on complex formation. The limit of detection (LOD) determined for Zn2+ quantitation was down to 37.7 nM. In addition, the probe BTT displays the ability to image both exogenous Zn2+ ions loaded into HeLa cells and endogenous Zn2+ distribution in living SH-SY5Y neuroblastoma cells.

Cadmium selenide (CdSe) nanostructures with different growth temperature viz. 25 °C, 60 °C, 100 °C, 150 °C and 200 °C have been synthesized through chemical route. The results of XRD reveals that as synthesized CdSe nanostructures possess polycrystalline cubic zinc blende structure. The particle sizes obtained from Scherer formula as well as W-H plot and are found to be 2.81 nm and 4.6 nm respectively. The strain induced in the crystal is obtained as −1.8 × 10−3 from the W-H plot. The results of UV–Vis and photoluminescence (PL) spectra show that growth temperature has a significant impact on the optical properties of the synthesized nanoparticles. Both the UV and PL spectra initially show a blue shift with the increase of temperature but after a particular temperature around 100 °C it starts showing red shift. The PL intensity also increases and possesses a maximum at growth temperature 100 °C but afterwards it again decreases at very high temperatures. From the observation of absorption, PL emission along with intensity it has been inferred that growth temperature ranging from 25 °C to 100 °C may be a suitable technique to modulate the optical properties of chemically synthesized CdSe nanoparticles.

A colorimetric analytical method, with wavelength change as a response, was developed for highly sensitive determination of dopamine (DA) based on gold nanorods (AuNRs). Even though AuNRs were unable to be etched by KIO3, however, they surrendered to I2 generated from IO3- in the presence of DA. This could result in a blue shift of their absorption peak of longitudinal localized surface plasma resonance (LSPR), accompanied by obvious color change of solution from wine red to blue. Under the optimum conditions such as KIO3 concentration of 0.7 mmol/L, reaction temperature at 50 °C, pH 2.6 and incubation time of 6 min, the amount of blue shift of AuNRs absorption wavelength was linear to DA concentration in the range of 0.80–60.0 μmol/L and the detection limit was 0.62 μmol/L (3σ/k). Furthermore, the common substances in urine did not interfere in the determination and the DA recovery rate in actual urine samples ranged from 103.0% to 110.8%.

The core/shell material shows novel properties depending upon their relative valance and conduction band shift. In the present work, PbO and PbO/ZnO core/shell nanoparticles are prepared through chemical technique using PVP as capping agent. The core/shell PbO/ZnO exhibits the X-Ray diffraction peaks of both the material, thereby confirming the formation of core/shell structure. The particle size and strain of all the material are calculated employing W.H technique. The UV visible absorption spectra of PbO show a blue shift of its absorption edge. However, after coating with ZnO shell the absorption edge become red shifted. The band gaps were estimated from Taue plots which were found to be reduced from 3.2 eV to 2.74 eV. The reduction of band gap is attributed to the incorporation of defects in terms of shell. The photoluminescence spectra show a band to band emission around 345 nm along with emission from other impurities. After coating the near band gap emission is red shifted towards 374 nm. The PL intensity of the core reduced after shelling. This effect may be attributed to the change of recombination kinetics governed by induced defects.

In this work, using β-Ca3(PO4)2 as a structural model, a series of [Ca9Na3xY1−x(PO4)7 (CNYPO-I, 0 ≤ x ≤ 1/2) ← Ca3(PO4)2 → Ca9+yNa3/2−y/2Y(1−y)/2(PO4)7 (CNYPO-II, 0 ≤ y ≤ 1)] phosphors were prepared using a cationic heterovalent substitution approach. The substitution of Y3+ and Na+ for Ca2+ led to a redistribution of Eu2+ within the lattice and was accompanied by changes to the corresponding luminescence behavior. As the x and y values increased, the vacancies in the structure were gradually occupied by Na+ to form Na(4) sites that are conducive to Eu2+ occupation. When y = 1, the vacancies were completely occupied, and the Eu2+ emission peaks from Ca(1/2) and Ca(3) sites showed a significant blue shift. The underlying mechanism of that shift is discussed. The CNYPO-I (x = 0) sample displayed the best thermal stability; the effects of vacancies, thermal ionization and cross-over mechanism on thermal quenching are also discussed. As x and y increase, the thermal stability of the samples gradually decreased. Eu2+ and Mn2+ co-doped CNYPO-I (0 ≤ x ≤ 1/2) and CNYPO-II (0 ≤ y ≤ 1) phosphors achieved full coverage of the visible light region (400–800 nm). These white LEDs have relatively high color-rendering indexes (>80) and adjustable color temperatures from 2854–7000 K. This work provides an effective strategy for designing novel luminescent materials and realizing multi-site adjustment of activator ions.

The spin coating method was employed to fabricate Yb-doped ZnO thin films at 0, 3, 5, 7, and 9 at.% over a glass substrate at low temperature. X-ray diffraction analysis revealed that the hexagonal wurtzite structure was retained even at high doping contents. With the incorporation of Yb+3 ions, a slight decrease in the lattice parameters and crystallite size was observed as the ytterbium content increased. X-ray photoelectron spectroscopy confirmed the presence of ytterbium in the doped ZnO films, and the oxidation state of ytterbium was 3+ for all the samples. Morphological studies revealed a surface microstructure formed by micro islands, which tended to be denser as the ytterbium content increased. Optical transmittance was observed at approximately 75–85%, a blueshift was observed, and consequently, an increase in the bandgap, which varies from 3.0 to 3.2 eV, was observed. The refractive index and extinction coefficient decreased as the ytterbium dopant concentration increased. The photoluminescence results exhibited a strong ultraviolet emission, allowing the use of these thin films in optoelectronic applications.

Photoluminescence (PL) and Raman spectra of GaAs1-xBix samples grown at different rates (0.09 to 0.5 µm/h) were investigated. The PL peak wavelength initially redshifted with the increase of growth rate and reached the longest wavelength (1158 nm) for sample grown at 0.23 µm/h. This is followed by PL peak wavelength blueshift for higher growth rates. The Raman data show peaks at 162, 228, 270, and 295 cm-1 which can be attributed to GaAs like phonons. GaBi like vibrational modes were also observed at 183 and 213 cm-1. However, the intensity of Bi induced phonons is significantly weaker compared to GaAs due to low concentration of Bi compared to As and thin GaAs1-xBix epilayer. The PL data and GaAs transverse optical (TO) to longitudinal optical (LO) phonons intensity ratio indicate that Bi concentration is highly dependent on the growth rate and the highest Bi concentration was obtained by sample grown at 0.23 µm/h. It is found that the full-width-at-half-maximum (FWHM) of GaAs LO mode increases significantly for samples grown at high growth rates suggesting crystal quality degradation due to lack of surfactant effects.

Study of structure and optical properties of magnesium ammonium phosphate hexahydrate crystal known as struvite is presented. Experimentally determined infrared (IR) and ultraviolet–visible (UV–vis) spectra are compared with the theoretical predictions of density functional methods. Examination of the interatomic bond lengths, Mulliken atomic charges, and binding energies of water in the magnesium hexahydrate cation, together with the analysis of the hydrogen bond pattern have allowed us to explain a special feature of the IR spectrum of struvite, a blueshift of the band corresponding to the O–H stretching mode. This mode has been assigned to a “dangling” hydroxyl group in one of the water molecules in magnesium hexahydrate. Using experimentally obtained UV–vis spectrum and performing Tauc plots analysis, optical bandgap of struvite has been narrowed to a range from 5.92 to 6.06 eV.

Herein, we demonstrate electrochromism of charged inverse opal photonic gel (IOPG) in aqueous solution for full color reflective display. Opal-templated polymerization of hydroxyethyl methacrylate with ionizable monomer and subsequent etching formed the IOPG exhibiting a structural color by Bragg diffraction of light. The IOPG contained acrylic acid (AA) (or vinyl imidazole (VI)) that can be ionized above the pKa (or below the pKb) of the gel. Application of 4 V bias induced apparent color changes of the AA-IOPG from red to green due to decreased osmotic pressure within the IOPG near the ITO surface. It was revealed that the local pH change by water-splitting under voltage bias is the main driving force for IOPG deswelling. The blue shift of the colors during voltage ON was found to be faster than the red shift at voltage OFF due to the electrophoretic migration of protons. The VI-IOPG, which swells at low pH due to a positively charged hydrogel, showed a slight red shift of the reflective color by voltage ON and blue shift upon when voltage OFF. The reproducible color changes of AA-IOPG upon the repeated ON/OFF bias clearly showed that the IOPG can be a promising candidate for a reflective display.

Octahedral indium oxide thin films with different precursor concentrations of 0.05, 0.075, 0.1 and 0.125 M were coated on glass substrates at 450 °C using jet nebulizer spray pyrolysis technique. Surface morphology of the prepared samples showed closely packed octahedrons for all concentrations. The measured root-mean-square value of the films was varied between 40.45 and 188.98 nm with increased precursor concentrations. From optical analysis, the calculated optical band gap was continuously decreased with increase in precursor concentrations. A slight blue shift was recorded through the PL spectrum while increasing the precursor concentration due to the oxygen vacancies. The nature of electrical conductivity of the In2O3 films was analysed. Interestingly, we have calculated two types of activation energies in the In2O3 films one is corresponding to low temperature and another is higher temperature. Further, p-Si/n-In2O3 junction diodes are fabricated with different precursor concentrations. Particularly, the 0.075 M of p-Si/n-In2O3 junction diode recorded a minimum ideality factor of n = 2.64 under light exposed condition, confirming the photo-conducting nature of the diodes in visible wavelength range.

In the present study, a novel plasmonic sensing platform was proposed for sequential colorimetric detection of dopamine (DA) and glutathione (GSH) in human serum sample by taking advantage of plasmon hybridization in graphene nanoribbons/sliver nanoparticles (GNR/Ag NPs) hybrid. DA was detected based on etching strategy and morphology transition of label-free Ag NPs hybridized with GNR. As a result of the etching process, hexagonal Ag NPs were changed to smaller corner-truncated nanoparticles and a blue shift was observed in its plasmonic band, accompanied by the color change from green to red. Sequentially, GSH induced aggregation of Ag NPs which resulted in a decrease in absorption intensity of Ag NPs plasmonic band and a color change from red to gray. By employing GNR/Ag NPs hybrid as a sensitive colorimetric sensor, DA and GSH were successfully detected in low concentrations of 0.04 μM and 0.23 μM, respectively. The same experiment was carried out in the absence of GNR and the detection limits were obtained 0.46 and 1.2 μM for DA and GSH, respectively. These results confirmed the effective role of GNR on the sensitivity improvement of GNR/Ag NPs hybrid. The proposed simple and sensitive sensing approach offered a beneficial and promising platform for sequential detection of DA and GSH in the biological samples.

YbxMnyOz:Eu3+ nanotube arrays have been synthesized in anodic aluminum oxide (AAO) templates with negative pressure filtration. The morphology, structure, and composition have been characterized by SEM, TEM, HRTEM, XRD and EDS, respectively. Compared with nanoparticles and nanowire arrays excited by 394 nm light wave, YbxMnyOz:Eu3+ nanotube arrays exhibit fluorescence enhancement and are accompanied by red and blue shift, and there are three fluorescence emission peaks at 480 nm, 590 nm and 702 nm, respectively. The peaks at 590 and 702 nm correspond to the 5D0–7F1 and 5D0–7F4 energy level transition of Eu3+, and the peak of 480 nm is from the “cooperative fluorescence” due to two-photon excitation. The fluorescence intensity of YbxMnyOz:Eu3+ nanotube arrays increases with the doping concentration of Eu3+, which reaches a maximum at 5 vol %, and remarkably decreases at higher concentrations.

Ca3(PO4)2:1mol%Ce3+/xGd3+ (where x = 0.5, 1.0, 3.0 and 5.0 mol%) phosphors were synthesized by the conventional combustion synthesis method. The X-ray diffraction patterns showed their rhombohedral structure with space group of R3c. The optical properties including reflectance, excitation and emission were investigated. The band gaps of the phosphors were calculated from diffuse reflectance spectra data using the Kubelka–Munk function. The photoluminescence (PL) excitation spectra exhibited the broadband 4f–5d transition of Ce3+ ions centered at ~265 nm. The PL emission properties of the Ca3(PO4)2:Ce3+/Gd3+ phosphors were studied as a function of the Gd3+ ion concentration. The Ca3(PO4)2:Ce3+/Gd3+ phosphor had a wide emission band ranging from 320 to 400 nm, and peaking at 365 nm. This emission is ascribed to the transition from the higher 5d band to 2F7/2, 2F5/2 states of the Ce3+ ion. The 365 nm peak shifted to longer wavelengths with increasing concentration of the Gd3+ ion. The CIE chromaticity diagram of Ca3(PO4)2:Ce3+/Gd3+ phosphor showed tunable emission colour from violet to violet-blue, suggesting that this phosphor can act as a source of violet-blue colour for application in information displays, phototherapy and photoluminescent liquid crystal displays.

Annealing of tris(8-hydroxyquinoline) gallium (Gaq3) film at various temperatures in dry N2 atmosphere has shown the existences of four different phases of molecular aggregations before the burning out of the film at about 310 °C. The first three phases, up to 235 °C, are amorphous molecular aggregations, while the fourth one at 255 °C is a crystalline structure, very likely α-polymorph. The photoluminescence (PL) intensity was increased to about five times greater than that of the pristine film at 235 °C, while the PL peak was blue shifted consistently. Although a small contribution of Rayleigh scattering cannot be excluded at high temperatures when crystallites appear, the PL blueshift was mainly attributed to the nanostructured molecular aggregations followed by enhanced PL intensity. These new findings can be a common characteristic of organometallic complexes at varied annealing temperatures. The presented results open a new route of fabricating highly emissive thin films of amorphous nanostructure, which are specifically important for organic light emitting diode (OLED) based displays.

Water-soluble Cd0.9−xZn0.1SnxS (0 ≤ x ≤ 0.06) quantum dots were prepared by dual doping of Sn and Zn via chemical co-precipitation technique. XRD results confirmed the cubic structure of CdS crystallites without generating any secondary peaks due to doping. TEM analysis revealed the structural information of the Sn-doped CdS host. The Sn substitution enhanced the particle size lightly. The surface morphological study revealed that the agglomeration of the samples was decreased. From UV–visible optical study, it was observed that the optical transmittance was suppressed owing to Sn substitution. Absorption peaks were blueshifted, and band gap values were widened due to incorporation of Sn. The strong PL emission peaks were received at 400 nm−1 and weak peaks near 490 nm−1. The peaks originated near the UV region were due to sulfur vacancies on the surface. EDX and FTIR studies confirmed the presence of Sn in the prepared samples. Since the possibility of tailoring the band gap toward a high energy gap, these materials composition may be selected for optoelectronic device fabrication.

MgxZn1−xO (x = 0.05, 0.10, 0.15, and 0.20) films prepared on quartz substrates by the sol–gel method were characterized and studied. According to scanning electron microscopy and x-ray diffraction data, the MgxZn1−xO films exhibited a particle-stacking morphology and a hexagonal wurtzite crystal structure. An increase in Mg content led to an obvious increase in particle size. However, a weakening of the hexagonal wurtzite structure was observed and indicated the transition of the MgxZn1−xO crystal structure, which was also confirmed by the Raman spectra results. An increase in bandgap energy from 3.38 eV to 3.55 eV with increased Mg content was determined from the transmittance spectra. Ultraviolet photodetectors based on MgxZn1−xO with interdigital electrodes were then fabricated. Dark current as low as 10 pA (corresponding to 5 nA/cm2) under bias of 10 V was achieved. A blueshift of the peak wavelength and cutoff wavelength was observed with increasing Mg content. Noise equivalent power as low as 2 × 10−15 W was achieved, detectivity was found to be about 1.2 × 1011 cm Hz1/2/W, and quantum efficiency was nearly 100%, which was related to the photoconductive gain.

The structural, optical, and electrical properties of undoped and Al-doped ZnO films deposited on p-Si (001) substrate were studied using DC-unbalanced magnetron sputtering. This study is motivated by the absence of detail reports concerning the orbital states inducing the optical bandgap (Eg) blueshift. Besides, the influences of Al on the possible modification of point defect and the photodetecting performance are highlighted to offer guidelines for better development in ZnO-based photodetector. It was found that the Al doping reduced the grain size. The doping increased the lattice parameters and slightly decreased the local-symmetry distortion at ZnO4. From the absorbance spectra, the doping increased Eg of ZnO film (3.28–3.36 eV), induced by the Burstein-Moss effect. From the density-functional calculation, the Burstein-Moss effect induced Eg from the valence band maximum (VBM) to Fermi level located above the lowest Zn 4s conduction state. From the photoluminescence spectra, the undoped film showed the transitions from O vacancy, Zn interstitial, and free-exciton states to the VBM. The doped film showed the transitions from Zn interstitial to O interstitial and few Zn vacancy states at the cost of O vacancies. Moreover, the energy level of free-exciton states slightly decreased. Notably, O interstitials increased the lattice parameters. From the electrical properties, the doping enhanced the ultraviolet-region photo-to-dark-current ratio up to 3.044 V, leading to the photodetecting sensitivity enhancement. This study emphasizes the significant effect of Al doping on the optical absorbance, point-defect evolution, and photodetecting performance of ZnO film for low-voltage ultraviolet photodetector applications. Keywords: ZnO, Optical properties, Point defect, Photodetecting, Local-symmetry distortion

Au nanorods were prepared through seed growth method. Their lengths and diameters were controlled by adjusting Ag+ content in the growth solution. Ethyl orthosilicate were hydrolyzed in alkali solutions to obtain SiO2-coated Au nanostructures. Au nanorods with ideal morphologies and sizes could only be obtained under the presence of a certain Ag+ concentration in the growth solution. Without Ag+, only some irregular nanoparticles were generated without nanorods. Longitudinal plasma absorption of Au nanorods shifts first to red shift and then to blue with the increase of Ag+ in the growth solution, while transverse plasma absorption hardly changes. However, longitudinal plasma absorption of silica-coated Au nanorods has a blue shift with the increase of the thickness of silica, while the transverse plasma has a slight red shift. Therefore, by coating Au nanorods with silica and by adjusting their aspect ratio by using different Ag+ concentration in the growth solution, Au nanoparticles can be synthesized for applications requiring absorption in specific UV regions.

In this paper, (ZnO)x-(MgO)1-x composites were deposited on glass and silicon substrate using E-Beam Deposition Technique. Doping of MgO is in atomic percentage for various compositions from 0% to 90%. XRD results show that MgO has been doped successfully. The investigation of Band gap has been done and the result displays as the MgO content is increased, the band gap is tuned from 3.16 eV to 3.55 eV and transmission band edge is blue shifted about 36 meV to the higher energy direction, this is closely related to formation of mesoporous structure. The Band Gap has been calculated using UV–Vis Spectroscopy. Investigation confirms that defects in surface have been increased with the increase in MgO Content.

We use photoinduced absorption spectroscopy (PAS) to study the ionic motion in CH3NH3PbI3 perovskite solar cells, consisting of indium tin oxide (ITO)/NiOx/perovskite/phenyl-C61-butyric-acid-methyl ester (PCBM)/aluminum-doped zinc oxide (AZO)/ITO. We observed a slow (∼50 mHz) spectral blue shift (∼10-4 eV) under modulated 520 nm illumination, which we interpreted in terms of the modulation in the bulk ion density. Numerical simulation shows that the mobile ion moves in and out from the double layers at the perovskite/charge transport layer interfaces in order to recover the bulk charge neutrality tipped off-balance by the photocarriers. The diffusion coefficient of the ion is 10-10 to 10-11 cm2 s-1, when we assume that the characteristic time constant of the ion motion is governed by the diffusion.

In this work, cadmium sulfide nanocrystals capped with β-mercaptoethanol: CdS–βME (NCs) formed at wurtzite structure were prepared by colloidal chemical method for structural and optical properties' investigation. The temperature dependence of the photoluminescence (PL) intensity and its quantum yield (QY), the PL pic position and FWHM and the PL lifetime were systematically studied over a broad temperature range of 10–300 K. PL enhancement, photoetching and photostability of CdS–βME NCs were investigated under light irradiation. XRD and TEM patterns showed that CdS–βME NCs have an hexagonal phase with wurtzite structure. A very narrow excitonic blue emission peak with relatively high intensity was detected, which is similar to the better results obtained via organic synthesis. The FWHM ($$\sim$$ 20 nm) is controlled by an inhomogeneous broadening due to the particle size/morphology distributions of the NCs. Dynamic studies reveal shorter lifetimes indicating weak contribution of the surface-related emission with the removal of surface defects. The photoetching process of CdS–βME NCs resulted in a high QY of up to 3.8% with an obvious blueshift in band emission. On the basis of these studies, it is established that the surface of CdS–βME is rich with Cd2+ ions, leading to the formation of a CdO layer as shell, which provides a better passivation by removing surface hole traps and confines the charge carriers with illumination by Hg lamp radiation. In conclusion, owing to their excellent dispersibility in water and high luminescence, the CdS–βME NCs that have been developed here can be a promising candidate for biolabelling and imaging applications.

A novel red emitting fluoride phosphor K2LiInF6:Mn4+ was synthesized by a cation exchange route. An increased blue shift in its emission spectrum was observed. This anomalous phenomenon can be attributed to the nephelauxetic effect and different interionic distances between the cations and ligands. Dependence of the emission intensity of Mn4+ on its concentration was investigated to optimize the luminescence properties of the prepared phosphors and the structure and morphology of the phosphor are studied in detail. The exchange charge model of the crystal field was used to calculate the crystal field parameters. The temperature-dependent emission spectra were measured to ascertain the thermal stability and the chromaticity shift of KLIFM.

A series of Y2.94-xLuxAl4GaO12: 0.06Ce3+ phosphors were prepared by the conventional solid-state reaction method. It was confirmed that the phosphors exhibit cubic garnet crystal structures by XRD and Rietveld refinements. The phosphors show an intense broad emission band from 475 nm to 650 nm, which attributed to the 5d→4f transitions of the Ce3+ ions under the excitation of 450 nm. Simultaneously, obvious blue shift is observed from 518 nm to 497 nm with increasing Lu3+ concentrations from 0 to 2.94. With the increase of Lu3+ concentrations the emission intensity increases and reaches to the maximum for x = 2.5. By optimizing Lu3+ concentration, the quantum efficiency up to 89.8% is obtained. The emission intensity at 453 K is up to 92% of that at room-temperature indicating a weak thermal quenching and a superior thermal stability. These results indicate that the phosphor can be used in blue LED-Chip based white LEDs in the future.

A flexible chemosensor has been developed based on colorimetric and fluorescent dual modes using tetraphenylethylene-centered tetraaniline (TPE4A) for rapid and sensitive detection of hypochlorite anion. The fluorescent probe TPE4A exhibits a unique aggregation-induced emission (AIE) character which is proved by a blue shift of the fluorescent peak from 544 to 474 nm with the water equivalents increasing. With the addition of hypochlorite in solution, the absorbance of the probe changes and the responding fluorescence color can be observed to change from light green to purple. The detection limit of hypochlorite is 1.80 × 10−4 M in solution, and the visual detection limit is 1.27 µg/cm2 with the naked eye for the flexible paper-based chemosensor. The proposed flexible chemosensors show a good selectivity and sensitivity which has great potential for effective detection of hypochlorite anions without any spectroscopic instrumentation.

MnxZn1−xO thin films (x = 0%, 1%, 3%, and 5%) were grown on corning glass substrates using sol–gel technique. Single-phase hexagonal wurtzite structure was confirmed using X-ray diffraction. Raman analysis revealed the presence of Mn content with an additional vibrational mode at 570 cm−1. The surface morphology of the samples was observed by scanning electron microscopy which suggested that the grain size increases with an increase in Mn concentration. The optical bandgap increases with increasing Mn concentration due to a significant blueshift in UV–visible absorption spectra. The alteration of the bandgap was verified by the I–V measurements on ZnO and Mn-ZnO films. The various functional groups in the thin films were recorded using FTIR analysis. Magnetic measurements showed that MnxZn1−xO films are ferromagnetic, as Mn induces a fully polarised state. The effect of Mn2+ ions doping on MnxZn1−xO thin films was investigated by extracting various parameters such as lattice parameters, energy bandgap, resistivity, and magnetisation. The observed coercivity is about one-fifth of the earlier published work data which indicates the structure is soft in nature, having less dielectric/magnetic loss, and hence can be used as ultra-fast switching in spintronic devices.

The drawbacks of utilizing nonrenewable energy have quickened innovative work on practical sustainable power sources (photovoltaics) because of their provision of a better-preserved decent environment which is free from natural contamination and commotion. Herein, the synthesis, characterization, and application of Mo chalcogenide nanoparticles (NP) as alternative sources in the absorber layer of QDSSCs is discussed. The successful synthesis of the NP was confirmed as the results from the diffractive peaks obtained from XRD which were positive and agreed in comparison with the standard. The diffractive peaks were shown in the planes (100), (002), (100), and (105) for the MoS2 nanoparticles, (002), (100), (103), and (110) for the MoSe2 nanoparticles, and (0002), (0004), (103), as well as (0006) for the MoTe2 nanoparticles. MoSe2 presented the smallest size of the nanoparticles, followed by MoTe2 and, lastly, by MoS2. These results agreed with the results obtained using SEM analysis. For the optical properties of the nanoparticles, UV–Vis and PL were used. The shift of the peaks from the red shift (600 nm) to the blue shift (270–5 nm and 287–9 nm (UV–Vis)) confirmed that the nanoparticles were quantum-confined. The application of the MoX2 NPs in QDSSCs was performed, with MoSe2 presenting the greatest PCE of 7.86%, followed by MoTe2 (6.93%) and, lastly, by MoS2, with the PCE of 6.05%.

The electronic structures and optical properties of pure, B-doped, Zn-doped and B-Zn co-doped tri-s-triazine g-C3N4 were studied by using first-principles method. The results show that the band gaps of all doped g-C3N4 systems decrease relative to that of pure g-C3N4. The band gap of B-doped g-C3N4 is the smallest, 1.546 eV. The band gaps of Zn-doped and B-Zn co-doped g-C3N4 are very close, 2.047 eV and 2.100 eV, respectively. Although the absorption peaks of all doped g-C3N4 systems exhibit blue shift, and the strength of absorption peak of B-Zn co-doped g-C3N4 decreases relative to that of pure g-C3N4, the optical absorptions of doped g-C3N4 are enhanced in visible light range. When the wavelength is larger than 405 nm and less than 526 nm, the optical absorption of B-Zn co-doped g-C3N4 is enhanced, while the optical absorptions of all doped g-C3N4 systems are enhanced when the wavelength is larger than 526 nm. The optical absorption of B-Zn co-doped g-C3N4 is the strongest between 539 nm and 750 nm, then B- and Zn-doped g-C3N4 in order, while that of B-doped g-C3N4 is the strongest when the wavelength is larger than 750 nm, then B-Zn co-doped g-C3N4, and Zn-doped g-C3N4.

CdSe:Sm nanocrystals (NCs) were synthesized by a water phase method, and their structures, shapes and optical properties were further characterized. X-ray diffraction (XRD) analysis suggested that both the CdSe and CdSe:Sm NCs contained (111), (220) and (311) lattice planes in the zinc blende structure overlapped with the (002), (110) and (112) lattice planes in the wurtzite structure, and the diameters were about 4.2, 3.3 and 2.3 nm for CdSe, CdSe:Sm(8%) and CdSe:Sm(10%) NCs, respectively. All of the CdSe:Sm NCs were monodispersed and uniform spherical nanocrystals. The CdSe:Sm(10%) NCs prepared with different reaction times exhibited constant absorption spectra at 430 nm and a fixed emission peak at 581 nm. Compared with those of pure CdSe NCs, the fluorescence emission of CdSe:Sm(10%) NCs blueshifted 20–36 nm, and the absorption peak initially redshifted and then blueshifted with the prolongation of reaction time. In addition, the Sm2+ doping decreased the fluorescence lifetime and increased the quantum yields (QYs) of CdSe NCs. The QYs of CdSe:Sm NCs increased initially and then decreased with the increase in the amount of doped Sm2+. The initial pH and charge compensator concentration also exhibited significantly enhanced fluorescence emission of CdSe:Sm NCs. CdSe and CdSe:Sm NCs were prepared via a water phase method. The structure and optical properties were investigated; the Sm2+ was doped into CdSe NCs successfully. CdSe and CdSe:Sm NCs all exhibit nearly spherical particles, doping Sm2+ increases the particle size, and the QYs are also enhanced. As the reaction time varies to 1, 2, 5, 8 and 10 h, the emission spectra of CdSe NCs present redshift, while the CdSe:Sm NCs have a fixed emission peak, which is the characteristic peak of Sm2+. As compared with pure CdSe NCs, the emission spectra of CdSe:Sm NCs appear blueshift by 20–36 nm. Doping Sm2+ into CdSe NCs can improve the optical properties.

In this work, two selenium layers of 500-nm thickness, nano-sandwiched with Ag nanosheets of 100-nm thickness (Se/Ag/Se), are subjected to in situ monitoring of the structural and optical transitions during heating over a temperature range of 303–473 K by x-ray diffraction and ultraviolet–visible light spectrophotometry, respectively. The Se/Ag/Se thin films are observed to exhibit a transformation from an amorphous to a polycrystalline phase at 343 K. Increasing the temperature above 363 K enhances the crystallinity of the hexagonal phase, reduces the microstrain, increases the crystallite size and reduces the defect density. Accordingly, the optical absorption spectra are redshifted upon heating. The redshift is accompanied by a transition in the energy band gap from 2.03 eV to 1.85 eV as the material structural phase is transformed from amorphous to polycrystalline. Increasing the temperature causes the energy band gap to shrink. Another permanent phase transformation from hexagonal to orthorhombic is detected when the Se/Ag/Se system is allowed to cool. Scanning electron microscopy images show that the phase transformation converts the grains of Se/Ag/Se films from wire-shaped to nanotubes. The second phase transformation causes a blueshift in the absorption coefficient spectra and increases the energy band gap. The structural and optical parameter enhancements achieved via heating render the Se thin films more suitable for optoelectronic applications.

Many studies, focused in TiO2 nanotubes obtained by anodization, uses frequently a NH4F salt concentration from 0.3 – 0.5 wt% and the information about how voltage and time affects to nanotubes morphology, are valid for these concentration, moreover, this range induces a long time of anodized. TiO2 nanotubes were prepared by anodization process of a set of titanium foils in order to study the influence of time and voltage on the morphology of them. The anodization process consists of an organic media of ethylene glycol and 1.2 wt% of NH4F salts, voltage from 5 to 30 V for a time period from 1 to 6 hours, constant potential of 30 V for a time lapse from 10 to 360 minutes and 5 to 480 seconds. All anodized samples are rinsed and annealed to 400 °C by 3 hours to obtain an anatase crystalline structure. The morphological characterization was carried out by Field Emission Scanning Electron Microscopy (FESEM) to verify the presence of the nanostructures: nanopores, nanotubes and nanograss, these nanostructures were identified to appear for a time period from 5 to 480 seconds, 10 to 60 minutes and 1 to 6 hours, respectively. The surface morphology, inner diameter and length of the nanotubes varied with the electrochemical anodization parameters. Raman spectroscopy was used for optical characterization in order to identify the changes in signal intensity and Eg mode Shift and it was observed that intensity suffers an increment and Eg mode suffers a blue shift as a thickness function.

We developed a sensitive and accurate colorimetric method to detect iodide (I–) and l-thyroxine by etching gold triangular nanoplates (AuTNPs) in the presence of H2O2. The morphological changes of AuTNPs resulted in vivid color variations of the nanoprism dispersion, accompanied by a blue shift of the in-plane localized surface plasmon resonance (LSPR) peak, enabling visual and photometric sensing. To improve the accuracy and the linear range, the overlapping out-of-plane and in-plane LSPR peaks of the AuTNPs were deconvoluted, and a new calibration model was established by plotting the square of the in-plane LSPR wavelength shift against the concentration of the analytes. Under optimum conditions, the limits of detection (LODs) for iodide reached 1 μM and 50 nM by the naked eye and photometry, respectively, and the corresponding LODs for l-thyroxine were 200 and 13.7 nM. Importantly, improved accuracy and linear range were obtained by the new data processing strategy. The method was applied in detecting ...

ZnO 50 nm/Ag 10 nm/SnO2 50 nm (ZAS) tri-layer films were deposited on a glass substrate by RF and DC magnetron sputtering and then underwent rapid thermal annealing in a low vacuum of 1×10-3 Torr to investigate the effects of post-deposition annealing on the optical and electrical properties of the films. The peak intensity of the XRD pattern related to the ZnO (002) peak of the annealed films was higher than that of the as-deposited film and the full width at half-maximum of the ZnO (002) diffraction peak of the annealed films was smaller than that of the as-deposited film. Therefore, the crystallinity of ZnO was improved by rapid annealing. However, crystallization of the Ag interlayer and SnO2 surface layer were not significantly affected by the annealing temperature, compared with the ZnO bottom layer. From the observed electrical properties and optical band gap, it was concluded that the blue shift in the optical band gap is related to the carrier density of the films. The band gap increased from 4.19 eV to 4.24 eV, with the carrier density increasing from 7.09 × 1021 cm-3 to 7.77 × 1021 cm-3. However, the film annealed at 450 ℃ showed a decreased band gap energy of 4.17 eV due to the decreased carrier density of 6.80 × 1021 cm-3. The as-deposited ZAS films showed a sheet resistance of 11.0 Ω/□ and a visible transmittance of 80.8%, whereas the films annealed at 450 ℃ had a higher visible transmittance of 82.3% and a lower sheet resistance of 6.55 Ω/□. The results indicate that ZAS thin films may be possible substitutes for conventional Sn-doped In2O3 transparent electrodes in various optoelectronic devices. (Received May 13, 2019; Accepted June 20, 2019)

The Mn-doped nano-ZnO powder was successfully synthesized via co-precipitation and vacuum annealing and the scanning electron microscopy (SEM), X-ray diffracton (XRD), ultraviolet visible absorption (Uv–vis) and photoluminescence (PL) of as-synthesized samples were characterized. The SEM and XRD show that the morphology of the synthesized samples was wurtzite nanosheets and nanoparticles at low doping concentration and with increasing Mn-doping concentration, mainly became to nanoparticle with a size of about 50nm. All of the ultraviolet absorption edges of Mn-doped ZnO have blue shift from Uiv-vis spectra and PL spectra show that Mn-doping significantly enhance the visible excitation band compared with pure ZnO, which indicates that Mn-doping not only produces elemental energy levels, but also affects the intrinsic defect energy levels of ZnO.

We synthesized BaAl12O19:Eu2+ phosphors by the molten salt flux method at the relatively low temperature. The phase and luminescent properties of the synthesized phosphors were investigated. To investigate the influence of synthesis temperature on the phase formation of phosphors, different synthesis temperatures were carried out in the work. With the increasing synthesis temperature, the phase of product transfers from BaAl2O4 to BaAl12O19. And the emission band shifts to shorter wavelength due to the phase transition with the increasing synthesis temperature. The reason of blue shift is revealed by the analysis of crystal field splitting. The synthesized BaAl12O19:Eu2+ phosphors also show high color purity and excellently thermal stability.

Superparamagnetic nanoparticles have astounding applications in the field of biomedical. Co-precipitated Nd3+ doped Mn0.5Zn0.5NdxFe2−xO4, where x = 0, 0.025, 0.050, 0.075, 0.1 ferrite nanoparticles are examined utilizing various characterization methods at room temperature. XRD, FE-SEM and FTIR analysis reveal the origination of cubical spinel ferrite structure. A transition from paramagnetic to superparamagnetic nature has been observed with Nd3+ addition (x > 0.025). To comprehend the relationship of structural and magnetic properties a cation distribution has been proposed and found to be in agreement with experimental observations. Absorption spectra show a red shift with Nd3+ doping. PL spectra show a blue shift in band edge emission upto x = 0.050. The results obtained from UV–visible spectroscopy and PL spectroscopy show an anti-Stokes shift with Nd3+ doping owing to the photon upconversion process. The obtained magnetic results in fusion with optical results for ferrite nanoparticles are prospective in imaging and biomedical applications.

We have used wet chemical methods to fabricate colloidal CdSe/CdSm/ZnSen core/intermediate/shell (C/I/S) nanocrystals (NCs), where m = 1 and 2 and n = 1–4 are the number of monolayers. The growth was monitored by using Raman and UV–vis spectroscopy, which demonstrated the formation of correct CdSe/CdSm/ZnSen C/I/S NCs. X-ray diffraction studies proved single-phase NCs crystallized in the zincblende-type structure. Photoluminescence (PL) studies have indicated that after photoexcitation C/I/S NCs generate simultaneously type-I and type-II emissions, namely EI and EII, associated with CdSe/CdSm and CdSm/ZnSen structures, respectively. For a specific value of m = 2, we have found the redshift of both EI and EII emissions when n is increased from 1 to 4. The PL studies versus the laser-excitation power (Pex) up to about four orders of magnitude allow us to identify the origin of two emissions. A large blueshift of the EII peak is ascribed to the band bending effect resulting from the spatially separated photoexcited carriers in type-II NCs. It appears that the dependence of the EII peak on the cube root of Pex ( P e x 1 / 3 ) is linear while that of the EI peak on P e x 1 / 3 is almost constant. In this work, we also point out that the emission intensity (I) of EI and EII can be tuned by changing the values of n and Pex, where I obeys a power law I ∝ P e x k , with k = 0.7–1.0 dependent on the emission type. The nature of these phenomena is discussed in comparison with previous studies on C/S and C/I/S nanoheterostructures.