Crystalline Structure Properties Research Articles

Crystallization of TiO2 on sputter deposited amorphous titanium thin films

Titanium and titanium dioxide are both very well-known and commonly used materials in today's world. They would also be very promising materials for years to come as their more novel properties are continued to be investigated. For meeting the demands of today's technology and to fine tune its properties, titanium dioxide is still in the scope of scientists from different branches of science.In our study, sputter deposited amorphous titanium thin films on glass substrates were anodically oxidized at 0.7 V for 250, 750, 1250 s in 0.5 M H2SO4 solution to observe their crystalline structure and electrochemical properties. X ray diffraction analysis revealed rutile and anatase crystalline peaks on 250 s and 1250 s anodized samples. Additionally, electrochemical impedance spectroscopy and atomic force microscopy analysis were carried out for investigating the effect of anodization on electrochemical and surface properties of amorphous titanium thin films. Both analysis showed compressive stress related findings in oxide films due to crystallization process.

The phthalocyanine blue-green pigments devices intended for optical filters

The crystalline structure, optical, morphological and optical filter properties of magnesium phthalocyanine (MPc) blue–green pigments layers, grown onto glass substrate by the spin coating route, are studied. Besides the capacitance voltage (C-V) characteristics and resistance versus voltage of MPc organic heterojunctions are investigated showing a negative capacitance (NC) within forward bias voltage at higher frequency. Optical analysis demonstrates a top and valley in transmittance profile within visible range which leads to the occurrence of optical filter properties in organic devices. The (123)-oriented monoclinic lattice is revealed by X-ray patterns, optical transmission attains 67% inside Vis range, and the band gap is found to be of 2.9 eV. Nonlinear optical properties of Mg-Phthalocyanine are studied. Nanotips are revealed by atomic force microscope and a size around of 22.76 nm, and the RMS is of 10.5 nm are evaluated. Obtained parameters from C-V characteristics of MgPc/GaAs heterojunction are described and recorded as a result of applied frequency. Such extracted parameters are Nd ranging in 5.1-31.2x1019 cm−3 and Vbi of 0.18-0.39 V and ΦB of 0.36 –0.41 eV.

Enhanced Thermal and Antibacterial Properties of Stereo-Complexed Polylactide Fibers Doped With Nano-Silver

Stereo-complexed polylactide (sc-PLA) fibers with excellent heat resistance and antibacterial properties were prepared by electrospinning. Due to poor heat resistance, common poly(L-lactide) (PLLA) fibers have poor dimensional stability at high temperatures and cannot be sterilized and recycled as a medical filter material. In this research, PLLA/poly(D-lactide) (PDLA) blends doped with silver nanoparticles (AgNPs) were electrospun to obtain the sc-PLA fibers. The effect of thermal induction temperature on the crystalline structure and thermal properties of sc-PLA fibers was investigated. Moreover, the influence of the addition amount of AgNPs on the crystal structure of sc-PLA fibers was studied, and the antibacterial properties of the sc-PLA fibers with different addition amounts of AgNPs were analyzed. The thermal induction is beneficial to the formation of stereo-complexed crystals of sc-PLA fibers, and finally completely stereo-complexed PLA fibers were obtained. The melting temperature of the completely stereo-complexed PLA fibers was 50°C higher than that of the PLLA fibers; therefore, the sc-PLA fibers have better heat resistance. The addition of AgNPs was conducive to the formation of stereo-complexed crystals of sc-PLA fibers. In addition, the antibacterial rate of sc-PLA fibers against E. coli and S. aureus was 99.99 ± 0.01% when the addition amount of AgNPs was only 0.15 wt%. The fiber membrane obtained in this experiment can be used as a reusable filter material, and the sc-PLA fiber membrane has broad application prospects in the biomedical field.

Tailoring the morphology of BiNbO4 of polymorph in 2D nanosheets for enhancement of photocatalytic activity in the visible range

In this study, BiNbO4 nanoplates were successfully synthesized by the molten salt's method. The morphology, crystalline structure, optical and photocatalysis properties were investigated in detail. The crystal structure and micrographs results confirm the existence of polymorph heterostructure and nanoplates like morphology of materials. The photocatalysis results show that the samples exhibit high performance toward decolorating two dyes and also phenol. The methylene orange and Rhodamine B were completely decolored within 80 min under-stimulated light. After 120 min, 20% of the phenol was photodegraded. The results indicated that BiNbO4 nanoplates have superior photocatalytic performance and appropriate conduction and valence band position. The design strategy that can control the morphology of BINbO4 has led to another route of synthesis; the method of synthesis has resulted in environmentally friendly materials that are suitable for photodegradation of pollutants and water splitting applications.

Enhancing the ultraviolet photosensing properties of nickel oxide thin films by Zn–La co-doping

In this work, co-doping effects of transition (Zn) and rare-earth (La) elements on the crystalline structure, surface morphology, photoluminescence, optical and photosensing properties of NiO thin films are studied. NiO, NiO:Zn(1%), NiO:La(1%), and NiO:Zn(1%):La(1%) thin films are fabricated using the nebulizer spray pyrolysis (NSP) method. X-ray diffraction study revealed the cubic NiO structure of all the films. Photoluminescence (PL) spectra of thin films exhibit various emission peaks centered at the wavelengths of 387, 414, 437, 451, 477, and 521 nm. The optical bandgap energy ( E g ) values are found to be 3.46, 3.43, 3.39 and 3.33 eV for NiO, NiO:Zn(1%), NiO:La(1%) and NiO:Zn(1%):La(1%) thin films, respectively. The fabricated (Zn, La) co-doped NiO i.e., NiO:Zn(1%):La(1%) photo-detector exhibits highest responsivity ( R ), external quantum efficiency (EQE) and detectivity ( D *) values of 0.50AW -1 , 169% and 14.5 × 10 9 Jones, respectively as compared to NiO, NiO:Zn(1%) and NiO:La(1%) photo-detectors. The present study revealed that the transition and rare-earth elements co-doping can be an effective approach for tuning the various physical properties of semiconducting oxide films.

Highly-Responsive Broadband Photodetector Based on Graphene-PTAA-SnS2 Hybrid.

The development of wearable systems stimulate the exploration of flexible broadband photodetectors with high responsivity and stability. In this paper, we propose a facile liquid-exfoliating method to prepare SnS2 nanosheets with high-quality crystalline structure and optoelectronic properties. A flexible photodetector is fabricated using the SnS2 nanosheets with graphene-poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine (PTAA) hybrid structure. The liquid-exfoliated SnS2 nanosheets enable the photodetection from ultraviolet to near infrared with high responsivity and detectivity. The flexible broadband photodetector demonstrates a maximum responsivity of 1 × 105 A/W, 3.9 × 104 A/W, 8.6 × 102 A/W and 18.4 A/W under 360 nm, 405 nm, 532 nm, and 785 nm illuminations, with specific detectivity up to ~1012 Jones, ~1011 Jones, ~109 Jones, and ~108 Jones, respectively. Furthermore, the flexible photodetector exhibits nearly invariable performance over 3000 bending cycles, rendering great potentials for wearable applications.

Synergistic effects of the hybridization between boron-doped carbon quantum dots and n/n-type g-C3N4 homojunction for boosted visible-light photocatalytic activity.

Dye wastewater has raised a prevalent environmental concern due to its ability to prevent the penetration of sunlight through water, thereby causing a disruption to the aquatic ecosystem. Carbon quantum dots (CQDs) are particularly sought after for their highly tailorable photoelectrochemical and optical properties. Simultaneously, graphitic carbon nitride (g-C3N4) has gained widespread attention due to its suitable band gap energy as well as excellent chemical and thermal stabilities. Herein, a novel boron-doped CQD (BCQD)-hybridized g-C3N4 homojunction (CN) nanocomposite was fabricated via a facile hydrothermal route. The optimal photocatalyst sample, 1-BCQD/CN (with a 1:3 mass ratio of boron to CQD) accomplished a Rhodamine B (RhB, 10mg/L) degradation efficiency of 96.8% within 4h under an 18W LED light irradiation. The kinetic rate constant of 1.39 × 10-2min-1 achieved by the optimum sample was found to be 3.6- and 2.8-folds higher than that of pristine CN and un-doped CQD/CN, respectively. The surface morphology, crystalline structure, chemical composition and optical properties of photocatalyst samples were characterized via TEM, FESEM-EDX, XRD, FTIR, UV-Vis DRS and FL spectrometer. Based on the scavenging tests, it was revealed that the photogenerated holes (h+), superoxide anions (∙O2-) and hydroxyl radicals (∙OH) were the primary reactive species responsible for the photodegradation process. Overall, the highly efficient 1-BCQD/CN composite with excellent photocatalytic activity could provide a cost-effective and robust means to address the increasing concerns over global environmental pollution.

Enhancement of enzymatic resistance in V-type starch inclusion complexes by hydrothermal treatments

Resistant starch (RS) is well known for its health beneficial effects for glycemic control and gut health. In addition to some commonly reported RS types, such as raw high amylose maize starch (HAMS), potato starch, retrograded starch, and cross-linked starch, formation of starch inclusion complexes could also contribute to an increase in RS content. In this study, V type starch inclusion complexes with two guest compounds, ascorbyl palmitate (AP) and palmitic acid (PA), were formed using the novel “empty” V type method, and hydrothermal treatments were performed to further enhance the RS contents. Complimentary X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were conducted to assess the crystalline structure and thermal properties of the raw and treated inclusion complexes, and simulated in vitro enzymatic digestion was performed to study the structure-digestibility relationship in the treated samples. Although the raw inclusion complex samples exhibited minimal RS contents, all the treatments retarded starch digestion by increasing RS or SDS levels. For both V6h-AP and V6h-PA inclusion complexes, annealing followed by long-term strong acid hydrolysis treatment (ANN-ACH) resulted in the greatest increase in RS content, followed by strong ACH treatments alone. In addition, while presenting a comparable RS level as traditional RS2, the ANN-ACH treated V6h-AP inclusion complex retained a V type crystalline structure, indicating its great potential as a novel type of RS, i.e., RS5. The study findings could have practical implications for the design and modification of RS-containing food for the control and modulation of glycemic response.

Structure and rheological studies of phosphorylated cellulose nanofibrils suspensions

Cellulose nanofibrils (CNFs) are normally handled in the form of aqueous suspensions. Therefore, their rheology and intrinsic flow features in an aqueous state also fascinated the researchers. However, understanding the structure-rheology relationship remains a profound challenge to design CNFs with desirable properties. For that purpose, jute fibers were used as source material (Corchorus olitorius) to produce CNFs, and pretreatment using phosphorylation was applied to facilitate the fibrillation during ultra-sonication. This study aims to investigate the relationship between the microstructure and their rheology for CNF aqueous suspensions as influenced by the temperature and concentration of CNF. The surface chemistry, fiber diameter distribution, crystalline structure, thermal stability, and rheological properties of the obtained CNFs were characterized and compared. The grafting of phosphorous moieties on the surface of the fibers was confirmed by the FTIR, XPS analyses, elemental analyses, and zeta potential. Despite influencing crystallinity, phosphorylation enhanced the diameter of nanofibers. The results demonstrated that phosphorylation did not alter the main chemical structure of cellulose. The crystallographic form of the obtained CNFs remained cellulose I. The resulting fibers have nanometric dimensions (<100 nm) with high absolute zeta potential values (>30 mV). A substantial improvement in flame retardancy has also been noted for CNF due to the presence of phosphate groups. Both steady-state and dynamic rheological measurements were improved significantly upon increasing concentration from 0.5 to 2.5 wt%. All the CNF suspensions demonstrated typical shear-thinning behavior and gel-like viscoelastic character even at low concertation (0.5 wt%) due to the construction of a wire-like matrix structure. The frequency and temperature alteration, however, do not affect the viscoelastic gel-like properties of the CNF suspensions.

Comparison of topotactic and magnetic structures for manganite oxide films

Deliberate manipulation of topotactic transformation via oxygen insertion/extraction offers a feasible way to precisely tune oxygen concentration, B–O coordination occupation and resultant electronic functionalities of perovskite (ABO3)-based oxides. Herein, two methods, a post-annealing CaH2 treatment and an in-situ oxygen-vacancy diffusion using oxygen getter layer, were conducted to achieve topotactic transitions from perovskite to brownmillerite of La0·7Sr0·3MnO3-δ (LSMO, 0 ≤ δ ≤ 0.5) films. The results revealed that delicate control of oxygen composition is the crucial factor for evolutions of crystalline structure and subsequent magnetic properties of LSMO films. In particular, the brownmillerite LSMO film treated by the in-situ oxygen getter layer possesses desirable structural stability over time. In contrast, the topotactic LSMO films using reduction agents CaH2 exhibit compositional and structural inhomogeneities. These findings suggest that adjustable topotactic transformation through anionic oxygen provides a facile strategy for designing multifunctional perovskite-derivative oxide materials.

Preparation and thermoelectric properties of Mn&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt;-doped Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; nanostructures

Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt;, especially its various nanostructures, has been considered as an excellent candidate for application in novel optoelectronic devices due to its ultrahigh mobility and good air-stability. Recent researches exhibited Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; as a candidate of thermoelectric materials by virtue of its ultralow thermal conductivity in comparison with other semimetals or metals. In this work, at first &lt;b&gt;(&lt;/b&gt; Cd&lt;sub&gt;1–&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Mn&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; (&lt;i&gt;x&lt;/i&gt; = 0, 0.05, 0.1) bulk alloys are prepared by high-pressure sintering to suppress the volatilization of As element, and then several kinds of Mn&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt;-doped Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; nanostructures are obtained on mica substrates by chemical vapor deposition (CVD), with bamboo-shoot-nanowire structure forming in a high-temperature region and films in a low-temperature region. Effects of Mn&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; doping on the crystalline structure, phase compositions, microstructures and thermoelectric properties of the Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; nanostructures are systematically studied. Energy-dispersive spectrometer (EDS) analysis at various typical positions of the Mn&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt;-doped Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; nanostructures shows that the Mn content in these nanostructures is in a range of 0.02%–0.18% (atomic percent), which is much lower than the Mn content in &lt;b&gt;(&lt;/b&gt; Cd&lt;sub&gt;1–&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Mn&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; (&lt;i&gt;x&lt;/i&gt; = 0, 0.05, 0.1) parent alloys. The main phases of these nanostructures are all body centered tetragonal &lt;i&gt;α&lt;/i&gt; phase with a small amount of primitive tetragonal &lt;i&gt;α&lt;/i&gt;′ phase. Doping results in the &lt;i&gt;α&lt;/i&gt;″ phase and Mn&lt;sub&gt;2&lt;/sub&gt;As impurity phase occurring. The Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; film presents a self-assembled cauliflower microstructure. Upon Mn&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; doping, this morphology finally transforms into a vertical-growth seashell structure. In a high temperature region of the mica substrate, a unique bamboo-shoot-nanowire structure is formed, with vertical-growth bamboo shoots connected by nanowires, and at the end of these nanowires grows a white pentagonal flower structure with the highest Mn content of 0.18% (atomic percent) for all the nanostructures. Conductivity of the Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; film and the bamboo-shoot-nanowire structure are ～20 and 320 S/cm, respectively. The remarkable conductivity enhancement can be attributed to higher crystallinity and the formation of nanowire conductive network, which significantly increase carrier concentration and Hall mobility. The Hall mobility values of the nanowire structures range from 2271 to 3048 cm&lt;sup&gt;2&lt;/sup&gt;/(V·s) much higher than the values of 378–450 cm&lt;sup&gt;2&lt;/sup&gt;/(V·s) for the films. The Seebeck coefficient for the bamboo-shoot-nanowire structure is in a range of 59–68 µV/K, which is about 15% higher than those for the films (50–61 µV/K). Although maximal power factor of the bamboo-shoot-nanowire structure is 14 times as high as that of the thin film, reaching 0.144 mW/(m·K&lt;sup&gt;2&lt;/sup&gt;) at room temperature, this value is still one order of magnitude lower than the previously reported value of 1.58 mW/(m·K&lt;sup&gt;2&lt;/sup&gt;) for Cd&lt;sub&gt;3&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt; single crystal.

Modifying Jahn–Teller distortion by epitaxial stress in LaMnO3 films for tunning electron localization

The effect of epitaxial stress on Jahn–Teller (JT) distortion in epitaxial LaMnO3 (LMO) films has been investigated. Both 2θ–ω scans and reciprocal space maps (RSMs) indicate that LMO samples are subjected to compressive stress. Obvious Laue oscillations can be detected in 2θ–ω scans, indicating the high quality of samples. RSMs of symmetry peak (001) and asymmetry peak (−103) imply different epitaxial stress for LMO films deposited on different substrates. Raman spectra measurements reveal that the degree of JT distortion can be well tuned via the epitaxial stress which may further influence on the electron localization in the films. This study might benefit to understanding the correlation between crystalline structure and electrical transport properties of LMO films and related LMO-based superlattices.

Observation of Dominant Nuclei and Magic-Sized CdS Nanoparticles in a Single-Phase System.

Cadmium sulfide nanoparticles (CdS NPs) were synthesized by using cadmium acetate and thiourea as precursors and sodium oleate as the surfactant under different cadmium acetate concentrations in anhydrous ethanol. Cadmium (Cd) precursor concentration greatly affected the nucleation-growth of CdS NPs. In extremely dilute solution with a Cd precursor concentration of 0.1 mmol · L-1, an overlapped nucleation and growth corresponding to two pronounced absorption peaks at 310 nm and 350 nm, respectively, was observed. Unparalleled nucleation was dominant within very long reaction time until 10 hours. The nuclei and the resulting magic-sized CdS NPs may be used as seeds to prepare size and shape controllable nanoparticles. On the contrary, at a high Cd precursor concentration (5 mmol · L-1), nucleation and growth were separated. Only one first exciton absorption peak standing for the growth of regular CdS NPs appeared at 440 nm. Many techniques including transmission electron microscopy (TEM), X-ray powder diffraction (XRD), ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) spectrometers were applied to characterize the morphology, crystalline structure, and optical properties of CdS NPs.

Influence of high energy (MeV) Au9+ ion irradiation for modification of properties in scaffold-assisted electro synthesized PbSe nanowires

Nanowires have attracted widespread attention as a result of breakthrough in nanotechnology due to their new features and potential applications. Lead selenide (PbSe) nanowires have acquired a lot of interest recently because of their exceptional performance and wide range of applications. Electrochemical deposition was used to create arranged PbSe nanowires in polycarbonate templates. Here, the effects of 120 MeV Au9+ swift heavy ion irradiation at fluence ranging from 1 × 109 to 1 × 1012 ions/cm2 on the morphology, crystalline structure, optical and electrical properties were investigated. In the Ion Distribution and Quick Calculation of Damage mode, the TRIM (Transport of Ions in Matter) simulation was employed, and the damage was computed using quick statistical estimates based on the Kinchin-Pease formalism. The primitive and ion irradiated nanowires were characterized by X-ray diffraction, Scanning electron microscopy, Raman spectroscopy, UV–Visible spectroscopy and Current-Voltage characteristics. The results of Raman spectroscopy and X-ray diffraction imply that irradiated nanowires with minimal strain retain their crystallinity. The irradiation has shown strong impact on the optical constants like optical band gap, refractive index, high frequency and static dielectric constant and electron effective mass with no morphological change. At room temperature, the results of electrical properties studies for both primitive and irradiated nanowires are also provided. Our findings encourage the employment of nanowires in the future for photonic and electronic applications.

Effects of Variety and Growing Location on Physicochemical Properties of Starch from Sweet Potato Root Tuber.

Three sweet potato varieties with purple-, yellow-, and white-fleshed root tubers were planted in four growing locations. Starches were isolated from their root tubers, their physicochemical properties (size, iodine absorption, amylose content, crystalline structure, ordered degree, lamellar thickness, swelling power, water solubility, and pasting, thermal and digestion properties) were determined to investigate the effects of variety and growing location on starch properties in sweet potato. The results showed that granule size (D[4,3]) ranged from 12.1 to 18.2 μm, the iodine absorption parameters varied from 0.260 to 0.361 for OD620, from 0.243 to 0.326 for OD680 and from 1.128 to 1.252 for OD620/550, and amylose content varied from 16.4% to 21.2% among starches from three varieties and four growing locations. Starches exhibited C-type X-ray diffraction patterns, and had ordered degrees from 0.634 to 0.726 and lamellar thicknesses from 9.72 to 10.21 nm. Starches had significantly different swelling powers, water solubilities, pasting viscosities, and thermal properties. Native starches had rapidly digestible starch (RDS) from 2.2% to 10.9% and resistant starch (RS) from 58.2% to 89.1%, and gelatinized starches had RDS from 70.5% to 81.4% and RS from 10.8% to 23.3%. Two-way ANOVA analysis showed that starch physicochemical properties were affected significantly by variety, growing location, and their interaction in sweet potato.

Synergistic effect of glass bead and glass fiber on the crystalline structure, thermal stability, and mechanical, rheological, and morphological properties of polyamide 6 composites

The effect of filler amount and kind on the crystalline structure, thermal stability, and mechanical, rheological, and morphological properties of polyamide 6 (PA6) was studied in this research. Glass bead and glass fiber were chosen as mineral fillers. They were incorporated to PA6 solely or in mixed formulations at different proportions (hybrid composites). Tensile strain, tensile strength, impact strength, flexural strain, flexural strength, melt flow index, crystallite size, and thermal degradation parameters were determined for all composites. The addition of glass bead or glass fiber increased the brittleness of pure PA6. The incorporation of glass fiber to pure PA6 improved flexural, impact, and tensile strengths, and mixing of glass bead with pure PA6 polymer caused deterioration of both (tensile and flexural) strengths, but enhanced impact strength. Among hybrid composites, the highest flexural, tensile, and impact strength values were achieved with 15 wt% glass bead and 15 wt% glass fiber content. The addition of glass bead and/or glass fiber to PA6 polymer caused a decrement in melt flow index value. X-ray diffraction results indicated that pure PA6 polymer had α- and γ-crystalline forms, and the reinforcement of glass bead or glass fiber would induce the crystallization into γ-form. It was also found that the incorporation of glass bead or glass fiber influenced the lamellar thickness, and pure PA6 gave thicker lamellar crystal than that of glass bead/fiber-reinforced PA6 and its hybrid composites. Higher thermal stability with glass bead or glass fiber incorporation was found as compared to pure PA6 polymer.

A Metastable p-Type Semiconductor as a Defect-Tolerant Photoelectrode.

A p-type Cu3Ta7O19 semiconductor was synthesized using a CuCl flux-based approach and investigated for its crystalline structure and photoelectrochemical properties. The semiconductor was found to be metastable, i.e., thermodynamically unstable, and to slowly oxidize at its surfaces upon heating in air, yielding CuO as nano-sized islands. However, the bulk crystalline structure was maintained, with up to 50% Cu(I)-vacancies and a concomitant oxidation of the Cu(I) to Cu(II) cations within the structure. Thermogravimetric and magnetic susceptibility measurements showed the formation of increasing amounts of Cu(II) cations, according to the following reaction: Cu3Ta7O19 + x/2 O2 → Cu(3−x)Ta7O19 + x CuO (surface) (x = 0 to ~0.8). With minor amounts of surface oxidation, the cathodic photocurrents of the polycrystalline films increase significantly, from <0.1 mA cm−2 up to >0.5 mA cm−2, under visible-light irradiation (pH = 6.3; irradiant powder density of ~500 mW cm−2) at an applied bias of −0.6 V vs. SCE. Electronic structure calculations revealed that its defect tolerance arises from the antibonding nature of its valence band edge, with the formation of defect states in resonance with the valence band, rather than as mid-gap states that function as recombination centers. Thus, the metastable Cu(I)-containing semiconductor was demonstrated to possess a high defect tolerance, which facilitates its high cathodic photocurrents.

Synthesis and enhanced photoluminescence properties of red emitting divalent ion (Ca2+) doped Eu:Y2O3 nanophosphors for optoelectronic applications

This work presents the synthesis of Y2O3:Eu3+,xCa2+ (x = 0 mol%, 1 mol%, 3 mol%, 5 mol%, 7 mol%, 9 mol%, 11 mol%) nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic, display, and lighting applications. The X-ray diffraction (XRD) patterns of the proposed nanophosphor reveal its structural properties and crystalline nature. The transmission electron microscope (TEM) results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca2+. Fourier transform infrared spectroscopy (FTIR) and Raman vibrations also confirm the presence of Y–O vibration and subsequently explain the crystalline nature, structural properties, and purity of the samples. All the synthesized nanophosphors samples emit intense red emission at 613 nm (5D0→7F2) under excitation with 235, 394 and 466 nm wavelengths of Eu3+ ions. The photoluminescence (PL) emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength, respectively. The emission intensity of Y2O3:Eu3+,xCa2+ (5 mol%) is increased 8-fold as compared to Eu:Y2O3. Doping with Ca2+ ions enhances the emission intensity of Eu:Y2O3 nanophosphors due to an increase in energy transfer in Ca2+→Eu3+ through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix. It is also observed that the optical band gap and the lifetime of the 5D0 level of Eu3+ ions in Y2O3:Eu3+,xCa2+ nanophosphor sample gets changed with a doping concentration of Ca2+ ions. Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%, respectively. CIE, CCT, and color purity values (>98%) show an improved red-emitting nanophosphor in the warm region of light, which makes this material superior with a specific potential application for UV-based white LEDs with security ink, display devices, and various other optoelectronics devices.

Sputter-grown Eu-doped WO3-Eu2(WO4)3 composite red phosphor thin films

Eu3+-activated WO3-Eu2(WO4)3 luminescent composite thin films are grown on low-cost slide glass substrates by radio frequency sputtering and then annealing in an air atmosphere furnace. The films obtained by sputtering 12 at.% of Eu-added WO3 target afforded a two-phase composite structure comprising Eu-doped WO3 and Eu2(WO4)3 after annealing. The composite thin films annealed at 600 °C exhibited strong red emission after growing at room temperature compared to those annealed at 500 °C under the excitation of 254, 394, and 465 nm corresponding to ultraviolet, near-ultraviolet, and blue light, respectively. The thin films grown at low temperatures without annealing did not emit under ultraviolet light. The crystalline structure, surface morphology, and optical properties, such as transmittance and photoluminescence, of the films grown at 500 °C were almost similar to those of the thin films grown at room temperature when they were annealed at the same temperature. Pure WO3 thin films without Eu doping showed similar crystallization behavior under the same annealing conditions as Eu-added composite films; however, they did not exhibit photoluminescence properties. Our report on the integration of thin-film red phosphors on glass substrates is promising for the development of low-cost and large-area optical devices activated at various excitation wavelengths.

Ultrafast synthesis of HKUST-1 nanoparticles by solvothermal method: Properties and possible applications

Although an astounding variety of Metal-Organic Frameworks (MOFs) has been synthesized so far, the search for fast and efficient methods that yield greener and superior crystalline structures is yet an ongoing challenge. For the first time, the Hong Kong University of Science and Technology (HKUST-1) MOF has been synthesized by an efficient non-conventional solvothermal method through a Monowave 50 (Anton Paar) reactor. The synthesis has been carried out at 5, 10, 15, and 30 min instead of staggering times of 10 to 24 h. Its crystalline structure, crystallite size, morphology, particle size, specific surface, and optical properties have been characterized. The presumed presence of monocrystalline structures along with a roughly band gap energy at 3.5 eV makes them compelling nanostructures for a variety of applications.