Large-scale synthesis of single-source,thermally stable,and dual-emissive Mn-doped Zn–Cu–In–S nanocrystals for bright white light-emitting diodes

The global demand for resource sustainability is growing. Thus, the development of single-source, environment-friendly colloidal semiconductor nanocrystal (NC) phosphors with broadband emission spectra is highly desirable for use as color converters in white light-emitting diodes (WLEDs). We report herein the gram-scale synthesis of single-source, cadmium-free, dual-emissive Mn-doped Zn–Cu–In–S NCs (d-dots) by a simple, non-injection, low-cost, one-pot approach. This synthesis method led to the formation of NCs with continuously varying compositions in a radial direction because each precursor had a different reactivity. Consequently, the d-dots exhibited two emission bands, one that could be attributed to Mn emission and a second that could be ascribed to the band edge of the Zn–Cu–In–S NCs. The emission peaks assigned to band edge were tunable by modifying the particle size and composition. The prepared d-dots also exhibited the characteristic zero self-absorption, a quantum yield of 46%, and good thermal stability. Combining a commercial blue light-emitting diode (LED) chip with optimized d-dots as color converters gave a high color rendering index of up to 90, Commission Internationale de l’eclairage color coordinates of (0.332, 0.321), and a correlated color temperature of 5,680 K. These results suggest that cadmium-free, thermally stable, single-phase d-dot phosphors have potential applications in WLEDs.

Open image in new window

     

Determination of required hydrophilic–lipophilic balance of citronella oil and development of stable cream formulation

Context: Citronella oil is reported to have excellent mosquito-repellent activity. To develop a stable cream formulation (emulsion), its hydrophilic–lipophilic balance (HLB) value is important.

Objective: To determine required hydrophilic–lipophilic balance (rHLB) value of citronella oil and to develop stable cream formulation.

Materials and Methods: Emulsions of citronella oil were prepared by phase inversion temperature technique using water, Tween 80 and Span 80. A first series of 11 emulsions with HLB values ranging from 5.0 to 15.0 and a second series of eight emulsions with smaller interval in HLB values from 11.0 to 13.8 were prepared. Emulsions were evaluated for creaming index, droplet size and turbidity to determine rHLB. Utilizing determined rHLB, citronella oil cream was formulated and evaluated for different texture parameters. rHLB of light liquid paraffin was also determined for validation of methodology.

Results: rHLB of light liquid paraffin and citronella oil was determined to be 11.80 and 12.60, respectively. Stable citronella oil cream was developed with 10% emulsifier blend. Texture parameters were found to be consistent over the entire storage period.

Discussion: Creaming index, droplet diameter, percent increase in droplet diameter and turbidity are the established parameters to determine rHLB and to develop stable emulsion. Emulsions with optimum emulsifier concentration resulted in less percentage creaming index, smallest droplet, less percentage increase in droplet diameter and highest turbidity. Texture properties evaluation ensures the stability of the developed cream.

Conclusion: rHLB value of citronella oil was found 12.6 and a stable cream was formulated utilizing determined rHLB.     

GET 8–2019 State Primary Standard of Units of Air Kerma,Air Kerma Rate,Exposure, Exposure Rate,and Energy Flux of X-Radiation and Gamma Radiation

Measurement Techniques - Results of studies designed to improve GET 8–2011, the State Primary Standard of the units of air kerma, air kerma rate, exposure, exposure rate, and energy flux of...     

Improvements in Get 163–2010, the State Primary Standard of the Units of Disperse Parameters of Aerosols,Suspensions, and Power-Like Materials

Measurement Techniques - Methods and devices for measurement of the disperse parameters of aerosols, suspensions, and powderlike materials included in the improved version of GET 163–2010 are...     

Microstructure and mechanical properties of V–Ti–N microalloyed steel used for fracture splitting connecting rod

A new kind of V–Ti–N high strength microalloyed medium carbon steel has been developed, which is used for fracture splitting connecting rod. In this article, the characteristics of this carbon steel and its production process were studied. The microstructure, precipitated phases and their effects on mechanical properties were investigated by optical microscope, SEM, and TEM. The results showed that the steel was constituted of ferrite and pearlite. By reducing the finish rolling temperature and accelerating the cooling rate after rolling, microstructure with fine grain ferrite and narrow lamellar space pearlite could be obtained in V–Ti–N microalloyed medium carbon, and a large number of precipitated phases distributed over ferrite. These led the tensile strength to be more than 1000 MPa, yield strength (YS) more than 750 MPa. The impact fractograph showed typically brittle fracture characteristic.     

Synthesis and characterization of mechanically strong carboxymethyl cellulose–gelatin–hydroxyapatite nanocomposite for load-bearing orthopedic application

Novel three-dimensional hybrid polymer–hydroxyapatite nanocomposites have been developed as load-bearing synthetic bone graft through in situ mineralization process, using natural polymers carboxymethyl cellulose (CMC) and gelatin (Gel) as matrix. This process is simple and does not involve any chemical cross-linker. Detailed structural and physicochemical characterization of the samples disclosed that incorporation of gelatin with CMC assists the formation of CMC-Gel polymeric network of new conformational structure through non-covalent interactions (H-bond). The formation of hydroxyapatite (HA) in this polymeric network was occurred in such a fashion that the HA serves as bridging molecule which strengthen the polymeric network more and formed a mechanically strong three-dimensional CMC-Gel-HA nanocomposite. The synthesized CMC-Gel-HA nanocomposites have compressive strength and modulus in the range of 40–86 MPa and 0.4–1.2 GPa, respectively, analogous to human cancellous as well as cortical bone. In vitro cell interaction of the synthesized nanocomposites with osteoblast-like MG-63 cells has been evaluated. Results showed that synthesized CMC-Gel-HA nanocomposite promote cells for high alkaline phosphatase activity and extracellular mineralization. Extracellular mineralization ability of nanocomposite was investigated by alizarin red staining and von Kossa staining. Biodegradable nature and bone apatite formation ability of CMC-Gel-HA nanocomposite under simulated physiological environment were investigated by different characterization processes. Results indicated that the synthesized CMC-Gel-HA nanocomposite has great potential to be used as regenerative bone graft in major load-bearing region.     

State Primary Standard of the Unit of Activity of Radionuclides,Unit of Specific Activity of Radionuclides,and Unit of Flux of Alpha and Beta Particles and of Photons of Radionuclide Sources Get 6–2016

Measurement Techniques - The composition of State Primary Standard of the unit of activity of radionuclides, unit of specific activity of radionuclides, and unit of flux of α and β...     

Synthesis,characterization and photocatalytic behavior of TiO2–SiO2 mesoporous composites in hydrogen generation from water splitting

TiO₂–SiO₂ mesoporous composite photocatalysts with different proportions (in wt%) of TiO₂ and SiO₂ (TiO₂–SiO₂ = 20:80, 40:60, 60:40, 80:20 and 100:0) were prepared by loading TiO₂ on as-synthesized Si–MCM-41 using sol–gel method. The physicochemical properties of composites were investigated by powder X-ray diffraction, N₂ adsorption–desorption measurements, transmission electron microscopy and UV–Vis diffuse reflectance spectroscopy. It is revealed that the titanium species are dispersed as TiO₂ having interaction with the surface of the support. Even at high TiO₂ loading, the mesostructural feature of MCM-41 was found to be intact without pore blockages. The change in morphology of TiO₂ particle was observed with increase in TiO₂ loading which may be due to different environment for the growth of TiO₂. The photocatalytic evaluation of composites was carried out in production of hydrogen by water splitting. Among the prepared samples, mesoporous composite containing 60 % TiO₂ (MTi60) has shown the best results (0.08805 mmol of H₂/h/g of TiO₂) compared to other composite photocatalysts. The catalytic performance of this sample was further enhanced (~8 times) after loading 1 % Pt in water splitting (0.70161 mmol of H₂/h/g of TiO₂). 1 % Pt loaded on pure TiO₂ (MTi100) showed hydrogen evolution of the magnitude 0.26 mmol of H₂/h/g of TiO₂. TiO₂–SiO₂ mesoporous composite photocatalyst showed much higher activity (~1.9 times) than amorphous silica-embedded titania catalyst having same composition.     

Highly stable,mesoporous mixed lanthanum–cerium oxides with tailored structure and reducibility

Pure and mixed lanthanum and cerium oxides were synthesized via a reverse microemulsion-templated route. This approach yields highly homogeneous and phase-stable mixed oxides with high surface areas across the entire range of La:Ce ratios from pure lanthana to pure ceria. Surprisingly, all mixed oxides show the fluorite crystal structure of ceria, even for lanthanum contents as high as 90%. Varying the La:Ce ratio not only allows tailoring of the oxide morphology (lattice parameter, pore structure, particle size, and surface area), but also results in a fine-tuning of the reducibility of the oxide which can be explained by the creation of oxygen vacancies in the ceria lattice upon La addition. Such finely controlled syntheses, which enable the formation of stable, homogeneous mixed oxides across the entire composition range, open the path towards functional tailoring of oxide materials, such as rational catalyst design via fine-tuning of redox activity.     

Development of strong and bioactive calcium phosphate cement as a light-cure organic–inorganic hybrid

In this research, light cured calcium phosphate cements (LCCPCs) were developed by mixing a powder phase (P) consisting of tetracalcium phosphate and dicalcium phosphate and a photo-curable resin phase (L), mixture of hydroxyethylmethacrylate (HEMA)/poly acrylic-maleic acid at various P/L ratios of 2.0, 2.4 and 2.8?g/mL. Mechanical strength, phase composition, chemical groups and microstructure of the cured cements were evaluated at pre-set times, i.e. before and after soaking in simulated body fluid (SBF). The proliferation of Rat-derived osteoblastic cells onto the LCCPCs as well as cytotoxicity of cement extracts were determined by cell counting and 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyl-2H-tetrazolium bromide assay after different culture times. It was estimated from Fourier transforming infrared spectra of cured cements that the setting process is ruled by polymerization of HEMA monomers as well as formation of calcium poly-carboxylate salts. Microstructure of the cured cements consisted of calcium phosphate particles surrounded by polymerized resin phase. Formation of nano-sized needlelike calcium phosphate phase on surfaces of cements with P/L ratios of 2.4 and 2.8?g/mL was confirmed by scanning electron microscope images and X-ray diffractometry (XRD) of the cured specimen soaked in SBF for 21?days. Also, XRD patterns revealed that the formed calcium phosphate layer was apatite phase in a poor crystalline form. Biodegradation of the cements was confirmed by weight loss, change in molecular weight of polymer and morphology of the samples after different soaking periods. The maximum compressive strength of LCCPCs governed by resin polymerization and calcium polycarboxylate salts formation was about 80?MPa for cement with P/L ratio of 2.8?g/mL, after incubation for 24?h. The strength of all cements decreased by decreasing P/L ratio as well as increasing soaking time. The preliminary cell studies revealed that LCCPCs could support proliferation of osteoblasts cultured on their surfaces and no cytotoxic effect was observed for the extracts of them.     

Time–temperature equivalence in the tack and dynamic stiffness of polymer prepreg and its application to automated composites manufacturing

A recently developed peel test designed to simulate the automated tape lay-up (ATL) process was used to measure tack and dynamic stiffness of newly developed ATL prepregs. Resin was extracted from the prepreg process before impregnation of the fibres. Isothermal small amplitude frequency sweeps were carried out in shear rheology to determine time–temperature superposition parameters in the form of Williams–Landel–Ferry equation. Gel permeation chromatography and differential scanning calorimetry demonstrated that the resin was not significantly changed during the prepregging process. The WLF parameters were used to transpose isothermal tack and dynamic stiffness results with excellent agreement found. This relationship offers manufacturers using composite prepreg a method to maximise and maintain tack levels at different feed rates by appropriate changes in temperature. This is of significant importance in improving the reliability of automated composite lay-up processes such as AFP and ATL, whose feed rate must vary to accommodate lay-up operations.     

Formulation and Comparative Characterization of Chitosan,Gelatin, and Chitosan–Gelatin-Coated Liposomes of CPT-11–HCl

Liposomes containing phosphatidylcholine and cholesterol (uncoated) and coated by chitosan, gelatin, and combination of chitosan and gelatin were prepared by the modified ethanol injection method. The aim of this work was to formulate and characterize liposomes of camptothecin (CPT)-11–HCl (Irinotecan HCl) containing chitosan, gelatin, and both polymers as coating materials; and also to increase its circulation longevity when compared with the free drug while maintaining the agent in its active lactone form. Size, shape, zeta potential, encapsulation efficiency, stability study, in vitro, and in vivo release study were used for characterization of liposomes. The size of liposomes was in the order of uncoated?<?chitosan coated?<?gelatin coated?<?combination of chitosan and gelatin coated. The zeta potential of liposomes was in the order of combination of chitosan and gelatin coated?>?chitosan coated?>?gelatin coated?>?uncoated. The formulations showed the long-term stability. The encapsulation efficiency of liposomes was in order of combination of chitosan and gelatin coated?>?gelatin coated?>?chitosan coated?>?uncoated. The in vitro and in vivo release of drug was observed in the order of combination chitosan and gelatin coated?>?gelatin coated?>?chitosan coated?>?uncoated.     

Superfluid State of 4He on Graphane and Graphene–Fluoride: Anisotropic Roton States

We explore the phase behavior of Helium films on two variants of graphene: graphane (graphene coated with H, denoted GH) and graphene–fluoride (GF). A semiempirical interaction with these substrates is used in T=0 K Path Integral Ground State and finite temperature Path Integral Monte Carlo simulations. We predict that ⁴He forms anisotropic fluid states at low coverage. This behavior differs qualitatively from that on graphite because of the different surface composition, symmetry and spacing of the adsorption sites. The ⁴He ground state on both substrates is thus a self-bound anisotropic superfluid with a superfluid fraction ρ _s /ρ lower than 1 due to the corrugation of the adsorption potential. In the case of GF such corrugation is so large that ρ _s /ρ=0.6 at T=0 K and the superfluid is essentially restricted to move in a multiconnected space, along the bonds of a honeycomb lattice. We predict a superfluid transition temperature T? 0.25 (1.1) K for ⁴He on GF (GH). We have studied the elementary excitation spectrum of ⁴He on GF at equilibrium density finding a phonon–maxon–roton dispersion relation that is strongly anisotropic in the roton region. We conclude that these new platforms for adsorption studies offer the possibility of studying novel superfluid phases of quantum condensed matter.     

Density and thermal expansion of Cr–Fe, Fe–Ni, and Cr–Ni binary liquid alloys

Densities and their temperature coefficients of liquid Cr–Fe, Fe–Ni, and Cr–Ni binary alloys have been measured containerless using the technique of electromagnetic levitation. Data have been obtained in a wide temperature range including the supercooled region. The density measurements indicate that these binary systems have a small and positive excess volume, whereas the excess free energies are negative. The temperature coefficients of these alloys can be estimated from those of the pure components. Hence, possible contributions from the temperature dependence of the excess volume can be ignored to calculate the temperature coefficient of density.