Liquid Phase Precursor Research Articles

Brominated graphene as a versatile precursor for multifunctional grafting.

A non-destructive and versatile chemical reduction method was used to dissolve and subsequently brominate few-layer graphene sheets (FLGs); the direct covalent attachment of bromine to the graphene framework was demonstrated by X-ray photoelectron spectroscopy (XPS). The brominated few-layer graphenes (FLG-Br) provide a convenient, stable, liquid-phase precursor, suitable for the synthesis of a variety of directly functionalised graphenes. As an example, the FLG-Br species was used to initiate atom transfer radical polymerisation (ATRP), to obtain poly(methyl methacrylate) (PMMA)-grafted graphene (FLG-PMMA), which was six times more dispersible in acetone than controls. In addition, the FLG-Br is active for nucleophilic substitution reactions, as illustrated by the preparation of methoxypolyethylene glycol (mPEG)- and OH-substituted derivatives. The products were characterised by thermogravimetric analysis coupled with mass spectrometry (TGA-MS), XPS and Raman spectroscopy. Grafting ratios (GR) for these polymer-grafted materials varied between 6 and 25%; even at these GRs, all graphene derivatives showed increased solubility in organic solvents.

Preparation of a Film Electrolyte Based on Calcium Zirconate on a Porous Electrode by a Chemical Liquid-Phase Method

A modification of a solution method for preparing solid oxide electrolyte films was developed. It is based on using a suspension consisting of a solution of inorganic salts and of a nanodispersed precursor powder prepared from the same solution. As demonstrated by the example of calcium zirconate, this procedure allows the number of applications of the liquid-phase precursor, required to obtain a dense electrolyte film on a porous support, to be considerably decreased relative to the procedure using a salt solution. The influence of the concentration of the precursor powder in the suspension on the microstructure of CaZr0.9Y0.1O3–δ films was analyzed.

Synthesis and optical properties of P5+ co-doped Ba3SiO5:Eu2+ orange persistent phosphor

By co-doping the P5+ ions into Ba3SiO5:Eu2+, we synthesized new orange persistent phosphor using cellulose assisted liquid phase precursor (LPP) method. The emission spectra showed a typically broad orange emission band centered at 575 nm attributed to the 4f65d1 → 4f7 transition of Eu2+ ions under 400 nm excitation source. The persistent luminescence property of Eu2+ doped Ba3SiO5 orange phosphor was enhanced by co-doping non-equivalent phosphorus ions into silicon sites. This enhancement can be explained by formation of the trapping center due to the charge compenstation. Consequently, the afterglow decay exhibited an orange emission for more than 5 min after irradiation at under 365 nm for 1 min.

Exquisite morphology, highly emissive yellow Sr1.44Ba0.46SiO4:0.1Eu2+ phosphor synthesized by a liquid phase precursor process

Yellow phosphors are the major components of contemporary solid-state lights. YAG:Ce3+ is a widely adopted yellow phosphor component; however, it too has limitations. Here, we report the synthesis and application of a very highly efficient yellow-emitting orthosilicate phosphor. Yellow-emitting Sr1.44Ba0.46SiO4:0.1Eu2+ was synthesized by an unconventional cellulose template liquid phase precursor process (CTLPP). The naturally abundant and nonhazardous cellulose template facilitates efficient synthesis at lower temperatures. The synthesized phosphor was indexed to α-Sr2SiO4 phase and exhibited broad excitation and broad emission with a peak at 545 nm, very high intensity, almost 130% of commercial YAG upon excitation at 450 nm. The morphology of the phosphors was also nearly spherical, which also enables their use in WLEDs. Use of non-stoichiometric Si precursors (i.e. Sr1.44Ba0.46SixO4:0.1Eu2+, x = 0.95, 1.0 and 1.05) in the process resulted in remarkable effects on the morphology (size and surface) and luminescent characteristics and exceptional quantum efficiencies of the phosphors.

Preparation of the Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte with high ionic conductivity

A new effective method is proposed for synthesis of the Li1.5Al0.5Ge1.5(PO4)3 powdered solid electrolyte of NASICON structure with high lithium ionic conductivity. The advantage of the method consists in use of a liquid-phase precursor based on the water-soluble Ge(IV) oxalate complex. Chemical interaction in a multicomponent solution containing a liquid-phase precursor results in a target product without the formation of intermediate compounds. This makes it possible to diminish considerably the synthesis temperature (to 650°C) and duration of preparation of Li1.5Al0.5Ge1.5(PO4)3 powders owing to a better homogenization of the reaction mixture and also to simplify the technological operations. The synthesized Li1.5Al0.5Ge1.5(PO4)3 powders are studied by the XRD, DSC/TG, and IR spectroscopy methods, as well as by chemical analysis, SEM, and impedance spectroscopy. The conditions are determined for production of polycrystalline Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte with the maximum bulk ionic conductivity of 1 × 10–3 S/cm at room temperature.

Synthesis of New Sr3RE2(Ge3O9)2 (RE=La, Y) cyclogermanates by liquid-phase precursor methods

New cyclogermanates Sr3RE2(Ge3O9)2 (RE=La, Y) with Ca3Y2(Si3O9)2 cyclosilicate structure type have been prepared by two liquid-phase precursor routes: the citrate and the Pechini methods. The phase composition, morphology and optical properties of the intermediate and final products have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance spectroscopy (DRS). The thermogravimetric (TGA) and differential thermal analyses (DTA) were used to study the thermal decomposition of the precursors. The powder XRD measurements indicate that the phase formation of Sr3RE2(Ge3O9)2 (RE=La, Y) (S.G. C2/c, Z=4) takes place after 20h annealing at 800°C. The DRS data revealed that the cyclogermanates are promising optical hosts.

Synthesis of Eu, Dy co-doped SrAl2O4 phosphors by using liquid phase precursor process

Synthesis of Eu, Dy co-doped SrAl2O4 phosphors by using liquid phase precursor process

Synthesis and photoluminescence properties of oxynitride phosphors M0.98Si2O2N2: [formula omitted] (M=Ba, Sr, Ca) using the cellulose assisted liquid phase precursor process

Oxynitride phosphors M0.98Si2O2N2: Eu0.022+ (M=Ba, Sr, Ca) for white LEDs were synthesized at 1300, 1400, and 1500°C by using the partially cellulose assisted liquid phase precursor (PLPP) process and compared with solid state reaction (SSR) process. MSi2O2N2 (M=Ba, Sr, Ca) crystal structure was obtained from M0.98Si2O2N2: Eu0.022+ phosphor fired at 1400°C using the PLPP process. However these phosphors were not synthesized through the SSR process at same temperature. M0.98Si2O2N2: Eu0.022+ (M=Ba, Sr, Ca) phosphors from PLPP produced a blue color emission at 487nm (380nm excitation), a green color emission at 528nm (374nm excitation), and a yellow color emission at 538nm (371nm excitation). M0.98Si2O2N2: Eu0.022+ phosphors from PLPP had higher luminescence and crystallinity compared with those obtained from the SSR process. The prepared phosphors were analyzed by X-ray diffraction (XRD), photoluminescence (PL) and field-emission scanning electron microscopy (FE-SEM).

Amorphous aluminum-carbide and aluminum–magnesium-carbide nanoparticles from gas phase activation of trimethylaluminum and octamethyldialuminummagnesium using simultaneous spatially and temporally focused ultrashort laser pulses

Gas-phase laser irradiation of head-space AlMe3(g) using simultaneous spatially and temporally focused pulses results in nucleation of Al-rich nanoparticles, which fall from the gas phase into the liquid-phase precursor to give a black suspension of nanoparticles. Isolation of the particles and characterization by transmission electron microscopy, X-ray dispersive energy, vibrational, and X-ray photoelectron spectroscopy identify the material as amorphous aluminum- and carbide-containing nanoparticles. An analogous experiment using Al2MgMe8 as a precursor results in nanoparticles containing both Al and Mg atoms.

New design of nano-structured SrTiO3 powder using a cellulose-assisted LPP method

Strontium titanate (SrTiO3) powder has been prepared through a liquid-phase precursor (LPP) method involving strontium (Sr) acetate and different types of titanium (Ti) raw materials; the powders were synthesized using two kinds of lactate complex and TiCl3. The effects from the addition of the Ti raw materials to the nanostructure and the resultant synthetic efficiency were investigated in this work for the development of nano-sized particles and a low firing temperature. The morphology and size of the SrTiO3 nanopowders were controlled by adjusting the Sr- and Ti-precursor concentrations and the selection of the type of Ti raw material. The most-effective raw material was selected and then used as the basis for the attainment of the results in accordance with the ratio. Using X-ray diffraction (XRD), phase analyses of the samples calcined at different temperatures and compositions were performed. SEM was used for the characterization of the morphologies of the raw materials and reaction products, and they varied from ~25nm to ~50nm.

Synthesis of high efficiency LaPO4: Ce3+, Tb3+ phosphors using the cellulose assisted liquid phase precursor method

Green emitted LaP1+xO4: Ce3+, Tb3+ (LAP) was synthesized using the cellulose assisted liquid phase precursor method (LPP). As the H3BO3 flux increased, the photoluminescence intensity became stronger linearly. With increasing phosphorous concentration, the crystallinity was enhanced. The excitation wavelength for the fabricated LAP was 290nm and the strongest emission was 546nm. By using the cellulose assisted LPP method, various liquid phased raw materials were reacted and synthesized, yielding homogeneous and nano-sized particles. The size of the obtained particles ranged from 300 to 500nm.

Synthesis of high intensity green emitting (Ba,Sr)SiO4:Eu2+ phosphors through cellulose assisted liquid phase precursor process

Green emitting phosphor (Ba1−x,Sr1−x)SiO4:2xEu2+, x=0.03, 0.05, 0.1, and 0.15 were synthesized through a Liquid Phase Precursor Process (LPP). Liquid phase precursor method is reported to result in phosphors with markedly increased emission intensities compared to other synthesis methods. Here microcrystalline cellulose (MCC) and hydroxypropyl cellulose (HPC) templates were studied to achieve high efficiency green phosphors. The phase formation was investigated by XRD analysis which showed the conformation of the Ba2SiO4 (JCPDS card number 761631) phase. The obtained samples exhibited broad excitation spectra with maximum at 430nm and a green emission centered around 520nm. An optimized dopant concentration was selected and the effect of two different types of cellulose, i.e. MCC and HPC templates on the emission properties was considered. It was found that the samples synthesized using HPC and fired at 1050°C under a reducing atmosphere, showed a high intensity of almost 2 times that of the MCC sample. Further experiments were conducted by varying viscosity, particle weight, and molecular weight of the HPC template. It was found that the green emission from the (Ba,Sr)SiO4:Eu2+ increased with the increase in viscosity and molecular weight of the template.

Influence of TiO2 precursors on BaTiO3 by liquid phase precursor method

Barium titanate (BaTiO3) powder was prepared from the liquid phase precursor reaction of barium acetate with different types of Ti raw materials. Powders were synthesized using barium titanate, lactate A, lactate B, and TiCl3 fired at 600, 800, 900, and 1000°C. The effects of the addition of titanium raw materials on the nanostructure and synthesis efficiency were investigated in this work to develop nano-sized particles at a low firing temperature. BaTiO3 nanopowders with different size distributions were synthesized using a liquid phase precursor with a titanium lactate complex as the Ti source at a low temperature. Also, the morphology and size of BaTiO3 nanopowders were controlled by adjusting the barium and titanium precursor concentration and the type of titanium raw materials. The X-ray diffraction of powders calcined at different temperatures and compositions was undertaken. The average size of the nanopowders was identified using a scanning electron microscope which varied from ~25nm to ~50nm.

Luminescence properties of nanosized Y3Al5O12Ce3+ phosphor synthesized by liquid phase precursor method.

A novel liquid-phase precursor (LPP) method using precursor nanoparticles (PNs) is proposed to synthesize yttrium aluminum garnet nano-sized phosphor (Y3Al5O12:Ce3+, nano-YAG:Ce) at 1100-1500 degrees C for 5 h. The influences of the heat-treatment and morphology properties of the PNs on the luminescence properties of the nano-YAG:Ce phosphor were investigated. Nano-YAG:Ce phosphor with better morphology and high luminescence efficiency was obtained with heat-treatment of PNs at 1200 degrees C. With more heat treatment, the phosphor particles agglomerated more, and the emission intensity increased. The broad photoluminescence excitation (PLE) and photoluminescence (PL) spectra of the nano-YAG:Ce phosphor were centered at 341 nm and 466 nm, respectively, due to the 4f --> 5d energy transition. The nonsymmetrical emission spectra range of 470-750 nm was centered at 529.2 nm due to the 5d --> 4f energy transition of Ce3+. The nano-YAG:Ce, and micro-YAG:Ce phosphors synthesized by the LPP method using precursor microparticles (PMs) and PNs were investigated and compared.

Influence of amorphous and crystalline type precursor intermediates on the morphology and luminescence properties of green emitting β-Ca2SiO4:Eu2+ phosphor synthesized using a liquid phase precursor method

Influence of precursor intermediates (PI) on the synthesis of high efficient green emitting β-Ca2SiO4:Eu2+ (β-C2S:Eu) phosphors were demonstrated by a novel liquid-phase-precursor (LPP) method utilizing (a) CaCl2–EuCl3, (b) Ca(NO3)2–EuCl3, (c) CaCl2–Eu(NO3)3, and (d) Ca(NO3)2–Eu(NO3)3 combinations as precursors. The crystallinity and morphology of the PI analyzed using X-ray diffraction and high-resolution transmission electron microscopy measurements showed both the amorphous and crystalline type precursor intermediates (API and CPI) depending upon the metal-source materials. The final morphology and luminescence properties of β-C2S:Eu phosphors were found to be strongly influenced by the crystallinity (amorphous and crystalline) and morphology of the PIs. The APIs have led to regular-shaped homogeneous phosphor particles with higher luminescence when compared with the CPIs.

Characterization of Carbon Nanotube Growth via CVD Synthesis from a Liquid Precursor

As novel theories and uses of carbon nanotubes (CNT) advance, it becomes increasingly important to characterize the methods of production. One such method of CNT production uses a liquid phase precursor (hydrocarbon with nanoparticle catalyst mix) that is injected into a tube furnace with a flowing carrier gas. The CNTs are grown in high purity and are collected on the surface of the quartz tube. The system allows for a number of variables to be tested such as growth temperatures, flow rate of the carrier gas, precursor injection rates and variations of precursor mix however, here only thermal effects are considered. Under thermal conditions ranging from 500 to 850°C, multi-walled carbon nanotubes (MWCNTs) are synthesized and characterized to determine inner and outer diameter as well as tube thickness.

Synthesis of α-SiC from tetramethylsilane by chemical vapor deposition at high temperature

Tetramethylsilane (TMS) is a common liquid-phase precursor that is used in the synthesis of β-SiC by chemical vapor deposition (CVD). At temperatures above 1500 °C, however, it has been shown that C is also formed together with SiC. In this study, based on thermodynamic modeling, we report on the successful synthesis of single-phase SiC with no evidence of the inclusion of C from TMS through CVD at temperatures over 1900 °C. X-ray diffraction data showed that α-SiC phases are formed at temperatures over 2000 °C. On the basis of these results, TMS can be used as a precursor for α-SiC synthesis.

Liquid Phase Precursor driven approach for the synthesis of Ca–Sr–Ba orthosilicate phosphors for white LED applications

Liquid Phase Precursor driven approach for the synthesis of Ca–Sr–Ba orthosilicate phosphors for white LED applications

Synthesis of High Luminescence Efficiency Nanosized Ca2SiO4:Eu2+ Phosphor Powder by Liquid Phase Precursor Technique

A high luminescence efficiency nanosized Ca2SiO4:Eu2+ (n-Ca2SiO4:Eu2+) phosphor powder has been synthesized from the nanosized precursor material using a new liquid phase precursor technique. Nanosized (≈100 nm) precursor materials were obtained after ball-mill treatment using various solvents. The synthesized Ca2SiO4:Eu2+ phosphor powder showed monoclinic structure with P21/n (number 14) space group. The n-Ca2SiO4:Eu2+ powder exhibited a broad excitation spectrum extending from 225 to 450 nm and highest excitation and emission peaks were located at ~365 and 502 nm due to the 4f65d1–4f7 (8S7/2) energy transitions of Eu2+. The emission intensity of the n-Ca2SiO4:Eu2+ powder synthesized by ball mill treatment using acetone and oleic acid was almost comparable (0.85) with the standard phosphor (P46-YAG; λex = 450 nm).

SrxAl2O4:Eu2+0.015Dy3+0.03 (x=1.1–1.7) green emitting phosphors with efficient emissive properties

Monophasic SrAl2O4:Eu2+ Dy3+ with varying Sr2+ concentration was synthesized in monoclinic symmetry by the Liquid Phase Precursor method. The composition Sr1.7Al2O4:Eu2+0.015Dy3+0.03 showed the 200% emission compared with commercial Sr0.97Al2O4:Eu2+0.01 Dy3+0.02. Time decay measurements of the doped samples were conducted for the green emission at 525nm. All the prepared samples exhibit rapid decay and ensued phosphorescence with the longer decay times which are comparable to the commercial sample. Quantum yield product measurements results suggested that the synthesized phosphors show enhanced emissive properties over the commercial phosphor. The composition Sr1.7Al2O4:Eu2+0.015Dy3+0.03 had a photoluminescence quantum yield of 31.63%, nearly 12.7% more than the commercial sample.