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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Carbon elimination from silicon kerf: Thermogravimetric analysis and mechanistic considerations

40% of ultrapure silicon is lost as kerf during slicing to produce wafers. Currently, kerf is not recycled due to engineering challenges and costs associated with removing its abundant impurities. Carbon left behind from the lubricant remains as one of the most difficult contaminants to remove in kerf without significant silicon oxidation. The present work enables to better understand the mechanism of carbon elimination in kerf which can aid the design of better processes for kef recycling and low cost photovoltaics. In this paper, we studied the kinetics of carbon elimination from silicon kerf in two atmospheres: air and N 2 , under a regime of no-diffusion-limitation. Here, we report the apparent activation energy in both atmospheres using three methods: Kissinger, and two isoconversional approaches. In both atmospheres, a bimodal apparent activation energy is observed, suggesting a two stage process. Furthermore, a reaction mechanism is proposed in which (a) C-C and C-O bond cleavage reactions occur in parallel with polymer formation; (b) at higher temperatures, this polymer fully degrades in air but leaves a tarry residue in N 2 that accounts for about 12% of the initial total carbon.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2015

Efficient nanorod-based amorphous silicon solar cells with advanced light trapping

We present a simple, low-cost, and scalable approach for the fabrication of efficient nanorod-based solar cells. Templates with arrays of self-assembled ZnO nanorods with tunable morphology are synthesized by chemical bath deposition using a low process temperature at 80 °C. The nanorod templates are conformally coated with hydrogenated amorphous silicon light absorber layers of 100 nm and 200 nm thickness. An initial efficiency of up to 9.0% is achieved for the optimized design. External quantum efficiency measurements on the nanorod cells show a substantial photocurrent enhancement both in the red and the blue parts of the solar spectrum. Key insights in the light trapping mechanisms in these arrays are obtained via a combination of three-dimensional finite-difference time-domain simulations, optical absorption, and external quantum efficiency measurements. Front surface patterns enhance the light incoupling in the blue, while rear side patterns lead to enhanced light trapping in the red. The red response in the nanorod cells is limited by absorption in the patterned Ag back contact. With these findings, we develop and experimentally realize a further advanced design with patterned front and back sides while keeping the Ag reflector flat, showing significantly enhanced scattering from the back reflector with reduced parasitic absorption in the Ag and thus higher photocurrent generation. Many of the findings in this work can serve to provide insights for further optimization of nanostructures for thin-film solar cells in a broad range of materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Effect of thermal annealing on microstructure evolution and mechanical behavior of an additive manufactured AlSi10Mg part

The powder-bed laser additive manufacturing (AM) process is widely used in the fabrication of three-dimensional metallic parts with intricate structures, where kinetically controlled diffusion and microstructure ripening can be hindered by fast melting and rapid solidification. Therefore, the microstructure and physical properties of parts made by this process will be significantly different from their counterparts produced by conventional methods. This work investigates the microstructure evolution for an AM fabricated AlSi10Mg part from its nonequilibrium state toward equilibrium state. Special attention is placed on silicon dissolution, precipitate formation, collapsing of a divorced eutectic cellular structure, and microstructure ripening in the thermal annealing process. These events alter the size, morphology, length scale, and distribution of the beta silicon phase in the primary aluminum, and changes associated with elastic properties and microhardness are reported. In conclusion, the relationship between residual stress and silicon dissolution due to changes in lattice spacing is also investigated and discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Defects in low-k organosilicate glass and their response to processing as measured with electron-spin resonance

Defect concentrations in low-k organosilicate glass films deposited on high-resistivity silicon were measured with electron-spin resonance. Bulk dangling bonds were detected. Both plasma exposure and ultraviolet exposure were used. During argon electron cyclotron resonance plasma exposure, ion and photon bombardment increased the measured defect concentrations. Ultraviolet lamp exposure was also shown to increase the defect concentrations. Dielectric samples with various dielectric constants were examined showing that as the value of the dielectric constant was lowered, the defect concentrations were shown to increase significantly.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Study of CMOS strip sensor for future silicon tracker

Monolithic silicon sensors developed with High-Voltage CMOS (HV-CMOS) processes have become highly attractive for charged particle tracking. Compared with the standard CMOS sensors, HV-CMOS sensors can provide larger and deeper depletion regions that lead to larger signals and faster charge collection. They can provide high position resolution, low material budget, high radiation hardness and low cost that are desirable for high performance tracking in harsh collision environment. Various studies have been conducted to explore the technology feasibility for the large-area tracking systems at future collider experiments. CHESS (CMOS HV/HR Evaluation for Strip Sensor) sensor series have been developed as an alternative solution to the conventional silicon micro-strip detectors for the ATLAS inner tracker upgrade. The first prototype (named CHESS1) was to evaluate the diode geometry and the in-pixel analog electronics. Obtained test results were used to optimize the second prototype (named CHESS2). CHESS2 was implemented with a full digital readout architecture and realized as a full reticle sized monolithic sensor. Here, the basic characteristics of the CHESS2 prototype sensors and their performance in response to different input signals are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

a-Si:H TFT-silicon hybrid low-energy x-ray detector

Direct conversion crystalline silicon X-ray imagers are used for low-energy X-ray photon (4-20 keV) detection in scientific research applications such as protein crystallography. In this paper, we demonstrate a novel pixel architecture that integrates a crystalline silicon X-ray detector with a thin-film transistor amorphous silicon pixel readout circuit. We describe a simplified two-mask process to fabricate a complete imaging array and present preliminary results that show the fabricated pixel to be sensitive to 5.89-keV photons from a low activity Fe-55 gamma source. Furthermore, this paper presented can expedite the development of high spatial resolution, low cost, direct conversion imagers for X-ray diffraction and crystallography applications.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Direct nanoscale mapping of open circuit voltages at local back surface fields for PERC solar cells

The open circuit voltage (V OC) is a critical and common indicator of solar cell performance as well as degradation, for panel down to lab-scale photovoltaics. Detecting V OC at the nanoscale is much more challenging, however, due to experimental limitations on spatial resolution, voltage resolution, and/or measurement times. Accordingly, in this work an approach based on Conductive Atomic Force Microscopy is implemented to directly detect the local V OC , notably for monocrystalline Passivated Emitter Rear Contact (PERC) cells which are the most common industrial-scale solar panel technology in production worldwide. This is demonstrated with cross-sectioned monocrystalline PERC cells around the entire circumference of a poly-Aluminum-Silicide via through the rear emitter. The V OC maps reveal a local Back Surface Field extending ~2 μm into the underlying p-type Si absorber due to Al in-diffusion as designed. Such high spatial resolution methods for photovoltaic performance mapping are especially promising for directly visualizing the effects of processing parameters, as well as identifying signatures of degradation for silicon and other solar cell technologies.

14 SOLAR ENERGY↗
DOE OSTI2018

Preferred Orientation Enhancement in FeCo/SiO{sub 2} Nanocomposite Films Induced by Cu Underlayer

We prepared FeCo/SiO{sub 2} thin films through depositng initial materials on various thickness Cu seed layers by sol-gel spin-coating and magnetron-sputtering methods. As-prepared composite films were reduced in hydrogen to induce texture growth. Structure, magnetic property, and surface topography of the films were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and atomic force microscopy (AFM). These experimental data indicate that the ratio values of I{sub (200)}/I{sub (110)} of the thin films are all larger than 1 for all the samples, indicating that FCC-copper is in favor of promoting (200) FeCo texture, but more thickness will reduce this advantage. Cu underlayers can also promote the out-of-plane magnetic anisotropy of the films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Low Solution Temperature Heat Treatment of AlSi{sub 9}Cu{sub 3}(Fe) High-Pressure Die-Casting Actual Automotive Components

Usually, high-pressure die-casting (HPDC) components cannot be heat-treated at high temperature without the occurrence of surface blisters, which are unacceptable for surface finish and may reduce the mechanical properties. In this context, the purpose of the present paper was to analyze the effectiveness of special low solution temperature T6 heat treatment in overcoming this limit for HPDC AlSi{sub 9}Cu{sub 3} alloy. Very low solution temperatures (< 450 °C, followed by 165 °C aging) to prevent the occurrence of blisters were combined with commonly used times (from 1 to 16 h) ensuring the feasibility of industrial application. Treatments were conducted on samples extracted from actual castings to evaluate the typical defects encountered in common production. Properties were analyzed by means of visual inspection, microstructural observations, image analysis, hardness, tensile tests and fractography. The results showed that it is possible to use solubilization temperatures below 450 °C for several hours in a T6 treatment to give strengthening without relevant blistering in AlSi{sub 9}Cu{sub 3} alloy. The optimum match of properties was provided by a solution treatment at 430 °C for 4 h followed by an aging at 165 °C for 8 h, which gave a yield increase of ~ 50 MPa, an increase in ductility and the best Quality Index value.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Friction Stir Processing on the Microhardness, Wear and Corrosion Behavior of Al6061 and Al6061/SiO{sub 2} Nanocomposites

An effect of the friction stir processing (FSP), its pass numbers and addition of the SiO{sub 2} nanoparticles on microhardness, wear behavior and corrosion performance of the Al6061 aluminum alloy was investigated. Scanning electron microscopy (SEM) and optical microscopy were utilized to characterize the microstructure of the alloy, FSPed and composite samples. SEM observations revealed that the SiO{sub 2} particles were not uniformly dispersed in the matrix after two passes of FSP. However, increasing the pass number more than two passes resulted in a great improvement in the distribution of the SiO{sub 2} particles. The application of FSP led to overall softening compared to the base metal. Softening of the Al6061 alloy was probably attributed to the coarsening of Mg{sub 2}Si. Corrosion resistance of the FSPed samples found a significant reduction compared to the base metal. Applying higher pass number of the process and also addition of the SiO{sub 2} nanoparticles improved the wear behavior of the samples.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Solid-state NMR study of geopolymer prepared by sol-gel chemistry

Geopolymers are a new class of materials formed by the condensation of aluminosilicates and silicates obtained from natural minerals or industrial wastes. In this work, the sol-gel method is used to synthesize precursor materials for the preparation of geopolymers. The geopolymer samples prepared by our synthetic route have been characterized by a series of physical techniques, including Fourier-transform infrared, X-ray diffraction, and multinuclear solid-state NMR. The results are very similar to those obtained for the geopolymers prepared from natural kaolinite. We believe that our synthetic approach can offer a good opportunity for the medical applications of geopolymer. -- Graphical abstract: Geopolymer prepared by the sol-gel route has the same spectroscopic properties as the sample prepared from the natural kaolinite. Display Omitted

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Luminescence of Tb-doped Ca{sub 3}Y{sub 2}(Si{sub 3}O{sub 9}){sub 2} oxide upon UV and VUV synchrotron radiation excitation

Powders of calcium yttrium silicate, Ca{sub 3}Y{sub 2}(Si{sub 3}O{sub 9}){sub 2}, containing 0.1-3% Tb{sup 3+} were prepared using a sol-gel method and characterized with XRD, IR, UV-vis and UV-VUV spectroscopies at room temperature and 10 K. Structural analysis revealed pure monoclinic phase of Ca{sub 3}Y{sub 2}(Si{sub 3}O{sub 9}){sub 2} after heat-treatment at 1000 deg. C. Infrared spectroscopy showed that between 800 and 900 deg. C a short-range structural organization of the components proceeded, yet without crystallization. A strong emission of Tb{sup 3+} had been observed both in the green part of the spectrum due to the {sup 5}D{sub 4}{yields}{sup 7}F{sub J} transitions and in the blue-violet region owing to the {sup 5}D{sub 3}{yields}{sup 7}F{sub J} radiative relaxation. The color of the light could be tuned from yellowish-green to bluish-white both by means of the dopant content and the temperature of synthesis. Efficient luminescence of Tb{sup 3+}-doped Ca{sub 3}Y{sub 2}(Si{sub 3}O{sub 9}){sub 2} phosphors could also be obtained upon stimulation with vacuum ultraviolet synchrotron radiation demonstrating that an energy transfer from the host to the Tb{sup 3+} ions takes place. - Graphical abstract: Luminescence of Ca{sub 3}Y{sub 2}(Si{sub 3}O{sub 9}){sub 2}:Tb covers the whole visible region of electromagnetic spectrum and the relative intensity of the blue part against the green one depends on the activator content and technological parameters of preparation. Highlights: > VUV-UV-vis luminescence of Ca{sub 3}Y{sub 2}(Si{sub 3}O{sub 9}){sub 2}:Tb at RT and 10 K was analyzed. > Tb{sup 3+} ion can be excited directly or through the host lattice. > Specific structure of the host allowed to get intense {sup 5}D{sub 3}{yields}{sup 7}F{sub J} luminescence. > At 10 K an exciton is formed and radiatively relaxes with the use of a defect.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Solid solubility of Yb{sub 2}Si{sub 2}O{sub 7} in {beta}-, {gamma}- and {delta}-Y{sub 2}Si{sub 2}O{sub 7}

This paper examines the structural changes with temperature and composition in the Yb{sub 2}Si{sub 2}O{sub 7}-Y{sub 2}Si{sub 2}O{sub 7} system; members of this system are expected to form in the intergranular region of Si{sub 3}N{sub 4} and SiC structural ceramics when sintered with the aid of Yb{sub 2}O{sub 3} and Y{sub 2}O{sub 3} mixtures. A set of different compositions have been synthesised using the sol-gel method to obtain a xerogel, which has been calcined at temperatures between 1300 and 1650 deg. C during different times. Isotherms at 1300 and 1600 deg. C have been analysed in detail to evaluate the solid solubility of Yb{sub 2}Si{sub 2}O{sub 7} in {beta}-Y{sub 2}Si{sub 2}O{sub 7} and {gamma}-Y{sub 2}Si{sub 2}O{sub 7}. Although Yb{sub 2}Si{sub 2}O{sub 7} shows a unique stable polymorph ({beta}), Yb{sup 3+} is able to replace Y{sup 3+} in {gamma}-Y{sub 2}Si{sub 2}O{sub 7} and {delta}-Y{sub 2}Si{sub 2}O{sub 7} at high temperatures and low Yb contents. IR results confirm the total solid solubility in the system and suggest a constant SiOSi angle of 180 deg. in the Si{sub 2}O{sub 7} unit across the system. The temperature-composition diagram of the system, obtained from powder XRD data, is dominated by the {beta}-RE{sub 2}Si{sub 2}O{sub 7} polymorph, with {gamma}-RE{sub 2}Si{sub 2}O{sub 7} and {delta}-RE{sub 2}Si{sub 2}O{sub 7} showing reduced stability fields. The diagram is in accordance with Felsche's diagram if average ionic radii are assumed for the members of the solid solution at any temperature, as long as the {beta}-{gamma} phase boundary is slightly shifted towards higher radii. - Graphical abstract: Polymorphism, as a function of average radii, in the systems Yb{sub 2}Si{sub 2}O{sub 7}-Y{sub 2}Si{sub 2}O{sub 7} (dotted symbols), Lu{sub 2}Si{sub 2}O{sub 7}-Y{sub 2}Si{sub 2}O{sub 7} (solid symbols) and Sc{sub 2}Si{sub 2}O{sub 7}-Y{sub 2}Si{sub 2}O{sub 7} (open symbols) compared to phase boundaries of Felsche for pure rare earth disilicates. Circles: {beta}-RE{sub 2}Si{sub 2}O{sub 7}. Squares: {gamma}-RE{sub 2}Si{sub 2}O{sub 7}. Triangles: {delta}-RE{sub 2}Si{sub 2}O{sub 7}. Highlights: > {beta}-Yb{sub 2}Si{sub 2}O{sub 7} and {beta}-Y{sub 2}Si{sub 2}O{sub 7} form a complete solid solution at 1300 deg. C. > Yb(III) replaces Y in {gamma}- and {delta}-RE{sub 2}Si{sub 2}O{sub 7}, at low Yb contents and high temperatures. > Phase diagram of the Yb{sub 2}Si{sub 2}O{sub 7}-Y{sub 2}Si{sub 2}O{sub 7} system is dominated by the {beta}-RE{sub 2}Si{sub 2}O{sub 7} phase. > {gamma}- and {delta}-phases show very reduced stability fields. > {beta}-{gamma} phase boundary in Felsche's diagram should be slightly shifted towards higher radii.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Preparation, characterization and catalyst application of ternary interpenetrating networks of poly 4-methyl vinyl pyridinium hydroxide-SiO{sub 2}-Al{sub 2}O{sub 3}

In this work, Al{sub 2}O{sub 3} was mixed with SiO{sub 2} and poly 4-vinylpyridine by the sol-gel method in order to make a composite which is used as a heterogeneous basic catalyst for Knoevenagel condensation reaction. The physical and chemical properties of the composite catalyst were investigated by XRD, FT-IR, TG, BET and SEM techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compound and malononitrile. The reactions were performed in solvent-free conditions and the product was obtained in high yield and purity after a simple work-up. The effects of the amount of catalyst, amount of monomer for the synthesis of composite and recyclability of the heterogeneous composite were investigated. The composite catalyst used for this synthetically useful transformation showed considerable level of reusability besides very good activity. - Graphical abstract: In this paper, we report the synthesis of poly 4-methyl vinyl pyridinium hydroxide-SiO{sub 2}-Al{sub 2}O{sub 3}. The novelty of this procedure is at easy preparation together with using inexpensive materials. Highlights: > P4MVPH-SiO{sub 2}-Al{sub 2}O{sub 3} composite was prepared as a novel polymer-inorganic hybrid. > The composite was prepared without using any bridged organosilanes compound. > SEM photograph showed that the composite is completely uniform. > P4MVPH-SiO{sub 2}-Al{sub 2}O{sub 3} could behave as a recyclable catalyst for Knoevenagel reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Multifunctional properties of CoNi alloy embedded in the SiO{sub 2} host: Role of interparticle interaction

Nanocrystalline CoNi alloy is synthesized using sol-gel technique having average size {approx}8.5 and {approx}12nm. High-resolution transmission electron microscopy confirms absence of any oxide phase at the grain boundary. We observe multifunctionality ascribed to large loop shift after the field-cooling and saturation magnetization (M{sub S}) depending on interparticle interaction in CoNi alloy embedded in SiO{sub 2} matrix. A large loop shift 1.2 kOe is noticed at 5 K for 10.5% volume fraction ({phi}). The loop shift decreases with increasing temperature and vanishes around {approx}210K where a maximum is observed in zero-field-cooled magnetization. The loop shift decreases with decreasing {phi} and vanishes at {phi}=0.01%. Interestingly, M{sub S} increases with decreasing {phi} and value at {phi}=0.01% approaches to the calculated value of M{sub S} for the bulk counterpart. A model has been proposed with ferromagnetic-core and disordered magnetic-shell structure to interpret the results. - Graphical abstract: Plot of loop shift (left axis) and saturation magnetization (right axis) with volume fraction ({phi}). Inset: loop shift after field-cooling with 50 kOe field and no shift after zero-field-cooling. Highlights: > Strong exchange bias (EB) effect is observed for 10.5% volume fraction. > EB decreases with decreasing volume fraction ({phi}) and vanishes at {phi}=0.01%. > In contrast, saturation magnetization increases with decreasing volume fraction. > Saturation magnetization (M{sub S}) approaches to bulk value at 0.01% volume fraction. > Large EB and M{sub S} at different {phi} are appealing for multifunctional applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Luminescence properties of core-shell structured SiO{sub 2}-CaMoO{sub 4}:Eu{sup 3+} phosphor

Uniform SiO{sub 2}-CaMoO{sub 4}:Eu{sup 3+} red phosphor has been synthesized by sol-gel method, and its luminescence properties have been studied by fluorescence spectrometer. The structure and morphology of the SiO{sub 2}-CaMoO{sub 4}:Eu{sup 3+} red phosphor have been investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and FT-IR spectrometer. Results indicate that phosphor particles have a core-shell structure and the thickness of the SiO{sub 2}-shell is about 60 nm. In addition, the luminescent intensity of SiO{sub 2}-CaMoO{sub 4}:Eu{sup 3+} red phosphor has been greatly enhanced with respect to CaMoO{sub 4}:Eu{sup 3+} phosphor. But the lifetime {tau} value of SiO{sub 2}-coated CaMoO{sub 4}:Eu{sup 3+} is slightly smaller than that of non-coated CaMoO{sub 4}:Eu{sup 3+}. - Graphical abstract: A SiO{sub 2} nano-layer with thickness of 60 nm and good uniformity was successfully coated on the surface of CaMoO{sub 4}:Eu{sup 3+} phosphor. This coating greatly increases luminescent intensity of the phosphor. Highlights: Black-Right-Pointing-Pointer SiO{sub 2}-CaMoO{sub 4}:Eu{sup 3+} was successfully synthesized by sol-gel method. Black-Right-Pointing-Pointer The SiO{sub 2} nano-layer increases luminescent intensity of the phosphor. Black-Right-Pointing-Pointer The SiO{sub 2} nano-layer reduces fluorescence lifetime of the phosphor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Monodisperse and core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho, and Tm) spherical particles: A facile synthesis and luminescent properties

The core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles were realized by coating the Lu{sub 2}O{sub 3}:Ln{sup 3+} phosphors onto the surface of non-aggregated, monodisperse and spherical SiO{sub 2} particles by the Pechini sol-gel method. The as-synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photolumiminescence (PL), and low-voltage cathodoluminescence (CL). The results indicate that the 800 Degree-Sign C annealed sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores, in spherical shape with a narrow size distribution. The as-obtained particles show strong light emission with different colors corresponding to different Ln{sup 3+} ions under ultraviolet-visible light excitation and low-voltage electron beams excitation, which have potential applications in fluorescent lamps and field emission displays. - Graphical Abstract: Representative SEM and TEM images of the core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Eu{sup 3+} particles; CIE chromaticity diagram showing the emission colors for SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+}; Multicolor emissions of SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles. Highlights: Black-Right-Pointing-Pointer The core-shell particles were realized by coating the phosphors onto the surface of SiO{sub 2} particles. Black-Right-Pointing-Pointer The sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores. Black-Right-Pointing-Pointer The particles show different light emission colors corresponding to Ln{sup 3+} ions. Black-Right-Pointing-Pointer They have potential applications in fluorescent lamps and field emission displays.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Photofunctional hybrid silica microspheres covalently functionalized with metalloporphyrins

The entrapment of metalloporphyrins (with Zn{sup 2+} and Yb{sup 3+}) in silica microspheres is achieved by modification of protoporphyrin IX (Pp-IX) molecules with three different organosilane precursors via the sol-gel method. The obtained hybrid materials are characterized by electronic absorption spectra, Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), {sup 29}Si MAS NMR spectrum, scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms and thermogravimetric analysis (TGA), and their luminescence properties have also been determined. The results reveal that the obtained porphyrins networks are covalently bonded to the inorganic matrix through the bridging action of the functionalized silica microspheres. Furthermore, it has also been observed that porphyrins molecules located in different environments exhibit different photophysical properties in the visible and near-infrared regions. - Graphical abstract: The entrapment of metalloporphyrins (with Zn{sup 2+} and Yb{sup 3+}) in silica microspheres is achieved by modification of protoporphyrin IX (Pp-IX) molecules with three different organosilane precursors via the sol-gel method. Highlights: Black-Right-Pointing-Pointer Novel functionalized silica microsphere is assembled. Black-Right-Pointing-Pointer Metal phorphyrin derivatives are used as a chemical linkage. Black-Right-Pointing-Pointer Luminescence is obtained in the visible and near infrared regions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗