CO_(2)-Induced Modulation of Si-O Bonds for Low Temperature Plastic Deformation of Amorphous Silica Nanoparticles with Enhanced Photoluminescence

Modulation of Si-O bonds under mild conditions has been a challenging issue in the field of material science,which is critical to manufacture highperformance silica-based optical and photonic devices.Herein,we introduce a nondestructive technique to achieve Si-O bond rearrangement,leading to plastic deformation and photoluminescence enhancement of amorphous silica nanoparticles using supercritical carbon dioxides in EtOH/H_(2)O solution under mild temperature.Specifically,plastic deformation is achieved by treating hollow mesoporous silica nanospheres using supercritical CO_(2)at 40°C under 20 MPa.Experimental and theoretical studies revealed the critical role of supercritical CO_(2)in the plastic deformation process,which can be intercalated into the hollow mesoporous silica nanospheres with anisotropic stresses and induces the rearrangement of Si-O bonds and transformation of ring structures.This work suggests a novel approach to engineer high-performance nano-silica glass components for numerous optical and photonic devices under mild condition.

Amine-silica composites for CO_2 capture: A short review

Amine-silica composite materials for post-combustion COcapture have attracted considerable attention because of their high COuptake at low COconcentrations, excellent COcapture selectivity in the presence of moisture, and lower energy requirements for sorbent regeneration. This review discusses the recent advances in amine-silica composites for COcapture, including adsorbent preparation and characterization, COcapture under dry and moisture conditions at different COpartial pressures, sorbent regeneration, and stability after many cyclic sorption-desorption runs.

Synthesis of Nanoscale Shell-core Titania Coated Silica Particles in the Presence of Polyether Polyamine and the Phase Transition

The nanoscale titania coated silica was prepared via a two-step precipitating approach, where the nanoscale silica nuclei were first prepared by passing an aqueous solution of sodium silicate through an ion-exchange resin bed, then coated with the precipitation from hydrolyzed butyl titanate in an ethanol-hexane mixture at a low pH value in the presence of poly(ethylene oxide) polyamine salt(PPA) at a high temperature of 90 ℃. In the second-step precipitating process, the spontaneously precipitated titania shell on the silica nuclei was stabilized in the suspension solution with the help of the adsorption of PPA on the particles. A possible precipitating mechanism was suggested. Furthermore, the amorphous titania shell could undergo crystallization from the amorphous to the anatase structure at a high temperature of 650 ℃, and a further phase transition from the anatase to the rutile structure in the different sintering processes at a rising temperature of 750 ℃.

Efficient CO_2 capture on low-cost silica gel modified by polyethyleneimine

In this work, a series of polyethyleneimine （PEI） functionalized commercial silica gel were prepared by wet impregnation method and used as CO2 sorbent. The as-prepared sorbents were characterized by N2 adsorption, FT-1R and SEM techniques. CO2 capture was tested in a fixed bed reactor using a simulated flue gas containing 15.1% CO2 in a temperature range of 25-100 ~C. The effects of sorption temperature and amine content on CO2 uptake of the adsorbents were investigated. The silica gel with a 30 wt% PEI loading manifested the largest CO2 uptake of 93.4 mgcoz/gadsorbent （equal to 311.3 mg^oz/gPEI） among the tested sorbents under the conditions of 15.1% （v/v） CO2 in N2 at 75 ~C and atmospheric pressure. Moreover, it was rather low-cost. In addition, the PEI-impregnated silica gel exhibited stable adsorption-desorption behavior during 5 consecutive test cycles. These results suggest that the PEI-impregnated silica gel is a promising and cost-effective sorbent for CO2 capture from flue gas and other stationary sources with low CO2 concentration.

Sol-Gel Preparation of Zn2 SiO4 :Mn Phosphor Layers on Silica Spheres and Their Luminescent Properties

The synthesis and luminescence properties of Zn2 SiO4: Mn phosphor layers on spherical silica spheres, i.e.,a kind of core-shell complex phosphor, Zn2SiO4: Mn@ SiO2 were described.Firstly, monodisperse silica spheres were obtained via the Stober method by the hydrolysis of tetraethoxysilane(TEOS) Si ( OC2H5 ) 4 under base condition ( using NH4 OH as the catalyst).Secondly, the silica spheres were coated with a Zn2 SiO4: Mn phosphor layer by a Pechini solgel process.X-ray diffraction ( XRD), scanning electron microscope ( SEM), energy-dispersive X-ray spectrum ( EDS )and photoluminescence (PL) were employed to characterize the resulting complex phosphor.The results confirm that1000 ℃ annealed sample consists of crystalline Zn2SiO4: Mn shells and amorphous SiO2 cores.The phosphor show the green emission of Mn2+ at 521 nm corresponding 4T1 (4G) - 6 A1 (6S) transition, and the possible luminescence mechanism is proposed.

Solid State Reaction Yielding a Mineral Utilizing Silica Obtained from an Agricultural Waste

Wollastonite, a mineral of wide industrial applications was synthesised from rice husk ash silica and limestone. A number of raw batches consisting of these starting materials, in 1:1 molar ratio, were heat treated to produce it through solid state reaction from 900℃ to 1300℃. The conducted reaction was monitored by XRD step by step. Amount of Wollastonite formed at every temperature was also studied to some extent. Analyses of the obtained data indicated that the target mineral formation was quite effective and almost proportional to a rise in temperature up to 1200℃. The results from both, XRD and chemical analysis were found in fair agreement with one another

Characterization of a Mineral Synthesized by Availing Silica from Plant Source

Rice husk was used to prepare the silica of amorphous nature being several times more reactive than that obtained from the mineral kingdom. Number of rice husk batches were pyroprocessed under varying time-temperature parameters for this purpose. The ash resulting from a batch pyroprocessed at 500℃ for 8 h contained 92.01% silica. It was upgraded to 98.50% by applying physicochemical purification procedures. The mineral, wollastonite (CaSiO3), was synthesized from thus prepared silica and limestone containing 55.91% CaO. Solid state reaction, between CaO and SiO2 was attempted at different temperatures in the presence of a mineralizer. The sintering temperature, for affecting the said synthesis, was ranged between 900℃ to 1300℃ with the steps of 100℃. Specific chemical analysis techniques were applied to determine the effectiveness of carried out reaction and promising batches were subsequently subjected to XRD investigations. The produced mineral was also characterized regarding its physical properties like: colour, hardness, melting point and specific gravity. Percent yield of the produced wollastonite was also estimated and compared with that of obtained by other researchers who synthesized it by using silica from mineral kingdom. Batches sintered at 1200℃ and 1300℃ for 1 h showed the overall best results.

Facile in‐situ synthesis and deposition of monodisperse palladium nanoparticles on polydopamine‐functionalized silica gel as a heterogeneous and recyclable nanocatalyst for aerobic oxidation of alcohols

This paper describes a facile in‐situ synthesis of palladium nanoparticles （Pd NPs） on silica gel/polydopamine composite（SiO2/PDA） without any stabilizer or reducing agent. In this approach, palladium ions were adsorbed on SiO2/PDA surfaces by immersing the PDA‐coated SiO2 particles in a palladium plating bath. Then, they were reduced in situ to Pd nanoclusters by the reducing ability of PDA＇s N‐containing groups. The structure, morphology, and physicochemical properties of the synthesized nanocomposites were characterized by different analytical techniques such as high‐resolution transmission electron microscopy, field‐emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray diffraction analysis, X‐ray photoelectron spectroscopy, inductively coupled plasma and Fourier‐transform infrared spectroscopy. The Pd NPs capped by the PDA groups had a strikingly small size（30–40 nm）. SiO2/PDA/Pd NPs exhibited high catalytic activ‐ity as a recyclable nanocatalyst in the aerobic oxidation of alcohols. Furthermore, recovery and multiple reuse of the catalyst revealed no detectable activity loss.

Insight on metal ions inducing chiral self-assembly of DNA in silica mineralization

The self-assembly of DNA provides an attractive approach to understanding structural formation mechanism in living organisms and to assisting applications in materials chemistry.Herein,we investigated the effect of metal ions on chiral self-assembly of DNA through the synthesis of chiral mesostructured silica via self-assembly of metal ions,DNA,and silica source.31 types of multivalent cationic metal ions were found to induce formation of chiral impeller-like DNA-silica complexes due to the chiral stacking of DNA.The strength of the interaction between the metal ion and phosphate group of DNA was speculated for the chiral stacking of DNA due to close distance of adjacent DNA to assure mutual recognition.Theoretical calculations indicated that chiral packing of DNA depends on the stability of the bridging phosphate-metal ion-phosphate bonds of DNA based on electron delocalization in d-orbital conjugation of metal ions.

Luminescent and Thermal Properties of Sm^(3+) Complex with Salicylate and o-Phenanthroline Incorporated in Silica Matrix

A ternary Sm（ Ⅲ ） complex with salicylate （sal-） and o-phenanthroline （phen） was synthesized and incorporated in silica matrix by sol-gel method. The luminescence behavior of the complex in silica gel was studied compared with that of the pure complex by means of emission, excitation spectra and thermogravimetic analysis. The results indicate that the fluorescence intensity ratio of the ^4G5/2→^6H9/2 transition to the ^4G5/2→^6H5/2 transition in silica gel doped with Sm（sal）3 （phen） is lower than that of the pure Sm（sal）3（phen）. The thermal stability of Sm（sal）3（phen） is enhanced greatly by the introduction of the complex into silica matrix. An isolated and chemical inert environment of the complex appears to be responsible for the thermal stability enhancement in silica gel.

Biomineralization Precursor Carrier System Based on Carboxyl- Functionalized Large Pore Mesoporous Silica Nanoparticles

Bone and teeth are derived from intrafibrillarly mineralized collagen fibrils as the second level of hierarchy.According to polymer-induced liquid-precursor process,using amorphous calcium phosphate precursor(ACP)is able to achieve intrafibrillar mineralization in the case of bone biomineral in vitro.Therefore,ACP precursors might be blended with any osteoconductive scaffold as a promising bone formation supplement for in-situ remineralization of collagens in bone.In this study,mesoporous silica nanoparticles with carboxyl-functionalized groups and ultra large-pores have been synthesized and used for the delivery of liquid like biomimetic precursors(ACP).The precursor delivery capacity of the nanoparticles was verified by the precursor release profile and successful mineralization of 2D and 3D collagen models.The nanoparticles could be completely degraded in 60 days and exhibited good biocompatibility as well.The successful translational strategy for biomineralization precursors showed that biomineralization precursor laden ultra large pore mesoporous silica possessed the potential as a versatile supplement in demineralized bone formation through the induction of intrafibrillar collagen mineralization.

Bilirubin adsorption property of mesoporous silica and amine-grafted mesoporous silica

Nephritic, hepatic and immune failures would lead to the overload of endogenous toxic molecules(e.g. bilirubin, cholic acid, uric acid, creatinine etc.) in human bodies. It is fatal in most cases and extracorporeal blood purification(ECBP) is powerful first-aid therapy. Adsorbents are key parts of ECBP apparatus. Mesoporous silicas should be promising candidates for these medical adsorbents, but there is no report about this. Herein, pure and amine-grafted mesoporous silicas have been applied to adsorb bilirubin, cholic acid, uric acid, creatinine and phenobarbital for the first time. These mesoporous materials show high adsorption capacities for bilirubin and uric acid in phosphate buffer solution(PBS). Effects of pore sizes, amine-modification, temperature and ionic strength on their bilirubin adsorption capacities have been studied in detail.

Direct Synthesis of Amine-functionalized Mesoporous Silica for CO_2 Adsorption

Amine-functionalized mesoporous silica was prepared by using lauric acid and N-stearoyl-l-glutamic acid as structure directing agents via the S-N+-I- mechanism and applied to CO2 adsorption at room temperature. With γ-aminopropyltriethoxysilane as co-structure directing agent and due to the direct electrostatic interaction with anionic surfactant, most of the amino groups were uniformly distributed at the inner surface of pores and the per- formance was stable. The amine-functionalized mesoporous silica was characterized by Fourier transform infrared spectrometer, X-ray diffraction, nitrogen physisorption and thermogravimetric analysis. The CO2 adsorption capacity was measured by digital recording balance. At the room temperature and under the atmospheric pressure, the adsorption capacity of LAA-AMS-0.2 for CO2 and N2 is 1.40 mmol·g-1 and 0.03 mmol·g-1, respectively, indicating high separation coefficient of CO2/N2.

Annealing Temperature dependence of Photoluminescence from Silicon-rich silica Films

The silicon-rich silica films were prepared by a dual-ion-beam co-sputtering method from a composite Target in an argon atmosphere. The structure of the films studied by the aid of TEM and XRD is amorphous. The photoluminescence (PL) spectra were found to have a 4- luminescent band peak at 320 nm, 410 nm, 560 nm, and 630 nm, respectively, at room temperature. The intensity and the wavelength position of PL are dependent on annealing temperature (Ta), and the luminescent mechanism is analyzed.

Iron Bearing Minerals Flotation from Silica Sand Using Hydroxyl Surfactants

A technological clayey sandstone sample from Wadi Qena locality, Eastern Desert of Egypt, was directed to processing. Fine kaolin and clean silica sand were produced after intensive attrition scrubbing of the sample. To increase the quality of the produced silica, it was subjected to reverse anionic flotation to minimize its iron content. In this respect, conventional flotation tests using three anionic oxyhydryl surfactants namely: sodium dodecyl benzene sulphonate, sodium naphtha sulphonate, and sodium dodecyl sulphate, were tried. Results showed a privilege action for sodium dodecyl sulphate to remove most of the iron oxide content of the sample. A statistical Box-Behnken design was constructed to optimize the process efficiency. It was shown that from a flotation feed contained 360 ppm Fe2O3 and 1190 ppm Al2O3, sand concentrate contained 29 ppm Fe2O3 and 564 ppm Al2O3, was produced. The optimum flotation conditions were 3.86 kg/t sodium dodecyl sulphate dose, 3.22 flotation pulp pH, 1226 rpm impeller speed, and 22.24 L/min airflow rate. Variables interaction effects results showed that flotation separation efficiency was significantly influenced by air flow rate and cell impeller speed of the process.

Light and temperature dual responsive pesticide release system based on mesoporous silica nanoparticles modified by dopamine

A light and temperature dual responsive copolymer,poly(7-(4-vinylbenzy-loxyl)-4-methylcoumarin-co-N vinyl caprolactam-co-tri(ethylene glycol)methyl ether methacrylate)(PVNM),was grafted on the surface of dopamine based mesoporous silica nanoparticles(MSNs).The resulting polymer brush,MSNs-g-PVNM,was characterized by FT-IR,TEM,TGA and XPS.The dual responsive behaviors of MSNs-g-PVNM were systematically studied.With imidacloprid as the model guest pesticide,the loading percentage and loading efficiency of the polymer brush were determined as 9.2%and 40.6%,respectively.The release efficiency of imidacloprid in MSNs-g-PVNM was the lowest value of 5.4%at 20℃ and 365 nm,and it reached the highest value of 52.4%at 50℃ and 254 nm.The loss percentage of imidacloprid on the leaves contained imidacloprid-loaded MSNs-g-PVNM(8.4%)was much less than that contained only imidacloprid(25.2%)after three rinses.It was confirmed that the release process of imidacloprid was well regulated through changing external conditions such as light and temperature.

Modified monolithic silica capillary for preconcentration of catecholamines

Preconcentration of catecholamines by the modified monolithic silica in the capillary was investigated in this study. In order to achieve a microchip-based method for determining catecholamines in the saliva,the monolithic silica was fabricated in the capillary and the monolithic silica was chemically modified by on-column reaction with phenylboronate. Different modified methods were compared. The concentration conditions were optimized. This study indicates the applicability of the modified monolithic silica capillary when it was used to concentrate catecholamines.

Low-cost preferential different amine grafted silica spheres adsorbents for DAC CO_(2)removal

DAC CO_(2)capture is gaining wide attention as one of the most difficult carbon approaches to tackle climate change.In this work,different pore-size silica spheres were grafted using different amine groups such as APTES,APTMS,and Diamine.Herein,all samples based on the wet and dry grafting method were used for CO_(2)adsorption isotherm at room temperature and pressure(298 K and 1 bar).The sample based on the wet grafting(Silica-APTES-W)sample shows the highest CO_(2)uptake 1.67 mmol/g.Also,the adsorption isotherm of the Silica-APTES-W sample was showed a high capacity of CO_(2)1.2 mmol/g at 25℃,which describes the strong physical interaction between CO_(2)and amine.The isosteric adsorption of Silica-APTES-W also confirmed that the physical adsorption was dominant because of low adsorption heat ranging from 23 to 37 k J/mol.Also,the fixed bed experiment was conducted with 2000 ppm CO_(2)that obtains the optimal working capacity 4.5 m L/g with the lowest regeneration temperature 90℃.It was shown that Silica-APTES-W sample was superior performance for DAC CO_(2)capture in practical applications.

Efficient Visible Photoluminescence from Self-Assembled Ge QDs Embedded in Silica Matrix

Measuring the growth parameters of Ge quantum dots （QDs） embedded in SiO2/Si hetero-structure is pre- requisite for developing the optoelectronic devices such as photovoltaics and sensors. Their optical properties can be tuned by tailoring the growth morphology and structures, where the growth parameters＇ optimizations still need to be explored. We determine the effect of annealing temperature on surface morphology, structures and optical properties of Ge//SiO2//Si hetero-structure. Samples are grown via rf magnetron sputtering and subsequent characterizations are made using imaging and spectroscopic techniques.

Adsorption of CO₂on Polyethyleneimine 10k—<i>Mesoporous silica</i>Sorbent: XPS and TGA Studies

A CO2 solid sorbent based on polyethyleneimine 10k (PEI-10k) impregnated into mesoporous silica (MPS) foam was synthesized and utilized to capture CO2 at temperatures ranged from 65°C to 95°C. The calculated nitrogen and carbon contents in the bulk of the PEI-10k/MPS sorbent were similar to the XPS results measured on the surface of the foam, suggesting that the PEI was homo-geneously distributed throughout the MPS support. After CO2 adsorptionthe N 1s peak was broadened and could be resolved into two components: a high binding energy component (~401 eV) and a lower binding energy one (396 eV), respectively. The former nitrogen states are consistent with a protonated amine, presumably, due to carbamate formation. The lower binding energy component (~396 eV) could possibly be due to strongly chemisorbed CO2. The maximum sorption capacity was about 4 mmole CO2/g sorbent at 85°C and 1 bar. This capacity was doubled by raising the CO2 pressure to 24.95 bars. The adsorption results can be described by a Langmuir adsorption isotherm.