SiO2 Shell Research Articles

Synthesis of TiO2 based superhydrophobic coatings for efficient anti-corrosion and self-cleaning on stone building surface

As the value of TiO2 in environmental protection continues to be explored, it has broad potential for stone building protection. However, the hydrophilicity of TiO2 makes it challenging to keep stable on the exterior of buildings and hydroxyl radicals generated under UV irradiation may be harmful to substrates. Herein, TiO2 was wrapped with the SiO2 shell by a modified Stöber method and superhydrophobic TiO2 was obtained by grafting methyl groups on the SiO2 shell. The TiO2@Si–Me core-shell system were dispersed in Paraloid B72 and applied on marble surfaces to investigate the self-cleaning effect of TiO2 on the substrate. The results showed that the superhydrophobic TiO2 nanoparticles significantly enhanced the surface roughness, which was beneficial to transform the acrylic resin coating from hydrophilic to hydrophobic and retain the original vapor permeability. The adsorption rate and degradation efficiency of methylene blue of TiO2@Si–Me core-shell system were 2.19 and 1.45 times higher than that of pure TiO2. Furthermore, the superhydrophobic TiO2 did not change the color of the stone after UV aging, which contributed to maintaining the appearance of buildings. These findings will help to understand the role of photocatalytic nanomaterials in developing protective layers for stone construction and expand the application in the self-cleaning of the architectural environment.

Enhanced luminescence and Judd-Ofelt analysis in SiO2 encapsulated CaWO4@CaWO4:Eu:Bi for visualization of latent fingerprints and anti-counterfeiting

Core nanoparticles (NPs) and core–shell particles have been synthesized using the low temperature reflux method. The structural and photo-physical properties of the developed phosphors have been investigated through various analytical techniques. The transmission electron microscopy (TEM) analysis evidences the formation of the shell on the core NPs. The optical band gap is estimated using the diffuse reflectance spectra. An 8-fold enhancement of emission intensity is observed in the core–shell particles as compared to that of core, due to the reduced surface quenchers after silica coating. In addition, the Judd-Ofelt (J-O) parameters have been calculated to reveal the site symmetry and coordination environment around Eu3+ ions. The tunable red emission on formation of core–shell structures is confirmed from the CIE diagram. These results are ascribed to the formation of the chemical bonds between CaWO4@ CaWO4:3%Eu3+:5%Bi3+ (core) and amorphous SiO2 shell via W – O – Si bridges. Better hydrophilicity developing from active functional groups in solutions and intense luminescence behavior with a quantum efficiency of 91% allow the developed phosphors for various potential applications such as solid state lighting, bio-labelling agent for the visualization of latent fingerprints (LFPs) and anti-counterfeiting, etc.

Effect of the Silica-Magnetite Nanocomposite Coating Functionalization on the Doxorubicin Sorption/Desorption.

A series of new composite materials based on Fe3O4 magnetic nanoparticles coated with SiO2 (or aminated SiO2) were synthesized. It has been shown that the use of N-(phosphonomethyl)iminodiacetic acid (PMIDA) to stabilize nanoparticles before silanization ensures the increased content of a SiO2 phase in the Fe3O4@SiO2 nanocomposites (NCs) in comparison with materials obtained under similar conditions, but without PMIDA. It has been demonstrated for the first time that the presence of PMIDA on the surface of NCs increases the level of Dox loading due to specific binding, while surface modification with 3-aminopropylsilane, on the contrary, significantly reduces the sorption capacity of materials. These regularities were in accordance with the results of quantum chemical calculations. It has been shown that the energies of Dox binding to the functional groups of NCs are in good agreement with the experimental data on the Dox sorption on these NCs. The mechanisms of Dox binding to the surface of NCs were proposed: simultaneous coordination of Dox on the PMIDA molecule and silanol groups at the NC surface leads to a synergistic effect in Dox binding. The synthesized NCs exhibited pH-dependent Dox release, as well as dose-dependent cytotoxicity in in vitro experiments. The cytotoxic effects of the studied materials correspond to their calculated IC50 values. NCs with a SiO2 shell obtained using PMIDA exhibited the highest effect. At the same time, the presence of PMIDA in NCs makes it possible to increase the Dox loading, as well as to reduce its desorption rate, which may be useful in the design of drug delivery vehicles with a prolonged action. We believe that the data obtained can be further used to develop stimuli-responsive materials for targeted cancer chemotherapy.

A facile synthesis of PEGylated Cu2O@SiO2/MnO2 nanocomposite as efficient photo-Fenton-like catalysts for methylene blue treatment.

The removal of toxic organic dyes from wastewater has received much attention from the perspective of environmental protection. Metal oxides see wide use in pollutant degradation due to their chemical stability, low cost, and broader light absorption spectrum. In this work, a Cu2O-centered nanocomposite Cu2O@SiO2/MnO2-PEG with an average diameter of 52nm was prepared for the first time via a wet chemical route. In addition, highly dispersed MnO2 particles and PEG modification were realized simultaneously in one step, meanwhile, Cu2O was successfully protected under a dense SiO2 shell against oxidation. The obtained Cu2O@SiO2/MnO2-PEG showed excellent and stable photo-Fenton-like catalytic activity, attributed to integration of visible light-responsive Cu2O and H2O2-responsive MnO2. A degradation rate of 92.5% and a rate constant of 0.086 min-1 were obtained for methylene blue (MB) degradation in the presence of H2O2 under visible light for 30min. Additionally, large amounts of •OH and 1O2 species played active roles in MB degradation. Considering the enhanced degradation of MB, this stable composite provides an efficient catalytic system for the selective removal of organic contaminants in wastewater.

Hollow Spherical Hierarchical MoO3/SiO2–TiO2 Structures for Photocatalytic Decomposition of Organic Pollutant in Water

In this study MoO3/TiO2–SiO2 layered spherical composites, having hierarchical structure, were synthesized on TOKEM-320Y anion exchanger template using by sol-gel methods. Properties of MoO3/TiO2–SiO2 composites were characterized by XRD, EDS, SEM, 3D X-ray microtomography, Raman, IR, DRS, BET, and PL techniques. The SEM, 3D X-ray microtomography and EDS analysis showed hollow spherical composites with diameters ranging from 200 to 400 μm with core/shell structure. The formation of TiO2–SiO2 shell on the MoO3 core results in lower oxygen vacancy concentrations in composite (0.0425) and a reduced bandgap width (2.56 eV in compare to 3.19 eV for MoO3 sample, which was analyzed through the UV–VIS DRS method). The performance of MoO3/TiO2–SiO2 composites was evaluated by photocatalytic degradation of methylene blue (MB) aqueous solution irradiated with an I2 excilamp (λmax = 312 nm). The photoabsorption energy properties of MoO3/TiO2–SiO2 composites are related to the interaction between TiO2–SiO2 and MoO3 which occurs through oxygen in Ti-O-Mo and Si-O-Mo. The MoO3/TiO2–SiO2 composites exhibited a much higher photocatalytic activity (rate constant is 0.0645 min‒1, degradation efficiency is 93% (20 min). This work demonstrates the relation between the formation of heterostructure in core/shell composite and its photocatalitic activity, providing fundamental guidance to improve photocatalytic performance of materials.

Single silica-coated CsPbBr3 perovskite quantum dots with enhanced stability and excellent optical properties

Halide perovskite quantum dots (PQDs) have been considered to be potential emitting materials for illumination and display applications. Unfortunately, the poor stability (air, water, and thermal) can greatly limit their practical applications. Herein, the mono-dispersed pure CsPbBr3 PQDs with cubic morphologies are prepared by using a modified hot-injection method, as a control group. Based on this, a new surface activation strategy for preparing single CsPbBr3@SiO2 core-shell PQDs with their initial cubic morphology and optical properties has been developed, using the CsPbBr3 PQDs as a precursor and choosing the APTES as the surface ligand which can form a Si–O–Si covalent bond with the subsequently added silane to help complete single CsPbBr3@SiO2 PQDs. The average thickness of the coated shell is about 2.3 nm and basically maintains the initial morphology and optical properties of PQDs. The PL intensity of CsPbBr3@SiO2 PQDs dispersed in a mixed solution of toluene and water can retained 35% of the initial value even after 13 h, which are much higher than the pure CsPbBr3 PQDs (9%). The photo-stability tests (air, water, and thermal stability) indicate that the CsPbBr3@SiO2 PQDs is markedly more stable than that of the CsPbBr3 PQDs owing to the complete encapsulation of the SiO2 shell, indicating that the host packaging is an effective way to improve the stability. This work provides a simple and reliable synthesis way to synthesize the single core-shell particles, which can be suitable for other perovskite systems.

Surface-potential-modulated piezoresistive effect of core–shell 3C-SiC nanowires

The effect of surface potential on the carrier mobility and piezoresistance of core–shell silicon carbide nanowires (SiC NWs) was investigated to realize small and sensitive SiC-microelectromechanical systems sensors. The p-type cubic crystalline SiC (3C-SiC) NWs were synthesized via the vapor–liquid–solid method and coated with silicon dioxide (SiO2) or aluminum oxide (Al2O3) dielectric shells to form core–shell structured NWs with different surface potentials. Four-point bending devices (FBDs) with a field-effect transistor (FET) configuration integrating a single core–shell 3C-SiC NW as the FET channel were fabricated to apply an additional electric field and strain to the core–shell 3C-SiC NWs. The fixed oxide charge densities of the SiO2 and Al2O3 shells showed positive and negative values, respectively, which were equivalent to electric fields of the order of several hundred thousand volt per centimeter in absolute values. In the core–shell 3C-SiC NWs with originally low impurity concentrations, the electric field induced by the fixed oxide charge of the shells can determine not only the electrical conduction but also the charge carriers in the NWs. Bending tests using the FBDs showed that the piezoresistive effect of the SiO2-coated NW was almost the same as that of the as-grown 3C-SiC NW reported previously, regardless of the gate voltage, whereas that of the Al2O3-coated NW was considerably enhanced at negative gate voltages. The enhancement of the piezoresistive effect was attributed to the piezo-pinch effect, which was more pronounced in the NW, where the carrier density at the core–shell interface is enhanced by the electric field of the dielectric.

Paraffin@SiO2 microcapsules-based phase change composites with enhanced thermal conductivity for passive battery cooling

Phase change materials (PCMs) are potential candidates in passive thermal regulation and energy storage fields due to their high latent heat capacity around phase transition temperature. However, the leakage problem and low thermal conductivity are two obstructive factors for the extended application of PCMs. Herein, a series of paraffin@silicon dioxide microcapsules (Pa@SiO2)/graphene sheets (GS)/silicone rubber (SR) phase change composites (PCCs) were prepared. It is found that the inorganic SiO2 shell is conducive to enhancing the thermal conductivity of PCCs and the double encapsulation by the SiO2 shell and SR skeleton can restrict the leakage of liquid Pa during phase transition. With a Pa@SiO2 content of 70 wt%, the PCCs have a high latent heat of 126.1 J/g and enhanced thermal conductivity of 0.37 W m−1 K−1, which is 131.25% higher compared to that of pure SR. In addition, the introduction of graphene sheets further boosts the thermal conductivity of PCCs to 2.69 W m−1 K−1. The obtained PCCs lead to a surprising temperature decline of nearly 35 °C of a commercial lithium-ion battery during a high discharge rate (7.4 C). This work provides an efficient route to fabricate microcapsules-based PCCs for passive thermal regulation.

Development of novel nanoabsorbents by amine functionalization of Fe3O4 with intermediate ascorbic acid coating for CO2 capture enhancement

Novel nanoabsorbents are developed CO2 capture enhancement by functionalized magnetite nanoparticles in a water-based nanofluid system. The functionalization of magnetic nanoparticles was performed using different organic and inorganic reagents: (3-Aminopropyl) triethoxysilane (APTES), tetraethyl orthosilicate (TEOS), and L(+)-ascorbic acid (AA). The first coating used AA followed by a secondary shell of SiO2, and then amine functionalization via APTES, creating the amine-functionalized double-coated magnetite (Fe3O4 @AA@SiO2-NH2). The CO2 adsorption capacity of the synthesized material was enhanced by 11% at ambient pressure, compared with that of amine functionalization without AA (Fe3O4 @SiO2-NH2). To evaluate the absorption enhancement of Fe3O4 @AA@SiO2-NH2 at 25 °C, concentrations ranging from 0.1 to 0.4 wt% were compared with those of the base fluid (water). The highest enhancement of 59.2% was obtained at a concentration of 0.3 wt%. A cyclic performance evaluation showed that the initial absorption capacity was reduced by only 7%. Owing to its nanoabsorbent stability, significant CO2 absorption enhancement, and high recyclability, Fe3O4 @AA@SiO2-NH2 will be a milestone in physical liquid absorption systems for a carbon free environment.

Enhanced switching electric field and breakdown strength of epoxy composites with core‐shell silicon carbide nanoparticles

AbstractSilicon carbide (SiC) is widely used to improve the non‐linear conductivity of non‐linear resistive field grading composite. In this paper, the SiC nanoparticles are modified into core‐shell nanoparticles with silica (SiO2) coating on the surface and are characterised by transmission electron microscopy and X‐ray diffraction, respectively. The 7 wt% SiC@SiO2/epoxy nanocomposite is then prepared, and the pure epoxy and 7 wt% SiC/epoxy nanocomposite are prepared as a contrast. The relative permittivity, thermally stimulated current, conductivity and breakdown strength are studied, respectively. The presence of SiO2 shell around SiC nanoparticles has a great effect on the relative permittivity and trap distribution. The epoxy nanocomposites show non‐linear conductivity characteristics, compared with pure epoxy. The 7 wt% SiC@SiO2/epoxy nanocomposite has higher switching electric field and breakdown strength than the 7 wt% SiC/epoxy nanocomposite, which is helpful for the application of non‐linear resistive field grading composite in higher‐voltage equipment or components.

Surface physicochemical characteristics for sodium ion removal with sodium silicate modified magnetite core-shell nanoparticles and activation of their plasmid DNA purification ability

In this study, it is investigated the elimination of residual sodium ions from sodium silicate (Na2SiO3) modified Fe3O4@SiO2 nanoparticles, via the additional acidic treatment. Residual sodium ions are generated from the Na2SiO3 precursor during the titration for the fabrication of the Fe3O4@SiO2 core-shell structure; however, they were entirely removed after the in situ additional titration at pH 3 using a 1 M of hydrochloric acid (HCl). The thickness of the SiO2 shell layer of each nanoparticle was measured to 10 nm and the morphology of SiO2 shell on the Fe3O4 core were not significantly different after acid treatment to remove the residual sodium ions. However, the absolute zeta potential of the Na2SiO3-modified Fe3O4@SiO2 was decreased about 20% after HCl treatment (−52.5 ± 3.0 mV). In addition, the mean particle size of the Na2SiO3-modified Fe3O4@SiO2 was increased (363.98 nm) and the polydispersity index, which indicates dispersibility was increased (0.23) since residual sodium ions were eliminated by the acid treatment. It is assumed that the reducing anions in the diffuse layer of the particle due to the elimination of the residual sodium, as the counter ion, decreased the surface charge, thereby reducing the repulsive force between the Fe3O4@SiO2 nanoparticles. Then Fe3O4@SiO2 nanoparticles were utilized for separating plasmid DNA and separated plasmid DNA was measured with agarose gel electrophoresis and the absorbance monitoring. The efficiency of the DNA purification of the Na2SiO3-modified Fe3O4@SiO2 measured to 43.3 ± 5.2 ng/μl which was 58% increased after acid treatment. As a result, the dispersion/magnetic properties and DNA purification efficiency of the Na2SiO3-modified Fe3O4 became equivalent to the characteristics of the TEOS-modified Fe3O4@SiO2 using the additional acid treatment for sodium ions removal.

Microstructure evolution and growth mechanism of core-shell silicon-based nanowires by thermal evaporation of SiO

Core-shell structured SiC@SiO2 nanowires and Si@SiO2 nanowires were prepared on the surface of carbon/carbon (C/C) composites by a thermal evaporation method using SiO powders as the silicon source and Ni(NO3)2 as the catalyst. The average diameters of SiC@SiO2 nanowires and Si@SiO2 nanowires are about 145 nm, and the core-shell diameter ratios are about 0.41 and 0.53, respectively. The SiO2 shells of such two nanowires resulted from the reaction between SiO and CO and the reaction of SiO itself, respectively, based on the model analysis. The growth of these two nanowires conformed to the vapor—liquid—solid (VLS) mode. In this mode, CO played an important role in the growth of nanowires. There existed a critical partial pressure of CO (pC) determining the microstructure evolution of nanowires into whether SiC@SiO2 or Si@SiO2. The value of pC was calculated to be 4.01×10−15 Pa from the thermodynamic computation. Once the CO partial pressure in the system was greater than the pC, SiO tended to react with CO, causing the formation of SiC@SiO2 nanowires. However, the decomposition of SiO played a predominant role and the products mainly consisted of Si@SiO2 nanowires. This work may be helpful for the regulation of the growth process and the understanding of the growth mechanism of silicon-based nanowires.

One-Step Synthesis of Multi-Core-Void@Shell Structured Silicon Anode for High-Performance Lithium-Ion Batteries.

The core-void@shell architecture shows great advantages in enhancing cycling stability and high-rate performance of Si-based anodes. However, it is usually synthesized by template methods which are complex and environmentally unfriendly and would lead to low-efficiency charge and mass exchange because of the single-point van der Waals contact between the Si core and the shell. Here, a facile and benign one-step method to synthesize multi-Si-void@SiO2 structure, where abundant void spaces exist between multiple Si cores that are multi-point attached to a SiO2 shell through strong chemical bonding, is reported. The corresponding electrode exhibits highly stable cycling stability and excellent electrochemical performance. After 200 cycles at a current density of 0.1 A g-1 and then another 200 cycles at 1.2 A g-1 , the electrode outputs a specific capacity of 1440 mAh g-1 . Even at 2.0 A g-1 , it outputs a specific capacity as high as 1182 mAh g-1 . Such an anode can match almost all the cathode materials presently used in lithium-ion batteries. These results demonstrate the multi-Si-void@SiO2 as a promising anode to be used in future commercial lithium-ion batteries of high energy density and high power density.

Electrochemiluminescence biosensor for determination of lead(II) ions using signal amplification by Au@SiO2 and tripropylamine-endonuclease assisted cycling process.

MXene@Au as the base and Au@SiO2 as signal amplification factor were used for constructing an ultrasensitive "on-off" electrochemiluminescence (ECL) biosensor for the detection of Pb2+ in water. The use of MXene@Au composite provided a good interface environment for the loading of tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)32+) on the electrode. Based on resonance energy transfer, the Au (core) SiO2 (shell) (Au@SiO2) nanoparticles stimulate electron transport and promote tripropylamine (TPrA) oxidation. The luminescence effect of Au@SiO2 was five times that of AuNPs and SiO2 nanomaterials alone, and the ECL intensity was greatly improved. In addition, Pb2+ activated the aptamer to exert its endonuclease activity, which realized the signal cycle amplification in the process of Pb2+ detection. When Pb2+ was added, the ECL signal weakened, and the Pb2+ concentration was detected according to the decreased ECL intensity. Under optimized experimental conditions, this aptamer sensor for Pb2+ has a wide detection range (0.1 to 1 × 106ng L-1) and a low detection limit (0.059ng L-1). The relative standard deviation (RSD) of the sensor is 0.39-0.99%, and the recovery of spiked standard is between 90.00 and 125.70%. The sensor shows good selectivity and high sensitivity in actual water sample analysis. This signal amplification strategy possibly provides a new method for the detection of other heavy metal ions and small molecules.

Preparation and characterization of ZnO/SiO2@n-octadecane nanocapsule for ultraviolet absorbing and photothermal conversion energy storage

In this work, PCM nanocapsules composed of ZnO/SiO2 shell and n-octadecane core were successfully synthesized by emulsion polymerization and hydrothermal method. The crystallinity of ZnO was enhanced on the SiO2 shell by MPTS modification. The granule-like ZnO were distributed on the SiO2 shell. The encapsulation rate of n-octadecane in nanocapsules was about 45.2 % with enthalpy of 95.0 J/g melting at room temperature 28.3 °C. Furthermore, due to the presence of ZnO, the synthesized PCM nanocapsules had excellent UV absorption properties for whole wavelengths, and the absorbed UV light can be converted into heat energy for storage, and the photothermal conversion efficiency had reached 25.0 %. Hence, the prepared ZnO/SiO2@n-octadecane nanocapsules had broad application prospects due to its thermal energy storage, UV protection and photothermal conversion performance.

Experimental investigations on the thermal performance and phase change hysteresis of composite phase change material Na2HPO4·12H2O/SiO2

Integrating hydrated salt phase change material (PCM) into building envelopes is a promising method for achieving building energy saving. However, the hydrated salt suffers from the issues of supercooling, phase separation, leakage and phase change hysteresis. In this work, a novel form-stable composite phase change material (CPCM) with mesoporous silica (SiO2) encapsulating Na2HPO4·12H2O(DHPD) was synthesized by porous matrix composite technology. Thereinto, Na4P2O7·10H2O(TPD) used as the nucleating agent suppressed the supercooling phenomenon, 3 % sucrose can solve the issue of the water molecules loss of DHPD and phase separation.18 % SiO2 was favored for preventing leakage. The modified CPCM exhibited good chemical compatibility, higher charge-discharge efficiency, and good thermal stability via DSC, SEM, XRD, FT-IR and TG tests. According to experimental results, the surface area and pore volume of CPCM decreased, and the weight loss rate was lower than that of pure DHPD. The FT-IR and XRD tests indicated that only physical interaction occurred between the DHPD core and the SiO2 shell. Moreover, it displayed excellent thermal reliability after 500 melting-freezing cycles. Furthermore, the phase change onset temperature, supercooling, and hysteresis degree of CPCM at different melting states during partial melting phase transition were studied. It was found that the hysteresis degree of CPCM decreases with the increase in melting ratio, which may be related to the volume-free energy of PCM.

Core-shell FeNi@SiO2 composite with enhanced microwave absorption performance

In this work, a core-shell FeNi@SiO2 composite is constructed by modified Stöber method. Through adjusting the content of Tetra-Ethyl OrthoSilicate (TEOS) to control the thickness of the SiO2 shell, four FeNi@SiO2 powder samples with different SiO2 mass fractions were prepared, where magnetic FeNi@SiO2 microsphere with the core of FeNi is completely coated by SiO2. Herein, the electromagnetic parameters of the composites are effectively tuned by the combination of magnetic FeNi with dielectric SiO2. Results show that when the mass fraction of SiO2 is 35 %, the prepared FeNi@SiO2 powder sample exhibits good absorption performance, the minimum reflection loss (RL) reaches − 36.25 dB at 2.6 mm with the effective absorption bandwidth (RL<−10 dB) of 6 GHz (9.5–15.5 GHz) at 2.0 mm. It is believed that its good absorbing performance originates from the synergistic effect of the conductivity loss, dielectric polarization loss and magnetic loss of core-shell FeNi@SiO2 composite. This work provides a versatile strategy for FeNi@SiO2 composite with unique core-shell structures on excellent and tunable microwave absorption performance.

Y2W3O12@SiO2 composite particles for regulating thermal expansion and interfacial reactions in BaZr0.1Ce0.7Y0.1Yb0.1O3-δ/AISI 441 joints

Y2W3O12 particles with negative thermal expansion (NTE) can offset the high thermal expansion of Ag-based sealants, thus relieving the residual stress of electrolyte/interconnect joints in protonic ceramic fuel cell (PCFC) stacks. Nevertheless, violent interfacial reactions between Y2W3O12 particles and BaZr0.1Ce0.7Y0.1Yb0.1O3-δ electrolyte have severely restricted the application of these NTE particles. Herein, novel Y2W3O12@SiO2 composite particles with a core-shell structure are successfully designed to address this conundrum. The thermal expansion coefficient of Ag-based sealant is lowered from 19.7 to 14.6 ppm/K by adding 20 wt% Y2W3O12@SiO2 particles. During joining, the SiO2 shell significantly reduces the reaction consumption of Y2W3O12, fully exploiting its NTE properties. Meanwhile, a tiny portion of SiO2 participates in and regulates interfacial reactions, generating mechanically matched reaction layers. Finite element simulation demonstrates that introducing Y2W3O12@SiO2 particles significantly releases the compressive X-stress near the BaZr0.1Ce0.7Y0.1Yb0.1O3-δ interface, thus increasing the joint strength from ∼25.3 to ∼32.4 MPa. Obtained joints maintain long-term stability in oxidizing and reducing atmospheres at 600 °C, suggesting the applicability of Y2W3O12@SiO2 composite particles in fabricating PCFC stacks. Our work provides a new strategy for preparing NTE materials with controllable interfacial reactions and service capability under extreme conditions.

Influence of acid and alkali reaction system on the morphology and thermal properties of paraffin@SiO2 phase change microcapsules for heat storage

Phase change materials are preferred in the field of thermal energy storage in low-medium temperature. Paraffin@SiO2 microcapsules were prepared by a sol–gel method at an acid and alkali reaction system. The field emission scanning electron microscope, Fourier transform infrared spectroscope, differential scanning calorimetry, and thermogravimetric analyzer were adopted to investigate the effect of the acid and alkali reaction system on the morphology, latent heat, and thermal stability of PA@SiO2 microcapsules. In the acid reaction system, the particle size and latent heat of PA@SiO2 microcapsules are in the range from 15 to 30 μm and from 132 to 174 J/g, respectively. However, comparing with the acid reaction system, there was a remarkable reduction in the particle size and latent heat of microcapsules prepared in the alkali reaction system. The initial weightlessness temperatures of PA@SiO2 microcapsules were 40 °C higher than that of paraffin, indicating that the SiO2 shell was beneficial to the microcapsule structure.

SPION nanoparticles for delivery of dopaminergic isoquinoline and benzazepine derivatives

Superparamagnetic iron nanoparticles (SPIONs) have become one of the most useful colloidal systems in nanomedicine. We report here the preparation of new hybrid core@shell systems based on SPION nanoparticles coated with a SiO2 shell (SPION@SiO2) and functionalized with carboxyl groups (SPION@SiO2-COOH). A series of new N-alkylamino- and N-alkylamido-terminated 1-phenyl- tetrahydroisoquinolines (THIQs) and 3-tetrahydrobenzazepines (THBs) derivatives presenting -SMe and -Cl groups, respectively, with potential dopaminergic activity, are synthesized and incorporated to the hybrid system. We include the synthetic details for THIQs and THBs derivatives preparation and investigate the influence of the terminal-functional group as well as the number of carbon atoms linked to THIQ and THB molecules during the coupling to the SPION@SiO2-COOH. Nuclear magnetic resonance (NMR) and electron ionization mass spectrometry (EI-MS) are used to characterize the synthesized THIQs and THBs. High-angle annular dark-field transmission electron microscopy (HAADF-TEM), energy dispersive X-ray transmission electron microscopy (EDX-TEM), and proton high-resolution magic angle spinning NMR spectroscopy1H HRMAS-NMR) are used to confirm the presence of THB and THIQ molecules onto the surface of the nanoparticles. The hybrid SPION@SiO2-THIQ and THB systems show significant activity toward the D2 receptor, reaching Ki values of about 20 nM, thus having potential application in the treatment of central nervous system (CNS) diseases.