Synthesis and Characterization of Core‐Shell Selenium/Carbon Colloids and Hollow Carbon Capsules

A novel Se/C nanocomposite with core‐shell structures has been prepared through a facile one‐pot microwave‐induced hydrothermal process. The new material consists of a trigonal‐Se (t‐Se) core and an amorphous‐C (a‐C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. These products were characterized by transmission electron microscopy (TEM), powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy‐dispersive X‐ray (EDX) spectroscopy, and X‐ray photoelectron spectroscopy (XPS).     

Synthesis of TiO2–SiO2/polymer core–shell microspheres with a microphase‐inversion method

A novel microphase‐inversion method was proposed for the preparation of TiO₂–SiO₂/poly(methyl methacrylate) core–shell nanocomposite particles. The inorganic–polymer nanocomposites were first synthesized via a free‐radical copolymerization in a tetrahydrofuran solution, and the poor solvent was added slowly to induce the microphase separation of the nanocomposite and result in the formation of nanoparticles. The average particle sizes of the microspheres ranged from 70 to 1000 nm, depending on the reaction conditions. Transmission electron microscopy and scanning electron microscopy indicated a core–shell morphology for the obtained microspheres. Thermogravimetric analysis and X‐ray photoelectron spectroscopy measurements confirmed that the surface of the nanocomposite microspheres was polymer‐rich, and this was consistent with the core–shell morphology. The influence of the synthetic conditions, such as the inorganic composition and the content of the crosslinking monomer, on the particle properties was studied in detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3911–3920, 2006     

Preparation and characterization of copper/silver bimetallic nanowires with core‐shell structure

Core‐shell copper/silver bimetallic nanowires were prepared by replacement reaction with citric acid and polyvinylpyrollidone at room temperature. A uniform silver coating was obtained by strictly controlling the molar ratio of Ag/Cu. The copper/silver composite was characterized by X‐ray diffraction, scanning electron microscopy, electron probe microanalysis and X‐ray photoelectron spectroscopy. Microscopic analysis shows that a well‐copper/silver core‐shell structure was formed. Thermo‐gravimetry and differential thermal analysis to the composite nanowires show that the silver coatings efficiently inhibit the oxidation of Cu. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of P(MBA‐co‐MAA)/Zr(OH)4/P(EGDMA‐co‐MAA)/TiO2 Tetra‐layer Hybrid Microspheres and the Corresponding ZrO2/TiO2 Double‐shelled Hollow Microspheres

Double‐shelled zirconia/titania (ZrO₂/TiO₂) hollow microspheres were prepared by the selective removal of the polymer components via the calcination of the corresponding tetra‐layer poly(N,N′‐methylenebisacryl amide‐co‐methacrylic acid) (P(MBA‐co‐MAA))/Zr(OH)₄/poly(ethyleneglycol dimethacrylate‐co‐methacrylic acid) (P(EGDMA‐co‐MAA))/TiO₂ hybrid microspheres. These tetra‐layer microspheres were synthesized by the combination of the distillation copolymerization of N,N(‐methylenebisacryl amide‐co‐methacrylic acid (MBA) or ethyleneglycol dimethacrylate (EGDMA) crosslinker and methacrylic acid (MAA) for the preparation of polymer core and third‐layer as well as the controlled sol‐gel hydrolysis of inorganic precursors for the construction of zirconium hydroxide (Zr(OH)₄) and titania (TiO₂) layers. The thicknesses of zirconia and titania shell‐layers were conveniently controlled via varying the feed of zirconium n‐butoxide (Zr(OBu)₄) and titanium tetrabutoxide (TBOT) during the sol‐gel hydrolysis, while the sizes of polymer layers were tuned through a multi‐stage distillation precipitation copolymerization. The structure and morphology of the resultant microspheres were characterized by transmission electron microscopy (TEM), X‐ray diffractometer (XRD), X‐ray photoelectronic spectroscopy (XPS), and thermogrametric analysis (TGA).     

Synthesis of core‐shell silver–polyaniline nanocomposites by gamma radiolysis method

Core‐shell silver (Ag)–polyaniline (PAni) nanocomposites have been synthesized by the in‐situ gamma radiation‐induced chemical polymerization method. Aqueous solution of aniline, a free‐radical oxidant, and/or silver metal salt were irradiated by γ‐rays. Reduction of the silver salt in aqueous aniline leads to the formation of silver nanoparticles which in turn catalyze oxidation of aniline to polyaniline. The resultant Ag‐PAni nanocomposites were characterized by using different spectroscopy analyses like X‐ray photoelectron, UV–visible, and infrared spectroscopy. The optical absorption bands revealed that the bands at about 400 nm are due to the presence of nanosilver and the blue‐shifted peak at ～ 555 nm is due to the presence of metallic silver within the PAni matrix. X‐ray diffraction pattern clearly indicates the broad amorphous polymer and the sharp metal peaks. Scanning electron microscopy and transmission electron microscopy of the nanocomposite showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the composites have a higher degradation temperature than polyaniline alone. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5741–5747, 2007     

One‐pot synthesis of composite microspheres with core‐shell structure

One‐pot synthesis of thermoresponsive magnetic composite microspheres with a poly(N‐isopropylacrylamide) (PNIPAM) shell and a Fe₃O₄ core is demonstrated. Temperature sensitivity of PNIPAM was adopted to design the novel synthesis pathway. The as‐prepared composite microspheres have an obvious core‐shell structure with a mean size of approximately 250 nm. The Fe₃O₄ core is approximately 5 nm and the thickness of the PNIPAM shell is approximately 10 nm. The content of Fe₃O₄ in the composite microspheres can be controlled by this method. The composite microspheres experience a swelling and shrinking process in water by adjusting the temperature below and above the lower critical solution temperature (LCST) around 32 °C. These microspheres also show fine response to an external magnetic field. This work presents a platform to synthesize organic/inorganic composite microspheres in a facile and efficient approach. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2702–2708     

One‐stage synthesis of narrowly dispersed polymeric core‐shell microspheres

A method of one‐stage soap‐free emulsion polymerization to synthesize narrowly dispersed core‐shell microspheres is proposed. Following this method, core‐shell microspheres of poly(styrene‐co‐4‐vinylpyridine), poly(styrene‐co‐methyl acrylic acid), and poly[styrene‐co‐2‐(acetoacetoxy)ethyl methacrylate‐co‐methyl acrylic acid] are synthesized by one‐stage soap‐free emulsion polymerization of a mixture of one or two hydrophobic monomers and a suitable hydrophilic monomer in water. The effect of the molar ratio of the hydrophobic monomer to the hydrophilic one on the size, the core thickness, and the shell thickness of the core‐shell microspheres is discussed. The molar ratio of the hydrophobic and hydrophilic monomers and the hydrophilicity of the resultant oligomers of the hydrophilic monomer are optimized to synthesize narrowly dispersed core‐shell microspheres. A possible mechanism of one‐stage soap‐free emulsion polymerization to synthesize core‐shell microspheres is suggested and coagglutination of the oligomers of the hydrophilic monomers on the hydrophobic core is considered to be the key to form core‐shell microspheres. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1192–1202, 2008     

Surface‐State‐Mediated Charge‐Transfer Dynamics in CdTe/CdSe Core–Shell Quantum Dots

Herein, we report the synthesis of aqueous CdTe/CdSe type‐II core–shell quantum dots (QDs) in which 3‐mercaptopropionic acid is used as the capping agent. The CdTe QDs and CdTe/CdSe core–shell QDs are characterized by X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HR‐TEM), steady‐state absorption, and emission spectroscopy. A red shift in the steady‐state absorption and emission bands is observed with increasing CdSe shell thickness over CdTe QDs. The XRD pattern indicates that the peaks are shifted to higher angles after growth of the CdSe shell on the CdTe QDs. HR‐TEM images of both CdTe and CdTe/CdSe QDs indicate that the particles are spherical, with a good shape homogeneity, and that the particle size increases by about 2 nm after shell formation. In the time‐resolved emission studies, we observe that the average emission lifetime (τ_av) increases to 23.5 ns for CdTe/CdSe (for the thickest shell) as compared to CdTe QDs (τ_av=12 ns). The twofold increment in the average emission lifetime indicates an efficient charge separation in type‐II CdTe/CdSe core–shell QDs. Transient absorption studies suggest that both the carrier cooling and the charge‐transfer dynamics are affected by the presence of traps in the CdTe QDs and CdTe/CdSe core–shell QDs. Carrier quenching experiments indicate that hole traps strongly affect the carrier cooling dynamics in CdTe/CdSe core–shell QDs.     

Rapid and efficient enantioseparation of (S)‐amlodipine by surface‐imprinted core–shell polymer microspheres

We present a protocol for the preparation of surface‐imprinted polymer microspheres by core–shell precipitation polymerization for the enantioseparation of (S)‐amlodipine. In this work, submicron mesoporous silica microspheres were prepared with gemini cationic surfactant as soft template. Molecularly imprinted polymers were coated on the silica supports with a low level of crosslinking, and the thickness of the thin‐walled imprinted shell was about 45 nm. The material showed fast binding kinetics for (S)‐amlodipine (within only 20 min for complete equilibrium), and the saturation adsorption capacity reached 309.2 mg/g, indicating the good accessibility of binding sites and improved mass transfer for target molecule. The imprinted microspheres exhibited an appreciable enantiomeric excess of (S)‐amlodipine of 11.3% when used as a glass chromatography column for the enantioseparation of (S)‐amlodipine from amlodipine besylate without extra chiral additives. The surface‐imprinted materials display potentially amplification for industrial enantioseparation of (S)‐amlodipine.     

dl‐Aspartic Acid‐Mediated Hydrothermal Synthesis of β‐ZnS Microspheres and Their Optical Properties

ZnS hollow microspheres were synthesized by a dl ‐aspartic acid mediated hydrothermal route. dl ‐aspartic acid plays an important role as crystal growth soft template, which regulates the release of Zn²⁺ ions for the formation of ZnS hollow spheres. The formation of these hollow spheres was mainly attributed to an Ostwald ripening process. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), electron diffraction (ED), UV/Vis spectroscopy (UV), and photoluminescence (PL). The shells of the microspheres were composed of ZnS quantum dots (QDs) with the average size of 2.31 nm. The average microspheres diameter is 0.5–3.5 μm. The shell thickness of the hollow sphere is ≈?300 nm. The optical bandgap energy increased significantly compared to the bulk ZnS material due to the strong quantum confinement effect. Two strong emissions at ≈?425 nm and ≈?472 nm in the photoluminescence (PL) spectrum of ZnS hollow microspheres indicate strong quantum confinement because of the presence of QDs.     

Quinone‐Rich Poly(dopamine) Magnetic Nanoparticles for Biosensor Applications

Novel core‐shell quinone‐rich poly(dopamine)–magnetic nanoparticles (MNPs) were prepared by using an in situ polymerization method. Catechol groups were oxidized to quinone by using a thermal treatment. MNPs were characterized by using X‐ray diffraction, X‐ray photoelectron spectroscopy, atomic force microscopy, magnetic force microscopy, UV/Vis, Fourier‐transform infrared spectroscopy, and electrochemical techniques. The hybrid nanomaterial showed an average core diameter of 17 nm and a polymer‐film thickness of 2 nm. The core‐shell nanoparticles showed high reactivity and were used as solid supports for the covalent immobilization of glucose oxidase (Gox) through Schiff base formation and Michael addition. The amount of Gox immobilized onto the nanoparticle surface was almost twice that of the nonoxidized film. The resulting biofunctionalized MNPs were used to construct an amperometric biosensor for glucose. The enzyme biosensor has a sensitivity of 8.7 mA M ^?1 cm^?2, a low limit of detection (0.02 mM ), and high stability for 45 days. Finally, the biosensor was used to determine glucose in blood samples and was checked against a commercial glucometer.     

Fe3O4‐supported Schiff‐base copper (II) complex: A valuable heterogeneous nanocatalyst for one‐pot synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives

A novel Cu (II) Schiff‐base complex immobilized on core‐shell magnetic Fe₃O₄ nanoparticles (Fe₃O₄@SPNC) was successfully designed and synthesized. The structural features of these nanoparticles were studied and confirmed by using various techniques including FT‐IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD), wavelength dispersive X‐ray spectroscopy (WDX), and inductively coupled plasma (ICP). These newly synthesized nanoparticles have been used as efficient heterogeneous catalytic system for one‐pot multicomponent synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives. Notably, the catalyst could be easily separated from the reaction mixture by using an external magnet and reused for several successive reaction runs with no significant loss of activity or copper leaching. The present protocol benefits from a hitherto unreported MNPs‐immobilized Cu (II) Schiff‐base complex as an efficient nanocatalyst for the synthesis of newly reported derivatives of pyrano[2,3‐b]pyridine‐3‐carboxamide from one‐pot multicomponent reactions.     

超临界二氧化碳中药物控制释放体系的一步法制备研究

用一步法首次制备了以N-异丙基丙烯酰胺类共聚物为基料的药物释放体系。在此法中,超临界二氧化碳同时作为聚合介质和渗透试剂。制得的聚合物微球用扫描电镜、差示扫描量热仪、透射电镜、X射线衍射仪等进行了表征,并用体外释放模拟考察了原位法制备的微凝胶对渗入的目标药物布洛芬的释放效果。     

Examination and analysis of Indian silver punch‐marked coins employing WD‐XRF and other noninvasive techniques

The archaeometallurgical analysis of ancient silver coins provides useful information regarding fabrication methodology, provenance, and trade route and explains large diversification in elementary composition, weight, and physical features. The present investigation deals with the chemical analysis and examination of the processing history of Indian punch‐marked silver coins dating to 400–200 bc . The chemical analysis was carried out by wavelength dispersive X‐ray fluorescence and X‐ray Diffraction (XRD). The microstructural examination was performed using field emission scanning electron microscope (FE‐SEM) and different phases were identified by Scanning Electron Microscopy coupled with Energy Dispersive X‐ray (SEM‐EDX) Spectroscopy. It was observed that all eight coins were manufactured with silver‐copper alloy. The ore used for obtaining silver was argentiferous galena, and cupellation was carried with perfection. The absence of slag inclusions as revealed by SEM examination indicated that coins (numbers 2, 4, 5, and 7) were cast from a molten state. The presence of Cu₂O, CuO, and Ag₂O on the surfaces of the coins was confirmed by XRD. The formed oxide layers provided protection and saved the coins from bulky corrosion products. The data reveal great divergence of coin surface from the composition of the core with the far better metallurgical process for refining of silver for this hoard.     

Thermoresponsive hydrophobic copolymer grafted on agar microspheres for all‐aqueous bioseparations

Agar microspheres were prepared by water–oil emulsification and cross‐linked under alkaline condition. The thermoresponsive hydrophobic copolymer, poly(N‐isopropylacrylamide‐co‐lauryl methacrylate‐co‐acrylamide), was grafted on the agar microspheres via atom transfer radical polymerization. The agar microspheres grafted with copolymers were characterized by light microphotography, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The chain lengths and hydrophobic monomer ratio of the grafting linear polymer had significant effects on the hydrophobicity and adsorption capacity of agar microspheres at different temperatures. The thermoresponsive microspheres were used for separation of proteins and showed binding and release behavior by change of temperatures without change in mobile phase composition. Thus, we suggest thermoresponsive agar microspheres as an alternative separation media for all‐aqueous bioseparations.     

Hydrophilic dual‐responsive magnetite/PMAA core/shell microspheres with high magnetic susceptibility and ph sensitivity via distillation‐precipitation polymerization

A facile and effective approach to preparation of dual‐responsive magnetic core/shell composite microspheres is reported. The magnetite(Fe₃O₄)/poly(methacrylic acid) (PMAA) composite microspheres were synthesized through encapsulating γ‐methacryloxypropyltrimethoxysilane (MPS)‐modified magnetite colloid nanocrystal clusters (MCNCs) with crosslinked PMAA shell. First, the 200‐nm‐sized MCNCs were fabricated through solvothermal reaction, and then the MCNCs were modified with MPS to form active vinyl groups on the surface of MCNCs, and finally, a pH‐responsive shell of PMAA was coated onto the surface of MCNCs by distillation‐precipitation polymerization. The transmission electron microscopy (TEM) and vibrating sample magnetometer characterization showed that the obtained composite microspheres had well‐defined core/shell structure and high saturation magnetization value (35 emu/g). The experimental results indicated that the thickness and degree of crosslinking of PMAA shell could be well‐controlled. The pH‐induced change in size exhibited by the core/shell microspheres reflected the PMAA shell contained large amount of carboxyl groups. The carboxyl groups and high saturation magnetization make these microspheres have a great potential in biomolecule separation and drug carriers. Moreover, we also demonstrated that other magnetic polymeric microspheres, such as Fe₃O₄/PAA, Fe₃O₄/PAM, and Fe₃O₄/PNIPAM, could be synthesized by this approach. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Preparation of Thermosensitive Hollow Imprinted Microspheres via Combining Distillation Precipitation Polymerization and Thiol‐ene Click Chemistry

Hollow molecular imprinted polymer microspheres were prepared by distillation precipitation polymerization with (S)‐(+)‐ibuprofen (S‐IBF) as template molecule and acrylamide (AM) as functional monomer. Using the silicon dioxide (SiO₂, 180 nm) modified by 3‐(trimethoxysilyl)propyl methacrylate (MPS) as the template microspheres, the molecular imprinted shells were coated on successfully (SiO₂@MIPs). The thermosensitive SiO₂@MIPs‐PNIPAM core‐shell microspheres were subsequently prepared by grafting the PNIPAM chains (M_n=1.21×10⁴ g/mol, polydispersity index=1.30), which were prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization, on the surface of SiO₂@MIPs microspheres via the thiol‐ene click chemistry. The grafting density of PNIPAM brushes on the SiO₂@MIPs microspheres was about 0.18 chains/nm². After HF etching, the hollow imprinted microspheres were finally obtained. For thermosensitivity analysis, the phase transition temperatures of multifunctional nanoparticles were measured by DSL at 25°C and 45°C respectively, and the sizes of the microspheres changed by about 35 nm. The modified microspheres presented excellent controlled release property to S‐IBF, moreover about half amount of the adsorptions passed into acetonitrile‐water solution through the specific holes of imprinted shell at 25°C under vibration.     

完全绿色路线获得的银纳米线的表面增强拉曼光谱

以硝酸银为银源,在硅片上成功地制备了银纳米线。该制备步骤在室温下操作,用环境友好的化合物乙二醇作还原剂。这是一个完全“绿色的”制备路线。用XRD、SEM和EDX对新制备的产物进行了表征,结果表明该银纳米线很纯,平均直径20nm。该银纳米线用于罗丹明6G的表面增强拉曼光谱测定,当罗丹明6G为10nM时,出现了特征峰。     

In situ formation of silver nanoparticles within an amphiphilic graft copolymer film

Silver nanoparticles were prepared by UV irradiation from silver salts, such as AgBF₄ or AgNO₃, when dissolved in an amphiphilic film of poly((oxyethylene)₉ methacrylate)‐graft‐poly((dimethyl siloxane)_n methacrylate), POEM‐g‐mPDMS. The in situ formation of silver nanoparticles in the graft copolymer film was confirmed by transmission electron microscopy (TEM), UV‐visible spectroscopy, and wide angle X‐ray scattering (WAXS). The results demonstrated that the use of AgBF₄ yielded silver nanoparticles with a smaller size (～5 nm) and narrower particle distribution when compared with AgNO₃. The formation of silver nanoparticles was explained in terms of the interaction strength of the silver ions with the ether oxygens of POEM, as revealed by differential scanning calorimetry (DSC) and X‐ray photoelectron spectroscopy (XPS). It was thus concluded that a stronger interaction of silver ions with the ether oxygens results in a more stable formation of silver nanoparticles, which produces uniform and small‐sized nanoparticles. DSC and small angle X‐ray scattering (SAXS) data also showed the selective incorporation and in situ reduction of the silver ions within the hydrophilic POEM domains. Excellent mechanical properties of the nanocomposite films (3–5 × 10⁵ dyn/cm²) were observed, mostly because of the confinement of silver nanoparticles in the POEM chains as well as interfaces created by the microphase separation of the graft copolymer film. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1283–1290, 2007     

Peak shape analysis of Ag 3d core‐level X‐ray photoelectron spectra of Au@Ag core‐shell nanoparticles using an asymmetric Gaussian–Lorentzian mixed function

This article reports on the peak shape analysis of X‐ray photoelectron spectra of gold‐silver core‐shell (Au@Ag) nanoparticles (NPs) using an asymmetric Gaussian–Lorentzian mixed function. Unlike Ag NPs, Au@Ag NPs have no oxide peak and show asymmetric line shape with a high energy tail in Ag 3d core‐level spectra. A monotonic increase in the Ag 3d binding energy and a decrease in the degree of asymmetry with increasing the Ag shell thickness were observed supporting the occurrence of charge transfer from Au core to Ag shell. Copyright © 2012 John Wiley & Sons, Ltd.