The effect of gamma irradiation and surfactants on the size distribution of nanoparticles based on soluble starch

The effect of three kinds of surfactants (anionic, cationic and nonionic) on the shape and size distribution of nanoparticles based on soluble starch fabricated under gamma irradiation was studied. Aqueous solution of soluble starch was irradiated with a dose of 20 kGy. The TEM micrograph and size distribution plots showed that when irradiations were made in presence of surfactants the smaller and more distinct nanoparticles were created in comparison to pure starch solution.     

Synthesis of iron oxide nanoparticles using chitosan and starch templates

Natural polymers like chitosan and starch have been employed as templates for the preparation of iron oxide nanoparticles. The templates offer selective binding sites for Fe(II) under aqueous conditions. Controlled drying and subsequent removal of the template backbone enables the synthesis of spatially separated iron oxide nanoparticles. The crystalline character of the iron oxide and near narrow particle size distribution pattern have been confirmed through powder XRD, Photon Correlation Spectroscopy, and TEM measurements. The crystallite sizes of the particles were found to be 26–35 nm irrespective of the nature of the template.     

Graft modification of starch nanoparticles with pH-responsive polymers via nitroxide-mediated polymerization

The grafting to approach and nitroxide-mediated polymerization (NMP) were used to graft modify starch nanoparticles (SNP) with pH-responsive polymers. SG1-capped poly(2-(dimethylamino)ethyl methacrylate-co-styrene), P(DMAEMA-co-S), and poly(2-(diethylamino)ethyl methacrylate-co-styrene), P(DEAEMA-co-S), with relatively low dispersity and high degree of livingness was synthesized in bulk via NMP using a commercial available alkoxyamine. These macroalkoxyamines were then grafted to vinyl benzyl-functionalized SNP (SNP-VBC) to obtain pH-responsive materials. The grafted SNP were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis confirming the successful synthesis of these new materials. Low grafting efficiencies (~6%) were observed for both SNP-grafted materials with pH-responsive polymers, as expected when using the grafting to approach. The pH-responsiveness of SNP-g-P(DMAEMA-co-S) and SNP-g-P(DEAEMA-co-S) was confirmed by measuring the ζ-potential at different pH values. At acidic conditions (pH 3–6) the grafted materials were protonated and exhibited positive ζ-potential, whereas at basic conditions (pH 10–13) the same grafted materials were deprotonated and exhibited negative ζ-potential.     

Mixed biopolymer systems based on starch

A binary mixture of starch-starch or starch with other biopolymers such as protein and non-starch polysaccharides could provide a new approach in producing starch-based food products. In the context of food processing, a specific adjustment in the rheological properties plays an important role in regulating production processing and optimizing the applicability, stability, and sensory of the final food products. This review examines various biopolymer mixtures based on starch and the influence of their interaction on physicochemical and rheological properties of the starch-based foods. It is evident that the physicochemical and rheological characteristics of the biopolymers mixture are highly dependent on the type of starch and other biopolymers that make them up mixing ratios, mixing procedure and presence of other food ingredients in the mixture. Understanding these properties will lead to improve the formulation of starch-based foods and minimize the need to resort to chemically modified starch.     

Electrosprayed maize starch and its constituents (amylose and amylopectin) nanoparticles

Starch consists of amylose and amylopectin. Properties such as being natural and highly hygroscopic as well as biodegradability have opened a considerable range of applications for amylose, amylopectin and starch. The performance of particles is highly dependent on their size which in turn determines the specific surface area. This work studies the application of electrospraying to fabricate maize starch and its constituents: amylose and amylopectin nanoparticles. This study showed that electrospraying technique is capable of producing amylose, amylopectin and starch nanopowder with an average particle size around 100 nm. FTIR analysis showed no reaction or interaction occurring in amylose, amylopectin and starch nanoparticle compared with their natural form. Basically, lower concentration, lower viscosity and lower surface tension of the electrospraying solution as well as higher nozzle–collector distance, higher voltage and lower feed rate lead to smaller nanoparticle size. Copyright © 2015 John Wiley & Sons, Ltd.     

Bio-barcodes based on oligonucleotide-modified nanoparticles

By utilizing oligonucleotide-modified Au nanoparticles encoded with sequences that act as biobarcodes, one can screen for multiple target polyvalent proteins simultaneously in one solution. This novel concept was demonstrated with two types of detection formats, a homogeneous assay and one based on oligonucleotide microarrays. With such an approach, one can prepare an extraordinarily large number of barcodes from synthetically accessible oligonucleotides (e.g., a 12-mer sequence offers 4(12) possible barcodes).     

Crystalline silicon carbide nanoparticles encapsulated in branched wavelike carbon nanotubes: synthesis and optical properties

A novel nanostructure, cubic silicon carbide (3C-SiC) nanoparticles encapsulated in branched wavelike carbon nanotubes have been prepared by a reaction of 1,2-dimenthoxyethane (CH3OCH2CH2OCH3), SiCl4, and Mg in an autoclave at 600 degrees C. According to X-ray powder diffraction, the products are composed of 3C-SiC and carbon. TEM and HRTEM images show that the as-synthesized products are composed of 3C-SiC nanoparticles encapsulated in branched carbon nanotubes with wavelike walls. The diameter of the 3C-SiC cores is approximately 20-40 nm and the thickness of the carbon shells is about 3-5 nm. In Raman scattering spectroscopy, both the TO (Gamma) phonon line and the LO (Gamma) phonon line have red shifts about 6 cm(-1) relative to that for the bulk 3C-SiC. The photoluminescence (PL) spectrum shows that there are two emission peaks: blue light emission (431 nm) and violet light emission (414 nm). A sequential deposition growth process (with cores as the templates for the shells) for the nanostructure was proposed.     

Hydrogels with Crystalline or Liquid Crystalline Structure

The formation of ordered structure in hydrogels derived from copolymers of hydrophilic and hydrophobic monomers with crystalline or liquid‐crystalline moieties is reviewed. The role of water in the formation of ordered structure and its influence on the thermal and mechanical properties of hydrogels are clarified. For example, by inducing a certain amount of water, an amorphous to crystalline transition occurs in gels of acrylic acid/alkyl acrylate copolymers. On the other hand, water induces a liquid‐crystalline (SmA) to liquid‐crystalline (SmI) transition in copolymers consisting of acrylic acid and 11‐(4′‐cyanobiphenyloxy)undecyl acrylate. These specific features regarding the formation of ordered structures in hydrogels might shed some light on the formation of ordered structure in biological tissues.     

液晶离聚物--液晶行为的研究

综述了液晶离聚物中离子的种类,位置、在链中浓度对液晶性能的影响,无论是主链还是侧链液晶离聚物,离子的种类,位置对中介区间的宽度有影响,但对中介相类型基本没有影响,当离子浓度增大到一定值时,液晶性能消失。     

Novel water-soluble photosensitizer based on starch and containing porphyrin

Novel water-soluble polymeric photosensitizers (SPO) based on starch and containing porphyrin chromophores were synthesized and studied. The polymers were soluble in water and in dimethyl sulfoxide. Photophysical studies and solubilization of molecular probes proved the formation of hydrophobic, rigid microdomains in an aqueous solution of SPO; they were created due to the clustering of porphyrin chromophores attached to the polymer chain. SPO polymers absorbed light from the UV-visible spectral region. The polymers could sensitize photochemical reactions mediated by electron transfer, energy transfer or both, from the singlet-excited state of porphyrin chromophores to the molecules of organic compounds solubilized in the hydrophobic microdomains or residing in the water phase.     

结晶的稀土配合催化剂活性体

在3d族过渡金属配合催化剂结构的研究中,作为活性中心的模型,引人注意的是金属和铝摩尔比1∶1和1∶2的活性体,但其摩尔比2∶1的活性体尚未见报道. 在稀土配合催化剂本质的研究中,人们也一直把注意力集中于催化剂结构,但成功地合成或分离出结晶的活性体只有两种双金属配合物.Ballard等报道的Er(η-C_5H_4R)_2(CH_3)Al(CH_3)_2使乙烯聚合有活性,我们合成出的(CF_3CO_2)HLnCl(C_2H_5)Al(C_2H_5)_2使双烯烃聚合得到高顺式聚合物. 本文利用(i-C_3H_7O)_3Ln-Et_2AlCl-Et_3Al(三元体系)和(i-C_3H_7O)_2LnCl-Et_3Al(二元体系)的可溶性,合成了摩尔比为1∶2∶3=Al∶Ln∶Cl(Ln=Gd,Dy,Er,Tm.Lu-Al活性体中1∶1∶1=Al∶Ln∶Cl)的四种新的Ln-Al-Ln结晶活性体.     

Crystalline Boragermenes

Boragermene 3 featuring a double bond between the Ge and dicoordinate B atoms has been synthesized for the first time by reacting the cyclic (alkyl)(boryl)germylene–PMe₃ adduct 1 with Cl₂BN(SiMe₃)₂ followed by reductive dehalogenation with KC₈. Addition of a Lewis base (^MeNHC) to 3 leads to the formation of the corresponding adduct 4 , which shows double bond character between the Ge and tricoordinate B atoms. Compound 3 undergoes hydrogenation with H₂ concomitant with a complete scission of the Ge=B bond.     

Crystalline Boragermenes

Boragermene 3 featuring a double bond between the Ge and dicoordinate B atoms has been synthesized for the first time by reacting the cyclic (alkyl)(boryl)germylene–PMe₃ adduct 1 with Cl₂BN(SiMe₃)₂ followed by reductive dehalogenation with KC₈. Addition of a Lewis base (^MeNHC) to 3 leads to the formation of the corresponding adduct 4 , which shows double bond character between the Ge and tricoordinate B atoms. Compound 3 undergoes hydrogenation with H₂ concomitant with a complete scission of the Ge=B bond.     

Electrochemical biosensing based on noble metal nanoparticles

The interest in the fabrication of electrochemical biosensors with high sensitivity, selectivity and efficiency is rapidly growing. In recent years, noble metal nanoparticles (NMNPs), with extraordinary conductivity, large surface-to-volume ratio and biocompatibility, have been extensively employed for developing novel electrochemical sensing platforms and improving their performances. Through distinct surface modification strategies (e.g. self-assembly, layer-by-layer, hybridization and sol-gel technology), NMNPs provide well control over the microenvironment of biological molecules retaining their activity, and facilitate the electron transfer between the redox center of biomolecules and electrode surface. Moreover, NMNPs have been involved into biorecognition events (e.g. immunoreactions, DNA hybridization and ligand-receptor interactions) by conjugating with various biomolecules, chemical labels and other nanomaterials, achieving the signal transduction and amplification. The aim of this review is to summarize different strategies for NMNP-based signal amplification, as well as to provide a snapshot of recent advances in the design of electrochemical biosensing platforms, including enzyme/protein sensors focused on their direct electrochemistry on NMNP-modified electrode surface; immunosensors and gene sensors in which NMNPs not only participate into biorecognition, but also act as electroactive tags to enhance the signal output. In addition, NMNP alloy-based multifunctional electrochemical biosensors are briefly introduced in terms of their unique heterostructures and properties.

Transparent superhydrophobic films based on silica nanoparticles

We demonstrate a layer-by-layer processing scheme that can be utilized to create transparent superhydrophobic films from SiO2 nanoparticles of various sizes. By controlling the placement and level of aggregation of differently sized nanoparticles within the resultant multilayer thin film, it is possible to optimize the level of surface roughness to achieve superhydrophobic behavior with limited light scattering. Transparent superhydrophobic films were created by the sequential adsorption of silica nanoparticles and poly(allylamine hydrochloride). The final assembly was rendered superhydrophobic with silane treatment. Optical transmission levels above 90% throughout most of the visible region of the spectrum were realized in optimized coatings. Advancing water droplet contact angles as high as 160 degrees with low contact angle hysteresis (<10 degrees ) were obtained for the optimized multilayer thin films. Because of the low refractive index of the resultant porous multilayer films, they also exhibited antireflection properties.