Solution-based direct readout surface enhanced Raman spectroscopic (SERS) detection of ultra-low levels of thiram with dogbone shaped gold nanoparticles

We report the use of two different sizes of dogbone shaped gold nanoparticles as colloidal substrates for surface enhanced Raman spectroscopy (SERS) based detection of ultra-low levels of thiram, a dithiocarbamate fungicide. We demonstrate the ability to use a solution based, direct readout SERS method as a quantitative tool for the detection of ultra-low levels of thiram. The two different sizes of dogbone shaped gold nanoparticles are synthesized by using the seed-mediated growth method and characterized by using UV-visible spectroscopy and transmission electron microscopy (TEM). The smaller dogbone shaped nanoparticles have an average size of 43 ± 13 nm. The larger dogbone shaped gold nanoparticles have an average size of 65 ± 15 nm. The nanoparticle concentration is 1.25 × 10(11) nanoparticles per mL for the smaller dogbone shaped gold nanoparticles and is 1.13 × 10(11) nanoparticles per mL for the larger dogbone shaped gold nanoparticles. Different concentrations of thiram are allowed to bind to the two different sizes of dogbone shaped gold nanoparticles and the SERS spectra are obtained. From the calibration curve, the limit of detection for thiram is 43.9 ± 6.2 nM when the smaller dogbone shaped gold nanoparticles are used as colloidal SERS substrates In the case of the larger dogbone shaped gold nanoparticles, the limit of detection for thiram is 11.8 ± 3.2 nM. The lower limit of detection obtained by using the larger dogbone shaped gold nanoparticles as colloidal substrates is due to the lightning rod effect, higher contributions from the electromagnetic enhancement effect, and larger number of surface sites for thiram to bind.     

Stoichiometric functionalization of gold nanoparticles in solution through a free radical polymerization approach

A new simple concept for the stoichiometrical functionalization of nanoparticles based on free radical polymerization of vinyl protected nanoparticles is presented. To demonstrate this concept 2-bis(4-vinylphenyl)disulfane was synthesized and used in the synthesis of gold nanoparticles, leading to 4-vinylthiophenol functionalized nanoparticles. Simple free radical polymerization of these particles initiated by 4,4'-azobis-(4-cyanopentanoic acid) delivered nanoparticles with a single carboxyl group. These monofunctionalized gold nanoparticles were utilized for chemical preparation of gold nanoparticle dimers as well as for construction of gold nanoparticle arrays via binding to polyallylamine.     

Synthesis of magnetite hydrosols in inert atmosphere

A setup is described for magnetite hydrosol synthesis in inert atmosphere via coprecipitation of bi- and trivalent iron salts in the presence of a base with the formation of nanoparticles having desired sizes and chemical composition. The size of nanoparticles is estimated based on analysis of light-scattering and transmission-electron-microscopy data. The chemical composition of magnetite nanoparticles is monitored by Raman spectroscopy.     

纳米粒子的制备及其在打印印刷领域的应用

本文简要介绍了几类纳米粒子的制备及其在打印印刷领域的应用.包括无机纳米粒子复合材料用于绿色打印制版、聚合物乳胶纳米粒子用于喷墨打印制备光子晶体、金属纳米粒子用于印刷电路以及纳米材料用于3D打印,并展望了其发展前景.     

Preparation and Characterization of Stearate-Capped Titanium Dioxide Nanoparticles

The preparation of titanium dioxide nanoparticles capped with stearate by sol-gel methods is presented in this paper. The nanoparticles are characterized by Fourier transform infrared spectroscopy and by X-ray photoelectron spectroscopy. Existence of the organic layer can be confirmed by the results of characterizations, which also indicate that the inorganic nuclei and organic surface layer are linked with chemical bonds. The nanoparticles are poorly crystallized based on the X-ray diffraction pattern. The mechanism of formation of the organo-capped nanoparticles is proposed to be competitive reactions between water and stearic acid, which is similar to a polymerization and inhibition processes. A structural model for organo-capped nanoparticles is also proposed. Copyright 2000 Academic Press.     

Electrochemical sensors based on metal and semiconductor nanoparticles

Metal and semiconductor nanoparticles exhibit unique optical, electrical, thermal and catalytic properties. Therefore, they have attracted considerable interest and have been employed for construction of various electrochemical sensors. This minireview gives a general view of recent advances in electrochemical sensor development based on metal and semiconductor nanoparticles covering genosensors, protein and enzyme-based sensors, gas sensors and sensor for other organic and inorganic substances. Different assay strategies based on metal and semiconductor nanoparticles for biosensor and bioelectronic applications are presented, including electrochemical, electrical, and magnetic signal transduction techniques. Electrochemical transduction principles provide signal changes in conductance, charge, potential and current. We have paid much attention to the potential-based and current-based sensors herein. Lastly, a brief introduction is given into advances concerning the role of nanoparticles, quantum dots and nanowires for nanomedicine, such as drug delivery and discovery.     

Cu‐Based Nanoparticles as Emerging Environmental Catalysts

This account provides an overview of current research activities on nanoparticles containing the earth‐abundant and inexpensive element copper (Cu) and Cu‐based nanoparticles, especially in the field of environmental catalysis. The different synthetic strategies with possible modification of the chemical/ physical properties of these nanoparticles using such strategies and/or conditions to improve catalytic activity are presented. The design and development of support and/or bimetallic systems (e. g., alloys, intermetallic, etc.) are also included. Herein, we report synthetic approaches of Cu and Cu‐based nanoparticles (monometallic copper, bimetallic copper and copper (II) oxide nanoparticles/nanostructures) and impregnation of such nanoparticles onto support material (e. g., Co₃O₄ nanostructure), along with their applications as environmental catalyst for various oxidation and reduction reactions. Finally, this account provides necessary advances and perspectives of Cu‐based nanoparticles in the environmental catalysis.     

Enzymatic biosensors based on the use of metal oxide nanoparticles

Over the past decades, various techniques have been developed to obtain materials at a nanoscale level to design biosensors with high sensitivity, selectivity and efficiency. Metal oxide nanoparticles (MONPs) are of particular interests and have received much attention because of their unique physical, chemical and catalytic properties. This review summarizes the progress made in enzymatic biosensors based on the use of MONPs. Synthetic methods, strategies for immobilization, and the functions of MONPs in enzymatic biosensing systems are reviewed and discussed. The article is subdivided into sections on enzymatic biosensors based on (a) zinc oxide nanoparticles, (b) titanium oxide nanoparticles, (c) iron oxide nanoparticles, and (d) other metal oxide nanoparticles. While substantial advances have been made in MONPs-based enzymatic biosensors, their applications to real samples still lie ahead because issues such as reproducibility and sensor stability have to be solved. The article contains 256 references.

Effect of the presence of silica nanoparticles in the coefficient of thermal expansion of LDPE

The effect of the presence of alumina microparticles and silica nanoparticles on the coefficient of thermal expansion (CTE) of films of low density polyethylene (LDPE) based composites was investigated. A new method based on the use of an atomic force microscope (AFM) is proposed for measuring nano-thermal expansion of films to finally obtain the CTE in polymer based materials. Nanocomposites based on silica nanoparticles and LDPE were prepared by mixing those constituents by high energy ball milling (HEBM). Pure alumina microparticles come from the milling tools used to mix the components of the composites. When silica nanoparticles are used as nanofiller of LDPE the effectiveness on reducing the CTE (about a 40% of CTE reduction) is higher than that obtained when high amount of alumina microparticles are present in the LDPE. Only when high amount of silica nanoparticles and low amount of alumina microparticles are present, the reduction of CTE expected from the Levin model is in accordance with the experimental results. This effect was associated to the high surface to volume ratio of nanoparticles considering uniform dispersions of them within the polymer. The region of polymer between particles must be so thin (few nanometers) that constraint effects must play an important role on reducing the chain mobility and therefore the thermal expansion.     

A rapid and simple route for the synthesis of lead and palladium nanoparticles in tetrazolium based ionic liquid

In the present work, we report a novel method for the synthesis of palladium and lead nanoparticles by the reduction method in tetrazolium ring based ionic liquid. Palladium and lead nanoparticles so-prepared were well characterized by powder X-ray diffraction measurements (pXRD), transmission electron microscopy (TEM) and quasi elastic light scattering (QELS) techniques. Powder X-ray diffraction (pXRD) analysis revealed all relevant Bragg's reflection for crystal structure of palladium and lead. Powder X-ray diffraction plots also revealed no oxidized material of palladium and lead nanoparticles. TEM showed nearly uniform distribution of the particles in methanol and confirmed by QELS. Typical applications of palladium nanoparticles include in vitro use and sensor design applications. Palladium nanoparticles is also ideal for spin coating, self-assembly and monolayer formation. Palladium nanoparticles can also be considered as potential new catalysts.     

The effect of silver nanoparticles on the phase state of comb-shaped liquid crystalline polymers with cyanobiphenyl mesogenic groups

A new approach is proposed for the preparation of a new class of hybrid polymer systems based on comb-shaped LC polymers with cyanobiphenyl mesogenic groups and silver nanoparticles with dimensions ranging from 5 to 54 nm. A correlation between copolymer composition and dimensions of the formed nanoparticles is established. As the concentration of nanoparticles in LC copolymer is increased, the resultant glass transition temperature increases, and the temperature interval of the existence of LC phase is reduced. This behavior is related to the adsorption of cyanobiphenyl and carboxylic polymer groups on the surface of silver nanoparticles. In this case, the conductivity and dielectric permittivity of the composites are also increased.     

Rapid analysis of gold nanoparticles in liver and river water samples

This paper describes a simple approach to determine gold nanoparticles in liver and river water samples. The method of purification of nanoparticles from the matrix is based on the stabilization of gold nanoparticles with a cationic surfactant followed by a microliquid-liquid extraction in ionic liquid. Finally, the extracted nanoparticles can be analysed by UV/Vis detection or Raman spectroscopy. The precision of the proposed method for the analysis of liver tissue and river water samples was 9.7% and 18% respectively for UV/Vis analysis. The sensitivity was 1.17 × 10(-12) M for the analysis of 3 mL of liver homogenate or river water sample.     

Stimuli‐responsive zein‐based nanoparticles as a potential carrier for ellipticine: Synthesis,release, and in vitro delivery

In the present research, we have investigated a drug delivery system based on the pH‐responsive behaviors of zein colloidal nanoparticles coated with sodium caseinate (SC) and poly ethylene imine (PEI). These systematically designed nanoparticles were used as nanocarriers for encapsulation of ellipticine (EPT), as an anticancer drug. SC and PEI coatings were applied through electrostatic adsorption, leading to the increased size and improved polydispersity index of nanoparticles as well as sustained release of drug. Physicochemical characteristics such as hydrodynamic diameter, size distribution, zeta potential and morphology of nanoparticles prepared using different formulations and conditions were also determined. Based on the results, EPT was encapsulated into the prepared nanoparticles with a high drug loading capacity (5.06%) and encapsulation efficiency (94.8%) under optimal conditions. in vitro experiments demonstrated that the release of EPT from zein‐based nanoparticles was pH sensitive. When the pH level decreased from 7.4 to 5.5, the rate of drug release was considerably enhanced. The mechanism of pH‐responsive complexation in the drug encapsulation and release processes was extensively investigated. The pH‐dependent electrostatic interactions and drug state were hypothesized to affect the release profiles. Compared to the EPT‐loaded zein/PEI nanoparticles, the EPT‐loaded zein/SC nanoparticles exhibited a better drug sustained‐release profile, with a smaller initial burst release and longer release period. According to the results of in vitro cytotoxicity experiments, drug‐free nanoparticles were associated with a negligible cytotoxicity, whereas the EPT‐loaded nanoparticles displayed a high toxicity for the cancer cell line, A549. Our findings indicate that these pH‐sensitive protein‐based nanoparticles can be used as novel nanotherapeutic tools and potential antineoplastic drug carriers for cancer chemotherapy with controlled release.     

Localized Template‐Driven Functionalization of Nanoparticles by Dynamic Combinatorial Chemistry

We have developed a method for the localized functionalization of gold nanoparticles using imine‐based dynamic combinatorial chemistry. By using DNA templates, amines were grafted on the aldehyde‐functionalized nanoparticles only if and where the nanoparticles interacted with the template molecules. Functionalization of the nanoparticles was controlled solely by the DNA template; only amines capable of interacting with DNA were bound to the surface. Interestingly, even though our libraries contained only a handful of simple amines, the DNA sequence influenced their attachment to the surface. Our method opens up new opportunities for the synthesis of multivalent, nanoparticle‐based receptors for biomacromolecules.     

Simultaneous detection of enterovirus 71 and coxsackievirus A16 using dual-colour upconversion luminescent nanoparticles as labels

We highlight a novel fluorescence analysis for sensitive and selective detection of EV-71 and CV-A16 by combining labelling technology based on dual-colour upconversion fluorescence nanoparticles (UCNPs) with magnetic bioseparation and concentration technology based on magnetite nanoparticles (MNPs).     

Designing the Hotspots Distribution by Anisotropic Growth

Changing the morphology of noble metal nanoparticles and polarization dependence of nanoparticles with different morphologies is an important part of further research on surface plasma enhancement. Therefore, we used the method based on Matlab simulation to provide a simple and effective method for preparing the morphologies of Au nanoparticles with different morphologies, and prepared the structure of Au nanoparticles with good uniformity and different morphologies by oblique angle deposition (OAD) technology. The change of the surface morphology of nanoparticles from spherical to square to diamond can be effectively controlled by changing the deposition angle. The finite difference time domain (FDTD) method was used to simulate the electromagnetic fields of Au nanoparticles with different morphologies to explore the polarization dependence of nanoparticles with different shapes, which was in good agreement with Raman spectrum.     

Quantitative Evaluation of the Total Magnetic Moments of Colloidal Magnetic Nanoparticles: A Kinetics‐based Method

A kinetics‐based method is proposed to quantitatively characterize the collective magnetization of colloidal magnetic nanoparticles. The method is based on the relationship between the magnetic force on a colloidal droplet and the movement of the droplet under a gradient magnetic field. Through computational analysis of the kinetic parameters, such as displacement, velocity, and acceleration, the magnetization of colloidal magnetic nanoparticles can be calculated. In our experiments, the values measured by using our method exhibited a better linear correlation with magnetothermal heating, than those obtained by using a vibrating sample magnetometer and magnetic balance. This finding indicates that this method may be more suitable to evaluate the collective magnetism of colloidal magnetic nanoparticles under low magnetic fields than the commonly used methods. Accurate evaluation of the magnetic properties of colloidal nanoparticles is of great importance for the standardization of magnetic nanomaterials and for their practical application in biomedicine.     

Nanoparticle-induced morphology and hydrophilicity of structured surfaces

Nanoparticles have been applied into the construction of micro- and nanoscaled surface structures with extreme wettability over the past few years. However, the details of processing and employing colloidal nanosuspensions for this purpose have not yet been fully investigated. In this work, we study the surface structures formed via nanosuspensions, in which nanoparticles of solid phase are presented, and the caused surface wettability. We disperse silica nanoparticles with different sizes into pure ethanol to prepare nanosuspensions with a series of concentrations. The suspensions are ultrasonically processed to prompt uniform distribution of nanoparticles before application. The deposited nanosuspensions are thermally treated to assist the regulation of surface patterns based on nanoparticles. Hence, the investigation explores a variety of experimental conditions that will lead to distinctive surface structures and wettabilities. Accordingly, the wettability of the induced surfaces is investigated using contact angle measurement, and the structures of those surfaces are mainly revealed by atomic force microscopy (AFM). Superhydrophilicity is observed on many of such formed surfaces, and the pattern of surface structures in micro- and nanoscale is closely related to the processing conditions and the size of nanoparticles. Thus, we report the characteristics of the surface patterns based on nanoparticles and the formed wettability.     

Stimuli responsive release of metalic nanoparticles on semiconductor substrates

Optically active metal nanoparticles have been of recent and broad interest for applications to biomarker detection because of their ability to enable high sensitivity enhancements in various optical detection techniques. Here, we report stimuli responsive release of metallic nanoparticles on a semiconductor thin film array structure based on pH change. The metallic nanoparticles are obtained by a simple redox procedure on the semiconductor surface. This approach allows controlling nanoparticle surface coatings in situ for biomolecule conjugation, such as DNA probes on nanoparticles, and rapid stimuli responsive release of these nanoparticles upon pH change.     

基于点击化学和活性自由基聚合方法制备双重响应金纳米粒子

采用点击化学和可逆加成断裂链转移活性自由基聚合方法制备了温度和pH双重响应的金纳米粒子. 通过红外光谱(FTIR)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)及热重分析(TGA)等方法对双重响应性金纳米粒子进行了表征. 该金纳米杂化粒子具有良好的分散性, 其表面接枝聚合物的密度约为0.6 Chain/nm2. 通过改变温度和pH条件, 考察了金纳米杂化粒子的可逆响应行为. 实验结果表明, 点击化学和可逆加成断裂链转移活性自由基聚合方法实现了金纳米粒子修饰的简单化、可控化以及功能化.