Fabrication of rice-like gold nanoparticles and application in surface-enhanced Raman scattering

A simple method for the synthesis of rice-like gold nanoparticles using gold nanorods (GNRs) as precursors in the aqueous phase was exploited. The method used in this work involves eroding GNRs with potassium ferricyanide in the aqueous phase. Surface plasmon resonance (SPR) bands of the resulting nanoparticles present a notable blue-shift from 670 to 570 nm with increasing amounts of potassium ferricyanide, and subsequently the shape of the resulting nanoparticles can be readily controlled. Most importantly, the SPR response is an almost linear function of the quantity of potassium ferricyanide added. The synthesis of the resulting nanoparticles with various aspect ratios has been extensively studied and is well established. The surface-enhanced Raman scattering (SERS) intensity enhancement of the adsorbate on the surface of these gold nanoparticles was also studied.     

咔唑和二氰基蒽掺杂纳米粒子的制备及光学性质

以蓝光染料咔唑为电子给体,黄光染料9,10-二氰基蒽为电子受体,采用再沉淀法制备了咔唑和二氰基蒽等摩尔掺杂的纳米粒子。掺杂纳米粒子与纯咔唑聚集体或二氰基蒽聚集体的形貌和发射光颜色明显不同,说明咔唑和二氰基蒽很好的掺杂到一起。吸收光谱表明咔唑和二氰基蒽在掺杂纳米粒子中没有形成电荷转移复合物,荧光发射光谱和荧光寿命表明咔唑和二氰基蒽在掺杂纳米粒子中形成激基复合物,激基复合物的出现使得掺杂纳米粒子的发射光颜色为橙色。     

Biocatalytically induced growth of gold nanoshells: using enzyme reaction for the controllable fabrication of nanomaterials

In the present work, the enzymatically controlled growth process of gold nanoshells (GNSs) in the presence of O2/glucose/glucose oxidase (GOx) and its chloroaurate ion electron acceptor is described. The biocatalytically stimulated growth process is one of the bio-inspired synthetic procedures directed by biological molecules which occur under ambient conditions. It is found that hydrogen peroxide (H2O2) could enlarge the gold nanoparticles (GNPs) on the surface of GNSs precursor composites, of which the preadsorbed GNPs serve as nucleation sites for further gold deposition. Here, GOx is harnessed for its unparalled level of catalytic activity and substrate specificity while H2O2 is produced as a by-product during the oxidation of D-glucose to gluconic acid by GOx. Then the bio-generated H2O2 is used as the reducing agent in the catalytic deposition process of GNSs formation. During the procedure, the localized surface plasmon resonance peaks range across hundreds of nanometers from visible to near infrared region accompanying by the resultant formation of uniform and continuous core-shell nanostructures. The corresponding optical, morphological and enzyme kinetic properties are all well investigated. The novel protocol offers a new perspective for the bio-directed synthesis method in nanotechnology.     

Development of bimetal-grown multi-scale carbon micro-nanofibers as an immobilizing matrix for enzymes in biosensor applications

This study describes the development of a novel bimetal (Fe and Cu)-grown hierarchical web of carbon micro-nanofiber-based electrode for biosensor applications, in particular to detect glucose in liquids. Carbon nanofibers (CNFs) are grown on activated carbon microfibers (ACFs) by chemical vapor deposition (CVD) using Cu and Fe as the metal catalysts. The transition metal-fiber composite is used as the working electrode of a biosensor applied to detect glucose in liquids. In such a bi-nanometal-grown multi-scale web of ACF/CNF, Cu nanoparticles adhere to the ACF-surface, whereas Fe nanoparticles used to catalyze the growth of nanofibers attach to the CNF tips. By ultrasonication, Fe nanoparticles are dislodged from the tips of the CNFs. Glucose oxidase (GOx) is subsequently immobilized on the tips by adsorption. The dispersion of Cu nanoparticles at the substrate surface results in increased conductivity, facilitating electron transfer from the glucose solution to the ACF surface during the enzymatic reaction with glucose. The prepared Cu-ACF/CNF/GOx electrode is characterized for various surface and physicochemical properties by different analytical techniques, including scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), BET surface area analysis, and transmission electron microscopy (TEM). The electrochemical tests show that the prepared electrode has fast response current, electrochemical stability, and high electron transfer rate, corroborated by CV and calibration curves. The prepared transition metal-based carbon electrode in this study is cost-effective, simple to develop, and has a stable immobilization matrix for enzymes.     

金属与非金属纳米颗粒增强葡萄糖生物传感器

为了提高葡萄糖传感器的灵敏度和抗干扰性,利用纳米增强效应,以Au、Ag、Pt、SiO2纳米颗粒及金属-无机复合纳米颗粒与聚乙烯醇缩丁醛(PVB)构成复合固定酶膜基质,采用溶胶-凝胶法固定葡萄糖氧化酶(GOD),组成葡萄糖生物传感器.研究表明,纳米颗粒可以大幅度地提高固定化酶的催化活性,增加电极的电流响应灵敏度,改进生物传感器的抗干扰性能,使信噪比提高了32倍.     

氧化铟空心球的合成和光致发光性能研究

在180℃水热处理葡萄糖和铟盐的混合物,然后在空气中烧结制备了氧化铟空心球.利用场发射扫描电镜、透射电镜、X射线衍射等对其形貌和结构进行分析.结果表明,氧化铟空心球为多孔结构,其粒径为800～1000nm,由密堆积的纳米粒子组装而成.讨论了氧化铟空心球的形成机制和光致发光特性.     

A Layer‐by‐Layer ZnO Nanoparticle–PbS Quantum Dot Self‐Assembly Platform for Ultrafast Interfacial Electron Injection

Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low‐cost, high‐performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy‐level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer‐by‐layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic‐energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis.     

Electrochemical behavior of gold nanoparticles modified nitrogen incorporated tetrahedral amorphous carbon and its application in glucose sensing

Gold nanoparticles (NPs) with 10-50 nm in diameter were synthesized on nitrogen incorporated tetrahedral amorphous carbon (ta-C:N) thin film electrode by electrodeposition. The deposition and nucleation processes of Au on ta-C:N surface were investigated by cyclic voltammetry and chronoamperometry. The morphology of Au NPs was characterized by scanned electron microscopy. The electrochemical properties of Au NPs modified ta-C:N (ta-C:N/Au) electrode and its ability to sense glucose were investigated by voltammetric and amperometric measurements. The potentiostatic current-time transients showed a progressive nucleation process and diffusion growth of Au on the surface of ta-C:N film according to the Scharifker-Hills model. The Au NPs acted as microelectrodes improved the electron transfer and electrocatalytic oxidation of glucose on ta-C:N electrode. The ta-C:N/Au electrode exhibited fast current response, a linear detection range of glucose from 0.5 to 25 mM and a detection limit of 120 microM, which hinted its potential application as a glucose biosensor.     

An electrochemical glucose sensor from an organically modified nanocomposite of viologen and TiO2

An organically modified TiO2 nanocomposite was explored for glucose detection. Bis-Butyl viologen (BBV) was mixed with TiO2 nanoparticles to generate highly dispersed nanocomposite solution, which provided organically modified nanocomposite film of TiO2 (BBV-TiO2). A transistor type sensor was fabricated using the BBV-TiO2 film and platinum gate electrode. The BBV-TiO2 nanocomposite sensor showed higher sensitivity to glucose sensing in low concentration region compared to that of TiO2 sensor. This result was ascribed to facilitated electron transport by the adsorbed viologen molecules on TiO2 nanoparticles, where viologen molecules act as an electron transfer mediator between enzyme and TiO2.     

Preparation of polypyrrole nanoparticles in reverse micelle and its application to glucose biosensor

Polypyrrole nanoparticles were successfully synthesized in cetyltrimethyl ammonium bromide (CTAB)/hexanol/water reverse micelle. The morphology and particle size of the obtained nanoparticles were characterized with transmission electron microscope (TEM) and scanning electron microscopy (SEM). Glucose biosensors were formed with glucose oxidase (GOx) immobilized in conducting composite material consisting of polypyrrole nanoparticles and ethyl cellulose. The effects of reaction conditions such as molar ratio of polypyrrole nanoparticles to ethyl cellulose, working voltage, glucose concentration, temperature and solution pH on the electrochemical response of the GOx electrode were studied. Experimental results showed that the linear range of GOx electrode was 1.0 x 10(-6)-6 x 10(-3) mol/L and the detection limit was 1.0 x 10(-7) mol/L. The electrode exhibited fine repeatability and selectability, and its lifetime was greater than one month. AFM showed that the surface of conducting composite material-glucose oxidase electrode's presents uniform granular after washing paraffin wax with cyclohexane, which was favorable for enzyme-catalyzed reaction.     

Scanning electrochemical microscopy of quinoprotein glucose dehydrogenase

The activity of immobilized glucose dehydrogenase (GDH), a typical PQQ-dependent quinoprotein, was studied qualitatively and quantitatively by scanning electrochemical microscopy (SECM). PQQ-dependent GDH is of interest because of its high activity and independence of dissolved oxygen in catalyzing the transfer of electrons from glucose to an electron mediator. Biotinylated glucose dehydrogenase was bound to streptavidin-coated paramagnetic beads (surface concentration > or = 1.8 x 10(-11) mol cm(-2)) which were deposited as microscopic microspots on a hydrophobic surface. The catalytic activity of immobilized GDH was mapped in SECM feedback mode and generation-collection mode using ferrocenemethanol, ferrocenecarboxylic acid, p-aminophenol, and ferricyanide as electron mediators, respectively. The apparent steady-state kinetics of catalysis were measured under conditions of high d-glucose concentration using the theory developed for the SECM feedback and generation collection (GC) modes. In feedback mode, curves of the kinetically controlled substrate current against normalized distance were plotted, and it was found that GDH catalysis follows pseudo-first-order kinetics. In GC mode detection, the catalysis follows zero-order kinetics in the presence of high concentration of both substrates for GDH. The turnover rate obtained for immobilized GDH is lower than that of native GDH but much higher than that generally observed for glucose oxidase.     

Effects of Fe/SDS and Au nanoparticles on P. aeruginosa bacterial growth and biosurfactant production

The aim of this study was to evaluate the effects of iron (Fe)/SDS and gold (Au) nanoparticles on growth and biosurfactant production of Pseudomonas aeruginosa PBCC5. The concentrations of the nanoparticles used were 1, 500 and 1000 mg/l. In this research, the surface tension of biosurfactant, dry weight of biosurfactant and biomass, emulsification indexes (E₂₄) were measured and transmission electron microscopy analysis was used to monitor the nanoparticles. The test results showed that the effect of nanoparticles on the bacterial growth and biosurfactant production varied corresponding to the type and concentration of nanoparticles. Fe/SDS nanoparticles showed no bacterial toxicity when the concentration of nanoparticles was 1 mg/ml and increased the growth and biosurfactant production, 23.21 and 20.73%, respectively. While at higher concentrations (500, 1000 mg/l), the nanoparticles suppressed bacterial growth as well as biosurfactant production. Similarly, Au nanoparticles had no bacterial toxicity and also increased bacterial growth and biosurfactant production. The surface tensions of all samples decreased from 72 of distiled water to 32–35 mN/m.Inspec keywords: nanoparticles, iron, gold, nanofabrication, nanomedicine, surfactants, biomedical materials, surface tension, renewable materials, transmission electron microscopy, microorganismsOther keywords: Au nanoparticles, P. aeruginosa bacterial growth, biosurfactant production, Pseudomonas aeruginosa PBCC5, surface tension, biomass, emulsification indexes, dry weight, transmission electron microscopy, Fe‐SDS nanoparticles, distiled water, Fe, Au     

Impact of Zinc oxide nanoparticles on eggplant (S. melongena): studies on growth and the accumulation of nanoparticles

The increasing use of nanoparticles and their occurrence in the environment has made it imperative to elucidate their impact on the environment. Although several studies have advanced the authors’ understanding of nanoparticle–plant interactions, their knowledge of the exposure of plants to nanoparticles and their effects on edible crop plants remain meager and is often paradoxical. The aim of this study was to increase their knowledge on the effect of zinc oxide (ZnO) nanoparticles on eggplant seed germination and seedling growth. ZnO nanoparticles had a negative effect on the growth of eggplant in plant tissue‐culture conditions, as the growth of seedlings decreased with the increase in the concentration of ZnO nanoparticles. In contrast, ZnO nanoparticles enhanced eggplant growth under greenhouse conditions. The accumulation of ZnO nanoparticles in various parts of eggplant was observed through scanning electron microscopy of both plant tissue‐culture and greenhouse‐raised eggplant seedlings. To the best of their knowledge, this is the first study to report on ZnO nanoparticle accumulation in eggplant and its effect on seed germination and seedling growth.Inspec keywords: crops, zinc compounds, scanning electron microscopy, II‐VI semiconductors, nanoparticles, agriculture, cellular biophysics, nanofabricationOther keywords: plant tissue‐culture, greenhouse‐raised eggplant seedlings, ZnO nanoparticle accumulation, seedling growth, ZnO nanoparticles, nanoparticle–plant interactions, zinc oxide nanoparticles, eggplant seed germination, eggplant growth, ZnO     

Photovoltaic characterization of hybrid solar cells using surface modified TiO(2) nanoparticles and poly(3-hexyl)thiophene

We report on the photovoltaic performance of bulk heterojunction solar cells using novel nanoparticles of 6-palmitate ascorbic acid surface modified TiO(2) as an electron acceptor embedded into the donor poly(3-hexyl)thiophene (P3HT) matrix. Devices were fabricated by using P3HT with varying amounts of red TiO(2) nanoparticles (1:1, 1:2, 1:3?w-w ratio). The devices were characterized by measuring current-voltage characteristics under simulated AM 1.5 conditions. Incident photon to current efficiency (IPCE) was spectrally resolved. The nanoscale morphology of such organic/inorganic hybrid blends was also investigated using atomic force microscopy (AFM).     

Preparation of multiwalled carbon nanotubes-platinum-Nafion-glucose oxidase nanobiocomposite and its application to glucose biosensor

Platinum (Pt) nanoparticles were electrodeposited within multiwalled carbon nanotubes-Nafion-glucose oxidase (MWNTs-Nafion-GOx) nanobiocomposite by a potentiostatic method. The morphology and nature of the resulting MWNTs-Pt-Nafion-GOx nanobiocomposite were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The electrocatalytic properties of the MWNTs-Pt-Nafion-GOx nanobiocomposite film modified glassy carbon electrode were characterized by cyclic voltammetry and amperometry in the presence of hydrogen peroxide. The glucose biosensor sensitivity was strongly influenced by the deposits of Pt nanoparticles and amount of GOx concentration within the MWNTs-Pt-Nafion-GOx nanobiocomposite film. The optimized glucose biosensor displayed a sensitivity of 640 nA mM(-1), a linear range of up to 4 mM, a detection limit of 4 microM, and a response time of less than 4 s at an operating potential of +500 mV versus Ag/AgCl (3 M KCl).     

Ultrastable Near‐Infrared Conjugated‐Polymer Nanoparticles for Dually Photoactive Tumor Inhibition

It is highly desired that satisfactory photoactive agents with ideal photophysical characteristics are explored for potent cancer phototherapeutics. Herein, bifunctional nanoparticles of low‐bandgap donor–acceptor (D–A)‐type conjugated‐polymer nanoparticles (CP‐NPs) are developed to afford a highly efficient singlet‐to‐triplet transition and photothermal conversion for near‐infrared (NIR) light‐induced photodynamic (PDT)/photothermal (PTT) treatment. CP‐NPs display remarkable NIR absorption with the peak at 782 nm, and perfect resistance to photobleaching. Photoexcited CP‐NPs undergo singlet‐to‐triplet intersystem crossing through charge transfer in the excited D–A system and simultaneous nonradiative decay from the electron‐deficient electron acceptor isoindigo derivative under single‐wavelength NIR light irradiation, leading to distinct singlet oxygen quantum yield and high photothermal conversion efficiency. Moreover, the CP‐NPs display effective cellular uptake and cytoplasmic translocation from lysosomes, as well as effective tumor accumulation, thus promoting severe light‐triggered damage caused by favorable reactive oxygen species (ROS) generation and potent hyperthermia. Thus, CP‐NPs achieve photoactive cell damage through their photoconversion ability for synergistic PDT/PTT treatment with tumor ablation. The proof‐of‐concept design of D–A‐type conjugated‐polymer nanoparticles with ideal photophysical characteristics provides a general approach to afford potent photoactive cancer therapy.     

Fabrication of multiwalled carbon nanotubes/polypyrrole/Prussian blue ternary composite nanofibers and their application for enzymeless hydrogen peroxide detection

In this article, Prussian blue (PB) covered multiwalled carbon nanotubes (MWCNTs)/polypyrrole (PPy) ternary composite nanofibers with good dispersibility in water and ethanol have been prepared by directly mixing ferric-(III) chloride and potassium ferricyanide in the presence of MWCNT/PPy coaxial nanofibers under ambient conditions. Transmission electron microscopy shows that the as-synthesized PB nanoparticles covered on the surface of MWCNT/PPy nanofibers. Fourier-transform infrared spectroscopy, UV–Visible spectroscopy, and X-ray diffraction patterns have been used to characterize the obtained MWCNT/PPy/PB ternary composite nanofibers. The MWCNT/PPy/PB ternary composite nanofibers exhibit good electrocatalytic response to detection of H₂O₂ and provide a new material to modify electrode for amperometric biosensors.     

Direct Electron Transfer Reactivity of Glucose Oxidase on Electrodes Modified With Zirconium Dioxide Nanoparticles

The direct electron transfer between electrodes and glucose oxidase (GOD) immobilized in a matrix containing zirconium dioxide nanoparticles (ZrO₂) is described. The protein-nanoparticle assembly is stabilized by charged and uncharged compounds and the direct electron transfer is enhanced. The effects of different compositions on the electrochemical parameters, formal potential, surface loading, and constant heterogeneous electron transfer rate are characterized with cyclic voltammetry. The fastest electron transfer rate with the smallest deviation of the is obtained when GOD is immobilized with ZrO₂ nanoparticles, colloidal platinum and poly-Lysine (PLL). Incorporation of charged compounds for immobilization of GOD causes a larger positive shift of the formal potential. Electrochemical and spectroscopic measurements show that the GOD entrapped in ZrO₂/Pt-PLL or ZrO₂/Pt-PVA film retains its bioactivity efficiently and exhibits excellent electrocatalytic behavior towards glucose. No enzymatic activity of the immobilized GOD can be observed on ZrO₂/DMSO and ZrO₂/DDAB film.     

The effect of adsorption on the conductivity of self-organized metal-poly(<Emphasis Type="Italic">para</Emphasis>-xylene) nanocomposites

The effect of adsorbed electron donor (ammonia, alcohols, water) and electron acceptor (molecular hydrogen, dichlorobutene, chloroform) molecules on the conductivity of polymeric nanocomposites, representing poly(p-xylene) containing metal (lead, copper, or palladium) nanoparticles (∼10 nm in size), was studied as dependent on the metal content and the gas or vapor pressure at room temperature. It was found that the conductivity significantly (up to eight orders of magnitude) increases due to the adsorption of electron donor molecules and decreases upon the adsorption of electron acceptors. A mechanism of the sensor response is proposed according to which the adsorption simultaneously changes the fractal characteristics of the nanocomposites and the electron work function of metal nanoparticles.