Characterization of gold nanoparticle pentacene memory device with polymer dielectric layer

We report on the electrical behavior of gold nanoparticles (Au NPs) intervened metal-pentacene-insulator-semiconductor structures. The structure adopts polyvinyl alcohol (PVA) and pentacene as gate insulator and semiconductor, respectively. On the PVA (250 nm) film which was spin-coated and UV cross-linked, 3-aminopropyl triethoxysilane was functionalized for self assembling of the Au NPs monolayer. The devices exhibited clockwise hysteresis in their capacitance-voltage characteristics, with a memory window depending on the range of the voltage sweep. A relatively large memory window of about 4.7 V, which was deduced from control devices, was achieved with voltage sweep of (−/+)7 V. Formation of the monolayered Au NPs was confirmed by field effect scanning electron microscopy and atomic force microscopy.     

Preparation of carbon nanotube/chitosan/gold nanoparticle composite microspheres

The electrostatic layer-by-layer (LbL) assembly of acid-modified multi-walled carbon nanotubes (MWNTs) and biopolymer chitosan (CHIT) is realized on planar substrates and polystyrene (PS) microsphere templates, respectively. The successful stepwise growing process of the composite films on planar substrates is investigated and confirmed by scanning electron microscopy and UV-vis spectroscopy. The transfer of the LbL assembly of MWNTs and CHIT to spherical PS microspheres leads to novel (MWNT/CHIT)PS core-shell structure, on which the gold nanoparticles (GNPs) are deposited to fabricate GNP(MWNT/CHIT)PS composite microspheres. The glass carbon electrodes modified with such (MWNT/CHIT)PS or GNP(MWNT/CHIT)PS composites exhibit satisfactory electrocatalytic activities for biomolecule dopamine.     

Probing metabolic stability of CdSe nanoparticles: alkaline extraction of free cadmium from liver and kidney samples of rats exposed to CdSe nanoparticles

Cadmium selenide nanoparticles (CdSe NPs) exhibit novel optoelectronic properties for potential biomedical applications. However, their metabolic stability is not fully understood because of the difficulties in measurement of free Cd from biological tissues of exposed individuals. In this study, alkaline dissolution with tetramethylammonium hydroxide (TMAH) is demonstrated for selective determination of free Cd and intact NPs from liver and kidney samples of animals that were exposed to thiol-capped CdSe NPs. Aqueous suspensions of CdSe NPs (3.2 nm) were used to optimize the conditions for extracting free Cd without affecting NPs. Nanoparticles were found to aggregate when heated in TMAH without releasing any significant Cd to solution. Performance of the method in discriminating free Cd and intact NPs were verified by Dogfish Liver (DOLT-4) certified reference material. The samples from the animals were digested in 4 mL TMAH at 70 °C to extract free Cd followed by analysis of aqueous phase by ICP-MS. Both liver and kidney contained significant levels of free Cd. Total Cd was higher in the liver, while kidney accumulated mostly free Cd such that up to 47.9% of total Cd in the kidney was free Cd when NPs were exposed to UV-light before injection.     

Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe3O4 magnetic nanoparticles using ionic liquid as modifier

The nanoparticles of Fe₃O₄ as well as the binary nanoparticles of ionic liquid and Fe₃O₄ (IL-Fe₃O₄) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe₃O₄ nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60 mg, a pH of 2.5, and a contact time of 2 min when initial dyes concentrations of 10-200 mg L⁻¹ were used. The maximum adsorption capacity of IL-Fe₃O₄ was 166.67 and 49.26 mg g⁻¹ for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62 L mg⁻¹ for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe₃O₄ by using a mixed NaCl-acetone solution and adsorbent was reusable.     

SERS effects in silver-decorated cylindrical nanopores

Optimization of pore diameter, the placement of nanoparticles, and the transmission of surface-enhanced Raman scattering (SERS) substrates are found to be very critical for achieving high SERS activity in porous alumina-membrane-based substrates. SERS substrates with a pore diameter of 355 nm incorporating silver nanoparticles show very high SERS activity with enhancement factors of 10(10) .     

Molecular Dynamics Study of Interactions between the Water/ice Interface and a Nanoparticle in the Vicinity of a Solid Surface

ABSTRACT

In this study, non-equilibrium molecular dynamics simulations were conducted for a coexistence system of water and ice on a wall surface with a single nanoparticle to reveal the effects of water solidification on the nanoparticle in the vicinity of a wall surface. We further investigated the effect of the presence and size of particles on the density profile of water in the vicinity of the wall surface and the force acting on particles from water molecules, when the solidification interface contacted the wall and the particles. The results revealed that a strong mutual influence exists between the solidification interface and the nanoparticle on the wall’s surface; the nanoparticle on the wall prevents water solidification in proximity to the wall. Moreover, the force acting on the nanoparticle from water molecules changes as the solidification interface approaches; the cooling temperature is shown to affect the direction of this force. It indicates that the solidification process is a key influential factor which affects nanoparticle movements on a wall surface at molecular scales.     

Use of Coated Silver Nanoparticles to Understand the Relationship of Particle Dissolution and Bioavailability to Cell and Lung Toxicological Potential

Since more than 30% of consumer products that include engineered nanomaterials contain nano‐Ag, the safety of this material is of considerable public concern. In this study, Ag nanoparticles (NPs) are used to demonstrate that 20 nm polyvinylpyrrolidone (PVP or P) and citrate (C)‐coated Ag NPs induce more cellular toxicity and oxidative stress than larger (110 nm) particles due to a higher rate of dissolution and Ag bioavailability. Moreover, there is also a higher propensity for citrate 20 nm (C20) nanoparticles to generate acute neutrophilic inflammation in the lung and to produce chemokines compared to C110. P110 has less cytotoxic effects than C110, likely due to the ability of PVP to complex released Ag⁺. In contrast to the more intense acute pulmonary effects of C20, C110 induces mild pulmonary fibrosis at day 21, likely as a result of slow but persistent Ag⁺ release leading to a sub‐chronic injury response. Interestingly, the released metallic Ag is incorporated into the collagen fibers depositing around airways and the lung interstitium. Taken together, these results demonstrate that size and surface coating affect the cellular toxicity of Ag NPs as well as their acute versus sub‐chronic lung injury potential.     

Tumor‐Responsive Fluorescent Light‐up Probe Based on a Gold Nanoparticle/Conjugated Polyelectrolyte Hybrid

A tumor‐responsive nanoprobe based on a conjugated polyelectrolyte and gold nanoparticle (AuNP) hybrid was designed to response to the low pH extracellular microenvironment in tumor with light‐up fluorescence. AuNPs with positive surface charges were prepared by direct reducing Au salt with sodium borohydride and stabilized by cystamine. A pH triggered charge‐reversible polymer and a water‐soluble cationic conjugated polyelectrolyte (CPE) were sequentially deposited onto the AuNP surface through electrostatic interaction. The obtained hybrid probe is monodispersed with an average diameter of 68.3 nm by dynamic light scattering measurement. In physiological conditions (pH ≈ 7.4), the hybrid probe is almost non‐fluorescent due to the super‐quenching of CPE by AuNPs via energy/charge transfer and efficient exciton migration along the polymer backbone. When exposed to acidic extracellular microenvironments in tumor (pH_e ≈ 6.5), the acid‐labile amides hydrolyze into primary amines. The generated amine groups result in strong electrostatic repulsion between CPE and AuNPs, leading to recovered probe fluorescence. The fluorescence turn‐on is further utilized for tumor extracellular acidic microenvironment imaging. In addition, under in vivo conditions, the nanosized hybrid probe exhibits specific accumulation in tumor tissue with light‐up fluorescence, which provides new opportunities for easy tumor imaging and identification.     

Plasmon-enhanced Performance of Dye-sensitized Solar Cells Based on Electrodeposited Ag Nanoparticles简

In the present work,pulse current deposition is used to deposit evenly distributed and uniformly sized Ag nanoparticles onto a TiO_2 nanotube array as photoelectrode in dye-sensitized solar cells(DSSCs),and the size and amount of loading Ag nanoparticles are controlled by the pulse deposition time.Due to the enhanced light absorption and electron—hole separation caused by plasmon effect,DSSCs based on Ag-modified TiO_2nanotube arrays show higher energy conversion efficiencies than those based on bare nanotubes with the same tube length.Particularly,DSSC based on nanotubes modified using pulse deposition time 1 s/3 s delivers the highest energy conversion efficiency of 1.68%and the largest short-circuit current of 4.37 mA/cm~2,while DSSC consisting of bare nanotubes exhibits efficiency of 1.20%and short-circuit current of2.27 mA/cm~2,which represents a 40%enhancement of cell efficiency in DSSC based on Ag-modified TiO_2nanotubes.It is also noted that overly long pulse deposition time will not further increase DSSC efficiency due to agglomeration of Ag particles.For example,when the pulse deposition time is increased to 2 s/6 s,DSSC based on Ag-modified nanotubes exhibits a lower efficiency of 1.42%.Moreover,high-concentration TiCl_4treatment on TiO_2 nanotube arrays can further increase the energy conversion efficiencies to 3.82%and2.61%for DSSC based on Ag-modified TiO_2 nanotubes and DSSC based on bare TiO_2 nanotubes,respectively,by significantly creating more surface area for dye loading.     

Ag纳米颗粒对Er3+/Tm3+/Yb3+共掺铋锗酸盐玻璃上转换发光特性的影响

采用传统熔融淬冷法制备了系列Er³⁺/Tm 3+/Yb³⁺共掺复合Ag纳米颗粒的铋锗酸盐玻璃样品。从吸收光谱中 确定了Ag纳米颗粒表面等离子体共振(SPR)峰位于545nm附近;透射 电镜(TEM)图像中观察到均匀分布的Ag纳米颗粒,尺寸 约为6～18nm。研究了纳米Ag含量对Er3＋/Tm3＋ 共掺复合Ag纳米颗粒铋锗酸盐玻璃上转换发光特性的影响,结果表 明,Tm³⁺离子472nm处的上转换蓝光、Er³⁺离子525nm处的上转换绿光、543nm处的上转换 绿光和661nm处的上转换红光发光强度在AgCl含量的质量百分数为 1%时达到最大值,与未掺杂AgCl的基质玻璃相比,分别提高了约3.2、3.8、5.4倍。