Great Interest In Nanotechnology Research Articles

Controlling the transverse proton relaxivity of magnetic graphene oxide

The engineering of materials with controlled magnetic properties by means other than a magnetic field is of great interest in nanotechnology. In this study, we report engineered magnetic graphene oxide (MGO) in the nanocomposite form of iron oxide nanoparticles (IO)-graphene oxide (GO) with tunable core magnetism and magnetic resonance transverse relaxivity (r2). These tunable properties are obtained by varying the IO content on GO. The MGO series exhibits r2 values analogous to those observed in conventional single core and cluster forms of IO in different size regimes—motional averaging regime (MAR), static dephasing regime (SDR), and echo-limiting regime (ELR) or slow motion regime (SMR). The maximum r2 of 162 ± 5.703 mM−1s−1 is attained for MGO with 28 weight percent (wt%) content of IO on GO and hydrodynamic diameter of 414 nm, which is associated with the SDR. These findings demonstrate the clear potential of magnetic graphene oxide for magnetic resonance imaging (MRI) applications.

Fabrication and manipulation of nanopillars using electron induced excitation

Controlled fabrication and maneuvering of nanostructures has been of great interest in nanotechnology because of the potential applications it could deliver. In this study, we demonstrate the in situ fabrication and manipulation method of nanopillars made of a Pt-C composite by means of electron induced bending. Hereafter, we propose novel experiments contributing to unfold the mechanisms responsible for the bending process. Our results confirm that this bending is due to the phase transformation of the as-grown Pt-C nanopillars induced by the electron beam irradiation. The optimized beam energy and the beam irradiation dose necessary for the bending have been experimentally determined and corroborated by Monte Carlo simulations. The results further advance the understanding of electron matter interaction and pave the way for designing 3D nanostructures for various applications.

Porous three-dimensional network of Pd-Cu aerogel toward formic acid oxidation.

New self-assembled architectures have received great interest in nanotechnology, and are a highly desired target in recent studies. Among self-assembled architectures, noble metal aerogels are an important class owing to their collective characters as well as widespread applications. The synthesis of noble metal aerogels still faces several obstacles such as long hydrogel creation time and complicated multistep strategies. In this paper, we propose an efficient and useful approach to create the three-dimensional network of a Pd–Cu aerogel. This way offers a number of advantages including one-pot synthesis, simplicity, and short time to prepare the hydrogel. The Pd–Cu aerogel was prepared by the reduction of H2PdCl4 and CuCl2 in the presence of sodium carbonate by using glyoxylic acid monohydrate as a reducing agent followed by supercritical CO2 drying. The Pd–Cu aerogel was applied as an anode catalyst for electrooxidation process of formic acid, and depicts much higher electrocatalytic activity and durability compared to the Pd/C. We believe that the exceptional three-dimensional nanostructures fabricated by this route are powerful and promising catalysts for application in direct formic acid fuel cells (DFAFCs), which may open great opportunities for widespread applications such as catalysis, sensors, optoelectronics, electrochemical energy systems, etc.

Protein attachment to nanoporous anodic alumina for biotechnological applications: Influence of pore size, protein size and functionalization path

Nanoporous anodic alumina (NAA) is a material with great interest in nanotechnology and with promising applications to biotechnology. Obtaining specific and regularly functionalized NAA surfaces is essential to obtain meaningful results and applications. Silane-PEG-NHS (triethoxysilane-polyethylene-glycol-N-hydroxysuccinimide) is a covalent linker commonly used for single-molecule studies. We investigate the functionalization of NAA with silane-PEG-NHS and compared with two common, but not single-molecule, grafting agents, APTMS (3-aminopropylotrimethoxysilane) as an electrostatic linker, and APTMS-GTA (3-aminopropylotrimethoxysilane-glutaraldehyde) as covalent. Another outcome of this study is to show how two proteins (collagen and bovine serum albumin, BSA) with different properties differentially arrange for different functionalizations and NAA pore sizes. FTIR is used to demonstrate the surface modification steps and fluorescence confocal microscopy reveals that silane-PEG-NHS results in a more homogeneous protein distribution in comparison to the other linkers. Reflection interference Fourier transform spectroscopy confirms the confocal fluorescence microscopy results and permits to estimate the amounts of linker and linked proteins within the pores. These results permit to obtain uniformly chemical modified NAA supports with a great value in biosensing, drug delivery and cell biology.

Biosynthesis, characterization and antibacterial activity of silver nanoparticles by aqueous Annona squamosa L. leaf extract at room temperature

Silver nanoparticles (AgNPs) have gained great interest in nanotechnology, biotechnology and medicine. The green synthesis of nanoparticles has received an increasing attention because of it’s maximize efficiency and minimize health and environmental hazards as compared to other conventional chemical synthesis. In this study, we reported biosynthesis of AgNPs by aqueous Annona squamosa L. leaf extract and its characterization by UV-visible spectroscopy (UV–vis), Field emission gun scanning electron microscopy (FEG-SEM), X-ray energy dispersive spectroscopy (EDX), Transmission electron microscopy (TEM), Selected-area electron diffraction (SAED) and Fourier transform infra-red spectroscopy (FTIR). The results indicated that AgNPs formed were spherical in shape with size ranging from 14 to 40 nm with an average diameter 28.47 nm. Furthermore, it was observed that the AgNPs exhibited an antibacterial activity against different Gram positive and Gram negative microorganisms. Our report confirmed that the ALE is a very good eco-friendly and nontoxic bioreductant for the synthesis of AgNPs and opens up further opportunities for fabrication of antibacterial drugs, medical devices and wound dressings.

LDI and ESI MS as well as low energy CID of a self‐assembling nanorod‐forming fullerene derivative

An amphiphatic fullerene derivative (8-(N-Methyl-Fullero-Pyrrolidinium-1-yl-chloride)-3,6-Dioxaoctan-1-Ammonium Chloride (MFPDAC)), which is of great interest in nanotechnology due to the fact that it forms self-assembling fullerenic nanorods, has been structurally characterized with emphasis to its purity and thermal treatment of a formed nanorod film (on a LDI target) by means of laser desorption/ionization (LDI) coupled with high-resolution curved field reflectron time-of-flight (TOF) mass spectrometry, and by low energy MS/MS as well as in-source fragmentation experiments applying an quadrupole ion trap (QIT) combined with a two-stage reflectron TOF analyzer. The interpretation of LDI results has been supplemented by ESI QIT MS(n) (n = 1-3), as well as high-resolution ESI reflectron TOF mass spectrometric experiments. Based on the experimental data obtained by both desorption/ionization techniques, various types of analyzers and sample treatments, we could completely characterize MFPDAC and further found out that the investigated sample was not entirely free of impurities. Furthermore, the envisaged loss of the derivative sidechain upon the heat treatment in vacuum of the self-assembled nanorod sample film on a metallic substrate could be successfully monitored by LDI MS.

Reversible end-to-end assembly of gold nanorods using a disulfide-modified polypeptide

Directing the self-assembly of colloidal particles into nanostructures is of greatinterest in nanotechnology. Here, reversible end-to-end assembly of gold nanorods(GNR) is induced by pH-dependent changes in the secondary conformation of adisulfide-modified poly(L-glutamic acid) (SSPLGA). The disulfide anchoring group driveschemisorption of the polyacid onto the end of the gold nanorods in an ethanolicsolution. A layer of poly(vinyl pyrrolidone) is adsorbed on the positively charged,surfactant-stabilized GNR to screen the surfactant bilayer charge and provide stabilityfor dispersion of the GNR in ethanol. For comparison, irreversible end-to-endassembly using a bidentate ligand, namely 1,6-hexanedithiol, is also performed.Characterization of the modified GNR and its end-to-end linking behavior usingSSPLGA and hexanedithiol is performed using dynamic light scattering (DLS),UV–vis absorption spectroscopy and transmission electron microscopy (TEM).Experimental results show that, in a colloidal solution of GNR–SSPLGA at apH∼3.5, where thePLGA is in an α-helical conformation, the modified GNR self-assemble into one-dimensionalnanostructures. The linking behavior can be reversed by increasing the pH(>8.5) to drive the conformation of the polypeptide to a random coil and this reversal with pHoccurs rapidly within minutes. Cycling the pH multiple times between low and high pHvalues can be used to drive the formation of the nanostructures of the GNR and dispersethem in solution.

Reversible aggregation of gold nanoparticles induced by pH dependent conformational transitions of a self-assembled polypeptide

Controlling the stable structures of metallic nanoparticles on mesoscopic and macroscopic length scales is of great interest in nanotechnology. Here, this task is accomplished using a synthetic biopolymer that is responsive to external stimuli and undergoes changes in secondary structure. Reversible aggregation of gold nanoparticles (GNP) is induced by pH dependent changes in a self-assembled monolayer of disulfide modified poly( l-glutamic acid) (SSPLGA) with M w ∼ 27000 . The disulfide anchoring group drives chemisorption onto the gold nanoparticles and leads to the formation of a self-assembled monolayer. Characterization of the modified GNP and its aggregation behavior is performed using dynamic light scattering (DLS), UV–vis and IR spectroscopy, and transmission electron microscopy (TEM). Experimental results show that decrease in pH near 5.5 leads to aggregation of the modified GNP. The change in aggregation behavior with pH occurs within minutes, is reversible, and happens within a narrow range of pH from about 4.5 to 5.5. Comparison with literature data on molar enthalpy of hydrogen bonding, specific optical rotation, and ionization for the helix–coil transition of PLGA indicates that the aggregation of the SSPLGA modified GNP corresponds to the transition in the secondary structure of the polyacid.