Morphological and electrical characteristics of amino acid–AuNP nanostructured two-dimensional ensembles

The interaction between amino acids (l-cysteine, l-lysine) and gold nanoparticle layers deposited on ITO glasses was investigated. The citrate capped gold nanoparticles (AuNP) were first deposited as a thin layer onto silanized ITO and subsequently linked with an amino acid, due to strong affinity of thiol and amine groups to gold. The gold nanoparticles had an elliptical shape, with size varying between 7 and 14 nm, as indicated by TEM analysis. After deposition on ITO substrate, the nanoparticles self-assembled into large aggregates with poor contact between, as revealed by AFM. After linking l-cysteine or l-lysine to the surface of nanoparticles layer, a change in morphology occured. A better contact between the gold aggregates boundary developed, which improved the conducting properties of the nanostructured layer. The electrical resistance of the AuNPs layer, obtained from I–V measurements, was very high (2.8 × 10¹³ Ω) and slightly decreased after linking the NPs with amino acids.     

Optimizing coverage of metal oxide nanoparticle prepared by pulsed laser deposition on nonenzymatic glucose detection

Metal oxide nanoparticles prepared by pulsed laser deposition (PLD) were applied to nonenzymatic glucose detection. NiO nanoparticles with size of 3 nm were deposited on glassy carbon (GC) and silicon substrates at room temperature in an oxygen atmosphere. Transmission electron microscope (TEM) image showed nanoparticles with the size of 3 nm uniformly scattered on the Si(0 0 1) substrate. Unlike co-sputtering nanoparticle and carbon simultaneously, the PLD method can easily control the surface coverage of nanoparticles on the surface of substrate by deposition time. Cyclic voltammetry was performed on the samples deposited on the GC substrates for electrochemical detection of glucose. The differences between peak currents with and without glucose was used to optimize the coverage of nanoparticles on carbon electrode. The results indicated that optimal coverage of nanoparticles on carbon electrode.     

A Bio-Inspired Magnetically Recoverable Palladium Nanocatalyst for the Ullmann Coupling reaction of Aryl halides and Arylboronic acids In Aqueous Media

Palladium nanoparticles supported on polydopamine-coated iron oxide nanoparticles (Pd/Fe₃O₄@PDA) were found to catalyze the Ullmann homocoupling of a wide variety of aryl halides, arylboronic acids and aryldiazonium salts in aqueous media in the presence of randomly methylated β-cyclodextrin (RM-β-CD). The synthesized nanoparticles were characterized by techniques such as TEM, SEM, EDX, XPS, ICP-AES and XRD. The synthesized catalyst can be easily recovered magnetically and reused up to five cycles without any significant loss of activity. This is the first report demonstrating the use of magnetically recoverable catalyst for Ullmann homocoupling reactions of aryl halides, arylboronic acids and aryldiazonium salts in water.     

Room temperature multicomponent synthesis of diverse propargylamines using magnetic CuFe2O4 nanoparticle as an efficient and reusable catalyst

We report the magnetic recoverable catalyst (CuFe₂O₄) catalyzed multicomponent reaction of aliphatic amines, formaldehyde, arylboronic acids and alkynyl carboxylic acids for the synthesis of diverse propargylamines at room temperature.     

A simple double-bead sandwich assay for protein detection in serum using UV-vis spectroscopy

In this study a double-bead sandwich assay, employing magnetic nanoparticles and gold nanoparticles is proposed. The magnetic nanoparticles allow specific capturing of the analyte in biological samples, while the optical properties of the gold nanoparticles provide the signal transduction. We demonstrated that a major improvement in the assay sensitivity was obtained by selecting an optimal gold nanoparticle size (60 nm). A detection limit of 5-8 ng/mL, a sensitivity of 0.6-0.8 (pg/mL)⁻¹ and a dynamic range of 3 orders of magnitude were achieved without any further amplification using the detection of prostate specific antigen in serum as a model system. The proposed assay has the ability to be easily implemented within a microfluidic device for point-of-care applications whereby the readout can be executed by a fast and cheap optical measurement.     

The nature of nanoparticles formed in the system PdCl2-elemental phosphorus

The state of palladium in nanoparticles formed in the system PdCl₂ — elemental phosphorus in an inert atmosphere was identified using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS). Palladium phosphides of different composition and Pd(0) clusters are shown to form as a result of a redox process. According to the XPS data, the structures of nanoparticles are of the core-shell type. The interaction of PdCl₂ with P₄ is followed not only by the hydrolysis of the solvent (DMF) accelerated by hydrochloric acid, but also by the decomposition catalyzed by palladium cluster of organic compounds. The formed graphite and phosphoric acids stabilize the nanoparticles.     

Aminopolycarboxyl-modified Ag2S nanoparticles: Synthesis, characterization and resonance light scattering sensing for bovine serum albumin

A novel method was proposed to prepare a series of functionalized Ag₂S nanoparticles capped with various aminopolycarboxylic acids. The as-prepared Ag₂S nanoparticles were characterized by UV-vis, FTIR, resonance light scattering spectra (RLS) and transmission electron microscopy (TEM). Based on the RLS intensities enhanced by BSA-induced Ag₂S nanoparticles aggregation, a sensitive RLS method for the detection BSA at nanogram levels was established. The detection limits for BSA are between 8.6 and 112.6 ng mL⁻¹, depending on the different capping agents. The effects of various capping agents on the detection limits of BSA have been investigated. The detection limit is found to be dependent on the stability constant (log K_MY) of the silver-aminopolycarboxyl complexes.     

Gold and silver nanoparticles‐based laser desorption/ionization mass spectrometry method for detection and quantification of carboxylic acids

A comparison of ionization efficiency for gold and silver nanoparticles used as an active media of matrix‐less laser desorption/ionization (LDI) mass spectrometry (MS) methods was made for carboxylic acids including fatty acids. The matrix‐assisted laser desorption/ionization (MALDI)‐type targets containing monoisotopic cationic ¹⁰⁹Ag nanoparticles (¹⁰⁹AgNPs) and Au nanoparticles (AuNPs) were used for rapid MS measurements of 10 carboxylic acids of different chemical properties. Carboxylic acids were directly quantified in experiments with 10 000‐fold concentration change conditions ranging from 1 mg/ml to 100 ng/ml which equates to 1 μg to 100 pg of carboxylic acids per measurement spot.     

CuO nanoparticles: an efficient and recyclable catalyst for cross-coupling reactions of organic diselenides with aryl boronic acids

We present here an efficient and ligand-free cross-coupling reaction of organic diselenides with aryl boronic acids using a catalytic amount of CuO nanoparticles in DMSO at 100 °C under air atmosphere. This is a general cross-coupling reaction and was performed with organic diselenides and aryl boronic acids bearing electron-withdrawing and electron-donating groups affording the corresponding selenides in good to excellent yields. The CuO nanoparticles can be easily recovered and utilized for further catalytic reactions.     

Electrospinning nanosuspensions loaded with passivated Au nanoparticles

Aqueous polyethylene oxide (PEO) solutions (2 MDa, 2-5 wt %) with or without citrate passivated Au nanoparticles (5.7×10⁻⁷ wt %) have been electrospun, producing fibres with diameters from 290 μm to 55 nm. The incorporation of nanoparticles suppresses the diameter of the fibres and increases the degree of crystallinity. Such nanocomposite fibres are of interest as self-assembled templates for bottom-up fabrication methodologies.     

The use of imidazolium ionic liquids for the formation and stabilization of ir0 and rh0 nanoparticles: efficient catalysts for the hydrogenation of arenes

Stable transition-metal nanoparticles of the type [M(0)](n) are easily accessible through the reduction of Ir(I) or Rh(III) compounds dissolved in "dry" 1-n-butyl-3-methylimidazolium hexafluorophosphate ionic liquid by molecular hydrogen. The formation of these [M(0)](n) nanoparticles is straightforward; they are prepared in dry ionic liquid whereas the presence of the water causes the partial decomposition of ionic liquid with the formation of phosphates, HF and transition-metal fluorides. Transmission electron microscopy (TEM) observations and X-ray diffraction analysis (XRD) show the formation of [Ir(0)](n) and [Rh(0)](n) nanoparticles with 2.0-2.5 nm in diameter. The isolated [M(0)](n) nanoparticles can be redispersed in the ionic liquid, in acetone or used in solventless conditions for the liquid-liquid biphasic, homogeneous or heterogeneous hydrogenation of arenes under mild reaction conditions (75 degrees C and 4 atm). The recovered iridium nanoparticles can be reused several times without any significant loss in catalytic activity. Unprecedented total turnover numbers (TTO) of 3509 in 32 h, for arene hydrogenation by nanoparticles catalysts, have been achieved in the reduction of benzene by the [Ir(0)](n) in solventless conditions. Contrarily, the recovered Rh(0) nanoparticles show significant agglomeration into large particles with a loss of catalytic activity. The hydrogenation of arenes containing functional groups, such as anisole, by the [Ir(0)](n) nanoparticles occurs with concomitant hydrogenolysis of the C-O bond, suggesting that these nanoparticles behave as "heterogeneous catalysts" rather than "homogeneous catalysts".     

Improving surface structure of photocatalytic self‐cleaning membrane by WO3/PANI nanoparticles

To create a self‐cleaning feature and improve antifouling property, polysulfone (PSf) membranes were modified with WO₃ and polyaniline (PANI) nanoparticles (0–2 wt%) via phase inversion method for ultrafiltration of landfill leachate. The mass ratio of WO₃ nanoparticles was varied between 0, 40 and 60 wt% in different loadings. All synthesized membranes were tested with and without UV irradiation to evaluate the self‐cleaning feature. The synthesized PANI was analyzed with scanning electron morphology (SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). The surface hydrophilicity of the modified membranes increases with increasing the nanoparticle loadings (0–2 wt%). The membrane morphology indicated higher porosity and more finger like pores for the modified membranes. The porosity of 86.8% was achieved for the membrane containing 2 wt% PANI. The flux recovery ratio (FR) of membranes without UV radiation was increased by increasing the ratio of PANI to WO₃ nanoparticles, while the antifouling ability of membranes including WO₃ nanoparticles improved and reached to 98.87% after UV radiation. The highest COD removal before (76.65 %) and after (78.42%) UV radiation was obtained for the membrane containing 2 wt% nanoparticle loading. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis of deprotonated acids with silicon nanoparticle-assisted laser desorption/ ionization mass spectrometry

Chemically modified silicon nanoparticles were applied for the laser desorption/negative ionization of small acids. A series of substituted sulfonic acids and fatty acids was studied. Compared to desorption ionization on porous silicon (DIOS) and other matrix-less laser desorption/ionization techniques, silicon nanoparticle-assisted laser desorption/ionization (SPALDI) mass spectrometry allows for the analysis of acids in the negative ion mode without the observation of multimers or cation adducts. Using SPALDI, detection limits of many acids reached levels down to 50 pmol/μl. SPALDI of fatty acids with unmodified silicon nanoparticles was compared to SPALDI using the fluoroalkyl silylated silicon powder, with the unmodified particles showing better sensitivity for fatty acids, but with more low-mass background due to impurities and surfactants in the untreated silicon powder. The fatty acids exhibited a size-dependent response in both SPALDI and unmodified SPALDI, showing a signal intensity increase with the chain length of the fatty acids (C12-C18), leveling off at chain lengths of C18-C22. The size effect may be due to the crystallization of long chain fatty acids on the silicon. This hypothesis was further explored and supported by SPALDI of several, similar sized, unsaturated fatty acids with various crystallinities. Fatty acids in milk lipids and tick nymph samples were directly detected and their concentration ratios were determined by SPALDI mass spectrometry without complicated and time-consuming purification and esterification required in the traditional analysis of fatty acids by gas chromatography (GC). These results suggest that SPALDI mass spectrometry has the potential application in fast screening for small acids in crude samples with minimal sample preparation.     

Nanoscale Pt(0) particles prepared in imidazolium room temperature ionic liquids: synthesis from an organometallic precursor,characterization, and catalytic properties in hydrogenation reactions

The reaction of Pt(2)(dba)(3) (dba = bis-dibenzylidene acetone) dispersed in room temperature 1-n-butyl-3-methylimidazolium (BMI) hexafluorophosphate ionic liquid with molecular hydrogen (4 atm) at 75 degrees C leads to stable and isolable nanometric Pt(0) particles. The X-ray diffraction analysis (XRD) of the material indicated that it is constituted of Pt(0). Transmission electron microscopy (TEM) analysis of the particles dispersed in the ionic liquid shows the formation of [Pt(0)](n) nanoparticles of 2.0-2.5 nm in diameter. A detailed examination of the nanoparticles imbibed in the ionic liquid and their environment shows an interaction of the BMI.PF(6) ionic liquid with the Pt(0) nanoparticles. The isolated [Pt(0)](n) nanoparticles can be redispersed in the ionic liquid or in acetone or used in solventless conditions for liquid-liquid biphasic, homogeneous, or heterogeneous hydrogenation of alkenes and arenes under mild reaction conditions (75 degrees C and 4 atm). The recovered platinum nanoparticles can be reused as a solid or redispersed in the ionic liquid several times without any significant loss in catalytic activity.     

Surfactant-free synthesis of nickel nanoparticles in near-critical water

Nickel nanoparticles have been produced by combining two well-tested methods: (i) the continuous flow supercritical reactor and (ii) the reduction of a nickel salt with hydrazine. The normal precipitation of a nickel-hydrazine complex, which would complicate pumping and mixing of the precursor, was controlled by the addition of ammonia to the precursor solution, and production of nickel nanoparticles with average sizes from 40 to 60 nm were demonstrated. The method therefore provides some size control and enables the production of nickel nanoparticles without the use of surfactants. The pure nickel nanoparticles can be easily isolated using a magnet.     

Self-assembly of polyoxometalate macroanion-capped pd0 nanoparticles in aqueous solution

The self-assembly behavior of polyoxometalate (POM) macroanion-capped 3-nm-radius Pd (0) nanoparticles in aqueous solution is reported. Pd(0) nanoparticles are synthesized from reducing K(2)PdCl(4) by using Dawson-type V-substituted POM K(9)[H(4)PV (IV)W(17)O(62)] (HPV(IV)) clusters as the reductant and stabilizer simultaneously in acidic aqueous solutions. The starting molar ratio of K(2)PdCl(4) to HPV(IV) (R value) in solution is important to the formation of Pd nanoparticles. When R < 0.6, approximately 20-nm-radius Pd(0) colloidal nanocrystals are formed. When R > or = 0.6, HPV-capped (and therefore negatively charged) 3-nm-radius Pd(0) nanoparticles are formed, which can further self-assemble into stable, hollow, spherical, 30-50-nm-radius supramolecular structures in solution without precipitation, as confirmed by light scattering and transmission electron microscopy studies. This structure resembles the unique supramolecular structure formed by hydrophilic POM macroanions in polar solvents, which we refer to as "blackberry" structures. It is the first evidence that the blackberry formation can occur in hydrophobic nanoparticle systems when the surface of nanoparticles is modified to be partially hydrophilic. Counterions play an important role in the self-assembly of Pd nanoparticles, possibly providing an attractive force for blackberry formation, which is the case for blackberry formation in POM macroanionic solutions. Our results suggest that the blackberry formation is not a specific property of POM macroions but most likely a general phenomenon for nanoparticles with relatively hydrophilic surfaces and suitable sizes and charges in a polar solvent.     

C-Glycosides of dodecanoic acid: new capping/reducing agents for glyconanoparticle synthesis

A concise synthesis of 12-C-glycosylated dodecanoic acids employing an olefin cross-metathesis reaction is developed. Examination of these acids as capping agents for the synthesis of metal nanoparticles reveals that they do not cap the Co-metal nanoparticles synthesized in aqueous phase, but that two of them can reduce and cap the Ag nanoparticles in water without any aggregation.     

Structural and optical characterization of colloidal Se nanoparticles prepared via the acidic decomposition of sodium selenosulfate

Colloidal selenium nanoparticles (NPs) were synthesized via acidic decomposition of sodium selenosulfate. The effects of synthesis and post-synthesis treatment conditions on the size, structure and size distribution of the Se nanoparticles are discussed. It is shown that the decomposition of sodium selenosulfate with non-oxidative acids (e.g., HCl) in aqueous solutions of polymers (sodium polyphosphate, gelatin, polyvinyl alcohol, polyethyleneglycole) and surfactants (sodium dodecylsulfonate, cetylpyridinium chloride) results in the formation of amorphous 25–200 nm Se nanoparticles converting upon ageing at 90 °C into trigonal 150–250 nm Se nanocrystals. Optical properties (absorption and Raman spectra) of freshly prepared and aged Se nanoparticles both in colloidal solutions and in polymeric (polyvinyl alcohol) films are analyzed.     

Nucleation activity of nanosized CaCO3 on crystallization of isotactic polypropylene, in dependence on crystal modification, particle shape, and coating

A detailed analysis of the effect of calcium carbonate nanoparticles on crystallization of isotactic polypropylene (iPP) is reported in this contribution. CaCO₃ nanoparticles with different crystal modifications (calcite and aragonite) and particle shape were added in small percentages to iPP. The nanoparticles were coated with two types of compatibilizer (either polypropylene-g-maleic anhydride copolymer, or fatty acids) to improve dispersion and adhesion with the polymer matrix.It was found that the type of coating agent used largely affects the nucleating ability of calcium carbonate towards formation of polypropylene crystals. CaCO₃ nanoparticles coated with maleated polypropylene can successfully promote nucleation of iPP crystals, whereas the addition of nanosized calcium carbonate coated with fatty acids delays crystallization of iPP, the effect being mainly ascribed to the physical state of the coating in the investigated temperature range for crystallization of iPP, as well as to possible dissolution by fatty acids of heterogeneities originally present in the polypropylene matrix.     

Analysis of organic acids and phenols of interest in the wine industry using Langmuir–Blodgett films based on functionalized nanoparticles

A chemically modified electrode consisting of Langmuir–Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (S_DODAuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The S_DODAuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10⁻⁶ mol L⁻¹ were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences.