Showing papers on "Nanoparticle published in 2004"
TL;DR: These nontoxic nanomaterials, which can be prepared in a simple and cost-effective manner, may be suitable for the formulation of new types of bactericidal materials.
5,309 citations
TL;DR: This work is able to synthesize as much as 40 g of monodisperse nanocrystals in a single reaction, without a size-sorting process, and the particle size could be controlled simply by varying the experimental conditions.
Abstract: The development of nanocrystals has been intensively pursued, not only for their fundamental scientific interest, but also for many technological applications. The synthesis of monodisperse nanocrystals (size variation <5%) is of key importance, because the properties of these nanocrystals depend strongly on their dimensions. For example, the colour sharpness of semiconductor nanocrystal-based optical devices is strongly dependent on the uniformity of the nanocrystals, and monodisperse magnetic nanocrystals are critical for the next-generation multi-terabit magnetic storage media. For these monodisperse nanocrystals to be used, an economical mass-production method needs to be developed. Unfortunately, however, in most syntheses reported so far, only sub-gram quantities of monodisperse nanocrystals were produced. Uniform-sized nanocrystals of CdSe (refs 10,11) and Au (refs 12,13) have been produced using colloidal chemical synthetic procedures. In addition, monodisperse magnetic nanocrystals such as Fe (refs 14,15), Co (refs 16-18), gamma-Fe(2)O(3) (refs 19,20), and Fe(3)O(4) (refs 21,22) have been synthesized by using various synthetic methods. Here, we report on the ultra-large-scale synthesis of monodisperse nanocrystals using inexpensive and non-toxic metal salts as reactants. We were able to synthesize as much as 40 g of monodisperse nanocrystals in a single reaction, without a size-sorting process. Moreover, the particle size could be controlled simply by varying the experimental conditions. The current synthetic procedure is very general and nanocrystals of many transition metal oxides were successfully synthesized using a very similar procedure.
3,704 citations
IBM1
TL;DR: As-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD and can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made.
Abstract: High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)3, with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe3O4) nanoparticles. Similarly, reaction of Fe(acac)3 and Co(acac)2 or Mn(acac)2 with the same diol results in monodisperse CoFe2O4 or MnFe2O4 nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe3O4 can be oxidized to Fe2O3, as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.
3,244 citations
TL;DR: The rates of reduction of the metal ions by Neem leaf extract are much faster than those observed by us in earlier studies using microorganisms such as fungi, highlighting the possibility that nanoparticle biological synthesis methodologies will achieve rates of synthesis comparable to those of chemical methods.
2,339 citations
TL;DR: Only amorphous silica and some colloidal polymer spheres can be routinely prepared with satisfactorily narrow size distributions, and surface modification almost unavoidable before use as supports or templates.
Abstract: Colloidal microand nanospheres have been of continuous research interest, since their intrinsic properties can be finely tuned by changing parameters such as diameter, chemical composition, bulk structure, and crystallinity. Up to now, they have found a broad range of applications in fields such as drug delivery, biodiagnostics, combinatorial synthesis, and photonic band-gap crystals (PBG). The success of these applications strongly depends on the availability of colloidal spheres with tightly controlled size and surface properties. However, until now, only amorphous silica and some colloidal polymer spheres can be routinely prepared with satisfactorily narrow size distributions. As-prepared colloidal nanoand microspheres usually have relatively inert surfaces, which make surface modification almost unavoidable before use as supports or templates.
2,102 citations
TL;DR: In this paper, the formation rate of 3-nm particles is often in the range 0.01-10 cm −3 s −1 in the boundary layer in urban areas and in coastal areas and industrial plumes.
2,028 citations
TL;DR: The size-dependent shift in the apparent Fermi level of the TiO(2)-Au composite shows the ability of Au nanoparticles to influence the energetics by improving the photoinduced charge separation.
Abstract: Photoexcited semiconductor nanoparticles undergo charge equilibration when they are in contact with metal nanoparticles. Such a charge distribution has direct influence in dictating the energetics of the composite by shifting the Fermi level to more negative potentials. The transfer of electrons to Au nanoparticles has now been probed by exciting TiO2 nanoparticles under steady-state and laser pulse excitation. Equilibration with the C60/C60- redox couple provides a means to determine the apparent Fermi level of the TiO2−Au composite system. The size-dependent shift in the apparent Fermi level of the TiO2−Au composite (20 mV for 8-nm diameter and 40 mV for 5-nm and 60 mV for 3-nm gold nanoparticles) shows the ability of Au nanoparticles to influence the energetics by improving the photoinduced charge separation. Isolation of individual charge-transfer steps from UV-excited TiO2 → Au → C60 has provided mechanistic and kinetic information on the role of metal in semiconductor-assisted photocatalysis and siz...
1,896 citations
TL;DR: In this paper, the authors apply the plasmon hybridization method to nanoparticle dimers, providing a simple and intuitive description of how the energy and excitation cross sections of dimer plasmons depend on nanoparticle separation.
Abstract: We apply the recently developed plasmon hybridization method to nanoparticle dimers, providing a simple and intuitive description of how the energy and excitation cross sections of dimer plasmons depend on nanoparticle separation. We show that the dimer plasmons can be viewed as bonding and antibonding combinations, i.e., hybridization of the individual nanoparticle plasmons. The calculated plasmon energies are compared with results from FDTD simulations.
1,577 citations
TL;DR: The discovery that the extract from the lemongrass plant, when reacted with aqueous chloroaurate ions, yields a high percentage of thin, flat, single-crystalline gold nanotriangles, which seem to grow by a process involving rapid reduction, assembly and room-temperature sintering of 'liquid-like' spherical gold nanoparticles.
Abstract: The optoelectronic and physicochemical properties of nanoscale matter are a strong function of particle size. Nanoparticle shape also contributes significantly to modulating their electronic properties. Several shapes ranging from rods to wires to plates to teardrop structures may be obtained by chemical methods; triangular nanoparticles have been synthesized by using a seeded growth process. Here, we report the discovery that the extract from the lemongrass plant, when reacted with aqueous chloroaurate ions, yields a high percentage of thin, flat, single-crystalline gold nanotriangles. The nanotriangles seem to grow by a process involving rapid reduction, assembly and room-temperature sintering of 'liquid-like' spherical gold nanoparticles. The anisotropy in nanoparticle shape results in large near-infrared absorption by the particles, and highly anisotropic electron transport in films of the nanotriangles.
1,473 citations
TL;DR: In this paper, the activation energies and the average rate constants were determined in the 298 K−318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (III) and thiosulfate ions using 4.8 ± 0.1 nm tetrahedral, 7.1 µm cubic, and 4.9 µm near spherical nanocrystals.
Abstract: The activation energies and the average rate constants are determined in the 298 K−318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (III) and thiosulfate ions using 4.8 ± 0.1 nm tetrahedral, 7.1 ± 0.2 nm cubic, and 4.9 ± 0.1 nm “near spherical” nanocrystals. These kinetic parameters are found to correlate with the calculated fraction of surface atoms located on the corners and edges in each size and shape.
1,112 citations
TL;DR: A critical size has been identified below which the shapes of complex nanocrystals evolve toward the equilibrium shape with lowest energy during the exchange reaction, above which the anion sublattice remains intact and the basic shapes of the initial nanocry crystals are retained throughout the cation exchange.
Abstract: Cation exchange has been investigated in a wide range of nanocrystals of varying composition, size, and shape. Complete and fully reversible exchange occurs, and the rates of the reactions are much faster than in bulk cation exchange processes. A critical size has been identified below which the shapes of complex nanocrystals evolve toward the equilibrium shape with lowest energy during the exchange reaction. Above the critical size, the anion sublattice remains intact and the basic shapes of the initial nanocrystals are retained throughout the cation exchange. The size-dependent shape change can also be used to infer features of the microscopic mechanism.
TL;DR: In this article, a multilayer SAM shell based on the interaction of HOOC(CH2)10SH and Cu2+ was assembled onto surface-confined noble metal nanoparticles and were monitored using UV−visible spectroscopy.
Abstract: The elucidation of the long range distance dependence of the localized surface plasmon resonance (LSPR) of surface-confined noble metal nanoparticles is the aim of this work It was suspected that the linear distance dependence found in CH3(CH2)xSH self-assembled monolayer (SAM) formation was the thin shell limit of a longer range, nonlinear dependence To verify this, multilayer SAM shells based on the interaction of HOOC(CH2)10SH and Cu2+ were assembled onto surface-confined noble metal nanoparticles and were monitored using UV−visible spectroscopy Measurement of the LSPR extinction peak shift versus number of layers and adsorbate thickness is nonlinear and has a sensing range that is dependent on the composition, shape, in-plane width, and out-of-plane height of the nanoparticles Theoretical calculations based on an accurate electrodynamics description of the metal nanoparticle plus surrounding layered material indicate plasmon resonance wavelength shifts that are in excellent agreement with the meas
TL;DR: With glucose oxidase (GOx) as an enzyme model, a GC or carbon fiber microelectrode-based biosensor is constructed that responds even more sensitively to glucose than the GC/GOx electrode modified by Pt nanoparticles or CNTs alone.
Abstract: Platinum nanoparticles with a diameter of 2-3 nm were prepared and used in combination with single-wall carbon nanotubes (SWCNTs) for fabricating electrochemical sensors with remarkably improved sensitivity toward hydrogen peroxide. Nafion, a perfluorosulfonated polymer, was used to solubilize SWCNTs and also displayed strong interactions with Pt nanoparticles to form a network that connected Pt nanoparticles to the electrode surface. TEM and AFM micrographs illustrated the deposition of Pt nanoparticles on carbon nanotubes whereas cyclic voltammetry confirmed an electrical contact through SWCNTs between Pt nanoparticles and the glassy carbon (GC) or carbon fiber backing. With glucose oxidase (GOx) as an enzyme model, we constructed a GC or carbon fiber microelectrode-based biosensor that responds even more sensitively to glucose than the GC/GOx electrode modified by Pt nanoparticles or CNTs alone. The response time and detection limit (S/N = 3) of this biosensor was determined to be 3 s and 0.5 microM, respectively.
TL;DR: The unique ability to interchange substrate-specific peptides into the linear self-assembled filamentous construct of the M13 virus introduces a material tunability that has not been seen in previous synthetic routes, and provides a genetic toolkit for growing and organizing nanowires from semiconducting and magnetic materials.
Abstract: We report a virus-based scaffold for the synthesis of single-crystal ZnS, CdS, and freestanding chemically ordered CoPt and FePt nanowires, with the means of modifying substrate specificity through standard biological methods. Peptides (selected through an evolutionary screening process) that exhibit control of composition, size, and phase during nanoparticle nucleation have been expressed on the highly ordered filamentous capsid of the M13 bacteriophage. The incorporation of specific, nucleating peptides into the generic scaffold of the M13 coat structure provides a viable template for the directed synthesis of semiconducting and magnetic materials. Removal of the viral template by means of annealing promoted oriented aggregation-based crystal growth, forming individual crystalline nanowires. The unique ability to interchange substrate-specific peptides into the linear self-assembled filamentous construct of the M13 virus introduces a material tunability that has not been seen in previous synthetic routes. Therefore, this system provides a genetic toolkit for growing and organizing nanowires from semiconducting and magnetic materials.
TL;DR: In this article, a co-precipitation method in the presence of ethylenediaminetetraacetic acid (EDTA) was used to obtain spherical particles of controlled size in the range of 37 to 166 nm diameter.
Abstract: Nanocrystalline infrared-to-visible up-conversion phosphors, ytterbium and erbium co-doped sodium yttrium fluoride, were synthesized. Spherical particles with narrow size distribution were prepared by a co-precipitation method in the presence of ethylenediaminetetraacetic acid (EDTA). Particles of controlled size in the range of 37 to 166 nm diameter were obtained by adjusting the molar ratio of EDTA to total lanthanides. Although the as-prepared nanoparticles emit very weak up-conversion fluorescence when excited by infrared light, the emission was enhanced by up to 40-fold after they were annealed at temperatures between 400 and 600 degreesC. By comparison with the bulk phosphor, the luminescence efficiency of the nanoparticle was estimated to be 1%. Factors affecting the particle size and their up-conversion fluorescence intensity were investigated by various microscopic and spectroscopic techniques. Preliminary results demonstrated the nanoparticles as promising up-converting fluorescence labels in the detection of biological interactions.
TL;DR: In this paper, the results of varying the humidity and molecular weight on the surface of electrospun polystyrene (PS) fibers were studied using optical microscopy, field emission scanning electron micros.
Abstract: Electrospinning is a technique used to produce micron to submicron diameter polymeric fibers. The surface of electrospun fibers is important when considering end-use applications. For example, the ability to introduce porous surface features of a known size is required if nanoparticles need to be deposited on the surface of the fiber or if drug molecules are to be incorporated for controlled release. Surface features, or pores, became evident when electrospinning in an atmosphere with more than 30% relative humidity. Increasing humidity causes an increase in the number, diameter, shape, and distribution of the pores. Increasing the molecular weight of the polystyrene (PS) results in larger, less uniform shaped pores. This work includes an investigation of how humidity and molecular weight affect the surface of electrospun PS fibers. The results of varying the humidity and molecular weight on the surface of electrospun PS fibers were studied using optical microscopy, field emission scanning electron micros...
TL;DR: In this article, an efficient bulk-heterojunction solar cells can be made using ZnO nanoparticles and a conjugated polymer, and the incident photon to current conversion efficiency (IPCE) closely resembles the absorption spectrum of the MDMO-PPV layer on glass, and reaches a value of 40 % at the absorption max.
Abstract: The authors show that efficient bulk-heterojunction solar cells can be made using ZnO nanoparticles and a conjugated polymer. These cells can be processed from soln. and exhibit an incident photon to current conversion efficiency up to 40 %. Nanocryst. ZnO (nc-ZnO) of approx. 5 nm diam. was synthesized and used. As the n-type semiconductor. Complexes with MDMO-PPV were used, with Aluminum and a PEDOT-PSS/ITO-coated glass hole-conducting electrode. The incident photon to current conversion efficiency (IPCE)closely resembles the absorption spectrum of the MDMO-PPV:nc-ZnO layer on glass, and reaches a value of 40 % at the absorption max. MDMO-PPV. Integration of this spectral response with the solar spectrum (AM1.5G, normalized 100 mW cm-2) affords an est. of the short-circuit c.d. of Jsc = 3.3 mA/cm2 under AM1.5 (1 sun) conditions. C.d.-voltage (J-V) measurements, carried out in the dark reveal excellent diode behavior, with electron current dominating the c.d. in forward bias. TEM micrographs showed intimate mixing of the ZnO and the MDMO-PPV, with the majority of the polymer domains smaller than a few tens of nanometers, which has been shown to be the exciton diffusion length in a similar PPV polymer.
TL;DR: The synthesis and successful testing of solution-phase, near-infrared sensors, with β-D-glucose sensing as a model system, using single-walled carbon nanotubes that modulate their emission in response to the adsorption of specific biomolecules are reported.
Abstract: Molecular detection using near-infrared light between 0.9 and 1.3 eV has important biomedical applications because of greater tissue penetration and reduced auto-fluorescent background in thick tissue or whole-blood media. Carbon nanotubes have a tunable near-infrared emission that responds to changes in the local dielectric function but remains stable to permanent photobleaching. In this work, we report the synthesis and successful testing of solution-phase, near-infrared sensors, with beta-D-glucose sensing as a model system, using single-walled carbon nanotubes that modulate their emission in response to the adsorption of specific biomolecules. New types of non-covalent functionalization using electron-withdrawing molecules are shown to provide sites for transferring electrons in and out of the nanotube. We also show two distinct mechanisms of signal transduction-fluorescence quenching and charge transfer. The results demonstrate new opportunities for nanoparticle optical sensors that operate in strongly absorbing media of relevance to medicine or biology.
TL;DR: The changes of some interesting properties in different colloidal semiconductor nanoparticles, such as the electronic relaxation rates as spherical nanoparticles change to nanorods, and the changes in the structure or size of very small nanoparticles upon adsorbing strongly bound molecules are described.
Abstract: As the size of material becomes equal to or falls below the nanometer length scale that characterizes the motion of its electrons and thus its properties, the latter become sensitive not only to the size but also to the shape and composition of the particles. In this Account, we describe the changes of some interesting properties in different colloidal semiconductor nanoparticles, such as the electronic relaxation rates as spherical nanoparticles change to nanorods, and the changes in the structure or size of very small nanoparticles upon adsorbing strongly bound molecules. We have also determined and explained the difference in the interfacial crossing rates of electrons and holes in a composite nanostructure.
TL;DR: Preliminary in‐vivo experiments reveal enhanced blood stability of the nanoparticles, which, coupled with sustained release of anti‐tumor agents, show good potential for cancer treatment.
Abstract: In recent decades, significant advances in drug-delivery systems have enabled more effective drug administration. To deliver drugs to specific organs, a range of organic systems (e.g., micelles, liposomes, and polymeric nanoparticles) have been designed. They suffer from limitations, including poor thermal and chemical stability, and rapid elimination by the immune system. In contrast, silica particles offer a biocompatible, stable, and “stealthy” alternative. Bioactive molecules can be easily encapsulated within silica particles by combining sol-gel polymerization with either spray-drying or emulsion chemistry. Spray-drying faces challenges, including low yield, surface segregation, and size limitations. In contrast, sol-gel emulsions enable the production of nanoparticles with homogeneous drug distribution, and permit ambient temperature processing, necessary for handling biologicals. Independent control of the size and release rate can be readily achieved. Preliminary in-vivo experiments reveal enhanced blood stability of the nanoparticles, which, coupled with sustained release of anti-tumor agents, show good potential for cancer treatment.
TL;DR: In this paper, a review describes recent advances in the handling and manipulation of magnetic particles in microfluidic systems, pointing out the advantages and prospects of these concepts for future analysis applications.
Abstract: This review describes recent advances in the handling and manipulation of magnetic particles in microfluidic systems. Starting from the properties of magnetic nanoparticles and microparticles, their use in magnetic separation, immuno-assays, magnetic resonance imaging, drug delivery, and hyperthermia is discussed. We then focus on new developments in magnetic manipulation, separation, transport, and detection of magnetic microparticles and nanoparticles in microfluidic systems, pointing out the advantages and prospects of these concepts for future analysis applications.
TL;DR: The results indicate that the size of the nanoparticle, perhaps because of the contributions of surface curvature, influences adsorbed protein structure and function.
Abstract: Adsorption of chicken egg lysozyme on silica nanoparticles of various diameters has been studied. Special attention has been paid to the effect of nanoparticle size on the structure and function of the adsorbed protein molecules. Both adsorption patterns and protein structure and function are strongly dependent on the size of the nanoparticles. Formation of molecular complexes is observed for adsorption onto 4-nm silica. True adsorptive behavior is evident on 20- and 100-nm particles, with the former resulting in monolayer adsorption and the latter yielding multilayer adsorption. A decrease in the solution pH results in a decrease in lysozyme adsorption. A change of protein structure upon adsorption is observed, as characterized by a loss in alpha-helix content, and this is strongly dependent on the size of the nanoparticle and the solution pH. Generally, greater loss of alpha helicity was observed for the lysozyme adsorbed onto larger nanoparticles under otherwise similar conditions. The activity of lysozyme adsorbed onto silica nanoparticles is lower than that of the free protein, and the fraction of activity lost correlates well with the decrease in alpha-helix content. These results indicate that the size of the nanoparticle, perhaps because of the contributions of surface curvature, influences adsorbed protein structure and function.
TL;DR: Au catalysts have been used for deodorizers in rest rooms in Japan and will find growing applications in indoor air quality control, pollutant emission control, production of hydrogen energy carrier, and innovations in chemical processes as discussed by the authors.
Abstract: Gold can be deposited as nanoparticles on a variety of support materials by coprecipitation or deposition-precipitation of Au(OH)3, grafting of organo-gold complexes such as dimethyl-Au(III)-acetylacetonate, mixing of colloidal Au particles, and vacuum deposition. Owing to the moderate adsorption of at least one of reactants (for example, CO) on the edges and corners of Au nanoparticles and to the activation of the counter reactant (for example, O2) at the perimeter interface with the supports, supported Au nanoparticle catalysts exhibit unique and practically useful catalytic properties at relatively low temperature below 473K. They have already been commercially used for deodorizers in rest rooms in Japan and will find growing applications in indoor air quality control, pollutant emission control, production of hydrogen energy carrier, and innovations in chemical processes. Cluster science of Au may also open an exciting area of research showing some magic numbers for dramatic changes in reactivity.
TL;DR: The preparation of a hierarchically structured mesoporous material from nanoparticles of CeO2 of strictly uniform size is reported, which possesses large pore volumes, high surface areas, and marked thermal stability, allowing it to be easily doped after synthesis whilst maintaining textural and mechanical integrity.
Abstract: Many properties provided by supramolecular chemistry, nanotechnology and catalysis only appear in solids exhibiting large surface areas and regular porosity at the nanometre scale In nanometre-sized particles, the ratio of the number of atoms in the surface to the number in the bulk is much larger than for micrometre-sized materials, and this can lead to novel properties Here we report the preparation of a hierarchically structured mesoporous material from nanoparticles of CeO(2) of strictly uniform size The synthesis involves self-assembly of these 5-nm CeO(2) pre-treated nanoparticles in the presence of a structure directing agent (poly(alkylene oxide) block polymer) The walls of this hexagonal structured CeO(2) material are formed from the primary nanoparticles The material possesses large pore volumes, high surface areas, and marked thermal stability, allowing it to be easily doped after synthesis whilst maintaining textural and mechanical integrity It also exhibits a photovoltaic response, which is directly derived from the nanometric particle size-normal CeO(2) does not show this response We have constructed operational organic-dye-free solar cells using nanometric ceria particles (in both mesostructured or amorphous forms) as the active component, and find efficiencies that depend on the illuminating power
TL;DR: Heterodimers of CdS and FePt with sizes of approximately 7 nm exhibit both superparamagnetism and fluorescence, indicating that the discrete properties of the individual parts of the dimers are preserved.
Abstract: Sequential addition of sulfur and Cd(acac)2 into the colloid solution of FePt nanoparticles (∼2.5 nm) under a reductive environment generates heterodimers of CdS and FePt with sizes of ∼7 nm. The heterodimers exhibit both superparamagnetism and fluorescence, indicating that the discrete properties of the individual parts of the dimers are preserved. This simple methodology may lead to the production of large quantities of various heterostructures with tailored properties on the nanoscale.
TL;DR: In this article, metal, semiconductor and magnetic particles act as functional units for electroanalytical applications, such as roughening of the conductive sensing interface, catalytic properties of the nanoparticles permiting their enlargement with metals and the amplified electrochemical detection of the metal deposits and the conductivity properties of nanoparticles at nanoscale dimensions.
Abstract: Metal, semiconductor and magnetic particles act as functional units for electroanalytical applications. Metal nanoparticles provide three important functions for electroanalysis. These include the roughening of the conductive sensing interface, the catalytic properties of the nanoparticles permiting their enlargement with metals and the amplified electrochemical detection of the metal deposits and the conductivity properties of nanoparticles at nanoscale dimensions that allow the electrical contact of redox-centers in proteins with electrode surfaces. Also, metal and semiconductor nanoparticles provide versatile labels for amplified electroanalysis. Dissolution of the nanoparticle labels and the electrochemical collection of the dissolved ions on the electrode followed by the stripping-off of the deposited metals represents a general electroanalytical procedure. These unique functions of nanoparticles were employed for developing electrochemical gas sensors, electrochemical sensors based on molecular- or polymer-functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme-based electrodes, immunosensors and DNA sensors. Semiconductor nanoparticles enable the photoelectrochemical detection of analytes. Several studies have revealed the photocurrent generation by enzyme-mediated processes and as a result of DNA hybridization. Magnetic particles act as functional components for the separation of biorecognition complexes and for the amplified electrochemical sensing of DNA or antigen/antibody complexes. Also, electrocatalytic and bioelectrocatalytic processes at electrode surfaces are switched by means of functionalized magnetic particles and in the presence of an external magnet.
TL;DR: In this paper, a stable colloidal suspension of magnetic nanoparticles is challenging owing to both van der Waals forces and magnetic dipolar interactions, which is why it is essential to coat magnetic particles with magnetic coatings.
Abstract: Stable colloidal suspension of magnetic nanoparticles is challenging owing to both van der Waals forces and magnetic dipolar interactions. Thus, it is essential to coat magnetic nanoparticles with ...
TL;DR: Based on protein folding considerations, a pentapeptide ligand, CALNN, which converts citrate-stabilized gold nanoparticles into extremely stable, water-solublegold nanoparticles with some chemical properties analogous to those of proteins, has been designed.
Abstract: Based on protein folding considerations, a pentapeptide ligand, CALNN, which converts citrate-stabilized gold nanoparticles into extremely stable, water-soluble gold nanoparticles with some chemical properties analogous to those of proteins, has been designed. These peptide-capped gold nanoparticles can be freeze-dried and stored as powders that can be subsequently redissolved to yield stable aqueous dispersions. Filtration, size-exclusion chromatography, ion-exchange chromatography, electrophoresis, and centrifugation can be applied to these particles. The effect of 58 different peptide sequences on the electrolyte-induced aggregation of the nanoparticles was studied. The stabilities conferred by these peptide ligands depended on their length, hydrophobicity, and charge and in some cases resulted in further improved stability compared with CALNN, yielding detailed design criteria for peptide capping ligands. A simple strategy for the introduction of recognition groups is proposed and demonstrated with bi...
TL;DR: The catalytic enlargement of aptamer-functionalized Au nanoparticles amplifies the optical detection ofaptamer-thrombin complexes in solution and on surfaces.
Abstract: The catalytic enlargement of aptamer-functionalized Au nanoparticles amplifies the optical detection of aptamer−thrombin complexes in solution and on surfaces.
TL;DR: The results illustrated the formation of gold and silver nanoparticles inside the nanoscopic polysaccharide templates as well as the morphology and size distribution of prepared gold andSilver nanoparticles varied with the concentration of both thepolysaccharides and the precursor metal salts.