Nanocluster Composites Research Articles

Hydrolase and Peroxidase Activity of Gold Nanocluster Composites with Lysozyme and Cross-Linked Lysozyme Crystals

Hydrolase and Peroxidase Activity of Gold Nanocluster Composites with Lysozyme and Cross-Linked Lysozyme Crystals

Ge-Doped Boron Nitride Nanoclusters Functionalized with Amino Acids for Enhanced Binding of Bisphenols A and Z: A Density Functional Theory Study.

This study uses density functional theory to investigate boron nitride nanoclusters functionalized with amino acids for enhanced binding of bisphenols A (BPA) and Z (BPZ) to mimic the estrogen-related receptor gamma. Three categories of nanoclusters were examined: pristine B12N12, and those which were germanium-doped for boron or nitrogen. The study reveals that hydrogen bonding patterns and molecular stability are significantly influenced by the type of functional group and the specific amino acids involved. Ge-doping generally enhances the binding stability and spontaneity of the nanocluster-amino acid-bisphenol complexes, with Glu 275 emerging as the most stable binding site. The analysis of electronic properties such as energy gap, ionization potential, electron affinity, and chemical hardness before and after bisphenol binding indicates a general trend of increased reactivity, particularly in Ge-doped nanoclusters. The findings highlight the potential of these nanocluster composites in applications requiring high reactivity and electron mobility, such as pollutant removal and drug delivery.

Simple synthesis of silver nanocluster composites AgNCs@PE-g-PAA by irradiation method and fluorescence detection of Cr3+

Simple synthesis of silver nanocluster composites AgNCs@PE-g-PAA by irradiation method and fluorescence detection of Cr3+

Gold nanocluster composites: preparation strategies, optical and catalytic properties, and applications

This review systematically summarizes the preparation strategies of gold nanocluster composites, analyzes their properties, and discusses their applications in sensing, bioimaging, and catalysis.

Novel Magnetic Nanocluster@Graphene Oxide Composites for Potential Application in Environmental Adsorption.

Graphene-oxide-wrapped magnetic Fe₃O₄ nanocluster (NC) composites (MC@GO) were prepared and their characteristics were analyzed by multiple characterization methods. Results indicated that the magnetic NCs (~400 nm in size) were composed of numerous Fe₃O₄ monocrystalline particles (30-50 nm in size) and MC@GO had stable structure, high saturation magnetization (61 emu/g) and specific surface area of 112.5 m²/g. The magnetic NCs were integrally and tightly encapsulated in the composites by silk-like GO sheets via electrostatic interaction. The formation mechanism for MC@GO is also discussed in detail herein. Fe3+ was reduced by ethylene glycol in the adopted synthesis scheme, to generate Fe₃O₄ monocrystalline particles that aggregated to form Fe₃O₄ NCs with rough surfaces. Subsequent SiO2 coating and positive charge introduction caused the GO sheets to firmly wrap around the magnetic NCs, resulting in novel GO wrapped magnetic NC composites. The Fe₃O₄ NCs contributed much to structure amelioration and performance enhancement of the final GO composites. The rough surfaces of Fe₃O₄ NCs were beneficial for the SiO2 coating and final wrapping of GO sheets. The good magnetic property and beneficial structure of MC@GO make it an ideal adsorbent, which was demonstrated in the current study using methylene blue (MB) as a model adsorbate. The maximum MB adsorption capacity for MC@GO reached 105.5 mg/g. This is the first study on GO-wrapped Fe₃O₄ NC composites and their potential use for environmental adsorption. Furthermore, this study provides a method for developing GO wrapped magnetic particle composites by tailoring the magnetic precursor.

Fabrication of graphene-magnetite multi-granule nanocluster composites for microwave absorption application

Ferrite multi-granule nanoclusters are fabricated for microwave absorption materials in different sized particles and granules by modified polyol process. Various sizes of ferrite nanoclusters are placed on graphene-based composites and the behavior of their microwave absorbing properties is studied. The absorbing properties are measured using the free-space method with two horn antennas for X-band range (8.2 GHz–12.4 GHz). Relative permittivity and permeability values are calculated in measured frequency domain. The absorption coefficient changes by forming ferrite-graphene composites are presented as well.

Iron Clusters Embedded in Graphene Nanocavities: Heat-Induced Structural Evolution and Catalytic C–C Bond Breaking

Metal nanoclusters can be anchored at defective sites of graphene sheets to strengthen their thermal stability for potential device applications. A previous transmission electron microscopy (TEM) experimental study on the morphology change of an ultrafine iron cluster embedded in a graphene nanocavity suggests that the underlying reaction mechanism is likely due to solid–solid transformation [ Sci. Rep. 2012, 2, 995]. The morphology change of the Fe cluster may also assist the enlargement of the graphene nanocavity. This TEM experiment reminds us that if the anchoring Fe nanocluster within the graphene nanocavity can efficiently catalyze graphene etching at a certain operation temperature, the device application of graphene–metal nanocluster composites would be largely limited. Herein, we have performed ab initio molecular dynamics (AIMD) simulations of a triangular hexagonal close-packed (HCP) Fe53 cluster in contact with either the edge of the graphene nanocavity or graphene nanoribbon to investigate it...

Homologous Gold Nanoparticles and Nanoclusters Composites with Enhanced Surface Raman Scattering and Metal Fluorescence for Cancer Imaging.

A large number of deaths from cancer can be attributed to the lack of effective early-stage diagnostic techniques. Thus, accurate and effective early diagnosis is a major research goal worldwide. With the unique phenomenon of localized surface plasmon resonance (LSPR), plasmonic nanomaterials have attracted considerable attention for applications in surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF). Both SERS and MEF are ultra-sensitive methods for the detection and identification of early tumor at molecular level. To combine the merits of the fast and accurate imaging of MEF and the stable and clear imaging of SERS, we propose a novel dual functional imaging nanoprobe based on gold nanoparticles and gold nanocluster composites (denoted AuNPC-RGD). The gold nanoparticles are used as LSPR substrates to realized enhancement of Raman or fluorescence signal, while the gold nanoclusters serve as a fluorophore for MEF imaging, and exhibit better biocompatibility and stability. Furthermore, target molecule of cyclic Arg-Gly-Asp (cRGD) is incorporated into the composite to improve delivery efficiency, selectivity and imaging accuracy. These integrated properties endow AuNPC-RGD composites with outstanding biocompatibility and excellent imaging abilities, which could be used to achieve accurate and effective diagnosis for early cancer.

Ni nanocluster composites for enhanced impact resistance of multilayered arc-PVD ceramic coatings

Optimally, hard protective coatings should effectively absorb impact energy to reduce the likelihood of failure events. In this work, an arc-PVD approach was utilised for the deposition of thick ceramic multilayer AlCrTiN/CrN-based coatings containing a distribution of metallic nickel inclusions throughout sequential CrN-based interlayers. The aim of such coatings is to provide resistance to impact loading in intensive application environments, such as drop forging of steel and turbine blades exposed to abrasive particles. The structure and micro-structural development of the ceramic was first investigated using transmission electron microscopy, where discrete Ni inclusions were observed as both larger discs (d ~ 600–800nm, h ~ 200nm) and smaller (d ~ 50nm) nanoclusters. Confirmation of the distribution and nanocluster chemistry was achieved using atom probe tomography. For mono-block coatings, XRD data showed drastically reduced internal stresses as a result of the Ni inclusions, enabling the creation of thicker protective coatings which minimise substrate stress concentration upon loading. Nickel inclusion additionally provides a softening of the containing hard ceramic layer, allowing for tuning of mechanical properties. Supporting this idea, in situ micropillar compression measurements of the multi-layered coating systems showed that Ni clusters hindered crack propagation through the coating during failure, while the fracture strength could be increased by incorporating both Ti and Ni in the softer CrN-based layer. High-load impact testing highlighted the influence of Ni ‘shock absorbers’ in reducing circumferential cracking, which was further confirmed by an industrial die forging test that demonstrated a 15–22% life-time increase compared to a much thicker hard-chrome plated reference. The results of this study demonstrate an exciting way to produce Ni nanocluster integrated hard ceramic multi-layers using arc-PVD in a single processing step. Such tuneable thin-film composite systems show great promise in minimising damage from impact loading, even under severe working conditions such as in hot forging.

Hyperbranched polyamine assisted synthesis of dual-luminescent gold composite with pH responsive character

We present a facile one-pot, two-step strategy to prepare water-soluble dual-luminescent gold nanodots (AuNDs) and few-atom gold nanocluster composites simultaneously by using high molecular weight and hyperbranched polyethyleneimine (hPEI) as the protection ligand and stabilization agent. It was found that in the presence of hPEI, Au(III) ion can be reduced to a metastable Au(I) charge state in aqueous solution. Subsequently, adding 11-mercaptoundonioic acid induces parallel pathways of restricted Au(I) assembly, leading to the formation of both red-emitting hPEI stabilized AuNDs and blue-emitting hPEI-protected Au8 nanoclusters. The intensity ratio between the blue and red species shows a sensitive and reversible response to the solution pH in the range 2–11 and the dual-luminescent gold composites can act as an effective and reversible pH indicator.

Selective‐area growth and magnetic reversals of ferromagnetic nanoclusters on semiconducting substrate for magnetic logic applications

The use of selective‐area metal‐organic vapor phase epitaxy, which is our bottom‐up formation approach, to fabricate MnAs nanocluster composite arrays in which two nanoclusters are formed in close proximity at an angle of 120° and with a spatial gap of around 20 nm on GaAs (111)B substrates is reported in this paper. The magnetic reversals of the nanoclusters in the composite arrays are observed depending on the strengths and directions of the applied external magnetic fields at room temperature. The applied external magnetic fields for the magnetic reversals in one of the nanoclusters in the composites are possibly from 750 to 1000 Gauss (G). The characterization results obtained using magnetic force microscopy show that the magnetic reversals in the nanoclusters are independently controlled in nanocluster composites. Finally, we discuss the designing of the nanocluster size, shape, and arrangement to control the magnetization directions in the nanoclusters in the composites for possible application to magnetic logic operations based on the results of the magnetic reversals in the nanoclusters.

A sensitive electrochemical nitrate sensor based on polypyrrole coated palladium nanoclusters

This study examines the synthesis and characterization of polypyrrole coated palladium nanocluster (Pd NCs-PPy) composites and their application in nitrate detection at pH=7.0. The synthesis was performed via the direct reduction of an aqueous solution of Pd (CH3COO)2 in the presence of pyrrole monomers in NaOH. X-ray diffraction and field emission scanning electron microscopy observations showed that the Pd cations were completely reduced to Pd with the formation of Pd NCs-PPy cluster morphology, respectively. Electrochemical properties of the Pd NCs-PPy electrode were studied by differential pulse voltammetry (DPV), cyclic voltammetry and electrochemical impedance spectroscopy. From the DPV results, the estimated limit of detection, limit of quantification (S/N=3) for the two linear segments (lower and higher concentration of nitrate) are 0.7444, 2.4815 and 0.4535, 1.5117μM, respectively. The sensitivity of these two linear segments is 0.124 and 0.204μAμM−1cm−2, respectively. Results from the reproducibility experiments show that the Pd NCs-PPy is feasible for the quantitative determination of certain concentration ranges of nitrate.

Enhanced microwave absorption properties of N-doped graphene@PANI nanorod arrays hierarchical structures modified by Fe3O4 nanoclusters

The hierarchical structures of N-doped graphene (NG)@PANI nanorod arrays modified with Fe3O4 nanocluster have been fabricated by a hydrothermal reaction. The as-prepared (NG@PANI@Fe3O4) composites were characterized by XRD, Raman and FTIR spectra, VSM, XPS spectroscopy, TEM and FESEM. The results reveal that the surfaces of NG@PANI nanorod arrays are randomly covered by Fe3O4 nanocluster with an average size of about 40nm. With Fe3O4 nanoclusters coated on the surfaces of NG@PANI nanorod arrays, the composites exhibit superparamagnetic characteristics at room temperature. Moreover, the microwave absorption properties of both NG@PANI nanorod arrays and NG@PANI@Fe3O4 nanocluster were investigated between 2 and 18GHz microwave frequency bands. The electromagnetic data demonstrates that NG@PANI@Fe3O4 nanocluster composites exhibit significantly enhanced microwave absorption properties compared with graphene@Fe3O4, which probably originates from improved level of impedance matching and interfacial polarization.

Graphene-Multiwall Carbon Nanotube-Gold Nanocluster Composites Modified Electrode for the Simultaneous Determination of Ascorbic Acid, Dopamine, and Uric Acid

In this paper, graphene-multiwall carbon nanotube-gold nanocluster (GP-MWCNT-AuNC) composites were synthesized and used as modifier to fabricate a sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrochemical behavior of the sensor was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The combination of GP, MWCNTs, and AuNCs endowed the electrode with a large surface area, good catalytic activity, and high selectivity and sensitivity. The linear response range for simultaneous detection of AA, DA, and UA at the sensor were 120-1,701, 2-213, and 0.7-88.3 μM, correspondingly, and the detection limits were 40, 0.67, and 0.23 μM (S/N=3), respectively. The proposed method offers a promise for simple, rapid, selective, and cost-effective analysis of small biomolecules.

Ferromagnetic MnAs Nanocluster Composites Position-Controlled on GaAs (111)B Substrates toward Lateral Magnetoresistive Devices

The authors report on the ordered planar arrangements of ferromagnetic MnAs/AlGaAs nanocluster (NC) composites grown on partially SiO2-masked GaAs (111)B substrates by selective-area metal–organic vapor phase epitaxy for lateral magnetoresistive device applications. Each of the NCs in the composites has an elongated shape and a different size to control their magnetized directions and coercive forces. By designing and optimizing the initial SiO2-mask openings formed by electron beam lithography on the template wafers, we fabricate elongated NC composites with a spatial gap of 5 to 10 nm between two NCs and an elongated NC connected to a relatively large MnAs NC electrode. Cross-sectional lattice images taken with a transmission electron microscope show that the interfaces between MnAs and AlGaAs layers of the NCs are atomically abrupt. Magnetic force microscopy at room temperature reveals that the magnetized directions in each of the NC composites are rotated by around 180° when the applied direction of the external magnetic fields is rotated in the opposite direction.

Computational simulations for ensembles of luminescent silicon nanocrystals: Implications for optical gain and stimulated emission

A Monte Carlo model that simulates energy transfer, radiative decay, and non-radiative trapping within densely packed, lognormally distributed ensembles of silicon nanocrystals (Si-ncs) is developed. The results illustrate the potential of the computational approach toward better understanding these complex materials, and imply that certain key parameters should be met in order for the ultimate application of silicon nanocluster composites in light emitting devices.

Effect of ingredient on optical properties of Ag/Cu metal alloy nanoclusters in silica glass

Formation of Ag-rich and Cu-rich Ag–Cu alloy nanoclusters in silica by Ag/Cu ion sequential implantation has been studied. The formation of alloy nanocluster has been evidenced by optical absorption spectra and transmission electron microscopy (TEM). Fast nonlinear refractive index and nonlinear absorption coefficient were measured at 790 nm of wavelength for Ag–Cu alloy nanocluster composites by the Z-scan technique. With different Ag/Cu ratio, linear absorption and nonlinear absorption are different in near infrared (NIR) region. It is suggested that by changing the ingredient percentage of metals in alloy, different optical nonlinearities could be selectively obtained.

Synthesis of gold nano-wire and nano-dumbbell shaped colloids and AuC60 nano-clusters

A technique for the fabrication of colloidal gold nano-wire and nano-dumbbell shaped particles using rod shaped viruses as templates is described. The gold (Au) encapsulation process was accomplished by the precipitation of gold chloride from aqueous solutions. When this process was conducted in the presence of C60, small nano-cluster composites of AuC60 formed.

Effect of ingredient concentration on structure and optical properties of Cu nanoclusters

Metal nanocluster composite glass prepared by Cu ion implantation have been studied. The formation of nanocluster has been evidenced by optical absorption spectra and transmission electron microscopy (TEM). Fast nonlinear optical refraction and nonlinear optical absorption coefficients were measured at 790 nm of wavelength for Cu nanocluster composites by the Z-scan technique. With an increase in the implanted dose, nanoshells were formed and the optical nonlinearity shows a significant change from positive to negative values. The reason for the enhancement and sign reversal of the optical nonlinearities of Cu nanocluster in silica are discussed. It is suggested that by changing the ingredient percentage of metals in silica, different optical nonlinearities could be selectively obtained.

Effect of thermal treatments on third-order nonlinear optical properties of hollow Cu nanoclusters

Metal nanocluster composites prepared by Cu ion implantation have been studied. The formation of nanoclusters has been evidenced by optical absorption spectra and transmission electron microscopy (TEM). Fast nonlinear optical refraction and nonlinear optical absorption coefficients were measured at 790 nm for Cu nanocluster composites by the Z-scan technique. With the increase of annealing temperature, the size of nanoclusters increased significantly, and optical nonlinearities was enhanced. It is suggested that by changing the ingredient configuration of metal nanoclusters in silica, different optical nonlinear properties could be selectively obtained.