Adding Gold Nanoparticles Research Articles

Effect of green gold nanoparticles synthesized with plant on the flexural strength of heat-polymerized acrylic resin.

The aim of this study was to investigate the effect of gold nanoparticle on the flexural strength of polymethyl methacrylate (PMMA). PMMA specimens (65 mm × 10 mm × 3.3 mm) containing different sizes (45 nm, 55 nm, and 65 nm) and concentrations (0.05% and 0.2%) of gold nanoparticles were prepared, along with a control group containing no added nanoparticles. Flexural strength of all specimens was measured, and one-way ANOVA and Tukey-Kramer post hoc multiple comparisons tests were performed to identify statistical differences between groups. The addition of gold nanoparticles increased the flexural strength of acrylic resin. Significantly greater increases were obtained with lower concentrations (0.05%) when compared to higher concentrations (0.20%). Differences in concentrations of gold nanoparticles added to PMMA have significantly different effects on PMMA flexural strength, whereas differences in sizes of gold nanoparticles added to PMMA do not significantly affect its flexural strength. Accordingly, adding gold nanoparticles to PMMA may enhance the mechanical properties of denture bases used in clinical practice.

A gold nanoparticle coated porcine cholecyst-derived bioscaffold for cardiac tissue engineering

Extracellular matrices of xenogeneic origin have been extensively used for biomedical applications, despite the possibility of heterogeneity in structure. Surface modification of biologically derived biomaterials using nanoparticles is an emerging strategy for improving topographical homogeneity when employing these scaffolds for sophisticated tissue engineering applications. Recently, as a tissue engineering scaffold, cholecyst derived extracellular matrix (C-ECM) has been shown to have several advantages over extracellular matrices derived from other organs such as jejunum and urinary bladder. This study explored the possibility of adding gold nanoparticles, which have a large surface area to volume ratio on C-ECM for achieving homogeneity in surface architecture, a requirement for cardiac tissue engineering. In the current study, gold nanoparticles (AuNPs) were synthesized and functionalised for conjugating with a porcine cholecystic extracellular matrix scaffold. The conjugation of nanoparticles to C-ECM was achieved by 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide/N-hydroxysuccinimide chemistry and further characterized by Fourier transform infrared spectroscopy, environmental scanning electron microscopy, energy dispersive X-ray spectroscopy and thermogravimetric analysis. The physical properties of the modified scaffold were similar to the original C-ECM. Biological properties were evaluated by using H9c2 cells, a cardiomyoblast cell line commonly used for cellular and molecular studies of cardiac cells. The modified scaffold was found to be a suitable substrate for the growth and proliferation of the cardiomyoblasts. Further, the non-cytotoxic nature of the modified scaffold was established by direct contact cytotoxicity testing and live/dead staining. Thus, the modified C-ECM appears to be a potential biomaterial for cardiac tissue engineering.

Properties of lasing in Rhodamine 6G solutions with nanoparticles free of plasmon resonance

The threshold characteristics of lasing in a 20-μm layer of colloidal solution of Rhodamine 6G dye with plasmon-resonance Au nanoparticles and non-plasmon-resonance Pt nanoparticles excited by 532-nm radiation are experimentally studied. The spectral dependence of the scattering and absorption cross sections of gold and platinum nanoparticles are calculated within the Mie theory. It is found experimentally that the addition of nanoparticles to the active medium decreases the lasing thresholds by two orders of magnitude. It is shown that the lasing thresholds are 1.5–2 times lower when adding gold nanoparticles than when adding platinum nanoparticles of the same concentration.

Enhancement of DSSC by Using Gold Nanoparticles

In this research, AuNPs prepared by laser ablation in liquid (PLAL) at 750 mJ energy and 90 pulses. They have been added to N719-dye to form (Au-N719) mixture. TiO2 paste was deposited on FTO substrates and immersion in a mixture dye and AuNPs. DSSC was fabricated and enhancement of the DSSC conversion efficiency was achieved. Scanning electron microscope, X-ray diffraction and UV-Visible spectrophotometer were used to characterize and study the DSSC components. The UV-Vis data show high absorbance of AuNPs+N719 dye compared to N719 dye only; that means the immersion of AuNPs in the N719-dye solution tend to increase the total absorbance of the dye. The XRD pattern of AuNPs has diffraction peaks at 38.2° and 44.4° which can be indexed by (111), (200) plane of Au in the cubic phase. The shape and size distribution shows spherical AuNPs with particle size about (50-60) nm. The relative increase of short circuit current density after the adding gold nanoparticles was about 76%. In the same way the relative increase of open circuit voltage after adding gold nanoparticles was about 6.7%. The total photon-to-current energy conversion efficiency for the standard DSSC is 1.75 while its 2.8 of the enhanced DSSC with gold NPs.The maximum enhancement is about 60 % under illumination (105 mW/cm2, (AM1.5).

Enhanced transparent conducting performance of Bi2Sr2Co2O8 thin films by adding gold nanoparticles

Gold (Au) nanoparticles were introduced into thin films of layered cobaltites to decrease the sheet resistance and improve the transparent conducting performance of the films. c-axis-oriented Bi2Sr2Co2O8 thin films dispersed with Au particles with diameters of about 5–10 nm were obtained by pulsed laser ablation of a Bi2Sr2Co2O8 ceramic target on which a piece of fan-shaped Au foil was attached. The resulting Bi2Sr2Co2O8/Au composite thin films, with the Au concentration of about 1.6 at.%, showed a very low resistivity of about 3.0 mΩ cm at room temperature and a reasonable optical transmittance of about 48 % in the visible range, resulting in a high figure of merit of about 2270 MΩ−1. This value is comparable to those reported for the state-of-the-art p-type transparent conducting oxides and is about 1.7-fold higher than that of the pure Bi2Sr2Co2O8 thin films.

Microchip-based human serum atherogenic lipoprotein profile analysis

Owing to the mounting evidence of serum lipid changes in atherosclerosis, there has been increasing interest in developing new methods for analyzing atherogenic lipoprotein profiles. The separation of lipoprotein and lipoprotein subclasses has been demonstrated using a microchip capillary electrophoresis (CE) system [Chromatographia 74 (2011) 799–805]. In contrast to this previous study, the current report demonstrates that sdLDL peak efficiencies can be improved dramatically by adding gold nanoparticles (AuNPs) to the sample. Moreover, NBD C6-ceramide was identified as a satisfactory dye for specific labeling and quantitation of individual serum lipoproteins. The accuracy of the method was evaluated by comparison with ultracentrifuge separated small, dense, low-density lipoprotein (sdLDL). A high correlation was observed between these two methods for sdLDL cholesterol. Lipid levels were investigated between atherosclerotic patients and healthy controls. The variation of serum atherogenic lipoprotein profiles for atherosclerotic patients pre- and post-treatment was assessed by microchip CE. This method has potential for the rapid and sensitive detection of different lipoprotein classes as well as their subclasses and, therefore, is suitable for routine clinical applications. Microchip-based atherogenic lipoprotein profile assays will greatly improve the analysis of risk factors in atherosclerosis and will provide useful information for monitoring the effect of therapies on atherosclerotic disease.

The effect of added gold nanoparticles on the volume phase transition behavior for PVCL-based microgels

The volume phase transition (VPT) behavior of poly(N-vinylcaprolactam-co-4-vinylpyridine) P(VCL-co-4VP) microgels and their hybrid counterparts containing Au nanoparticles (AuNPs) is explored and compared by FTIR measurements in combination with the perturbation correlation moving window (PCMW) technique and two-dimensional correlation spectroscopy (2Dcos) analysis. It is demonstrated that the incorporation of AuNPs inside the microgels cause a slight dehydration effect on the microgels in the swollen state and an increase of the VPT temperature. Moreover, the interaction between CO and AuNPs can be confirmed by combining the conventional IR and 2Dcos analysis. It is with the help of the additional cross-links between AuNPs and the polymer chains (CO and pyridine groups) in the microgel network and the tendency of AuNPs to aggregate that the hybrid microgels exhibit a much greater dehydration during the VPT, as compared with the nonhybrid ones.

Preparation of gold nanoparticles–agarose gel composite and its application in SERS detection

Agarose gel/gold nanoparticles hybrid was prepared by adding gold nanoparticles to preformed agarose gel. Nanocomposite structures and properties were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV–Vis–NIR absorption spectroscopy. Based on the swelling–contraction characteristics of agarose gel and the adjustable localized surface plasmon resonance (LSPR) of the gold nanoparticles, the nanocomposites were used as surface enhanced Raman scattering (SERS) substrate to detect the Raman signal molecules (NBA, MBA, 1NAT). Results revealed that the porous structure of the agarose gel provided a good carrier for the enrichment of the gold nanoparticles. The gold nanoparticles dynamic hot-spot effect arising from the agarose gel contraction loss of water in the air greatly enhanced the Raman signal. Furthermore, the gel could be cleaned with washing solution and recycling could be achieved for Raman detection.

Photoluminescence decay rate engineering of CdSe quantum dots in ensemble arrays embedded with gold nano-antennae

We discuss experimental results on the ability to significantly tune the photoluminescence decay rates of CdSe quantum dots embedded in an ordered template, using lightly doped small gold nanoparticles (nano-antennae), of relatively low optical efficiency. We observe both enhancement and quenching of photoluminescence intensity of the quantum dots varying monotonically with increasing volume fraction of added gold nanoparticles, with respect to undoped quantum dot arrays. However, the corresponding variation in lifetime of photoluminescence spectra decay shows a hitherto unobserved, non-monotonic variation with gold nanoparticle doping. We also demonstrate that Purcell effect is quite effective for the larger (5 nm) gold nano-antenna leading to more than four times enhanced radiative rate at spectral resonance, for largest doping and about 1.75 times enhancement for off-resonance. Significantly for spectral off-resonance samples, we could simultaneously engineer reduction of non-radiative decay rate along with increase of radiative decay rate. Non-radiative decay dominates the system for the smaller (2 nm) gold nano-antenna setting the limit on how small these plasmonic nano-antennae could be to be effective in engineering significant enhancement in radiative decay rate and, hence, the overall quantum efficiency of quantum dot based hybrid photonic assemblies.

Study of a pre-treatment process for electroless copper plating on ceramics

In this paper, a pre-treatment process for electroless copper plating on the ceramics was explored. Due to the catalytic activity of gold nanoparticles, the traditional three-step coarsening-sensitization-activation pre-treatment process has been optimized to a two-step coarsening-activation process. In our study, the following results were observed: electroless copper coating on the ceramics was formed after activating the substrate by gold nanoparticles; a more flat and compact nano-composite coating was also obtained by adding gold nanoparticles to the plating solutions. The mechanisms of pre-treatment and composite plating with gold nanoparticles were discussed.

Laser Desorption Ionization Mass Spectrometry by Using Surface Plasmon Excitation on Gold Nanoparticle

We show development of a laser desorption/ionization (LDI) method with ultrahigh sensitivity by adding gold nanoparticles with a diameter of several tens of nanometers into a sample solution. In this paper, we succeeded in detection of an ultratrace amount of sample molecules, which is less than several hundred zeptomoles. This result suggest that the charge interaction based on surface plasmon (SP) excitation is very effective for ultrahigh sensitivity in LDI method.

Chemiluminescence from the Decomposition of Peroxymonocarbonate Catalyzed by Gold Nanoparticles

In this work, an online preparation of peroxymonocarbonate was formed innovatively, which offered the reliable intermediate for further investigation. Gold colloids with nanoparticles of different sizes were found to enhance the chemiluminescence (CL) of the peroxymonocarbonate-eosin Y system, and the most intensive CL signals were obtained with 50 +/- 1 nm diameter gold nanoparticles. UV-visible adsorption spectra, fluorescence spectra, transmission electron microscopy images, electron paramagnetic resonance spin-trapping spectra, and mass spectra were obtained in order to study the CL enhancement mechanism. Peroxymonocarbonate, a reactive oxygen species, can be decomposed to singlet oxygen which transfers its energy to eosin Y. The CL can be induced by excited eosin Y. Gold nanoparticles facilitated the radical generation and singlet oxygen molecular formation on the surface of the gold nanoparticles. Thus, the CL emission enhanced greatly by adding gold nanoparticles into the system.

Capillary electrophoresis with gold nanoparticles enhanced electrochemiluminescence for the detection of roxithromycin

Tris(2,2′-bipyridyl) ruthenium(II) (Ru(bpy) 3 2+)–roxithromycin based electrochemiluminescence (ECL) was enhanced greatly by gold nanoparticles 10 nm in diameter. Capillary electrophoresis (CE) was coupled with the resultant ECL system as a detector for roxithromycin. This ECL emission is explained by the coreactant mechanism where roxithromycin behaves as a coreactant to generate strong reducing species and gold nanoparticles act as “floating nanoelectrodes”. The reaction of Ru(bpy) 3 3+ with the generated strong reducing species on the Pt working electrode as well as on “floating nanoelectrodes” releases Ru(bpy) 3 2+*, resulting in enhancement of ECL emission. The selectivity of this detection system towards roxithromycin was examined by CE. Under the optimized conditions, the intensity of ECL emission varies linearly with the concentration of roxithromycin from 24 nM to 0.24 mM. The detection limit is 8.4 nM, while without adding gold nanoparticles it is only 84 nM. The detection of roxithromycin in pharmaceutical and urine samples was also performed by the proposed CE–ECL method.

Study on the nano-composite electroless coating of Ni–P/Au

The nano-composite coating of Ni–P/Au was obtained by adding gold nanoparticles to the Ni–P electroless plating solutions. The scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD) and microsclerometer were used to characterize the compositions, structures, morphologies and hardness of the coatings, respectively. The Ni–P electroless coating contains 11.0 wt.% P while the composite coating of Ni–P/Au contains 9.85 wt.% P and 2.38 wt.% Au. The composite coatings, which contain gold nanoparticles, exhibit better properties of hardness, corrosion resistance and uniformity than the particle-free coatings. The coatings deposited from an electroless bath have the increased hardness after heat treatment due to the transformation of amorphous phase Ni–P to crystalline phase Ni 3P. The composite coating with gold nanoparticles has bigger hardness value than Ni–P coating.

Characterizing Optical Properties of Self-Assembled Gold Nanoparticles for Surface Plasmon Resonance Device Applications

In this study, the optical constants of gold nanoparticles are evaluated for surface plasmon-based sensor applications. Using an effective medium approximation (EMA) and ellipsometry, approaches to monitor the self-assembly of gold nanoparticles are also demonstrated. Spectroscopic ellipsometric parameters measured (tan Ψ, cos Δ) before and after adding gold nanoparticles to a substrate are used to calculate the optical constants of gold nanoparticles. The film thickness is measured by grazing incidence X-ray reflectivity (XRR). The optical constants (refractive index, extinction coefficient) of gold nanoparticles can be obtained from the measured ellipsometric parameters and thickness. We also show that particles density can be well predicted and detected nondestructively by this method.