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Nanopartz - The Gold Nanoparticle for Nanotechnology
Nanopartz - The Gold Nanoparticle for Nanotechnology

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New Publication using Nanopartz In Vivo Gold Nanoparticles

Pradeep Kumar et al. from the Emory University School of Medicine published "Adiponectin Agonist ADP355 Attenuates CCl4-Induced Liver Fibrosis in Mice" in PLOS One DOI: 10.1371/journal.pone.0110405 (2014). (http://scholar.google.com/scholar_url?hl=en&q=http://dx.plos.org/10.1371/journal.pone.0110405&sa=X&scisig=AAGBfm1MfrE5gE5lJdTNJ1MJ51sl92AwyA&oi=scholaralrt); using Nanopartz In Vivo Gold Nanoparticles (http://www.nanopartz.com/invivo_gold_nanoparticles.asp).

Abstract: 
Liver fibrosis is a growing global health problem characterized by excess deposition of fibrillar collagen, and activation of hepatic stellate cells (HSCs). Adiponectin is known to possess anti-fibrotic properties; however a high physiological concentration and multiple forms circulating in blood prohibit clinical use. Recently, an adiponectin-like small synthetic peptide agonist (ADP355: H-DAsn-Ile-Pro-Nva-Leu-Tyr-DSer-Phe-Ala-​DSer-NH2)was synthesized for the treatment of murine breast cancer. The present study was designed to evaluate the efficacy of ADP355 as an anti-fibrotic agent in the in vivo carbon tetrachloride (CCl4)-induced liver fibrosis model. Liver fibrosis was induced in eight-week old male C57BL/6J mice by CCl4-gavage every other day for four weeks before injection of a nanoparticle-conjugated with ADP355 (nano-ADP355). Control gold nanoparticles and nano-ADP355 were administered by intraperitoneal injection for two weeks along with CCl4-gavage. All mice were sacrificed after 6 weeks, and serum and liver tissue were collected for biochemical, histopathologic and molecular analyses. Biochemical studies suggested ADP355 treatment attenuates liver fibrosis, determined by reduction of serum aspartate aminotransferase (AST), alanine aminotransferase ALT) and hydroxyproline. Histopathology revealed chronic CCl4-treatment results in significant fibrosis, while ADP355 treatment induced significantly reversed fibrosis. Key markers for fibrogenesis–α-smooth muscle actin (α-SMA), transforming growth factor-beta1 (TGF-β1), connective tissue growth factor (CTGF), and the tissue inhibitor of metalloproteinase I (TIMP1) were also markedly attenuated. Conversely, liver lysates from ADP355 treated mice increased phosphorylation of both endothelial nitric oxide synthase (eNOS) and AMPK while AKT phosphorylation was diminished. These findings suggest ADP355 is a potent anti-fibrotic agent that can be an effective intervention against liver fibrosis.

Figure 1. Histological analysis of CCl4-induced chronic liver injury.
A) Representative H&E stained liver section are shown. B) Representative Sirius Red staining liver sections obtained from control (saline group) revealed normal lobular structure while in CCl4-gavaged mice liver sections reveal extensive collagen deposition and bridging fibrosis. The degree of collagen deposition was significantly decreased in CCl4–ADN treated mice (N = 5 mice/cohort).

Figure 2. Effect of ADP355 on CCl4-induced liver fibrosis in mice.
A) Representative immunohistochemical (α-SMA) stained liver sections obtained for various treatments outlined (left panel); antibody control were presented in right panel. The original magnification was 4X. B) Representative Western blot analysis and densitometry for α-SMA liver lysates obtained from saline, CCl4, CCl4–CTN and CCl4–ADN treated mice. C) Hepatic α-SMA mRNA expression was assessed by qRT-PCR compared to housekeeping gene 18 s. *p<0.05 (N = 5 mice/cohort).
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2015-01-28
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New Publication using Nanopartz Gold Nanorods

Yunfei Zhao et al. from the Department of Electrical and Computer Engineering, Iowa State University published "Enhanced photoacoustic detection using photonic crystal substrate" in APPLIED PHYSICS LETTERS 104, 161110 (2014). (http://scholar.google.com/scholar_url?hl=en&q=http://lib.dr.iastate.edu/cgi/viewcontent.cgi%3Farticle%3D5079%26context%3Detd&sa=X&scisig=AAGBfm2KYeQtJl4LImaiA2uLmZ1CeV_RjQ&oi=scholaralrt); using Gold Nanorods Nanopartz (http://www.nanopartz.com/bare_gold_nanorods.asp).

Abstract: 
This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

Figure 1. Measured PA signal intensity of AuNPs on a PC surface as a function of incident angle between 0 and 6. Inset: SEM image of the PC substrate with Au nanorods dispersed at 1010 NPs/ml.
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New Publication using Nanopartz Self Assembled Monolayer Spherical Gold Nanoparticles

Flavio Zamponi et al. from the Department of Chemistry and Applied Biosciences, ETH Zurich, Switzerland published "Probing the dynamics of plasmon-excited hexanethiol-capped gold nanoparticles by picosecond X-ray absorption spectroscopy" in Phys. Chem. Chem. Phys., 2014,16, 23157-23163. (http://scholar.google.com/scholar_url?hl=en&q=http%3A%2F%2Fpubs.rsc.org%2Fen%2Fcontent%2Farticlehtml%2F2014%2Fcp%2Fc4cp03301a&sa=X&scisig=AAGBfm2zxt0KQ4ZZGdCfb-7vj77FW_VU4g&oi=scholaralrt); using Self Assembled Monolayer Spherical Gold Nanoparticles from Nanopartz (http://www.nanopartz.com/analytical_gold_nanoparticles.asp).

Abstract: 
Picosecond X-ray absorption spectroscopy (XAS) is used to investigate the electronic and structural dynamics initiated by plasmon excitation of 1.8 nm diameter Au nanoparticles (NPs) functionalised with 1-hexanethiol. We show that 100 ps after photoexcitation the transient XAS spectrum is consistent with an 8% expansion of the Au–Au bond length and a large increase in disorder associated with melting of the NPs. Recovery of the ground state occurs with a time constant of [similar]1.8 ns, arising from thermalisation with the environment. Simulations reveal that the transient spectrum exhibits no signature of charge separation at 100 ps and allows us to estimate an upper limit for the quantum yield (QY) of this process to be <0.1.

Figure 1. Upper panel: the UV-vis absorption spectrum of the hexanethiol functionalised Au NPs. The cuvette thickness was 1 mm. The SPR of the gold nanoparticles is clearly visible as a peak in the range between 500 and 700 nm. Lower panel: the corresponding TEM image with a resolution bar of 25 nm.
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New Publication using Nanopartz Gold Nanorods

Cristina Sánchez López de Pablo et al. from the Centre for Biomedical Technology (CTB), Universidad Politécnica de Madrid
(UPM) published "A method to obtain the thermal parameters and
the photothermal transduction efficiency in an
optical hyperthermia device based on laser
irradiation of gold nanoparticles" in Nanoscale Research Letters 2014, 9:441 (http://scholar.google.com/scholar_url?hl=en&q=http%3A%2F%2Fwww.nanoscalereslett.com%2Fcontent%2Fpdf%2F1556-276X-9-441.pdf&sa=X&scisig=AAGBfm3_mC6OOOvrKNCtkug_9_x_MJwUyA&oi=scholaralrt); using Gold Nanorods from Nanopartz (http://www.nanopartz.com/bare_gold_nanorods.asp).

Abstract: 
Optical hyperthermia systems based on the laser irradiation of gold nanorods seem to be a promising tool in the
development of therapies against cancer. After a proof of concept in which the authors demonstrated the efficiency of
this kind of systems, a modeling process based on an equivalent thermal-electric circuit has been carried out to determine
the thermal parameters of the system and an energy balance obtained from the time-dependent heating and cooling
temperature curves of the irradiated samples in order to obtain the photothermal transduction efficiency. By knowing this
parameter, it is possible to increase the effectiveness of the treatments, thanks to the possibility of predicting the response
of the device depending on the working configuration. As an example, the thermal behavior of two different kinds of
nanoparticles is compared. The results show that, under identical conditions, the use of PEGylated gold nanorods allows
for a more efficient heating compared with bare nanorods, and therefore, it results in a more effective therapy.

Figure 1. Temperature curves of heating, stabilization, and
cooling (average values). Obtained for the irradiated samples of
B-GNRs, PEG-GNRs, and deionized water (500 μl,
Aλ = 1, PLASER = 2.0 W).
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New Publication using Nanopartz Functionalized Gold Nanorods

Quan et al. from the Rowland Institute at Harvard University published "Nanoscale Label-free Bioprobes to Detect Intracellular Proteins in Single Living Cells" in Scientific Reports 4, Article number: 6179 doi:10.1038/srep06179; using Functionalized Gold Nanorods from Nanopartz (http://www.nanopartz.com/invitro_gold_nanoparticles.asp).

Abstract: 
Label-free technology is ideal for in vivo and in situ detection in primary cells, tissue, or living systems. To date, intracellular action potential has been measured with three-dimensional nanowire field-effect transistors, intracellular pH has been measured with nanofibers, and cellular endoscopy has been illustrated with carbon nanotubes, nanowires, and nanobeams. Vo-Dinh et. al. further demonstrated the detection of enzymatic fluorescent intracellular proteins by integrating immunoassay with nanofibers, However, label-free tracking of protein concentrations in live cells repeatedly over time has yet to be developed. Here we describe a localized surface plasmon resonance (LSPR) fiber tip probe (FTP) system and demonstrate label-free detection of intracellular p53 tumor suppressor protein, which has been widely regarded as a key target for cancer therapy. We demonstrate our technology by detecting the concentration of p53 in single HeLa cells in response to ultraviolet radiation and treatment with neocarzinostatin (NCS). Our method is widely applicable to other intracellular proteins, as well as having the potential to determine when, where, and under what conditions specific proteins are created and disintegrated.

The FTP is a tapered optical fiber that has a sub-5 micrometer length and sub-100 nanometer diameter tip (Fig. 1a and b). A single gold nanorod (Nanopartz Inc.) was attached to the end of the tip, the surface of which was functionalized with antibodies specific to the target analyte proteins. The collective oscillation of the conductive electrons in the gold nanorod couples strongly to light and generates a resonant scattering signal (LSPR). The light, strongly localized on the surface of the gold nanorod, is sensitive to small perturbations of its optical mode near its surface. Therefore, by monitoring the resonance shift of the LSPR, one can quantify the binding of analyte proteins to the sensor surface. Due to the nanoscale tip size, the FTP entails minimum invasiveness when inserted into the cell membrane.

Figure 1. (a), Scanning Electron Microscope (SEM) image of a FTP. The optical fiber is gradually tapered from 125 um to sub-100 nm. (b), Enlarged SEM image of the end of a FTP showing a single nanorod immobilized on the FTP. (c), Optical image of the LSPR FTP with excitation light source off (left) and on (right) in air. A red dot (right) corresponds to the LSPR of a gold nanorod. In this experiment, white-light from Halogen source was coupled into the fiber and used to excite the gold nanorod at the fiber tip. (d), Image from the spectrometer CCD at the zeroth order grating (left) and a LSPR spectrum at the first order grating (right). This FTP was immersed in 10 mM phosphate buffered saline (PBS).

Figure 2. (a), Schematic setup for in-vitro characterization of the LSPR FTP. The FTP sensor was assembled into a home-made PDMS channel. The LSPR signal excited through the fiber was collected via an inverted microscope and analyzed by a spectrometer. (b), Normalized LSPR signal in various glycerol/water concentrations. Inset shows the zoomed-in view of LSPR peaks (c), Real-time monitoring of the LSPR when different concentrations of solutions are injected in the channel. The resonance wavelength is obtained by fitting LSPR signals to the Lorentzian equation. (d), Dependence of the LSPR position on the refractive indices of the solvents. The error bar is from the measurements of five different nanorods. A bulk index sensitivity of 187 ± 25 nm/RIU is obtained from linear fit.
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2015-01-07
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New Publication using Nanopartz Functionalized Spherical Gold Nanoparticles for cell uptake

Tiwari et al. from the Center for NanoBiotechnology Research and Department of Biological Sciences, Alabama State University published "Enhanced intracellular translocation and biodistribution of gold nanoparticles functionalized with a cell-penetrating peptide (VG-21) from vesicular stomatitis virus" in Biomaterials Volume 35, Issue 35, November 2014, Pages 9484–9494,(http://scholar.google.com/scholar_url?hl=en&q=http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0142961214008412&sa=X&scisig=AAGBfm1UcYifjQyzivEBGn6UoPT8wRaFFw&oi=scholaralrt) using cell uptake peptide Functionalized Spherical Gold Nanoparticles from Nanopartz (http://www.nanopartz.com/invitro_gold_nanoparticles.asp).

Abstract: 
Reduced toxicity and ease of modification make gold nanoparticles (GNPs) suitable for targeted delivery, bioimaging and theranostics by conjugating cell-penetrating peptides (CPPs). This study presents the biodistribution and enhanced intracellular uptake of GNPs functionalized with VG-21, a CPP derived from vesicular stomatitis virus glycoprotein (G). Cell penetrating efficiency of VG-21 was demonstrated using CellPPD web server, conjugated to GNPs and were characterized using, UV-visible and FTIR spectroscopy, transmission electron microscopy, dynamic light scattering and zeta potential. Uptake of VG-21 functionalized GNPs (fGNPs) was tested in eukaryotic cell lines, HEp-2, HeLa, Vero and Cos-7, using flow cytometry, fluorescence and transmission electron microscopy (TEM), and inductively coupled plasmon optical emission spectroscopy (ICP-OES). The effects of nanoparticles on stress and toxicity related genes were studied in HEp-2 cells. Cytokine response to fGNPs was studied in vitro and in vivo. Biodistribution of nanoparticles was studied in BALB/c mice using TEM and ICP-OES. VG-21, GNPs and fGNPs had little to no effect on cell viability. Upon exposure to fGNPs, HEp-2 cells revealed minimal down regulation of stress response genes. fGNPs displayed higher uptake than GNPs in all cell lines with highest internalization by HEp-2, HeLa and Cos-7 cells, in endocytotic vesicles and nuclei. Cytokine ELISA showed that mouse J774 cells exposed to fGNPs produced less IL-6 than did GNP-treated macrophage cells, whereas TNF-α levels were low in both treatment groups. Biodistribution studies in BALB/c mice revealed higher accumulation of fGNPs than GNPs in the liver and spleen. Histopathological analyses showed that fGNP-treated mice accumulated 35 ng/mg tissue and 20 ng/mg tissue gold in spleen and liver respectively, without any adverse effects. Likewise, serum cytokines were low in both GNP- and fGNP-treated mice. Thus, VG-21-conjugated GNPs have enhanced cellular internalization and are suitable for various biomedical applications as nano-conjugates.

Figure 1. Characterization of GNPs and fGNPs. UV–Vis spectra of GNPs and fGNPs (A), FTIR spectra of GNP and fGNPs with additional peaks at 1365 cm−1 and 1216.4 cm−1 appearing for fGNPs (B), DLS characterization for GNPs before and after functionalization (C), TEM images of GNPs and fGNPs (D), Cell viability assay of VG-21 (E), GNPs (F), and fGNPs (G). For VG-21 treatment cell viability for HeLa and Cos-7 cells was82% and 88% whereas for HEp-2 cells showed 74% viability as compared to Vero cells with no cytotoxicity (100% viability). GNPs and fGNPs at 1 nm showed 100% viability to Vero, HeLa and Cos-7 cells compared with HEp-2 cells exhibiting 75% and 73% viability for GNPs and fGNPs respectively.

Figure 2. Cellular uptake of GNPs and fGNPs by HEp-2 (A), HeLa (B), Vero (C) and Cos-7 (D) cells. Each panel represents untreated cells, GNP and fGNP treated cells; N-Nucleus, CY-Cytoplasm. Insets are magnified below each image highlighted with respective colored box (Black for untreated cells, blue for GNP and red for fGNPs).
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2015-01-06
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New Publication using Nanopartz Gold Nanorods

Hong et al. from the Department of Chemistry and Chemical Biology, Harvard University published "Nanoscale Label-free Bioprobes to Detect Intracellular Proteins in Single Living Cells" in Scientific Reports 4, Article number: 6179 doi:10.1038/srep06179, (http://scholar.google.com/scholar_url?hl=en&q=http://proceedings.spiedigitallibrary.org/proceeding.aspx%3Farticleid%3D1901281&sa=X&scisig=AAGBfm0QN2e8tIDQQovULdPlWXl9Awyfyw&oi=scholaralrt) using Gold Nanorods from Nanopartz (http://www.nanopartz.com/bare_gold_nanorods.asp).

Abstract: 
Fluorescent labeling techniques have been widely used in live cell studies; however, the labeling processes can be laborious and challenging for use in non-transfectable cells, and labels can interfere with protein functions. While label-free biosensors have been realized by nanofabrication, a method to track intracellular protein dynamics in real-time, in situ and in living cells has not been found. Here we present the first demonstration of label-free detection of intracellular p53 protein dynamics through a nanoscale surface plasmon-polariton fiber-tip-probe (FTP).

Figure 1. (a), Scanning Electron Microscope (SEM) image of a FTP. The optical fiber is gradually tapered from 125 um to sub-100 nm. (b), Enlarged SEM image of the end of a FTP showing a single nanorod immobilized on the FTP. (c), Optical image of the LSPR FTP with excitation light source off (left) and on (right) in air. A red dot (right) corresponds to the LSPR of a gold nanorod. In this experiment, white-light from Halogen source was coupled into the fiber and used to excite the gold nanorod at the fiber tip. (d), Image from the spectrometer CCD at the zeroth order grating (left) and a LSPR spectrum at the first order grating (right). This FTP was immersed in 10 mM phosphate buffered saline (PBS).

Figure 2. (a), Schematic set-up of the FTP system. The probe, consisting of a nanorod immobilized on the sub-100 nm tapered tip of an optical fiber, is inserted into a single living cell at designated positions using a three-axis micromanipulator. (b), Sequence of EMCCD images of a FTP penetrating a single HeLa cell, viewed from below. The FTP was first positioned outside the cell with its tip lying slightly flat against the petri dish substrate. It is then punctured into the side of the cell. Without background illumination, we could clearly see the LSPR signal from the nanorod glowing inside the cell. (c), p53 dynamics in the intact, UV exposed and NCS treated HeLa cells. The p53 showed sustained concentration increase under UV, and pulsed oscillation under NCS. (d), Phase-contrast and fluorescent image of cells that have been punctured by FTP. A cell in the green circle fluoresced in green after treatment with calcein viability dye and thus was alive after a series of measurement (8 hours long) with nanosize FTP. The cell showed similar levels of green fluorescence intensity indicating the viability of both poked and intact cells. However, a cell in the white circle was dead after being punctured once by a FTP with 5-micrometer tip in diameter.
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2014-10-16
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New Publication - Nanopartz Accurate Spherical Gold Nanoparticles

Slaughter et al. from the Department of Chemistry, Rice University published "Plasmonic polymers unraveled through single particle spectroscopy" in Nanoscale, 2014, 6, 11451-11461, DOI: 10.1039/C4NR02839B, (http://scholar.google.com/scholar_url?hl=en&q=http://pubs.rsc.org/en/content/articlehtml/2014/nr/c4nr02839b&sa=X&scisig=AAGBfm3flF4KBVvzy0EAEcsA0rZ65-Wcpg&oi=scholaralrt) using Accurate Spherical Gold Nanoparticles from Nanopartz (http://www.nanopartz.com/bare_spherical_gold_nanoparticles.asp).

Excerpt:
"... the Au NPs (NanoPartz) had diameters of 25 (±3) nm, 47 (±4), and 94 (±8) nm as determined by transmission electron microscopy." 

Abstract: 
Plasmonic polymers are quasi one-dimensional assemblies of nanoparticles whose optical responses are governed by near-field coupling of localized surface plasmons. Through single particle extinction spectroscopy correlated with electron microscopy, we reveal the effect of the composition of the repeat unit, the chain length, and extent of disorder on the energies, intensities, and line shapes of the collective resonances of individual plasmonic polymers constructed from three different sizes of gold nanoparticles. Our combined experimental and theoretical analysis focuses on the superradiant plasmon mode, which results from the most attractive interactions along the nanoparticle chain and yields the lowest energy resonance in the spectrum. This superradiant mode redshifts with increasing chain length until an infinite chain limit, where additional increases in chain length cause negligible change in the energy of the superradiant mode. We find that, among plasmonic polymers of equal width comprising nanoparticles with different sizes, the onset of the infinite chain limit and its associated energy are dictated by the number of repeat units and not the overall length of the polymer. The intensities and linewidths of the superradiant mode relative to higher energy resonances, however, differ as the size and number of nanoparticles are varied in the plasmonic polymers studied here. These findings provide general guidelines for engineering the energies, intensities, and line shapes of the collective optical response of plasmonic polymers constructed from nanoparticles with sizes ranging from a few tens to one hundred nanometers.

Figure 1. Dependence of the spectral response of plasmonic polymers on the number of repeat units NL. (a) Broadband extinction spectra of chains consisting of 94 nm Au NPs with varying NL and corresponding SEM images. The scale bar represents 200 nm. For NL = 2, the dark-field scattering spectrum is shown as the coupled mode is still within the spectral response of the CCD camera. All spectra were normalized to the peak of the lowest energy mode. (c) Measured and simulated scaling of the peak wavelength of the superradiant mode with chain length expressed as NL.

Figure 2.  Extinction spectra of chains having the same LTot and width and their corresponding SEM images. Extinction spectra for (a) chain 5N1 with d = 94 nm, (b) chain 9N2 with d = 47 nm, and (c) chain 20N4 with d = 25 nm. The inset of (c) shows the scattering spectrum measured for the repeat unit of chain 20N4, the linear tetramer. The scale bars in the SEM images represent 100 nm.

Figure 3. Representative TEM and corresponding histograms of Nanopartz NP sizes for three Au NP samples studied.  The mean diameters are (a) 94 +/- 8nm, (b) 47 +/- 4nm, and (c) 25 +/- 3nm.
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2014-10-15
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New Publication - Nanopartz Gold Nanoburst

Mundoor et al. from the Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder published "Optically and elastically assembled plasmonic nanoantennae for spatially resolved characterization of chemical composition in soft matter systems using surface enhanced spontaneous and stimulated Raman scattering" in the Journal of Applied Physics (2014) (http://scholar.google.com/scholar_url?hl=en&q=http://scitation.aip.org/content/aip/journal/jap/116/6/10.1063/1.4892932&sa=X&scisig=AAGBfm3JLKN2Hbeyz4-JMu89dvDQsVVlbw&oi=scholaralrt) using Gold Nanoburst from Nanopartz. 

Abstract: 
We present a method to locally probe spatially varying chemical composition of soft matter systems by use of optically controlled and elastically self-assembled plasmonic nanoantennae. Disc-shaped metal particles with sharp irregular edges are optically trapped manipulated and assembled into small clusters to provide a strong enhancement of the Raman scattering signal coming from the sample regions around and in-between these particles. As the particles are reassembled and spatially translated by computer-controlled laser tweezers we probe chemical composition as a function of spatial coordinates. This allows us to reliably detect tiny quantities of organic molecules such as capping ligands present on various nanoparticles as well as to probe chemical composition of the interior of liquid crystal defect cores that can be filled with for example polymer chains. The strong electromagnetic field enhancement of optically manipulated nanoparticles' rough surfaces is demonstrated in different forms of spectroscopy and microscopy including enhanced spontaneous Raman scattering coherent anti-Stokes Raman scattering and stimulated Raman scattering imaging modes.

Figure 1. (a) TEM image of the NB particles. (b) and (c) Simulations showing the electromagnetic field enhancement by NB particles in the LC medium with linear polarization (electric field E) of the incident light. The spatial distributions of the electromagnetic field strength at the mid-plane of the NB nanoparticle (XY plane) oriented orthogonally to n 0 were calculated and displayed (b) and (c) for two orthogonal directions of incident linearly polarized light (b) parallel and (c) perpendicular to the particles' center-to-center separation vector. Only the field inside the 5CB is shown for clarity. (d)–(g) Transmission-mode optical micrographs of (d) two, (e) three, (f) four, and (g) five NB particles assembled by use of optical trapping system in LC and held together by the LC elastic forces after the optically guided assembly.
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New Publication - Nanopartz Bare Gold Nanorods

Vasa et al. from the Department of Physics, Indian Institute of Technology Bombay, Mumbai published "Generation of stable colloidal gold nanoparticles by ultrashort laser-induced melting and fragmentation" in Materials Research Express (2014) (http://scholar.google.com/scholar_url?hl=en&q=http://iopscience.iop.org/2053-1591/1/3/035028&sa=X&scisig=AAGBfm2AYptxESivgnSw3HAfosD_uXm-8Q&oi=scholaralrt) using Gold Nanorods from Nanopartz (http://www.nanopartz.com/bare_gold_nanorods.asp). 

Abstract: 
We report on generation of stable colloidal gold nanoparticles by ultrashort laser-induced melting and fragmentation. Irradiation of colloidal gold nanoparticles (of initial size larger than 25 nm) by 56 fs long, near-IR pulses of moderate fluence (1.3–5.3 J cm−2) generates very small (2.5 nm) nanoparticles with a narrow size distribution (±0.5 nm). Systematic measurements show the final size of fragmented nanoparticles to be (i) very weakly dependent on the original size and particle shape as well as of pump laser wavelength (800 nm, 1200 nm and 1350 nm), but (ii) strongly dependent on laser parameters; moreover, fragmentation is effectively controllable by pulse fluence and irradiation time. The fragmented particles appear to be contaminant free and have high crystalline quality. We find that the fragmented particles are stable over a time period of more than three months. Stable, contaminant-free, crystalline colloidal gold nanoparticles of sizes around 3 nm, with very narrow size distribution, have potential utility in diverse nanotechnological applications, ranging from biologically relevant imaging to nanoscopic generators of high-frequency mechanical vibrations in the GHz range.

Figure 1. TEM images of gold nanoparticles used in our experiments.(a) Nanospheres, 50nm diameter (b) nanorods, 25nm dia, 55nm length; and (c) nanorods with 25nm dia,75 nm length.  Each type of nanoparticles is characterized in terms of size-and shape-dependent longitudinal-surface plasmon resonance (SPR) wavelength (d)–(f) Size distributions and standard deviations (σ/σ1(dia)/σ2(length)) deduced from images showing at least 100 particles ,see supporting information. (e),(f)  The nanorods shown in (b),(c)exhibit bimodal size distribution with peaks corresponding to diameter and length.(g) Linear absorption spectra of colloidal gold nanoparticles showing prominent λ peaks along with the transverse-mode plasmon resonance at λ=515nm. The transverse mode resonance position is relatively size and shape independent.
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