Shape Of Gold Nanoparticles Research Articles

Green Formation of Nano-Hexagon from Nano-Triangle of Gold Nanoparticles Using Palm Oil Fronds Extracts

A simple method to synthesized nanoparticles was satisfied by reduction of tetrachloroauric acid in the presence of palm oil fronds extracts as capping and reduced agents. The as-synthesized gold nanoparticles structures have a triangular and hexagonal shape that are of tens of nanometre in size. It was realized that good control shape of nano-hexagonal gold nanoparticles were obtained from nano-triangular gold nanoparticles in the absence of any soft template. The production techniques of the gold nanoparticles were examined by using UV-vis spectroscopy, EFTEM and XRD patterns, which showed peaks at (111), (200), (220), (311) and (222), that described the preferential structure of the AuNPs as face-centered cubic crystal

Shape Matters: Gold Nanoparticle Shape Impacts the Biological Activity of siRNA Delivery.

Plasmon-resonant nanoparticles provide unprecedented spatiotemporal control over the release of diverse cargoes into cells. Here we compare the loading, release and internalization efficiencies, and effectiveness of post transcriptional gene silencing of hollow gold nanoshells, hollow gold nanocages, and gold nanorods with plasmons tuned to absorb near-infrared light at 800 nm. The hollow gold nanoshells can be loaded with up to three times more siRNA cargo compared to nanocages and nanorods; however, nanorods exhibit the highest efficiency of release of attached siRNA strands when exposed to pulsed 800 nm laser excitation. In cellular treatments, all particles demonstrated efficient internalization into HeLa cells, but the nanoshells and nanocages display the highest downregulation of GFP expression 72 h after treatment. These results provide novel insights into the relative efficiencies of three structurally distinct types of gold nanoparticles as siRNA carriers and we examine different parameters that may influence their efficacy.

Using Silver Nanoclusters as a New Tool in Nanotechnology: Synthesis and Photocorrosion of Different Shapes of Gold Nanoparticles

Until now, the concept of metal (0) atomic quantum clusters or nanoclusters (NCs) and their increasing role in nanotechnology due to their novel and exceptional properties in important industrial fields (such as catalysis) has not been included at the education level. Here, syntheses of both metal nanoparticles (NPs) and metal nanoclusters (with sizes below ≈1–2 nm) are used for understanding the large differences between both types of nanomaterials. In this experiment we highlight the catalytic and photocatalytic properties of silver NCs, as well as the plasmon band, as the main optical difference between metal NPs and NCs. In the first step of the experiment, the synthesis of different sizes and shapes of AuNPs is carried out and changes in their plasmon band are discussed. In a second step, students conduct the anisotropic growth of AuNPs, catalyzed by silver NCs (Agn, where n is the number of atoms forming the cluster), which do not display a plasmon band. Finally, it is shown that Agn NCs can induce AuNP photocorrosion, which can be avoided by introducing molecules with more negative redox potential (called hole scavengers). Redox properties of Agn NCs are used in this laboratory experiment to discuss with the students several important physicochemical issues, such as absolute and hydrogen redox potential scales, electronic and optical properties of nanomaterials, semiconductor band gap, photogenerated electron–hole pairs (excitons), catalysis and photocatalysis, the role of hole scavengers, or spontaneous process and free energy. This very new area at the bottom of nanotechnology is ideal to make chemistry relevant and engaging for students. It allows them to learn fundamentals by using chemistry that is at the frontier of research, and they are able to do this in an accessible way.

A Water Solvation Shell Can Transform Gold Metastable Nanoparticles in the Fluxional Regime

Solvated gold nanoparticles have been modeled in the fluxional regime by density functional theory including dispersion forces for an extensive set of conventional morphologies. The study of isolated adsorption of one water molecule shows that the most stable adsorption forms are similar (corners and edges) regardless of the nanoparticle shape and size, although the adsorption strength differs significantly (0.15 eV). When a complete and explicit water solvation shell interacts with gold nanoclusters, metastable in vacuum and presenting a predominance of (100) square facets (ino-decahedra Au55 and Au147), these nanoparticles are found unstable and transform into the closest morphologies exhibiting mainly (111) triangular facets and symmetries. The corresponding adsorption strength per water molecule becomes independent of shape and size and is enhanced by the formation of two hydrogen bonds on average. For applications in radiotherapy, this study suggests that the shapes of small gold nanoparticles should be homogenized by interacting with the biological environment.

Impact of gold nanoparticles shape on their cytotoxicity against human osteoblast and osteosarcoma in in vitro model. Evaluation of the safety of use and anti-cancer potential

Due to development of nanotechnology and gold nanoparticles (AuNPs) increasing use in different areas of medicine, especially in oncology, better understanding of their potential cytotoxicity is necessary to protect patients safety. Shape and size of AuNPs is an important modulator of their cytotoxicity. Therefore, we investigated the cytotoxicity of AuNPs rods (≈39 nm length, 18 nm width), AuNPs stars (≈ 215 nm) and AuNPs spheres (≈ 6.3 nm) against human fetal osteoblast (hFOB 1.19), osteosarcoma (143B, MG63) and pancreatic duct cell (hTERT-HPNE) lines by MTT and neutral-red uptake assay. Moreover, influence of AuNPs on level of proapoptotic protein (Bax) and anti-apoptotic protein (Bcl-2) was measured by western blot. Cellular uptake of nanoparticles and ultrastructure changes were examined by transmission electron microscopy (TEM). In the present study we have proven that AuNPs stars are the most cytotoxic against human cells. We observed that cancer cells are more susceptible to AuNPs cytotoxic effect. Furthermore, AuNPs rods and AuNPs stars caused increased expression of Bax and decreased expression of Bcl-2 protein in osteosarcoma cells. We found that AuNPs penetrated through the cell membrane and caused ultrastructural changes. Our results clearly demonstrated that the cytotoxicity of AuNPs was shape-dependent. AuNPs stars with the highest anti-cancer potential were also the most cytotoxic type of tested NPs, whereas AuNPs spheres which appears to be the safest one had small anti-cancer potential.

Synthesis of Gold Nanoparticles Using <i>p</i>-Aminobenzoic Acid and <i>p</i>-Aminosalicylic Acid as Reducing Agent

Synthesis of gold nanoparticles (AuNPs) by reduction of HAuCl4 with p-aminobenzoic acid and p-aminosalicylic acid as a reducing agent was investigated. This work was conducted in order to determine the optimum condition of AuNPs synthesis and examine the effect of the hydroxyl group in p-aminosalicylic acid towards the size, shape, and stability of the synthesized gold nanoparticles (AuNPs). The optimum condition of the gold nanoparticles synthesis was determined by UV/Vis spectrophotometer, the shape and size of gold nanoparticles were measured by Transmission Electron Microscope (TEM). The synthesis process was started by reacting HAuCl4 and the reducing agents in an aqueous solution at 86 ºC. The initial gold concentration, reducing agents concentration and pH were varied in order to obtain the optimum condition. In the optimum condition, the results showed that p-aminosalicylic acid containing both hydroxyl and amino groups performed higher reduction ability compared to p-aminobenzoic acid that only containing an amino group. Reducing agents which have a hydroxyl group (p-aminosalicylic acid) could produce AuNPs with a smaller concentration of HAuCl4 than p-aminobenzoic acid. Gold nanoparticles that were synthesized with p-aminosalicylic acid were more stable and had a smaller particle size compared to its counterpart that is synthesized with p-aminobenzoic acid.

Shape dependent catalytic activity of unsupported gold nanostructures for the fast reduction of 4-nitroaniline

A one step seed mediated strategy is adopted here for synthesizing spherical, dog bone and rod shaped gold nanoparticles. Usually noble metals decorated by supporting materials are used for chemical catalysis. Here, a variety of unsupported gold nanoparticles (spherical, dog bone and rod shaped) originating from the same growth procedure are used for the catalytic reduction of para-nitroaniline (4-NA). The product obtained, para-phenylenediamine, is an important material, especially in the field of dye industry. The reaction kinetic values were analyzed based on to the Langmuir–Hinshelwood (LH) mechanism. A comparison of the rate constants obtained for gold nanoparticles of different shapes with almost similar volume pointy that gold nanorods are superior to that of spherical and dog bone like nanoparticles. The turnover frequency obtained here is high compared to other reported results and is found to be sensitive to the shape of the nanoparticles.

Efficient Electrochemical Detection of Lethal Environmental Pollutant Hydroquinone Based on Functionalized Carbon Black/Polytyramine/Gold Nanoparticles Nanocomposite

An efficient detection of lethal environment pollutants via the simple and sensitive analytical method has drawn the central importance. In this work, the cotton flower like structured gold nanoparticle decorated functionalized carbon black/polytyramine (f-CB-PTy-Au) ternary nanocomposite was synthesized via the sonochemical synthesis method. The strong covalent interaction between the hydroxyl and amine group from the f-CB and PTy enhances the polymerization. Besides, the flower shaped gold nanoparticles (AuNPs) decorated on the surface of the f-CB-PTy via the non-covalent interaction. The structural properties of the f-CB-PTy-Au nanocomposite were probed by various spectrophotometric techniques. Then, the as-prepared nanocomposite was used to fabricate the electrochemical sensor for the amperometric determination of hazardous pollutant hydroquinone (HQ). Outstandingly, the proposed sensor demonstrated the wide linear response ranges from 0.006 μM to 2400 μM and the lowest LOD value around 0.1 nM was achieved. The favorable sensitivity of the proposed sensor was calculated about 3.423 μA μM−1 cm−2. Furthermore, the practical applicability was investigated in different water samples such as tap water, waste water and river water.

Detailed Investigation of Phenol Degradation on Au/TiO₂ Composite Materials.

Photocatalytic applicability of different TiO₂-based nanomaterials is a current hot topic. Therefore, our interest for the present research was to elucidate the formation of primary and secondary intermediates during the phenol degradation by photocatalysis, in the presence of Au/TiO₂ nanocomposites. The composites consisted of differently shaped gold nanoparticles and commercial titania (Evonik Aeroxide P25). The obtained composites and the noble metal nanoparticles' morphology was investigated by Transmission Electron Microscopy (TEM), their optical properties were explored using Diffuse Reflectance Spectroscopy (DRS), while the crystal structure was characterized by X-ray diffraction (XRD). The photocatalytic activity was investigated by photodegradation of phenol and methyl orange. In case of phenol it was shown that, the formation of degradation intermediates, was dependent on the Au nanoparticles' shape, leading to high amounts of different intermediates as follows: hydroquinone for composites with spherical Au nanoparticles, 1,2,4-trihydroxy-benzene for triangle shaped nanoparticles, and pyrocatechol for TiO₂.

Effect of gold nanoparticle shape on the photophysicochemical properties of sulphur containing metallophthalocyanines

In this work tetrakis–[(thiopheneethoxy) phthalocyaninato] zinc(II) (1), tetrakis–[(thiopheneethoxy) phthalocyaninato] indium (II) chloride (2), tetrakis [(benzo [d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (3), and tetrakis [(benzo [d]thiazol-2-yl phenoxy)phthalocyaninato] indium (II) chloride (4) were linked to both gold nanospheres (AuNSs) and gold nanotriangles (AuNTs) via Au-S and Au-N (the latter for complexes 3 and 4 only) self assembly. The photophysicochemical behaviour of complexes and their conjugates were studied. The conjugates yielded improved triplet and singlet quantum yields, with nanospheres displaying better properties than nanotriangles. The conjugates with a benzothiazole phenoxy substituent also yielded better properties than their thiophene ethoxy counterpart. These conjugates especially those with a benzothiazole phenoxy substituent have potential as photosensitisers for photodynamic therapy applications.

Gold nanoparticles of different shape for bicolor lateral flow test

Spherical gold nanoparticles are the most commonly used marker in lateral flow assays. However, the widespread practice of using identical coloration for the test and control zones of test strips can lead to erroneous interpretations of the assay's results. We propose an immunochromatographic test strip with lines of different colors. For this purpose, gold nanoparticles of different shapes were used, namely blue nanoflowers in the test zone and red gold nanospheres in the control zone. A detailed synthesis procedure for nanoparticles and their conjugates is considered and design parameters for optimal results are described. For the first time, nanoparticles of different shapes have been combined in the test strip with indirect labeling of specific antibodies (via their interaction with labeled secondary antibodies). Using the T-2 toxin (T2T) as an example, an instrumental detection limit of 30 pg/ml and a working range 0.06–0.9 ng/mL were achieved in an analysis of water-organic corn extracts.

Gold Nanoparticles in Cancer Treatment.

Colloidal gold has been studied for its potential application in medicine for centuries. However, synthesis and evaluation of various gold nanoparticles have only recently been met with a wide interest of scientists. Current studies confirm numerous advantages of nanogold over different nanomaterials, primarily due to highly optimized protocols for the production of gold nanoparticles of countless sizes and shapes, featured with unique properties. The possibility to modify the surface of nanogold particles with different targeting and functional compounds significantly broadens the range of their potential biomedical applications, with particular emphasis on cancer treatment. Functionalized gold nanoparticles exhibit good biocompatibility and controllable biodistribution patterns, which make them particularly fine candidates for the basis of innovative therapies. Considering the high amount of scientific data on nanogold, this review summarizes recent advances in the field of medical application of gold nanoparticles for the therapy of cancer.

Photothermal-Assisted Optical Stretching of Gold Nanoparticles.

The synergy of photothermal energy and optical forces generated by tightly focused laser beams can be used to transform the shape of gold nanoparticles. Here, the combination of these two effects is demonstrated to be an effective way of elongating gold nanoparticles (Au NPs), massively tuning their plasmonic properties. The photothermal effect of the laser increases the temperature of Au NPs above the melting point, and optical forces deform the molten Au NPs. As a result, the shape of Au NPs transforms from nanospheres into nanorods or dimers, depending on the power and time of irradiation as well as the surface energy of the substrate. This process is reversible by using high laser power to transform nanorods back to nanospheres due to capillary dewetting. Such light-induced transformations of nanostructures not only provide a facile way to tune plasmon resonances but also shed light on how the synergistic effect of photothermal energy and optical forces works on plasmonic nanoparticles.

Melamine detection in liquid milk based on selective porous polymer monolith mediated with gold nanospheres by using surface enhanced Raman scattering.

A rapid and fast detection of trace amounts of melamine in milk is reported by using Gold Nano Spheres embedded monolith conjugates. Monolith was synthesized by the polymerization of Glycidyl Methacrylate (GMA) and Ethylene Dimethacrylate(EDMA) (cross linker and functional monomer), Cyclohexanol (Porogen formation) and 2, 2-Dimethoxy-2-phenyl-acetophenone (photo-initiator) on gold coated silicon wafer. In order to gauge the influence of monolith on SERS signal activity, three shapes of gold nanoparticles namely Gold Nano Spheres (GNSs), Gold Nanorods (GNRs) and Triangular Gold Nanoprisms (GNPrs) were immobilized on monolithic surface and analyzed by the signal molecule Rhodamine (R6G). The Raman Enhancement efficiency of the above three shapes incorporated with monolith was monitored by calculating their maximum enhancement factors. Among three morphologies, Gold Nano Spheres integrated in GMA-EDMA Monolith Sensor (GNS@GEMS) was found more effective for detection of R6G than two others and was therefore projected in analysis of melamine sensing in commercial milk. A linear relationship of regression model (R2 = 0.99) was observed between melamine SERS intensity (at 710 cm-1) and varied concentrations (6.5 < mg/L < 0.125). The lower limit of detection (LOD) and limit of quantification (LOQ) for melamine was determined 0.11 mg/L and 0.38 mg/L respectively. The time window for detection of melamine was 10 min and hence our method is compatible with the FDA's tolerance limit in USA and China (1 mg/L).

Use of Invasive Weed to Synthesize Shape-Tunable Gold Nanoparticles and Evaluation of their Catalytic Activities in Dye Reduction

Background: Gold nanoparticles (GNPs) of different sizes and shapes are very important for technological applications. They possess unique catalytic behavior under mild conditions and also they are considered catalysts of choice due to higher stability and negligible poisoning as compared to other metal nanoparticles (NPs). Objective: The main aim of the work is to synthesize GNPs using the flower extract of the harmful invasive wild growing plant, Lantana camara as a reducing and stabilizing agent under ambient conditions and use them for catalytic applications. Methods: The as-synthesized GNPs were characterized using various spectroscopic, microscopic and diffractometric techniques. UV-vis spectroscopy was used to monitor the progress of the catalytic dye reduction reactions. Results: UV-vis spectroscopic results indicated that optical properties of GNPs can be tuned by varying the concentration of extract in the reaction medium. Zeta potential measurement confirmed that the surfaces of these GNPs are negatively charged which imparts stability to the colloids. Microscopic results confirmed that varying the concentration of flower extract; size and shape of the formed GNPs can be systematically tuned. Selected area electron diffraction analysis of spherical and polygonal GNPs indicated that spherical GNPs are mainly polycrystalline in nature whereas polygonal GNPs are single crystalline.X-ray diffraction analyses confirmed the formation of pure face-centered cubic gold. These GNPs showed excellent catalytic activity in the borohydride reduction of organic dye molecules. Conclusion: At higher extract concentration, spherical GNPs are formed predominantly. But when the concentration of extract is lowered, GNPs of mixed morphology are formed. Further lowering in the concentration of extract resulted in polygonal GNPs only. These gold nanoparticles can be used as an efficient catalyst for borohydride reduction of toxic organic dyes in an aqueous medium. Keywords: Gold nanoparticles, shape-tunable, Lantana camara, catalysis, waste-water, dye reduction.

Effect of gold nanoparticles shape and size on the photophysicochemical behaviour of symmetric and asymmetric zinc phthalocyanines

Glutathione (GSH) capped Au nanotriangles (AuNTs–GSH) and nanospheres (AuNSs–GSH) are covalently linked to symmetric Zn phthalocyanine (ZnPc) substituted with phenoxy propanoic acid substituents only (complex 1) and two asymmetric ZnPc, each containing one phenoxy propanoic acid and three benzothiazole phenoxy moieties (complex 2), and one phenoxy propanoic acid and no other ligands (complex 3). The photophysicochemical behaviour of Pc complexes and their conjugates were studied. All conjugates displayed improved triplet and singlet oxygen quantum yields with decreases in fluorescence quantum yields compared to their respective Pc complexes. The conjugates of asymmetric complexes 2 and 3, afforded much higher triplet and singlet oxygen quantum yields compared to the symmetric complex 1, and could serve as good candidates for photodynamic therapy.

Effect of Preliminary Binding of HAuCl4 with DNA and Cetyltrimethylammonium Bromide in Aqueous Solution on Morphology of the Formed Nanoparticles

Competitive interactions in the HAuCl4–DNA–cationic surfactant (cetyltrimethylammonium bromide) systems have been studied. Decisive role of the components binding on size and shape of gold nanoparticles obtained via reduction in these mixtures has been shown.

Controlling the Absorption Spectra of Gold Nanoparticles Synthesized via Green Synthesis Using Brown Seaweed (&lt;i&gt;Sargassum&lt;/i&gt; &lt;i&gt;crassifolium) &lt;/i&gt;Extract

Gold nanoparticles were synthesized using brown seaweed (Sargassum crassifolium) extract and chloroauric acid solution. This is an easy, cheap and environment friendly synthesis method for the formation of gold nanoparticles. The gold nanoparticles with varying amount of seaweed extract was characterized using Ultraviolet-visible spectroscopy. Moreover, Transmission Electron Microscopy characterization was used to observe the shape and size of gold nanoparticles. Experimental results revealed that varying the amount of brown seaweed extract can control the optical absorption spectra of the produced gold nanoparticles. Greater amount of brown seaweed extract will exhibit peak in the lower wavelength while smaller amount of seaweed extract will exhibit peak in the higher wavelength. It is believed that the wavelength of free surface electrons resonance is related to the shift of absorption peak. TEM images revealed a more spherical and smaller particles as the amount of brown seaweed extract was increased. This simple green synthesis method of gold nanoparticles will give a cost effective route in the mass production of gold nanoparticles for biomedical applications.

Synthesis of gold nanoparticles using Euphorbia tirucalli latex and the microwave method

Uniformly sized and shaped gold nanoparticles (AuNP) were produced by microwave irradiation using Euphorbia tirucalli latex. The AuNPs were characterized by ultraviolet visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering, zeta potential, and transmission electron microscopy (TEM). UV–Vis analysis was employed to detect the characteristic surface plasmon resonance pattern of the AuNPs (550 nm). The carboxylic and polyphenolic groups were associated with the euphol-capped AuNP, which was confirmed using FTIR spectroscopy. The AuNPs studied here show a z-average diameter varying from 35 to 500 ± 0.8 nm. TEM reveals that the particles were spherical and polydispersed. The latex itself is very toxic and can be harmful during manipulation, thus highlighting a negative aspect in it use. However, we have demonstrated that the isolation procedure did not impair the reduction action of the dry latex powder. This study provides a robust solution for the synthesis of stable capped gold nanoparticles. Furthermore, the dried powdered E. tirucalli latex seems to be an attractive capping agent for nanoparticles in drug delivery.

Glycosylated zinc phthalocyanine-gold nanoparticle conjugates for photodynamic therapy: Effect of nanoparticle shape

In this work, we report on the synthesis of tris-[(2,2,7,7-tetramethyltetrahydro-3aH-bis([1,3]dioxolo)[4,5-b:4′,5′-d]pyran-5-yl)methoxy)-2-(4-benzo[d]thiazol-2-ylphenoxyphthalocyaninato] zinc(II) (complex 3) and its linkage to gold nanoparticles (AuNPs) of different shapes through S-Au/N-Au self-assembly. The conjugates of complex 3 (with both gold nanorods (AuNR) and nanospheres (AuNS)), displayed decreased fluorescence quantum yield with corresponding improved triplet and singlet quantum yields compared to complex 3 alone, however 3-AuNR showed improved properties than 3-AuNS. Complex 3 showed relatively low in vitro dark cytotoxicity against the epithelial breast cancer cells with cell survival ≥ 85% at concentration ≤ 160 μg/mL but afforded reduced photodynamic therapy activity which may be due to aggregation. 3-AuNR afforded superior PDT activity with <50% viable cells at concentration ≥ 40 μg/mL in comparison to 3-AuNS with <50% viable cells at concentration ≥ 80 μg/mL. The superior activity of 3-AuNR is attributed to the photothermal therapy effect since nanorods absorb more light at 680 nm than nanospheres.