Triangular Nanoparticles Research Articles

Tridirectional Polarization Routing of Light by a Single Triangular Plasmonic Nanoparticle.

Achieving high directionality of scattered light in combination with high flexibility of the direction using plasmonic nanoparticles is desirable for future optical nanocircuits and on-chip optical links. The plasmonic characteristics of nanoparticles strongly depend on their geometry. Here, we studied directional light scattering by a single-element triangular plasmonic nanoparticle. Our experimental and simulation results demonstrated that the triangular nanoparticle spatially sorted the incoming photons into three different scattering directions according to their polarization direction, including circular polarization, despite its compact overall volume of ∼λ3/300. The broken mirror symmetry and rotational symmetry of the triangular nanoparticle enabled such passive tridirectional polarization routing through the constructive and destructive interference of different plasmon modes. Our findings should markedly broaden the versatility of triangular plasmonic nanodevices, extending their possible practical applications in photon couplers and sorters and chemo-/biosensors.

Optical properties of gold nanorods macro-structure: a numerical study

In this contribution, a numerical study of the optical properties of closely-packed gold nanorods was performed. The studied nano-objects are experimentally grown on a tilted polydimethylsiloxane (PDMS) substrate by using physical vapor deposition (PVD). This method creates nanorods tilted to a certain angle with respect to the substrate normal. This geometry allows exciting both transverse and longitudinal modes of the rods. As demonstrated in a previous experimental work, such PVD-grown nano-objects show promising possibilities both as strain gauges or strain-tunable metamaterials if fabricated on a stretchable dielectric substrate. This numerical study is based on experimental data from previous work and pushes further the subject by approaching an optimized nano-structure allowing better strain-sensitivity (particularly by changing the auto-organization of the said nanorods). Full Text: PDF ReferencesJ.W.M. Chon, C. Bullen, P. Zijlstra, M. Gu, "Spectral encoding on Gold Nanorods Doped in a Silica Sol?Gel Matrix and Its Application to High-Density Optical Data Storage", Adv. Funct. Mater. 17, 875 (2007). CrossRef C.-C. Chen, Y.-P. Lin, C.-W. Wang, H.-C. Tzeng, C.-H. Wu, Y.-C. Chen, C.-P. Chen, L.-C. Chen, Y.-C. Wu, "DNA?Gold Nanorod Conjugates for Remote Control of Localized Gene Expression by near Infrared Irradiation", J. Am. Chem. Soc. 128, 3709 (2006). CrossRef J.N. Anker, W.P. Hall, O. Lyandres, N.C. Shah, J. Zhao, R.P. Van Duyne, "Biosensing with plasmonic nanosensors", Nat. Mater 7, 442 (2008). CrossRef B. Sepulveda, P.C. Angelome, L.M. Lechuga, L.M. Liz-Marzan?, "LSPR-based nanobiosensors", Nano Today 4, 244 (2009). CrossRef A. Haes, R.P. Van Duyne, "A Nanoscale Optical Biosensor: Sensitivity and Selectivity of an Approach Based on the Localized Surface Plasmon Resonance Spectroscopy of Triangular Silver Nanoparticles", J. Am. Chem. Soc. 124, 10596 (2002). CrossRef J.C. Riboh, A.J. Haes, A.D. McFarland, C.R. Yonzon, R.P. Van Duyne, "A Nanoscale Optical Biosensor: Real-Time Immunoassay in Physiological Buffer Enabled by Improved Nanoparticle Adhesion", J. Phys. Chem. B 107, 1772 (2003). CrossRef C.R. Yonzon, E. Jeoung, S. Zou, G.C. Schatz, M. Mrksich, R.P. Van Duyne, "A Comparative Analysis of Localized and Propagating Surface Plasmon Resonance Sensors: The Binding of Concanavalin A to a Monosaccharide Functionalized Self-Assembled Monolayer", J. Am. Chem. Soc. 126, 12669 (2004). CrossRef A.J. Haes, L. Chang, W.L. Klein, R.P. Van Duyne, "Detection of a Biomarker for Alzheimer's Disease from Synthetic and Clinical Samples Using a Nanoscale Optical Biosensor", J. Am. Chem. Soc. 127, 2264 (2005). CrossRef R. Caputo, G. Palermo, M.Infusino L. De Sio, "Liquid Crystals as an Active Medium: Novel Possibilities in Plasmonics", Nanospectroscopy 1, 40 (2015). CrossRef T. Maurer, J. Marae-Djouda, U. Cataldi, A. Gontier, G. Montay, Y. Madi, B. Panicaud, D. Macias, P.-M. Adam, G. Lév?que, T. Bürgi, R. Caputo, "The beginnings of plasmomechanics: towards plasmonic strain sensors", Frontiers of Materials Science 9, 170 (2015). CrossRef X. Niu, S. P. Stagon, H. Huang, J.K. Baldwin, A. Misra, "Smallest Metallic Nanorods Using Physical Vapor Deposition", Phys. Rev. Lett. 110 136102 (2013). CrossRef Lumerical Solutions, Inc. DirectLink P.K. Jain, W. Huang, M.A.El-Sayed, "On the Universal Scaling Behavior of the Distance Decay of Plasmon Coupling in Metal Nanoparticle Pairs: A Plasmon Ruler Equation", Nanoletters 7, 2080 (2007). CrossRef P.K. Jain, M.A. El-Sayed, "Plasmonic coupling in noble metal nanostructures", Chem. Phys. Letters 487, 153 (2010). CrossRef

Chemists create colloidal clathrate crystals

As denizens of DNA, Chad A. Mirkin and his group at Northwestern University have used the biopolymer in combination with metal nanoparticles to assemble hundreds of differently shaped micrometer-scale colloidal crystals. Even so, they have just come up with one that hasn’t been seen before: a colloidal clathrate. The trick in making the clathrates, which are known for their cavities that can house molecules for storing, delivering, and sensing applications, was tuning the nanoparticle shape and the length and sequence of the DNA connectors. The engineering was guided by simulations carried out by Sharon C. Glotzer and her team at the University of Michigan (Science 2017, DOI: 10.1126/science.aal3919). The researchers prepared anisotropic, triangular bipyramidal gold nanoparticles that align into tetramers. Attaching a DNA monolayer to the gold leads to assembly of nanoparticle clusters that form the colloidal crystals with patterns that, rather than become densely packed, leave polygon-shaped holes. The

Experimental and theoretical investigation of methane hydrate induction time in the presence of triangular silver nanoparticles

Low formation rate of hydrates has restricted their industrial applications; however, new promoters could be introduced as appropriate solutions. In this study, the nucleation of the methane hydrate was theoretically and experimentally investigated in the presence of triangular silver nanoparticles in an aqueous solution (4.5, 9, 18, 27 and 36μM) at initial pressures of 4.5, 4.8, 5, 5.3 and 5.5MPa and temperatures of 275.15 and 276.15K. The results revealed that these nanoparticles reduced the induction time up to 97% in comparison with pure water. All of the obtained data were put into the Kashchiev–Firoozabadi model; however, the calculated error was not acceptable. As a result, a new model for calculating induction time in the presence of nanoparticles was carried out. The average absolute deviation between measured and predicted induction time was 13.82%. The methane hydrate/solution effective interfacial tension in the presence of nanoparticles according to heterogeneous nucleation was estimated. The model represented that increase in nanoparticles concentration contributes to declining of effective interfacial tension of methane hydrate/solution.

Visual detection of glucose using triangular silver nanoplates and gold nanoparticles

A sensitive spectrophotometric detection of glucose based on triangular silver nanoplates (Ag TNPs) coupled with gold nanoparticles (Au NPs) was carried out.

Design and simulate the properties of triangular periodic nanoparticle arrays with the structure of bi-layer hexagonal lattice

In this study, the discrete dipole approximation (DDA) method was used to simulate the hybrid bi-layer hexagonal lattice of triangular periodic nanoparticle arrays (PNAs). The PNAs nanophotonic devices could be fabricated with pure silver, but their performances would be easily degenerated because of the oxidation (forming Ag2O) and sulfuration (forming Ag2S). Theoretical results show that the oxidation and sulfuration of Ag thin film lead to a significant red shift in the wavelength to reveal the maximum extinction efficiency (λmax) and to a significant decrease in the maximum peak value of localized surface plasmon resonances (LSPRs). The structures with the bi-layer materials of Ag2O–Ag and Ag2S–Ag were used to prove the degeneration of the properties in the extinction spectra of the LSPRs by using DDA method for simulation. We would find that the maximum peak value of the wavelength of the extinction efficiency spectra critically decreased and λmax had a red shift as the thicknesses of Ag2O and Ag2S increased. The structures with the bi-layer materials of Au–Ag and TiO2–Ag were also used to investigate their extinction spectra of the LSPRs. The simulation results of DDA method found that the maximum peak value of the wavelength of the extinction efficiency spectra slightly decreased as the thicknesses Au and TiO2 increased. Based on the Ag triangular nanostructure, the use of Au and TiO2 to form hybrid Au–Ag and TiO2–Ag triangular nanostructure cannot only be used to put forth of preventing oxidation and sulfuration but have a better performance than the Ag2O–Ag and Ag2S–Ag hybrid triangular nanostructures. Meanwhile, the thicknesses of TiO2 or Au layers could be used to decide the refractive index sensitivity (RIS) and figure of merit (FOM) of the hybrid Au–Ag and TiO2–Ag PNAs.

Hydrothermal synthesis of triangular CeCO3OH particles and photoluminescence properties

Ru/CeO2 [RC] and Ru/CeO2/ethylene glycol (EG) [RCE] nanoparticles were produced by performing a simple hydrothermal reaction at 200°C for 24h and found to have two distinct morphologies. The RC nanoparticles are phase pure CeO2; triangular highly crystalline CeCO3OH nanoparticles are formed from the solution containing EG under the same hydrothermal reaction conditions at pH 8.5. EG plays an important role in the formation of the triangular CeCO3OH nanoparticles. The polycrystalline CeCO3OH nanoparticles retain their triangular structure even after calcination at 600°C in air but are transformed into a pure CeO2 phase. The room temperature photoluminescence of the RC and RCE nanoparticles and of RCE calcined at 600°C [RCE-600] was also investigated. It was found that the high crystallinity triangular RCE-600 sample exhibits the highest photoluminescence intensity.

Reverse Size Dependences of the Cellular Uptake of Triangular and Spherical Gold Nanoparticles.

Gold nanoparticles (GNPs) show promise as both drug and imaging carriers with applications in both diagnosis and therapy. For the safe and effective use of such gold nanomaterials in the biomedical field, it is crucial to understand how the size and shape of the nanomaterials affect their biological features, such as in vitro cellular uptake speed and accumulation as well as cytotoxicity. Herein, we focus on triangular gold nanoparticles (TNPs) of four different sizes (side length 46, 55, 72, and 94 nm; thickness 30 nm) and compare the cellular internalization efficiency with those of spherical nanoparticles (SNPs) of various diameters (22, 39, and 66 nm). Both surfaces were coated with anionic thiol ligands. Inductively coupled plasma-emission spectrometry (ICP-ES) data demonstrated that TNPs with longer sides showed higher levels of uptake into RAW264.7 and HeLa cells. On the other hand, in the case of SNPs, those with smaller diameters showed higher levels of uptake in both cells. Our results support the notion of a reverse size dependence of TNPs and SNPs in terms of cellular uptake. For HeLa cells, in particular, 20-fold more efficient internalization was observed for TNPs with longer sides (72 nm side length) compared to SNPs (66 nm) with a similar surface area. These results highlight the importance of the shape of nanomaterials on their interactions with cells and provide a useful guideline for the use of TNPs.

Localized surface plasmons in face to face dimer silver triangular prism nanoparticles

Using the discrete dipole approximation method, all plasmonic bands in 80 nm silver face to face dimer triangular prism nanoparticles were reported. The characteristics of plasmonics peaks were investigated with variations of dimer gap and refractive index of the surrounding medium of dimer. We found that there are three and four plasmonic bands, respectively, for dimer separation 2 and 4 nm. The extinction spectra and electric field distribution showed that the dipole–dipole interaction creates strong plasmonic band, but the quadrupole–quadrupole interaction relates to weak plasmonic band. The results revealed that the strong plasmonic bands have high sensitivity factors with respect to weak plasmonic bands. This study may be used in the synthesis of asymmetric dimers made of metal nanoparticles with new plasmonics properties.

Self-assembled triangular DNA nanoparticles are an efficient system for gene delivery

Developing an advanced nucleic acid drug delivery system is of great significance in order to achieve optimal gene delivery. Self-assembled nucleic acid nanoparticles are an excellent platform for the delivery of nucleic acids and other small molecular drugs. In this study, we developed the efficient, three-stranded, RNA/DNA hybrid triangular self-assembled nanoparticles, namely, mTOR single-stranded siRNA-loaded triangular DNA nanoparticles (ssRNA-TNP). The ssRNA-TNP is formed by the complementary association of the above mentioned three components and is more stable in complete medium than standard duplex siRNA. It could be efficiently transfected into NCI-H292 cells in a dose- and time-dependent manner, resulting in high transfection efficiency. Furthermore, ssRNA-TNP uptake is dependent on macropinocytosis and clathrin-mediated endocytosis pathways. Interestingly, ssRNA-TNP is more efficient to inhibit the expression of mTOR. This ssRNA-TNP has a simpler structure, better stability, and higher transfection efficiency; therefore it may become a novel nonviral nanosystem for gene delivery.

Characterization of Triangular Gold Nanoparticles Using Aloe arborescens Leaf Extract: A Green Synthesis Approach

Herein, the authors show the use of the Aloe arborescens leaf extract for green synthesis of gold nanoparticles in water at room temperature under very mild conditions. The synthesis of the gold nanoparticles was complete in several minutes, and no extra stabilizing or capping agents were necessary. The size of the nanoparticles could be controlled by varying the concentration of the leaf extract. The silver nanoparticles and reaction process were characterized by UV-vis spectrometer, Fourier transform infrared spectroscopy, and transmission electron microscopy. The UV-visible spectra of synthesized nanoparticles showed absorption maxima at 540 nm. Transmission electron microscopy images confirm that the nanoparticles are spherical and triangular in shape.

Effect of sapphire substrate on the localized surface plasmon resonance of aluminum triangular nanoparticles

In this paper, we explore the effect of the sapphire substrate on the localized surface plasmon resonance of Al triangular nanoparticles fabricated by nanosphere lithography. We find an obvious shoulder peak which is rarely noticed before as well as a main peak in the the ultraviolet range of the extinction spectrum. Then the electric field distributions surrounding the single Al triangular nanoparticle have been further investigated by numerical simulation using the finite-difference time-domain method. By analyzing the simulation results, we demonstrate that the two peaks in the extinction spectrum are originated from the hybridization of dipolar and quadrupolar modes when the sapphire substrate exists. And this work may provide a better understanding of the effect of sapphire substrate on the localized surface plasmon resonance properties of aluminum triangular nanoparticles.

Corrosion processes of triangular silver nanoparticles compared to bulk silver

Excessive corrosion of silver nanoparticles is a significant impediment to their use in a variety of potential applications in the biosensing, plasmonic and antimicrobial fields. Here we examine the environmental degradation of triangular silver nanoparticles (AgNP) in laboratory air. In the early stages of corrosion, transmission electron microscopy shows that dissolution of the single-crystal, triangular, AgNP (side lengths 50–120 nm) is observed with the accompanying formation of smaller, polycrystalline Ag particles nearby. The new particles are then observed to corrode to Ag2S and after 21 days nearly full corrosion has occurred, but some with minor Ag inclusions remaining. In contrast, a bulk Ag sheet, studied in cross section, showed an adherent corrosion layer of only around 20–50 nm in thickness after over a decade of being exposed to ambient air. The results have implications for antibacterial properties and ecotoxicology of AgNP during corrosion as the dissolution and reformation of Ag particles during corrosion will likely be accompanied by the release of Ag+ ions.

Noble Metal Nanoparticles and Their (Bio) Conjugates. II. Preparation

Hybrid nanoparticles of gold and silver can not only retain the beneficial features of both nanomaterials, but also possess unique advantages (synergism) over the other two types. Novel pseudospherical and anisotropic nanoparticles, bimetallic triangular nanoparticles, and core@shell nanoparticles were prepared by the different procedures for various applications and understanding both the particle evolution (nucleation) and nanoparticle anisotropy. Hybrid nanoparticles of gold and silver are considered to be low in toxicity, and exhibit facile surface functionalization chemistry. Furthermore, their absorption peaks are located in visible and near-infrared region. These nanoparticles provide significant plasmon tunability, chemical and surface modification properties, and significant advances in the growth into anisotropic nanostructures. The photoinduced synthesis can be used to prepare various (sub) nanoparticles and OD and 1D nanoparticles. Ostwald and digestive ripening provided narrower particle size distribution.

Parametric Study on Gold Nanoparticle Synthesis Using Aqueous Elaise Guineensis (Oil palm) Leaf Extract: Effect of Precursor Concentration

In this study, gold nanoparticles (AuNPs) were synthesized by using aqueous extract of Elaise guineensis (oil palm) leaves without addition of any external stabilizing agent. Effects of precursor concentrations (0.51 mM- 4.055mM) on SPR absorbance and AuNP particle size distribution were investigated. The synthesis reaction was monitored by measuring time-variant SPR spectrum of the reaction medium with a UV-vis spectrophotometer. Biosynthesized AuNPs were characterized using TEM, DLS, UV-vis and FTIR spectroscopy. TEM image analysis showed formation of predominantly spherical gold nanoparticles with mean particle diameter of 27.89±14.59nm were formed using 1.53mM gold concentration. DLS data showed that AuNPs with hydrodynamic diameter 55.22 ± 42.86nm were formed, indicating formation of multilayer coatings of biomolecules present in the leaf extract on nanoparticles. Spherical, triangular, pentagonal and hexagonal gold nanoparticles with mean particle diameter 22.88 ±8.21nm were formed when higher gold (III) precursor concentrations (4.055mM) were used. FTIR analysis revealed that carboxylic and phenolic compounds present in leaf extract played dual roles as reducing and stabilizing agents during synthesis of AuNPs.

Use of silver triangular nanoparticles for the colorimetric determination of ammonium persulfate concentration in water-borne adhesives for cigarettes

In this work, a simple method for detecting ammonium persulfate using silver triangular nanoparticles (silver TNPs) was developed.

Structural and morphological study of gamma‐irradiation synthesized silver nanoparticles

Silver nanostructured particles with controlled size, shape, and morphology were achieved by gamma irradiation of aqueous solution containing AgNO3, ploy (vinyl pyrrolidone), (PVP) or mixture of PVP and ploy (vinyl alcohol), (PVA). The reaction condition parameters such as solvent content, polymer type and irradiation dose were investigated. The physico‐chemical properties and morphological structures of the as‐prepared sliver nanostructures were characterized using UV/VIS spectroscopy, TEM, XRD, and Fourier transform infrared spectroscopy (FTIR) spectroscopy. Hexagonal and nanorods structures of sliver nanoparticles having single surface plasmon resonance peak and triangular (nanoprism) nanoparticles having different surface plasmon resonance peak were obtained. The XRD patterns of the as‐prepared silver nanostructure show four diffraction peaks at 2θ of 38.4°, 44.5°, 64.6°, and 77.6° of the face‐centered cubic structure silver nanoparticles. FTIR measurements indicated that the sliver nanoparticles were coordinated through the functional groups of PVA and/or PVP. POLYM. COMPOS., 38:2687–2694, 2017. © 2015 Society of Plastics Engineers

Triazene UV-triggered photogeneration of silver/gold nanoparticles in block copolymer templates

This article describes an attractive way to in situ create noble metal nanoparticles in block copolymer matrixes through the UV-triggered photodecomposition of the photolabile triazene units without the use of any conventional reducing agent. The poly(isodecyl methacrylate-co-triazene urethane methacrylate) random copolymer containing pendent photocleavable triazene junctions (COP-1) was synthesized under RAFT conditions and subsequently employed as macroinitiator to obtain a block copolymer, namely poly(isodecyl methacrylate-co-triazene urethane methacrylate)-block-poly(acrylic acid) (COP-2). The photogeneration of silver/gold metal nanoparticles (NPs) from noble metal precursors (1 wt% AgNO3 or AuBr3 metal salts) induced through the UV decomposition of triazene units with the formation of some radical active species was monitored in solution and thin films. The in situ growth of Ag/Au nanostructures into polymer matrixes for which the light is a key element has been confirmed by UV spectroscopy and TEM analysis. The TEM images allowed the visualization of the silver NPs (sizes of 4–16 nm in COP-1 and of 2–6 nm in COP-2) as well as of the gold NPs (sizes between 10 and 20 nm in COP-1 and from 15 to 25 nm in COP-2), which are mainly spherical in shape, even though there is some triangular or hexagonal gold nanoparticles.

Observation of Size-Dependent Electron–Phonon Scattering and Temperature-Dependent Photoluminescence Quenching in Triangular-Shaped Silver Nanoparticles

Research studies on plasmonic properties of triangular-shaped silver nanoparticles might lead to several interesting applications. However, in this work, triangular-shaped silver nanoparticles have been synthesized by simple solvothermal technique and reported the effect of size on the electron–phonon scattering in the synthesized materials by analyzing their temperature-dependent photoluminescence (PL) emission characteristics. It has been observed that total integrated PL emission intensity is quenched by 33 % with the increase in temperature from 278 to 323 K. The observed decrease in PL emission intensity has been ascribed to the increase of electron–phonon scattering rate with the increase in temperature. The values of electron–phonon coupling strength (S) for synthesized samples have been evaluated by theoretical fitting of the experimentally obtained PL emission data. Smaller sized triangular nanoparticle has been found to exhibit stronger temperature dependence in PL emission, which strongly suggests that smaller sized triangular silver nanostructures have better electron–phonon coupling.

Investigating the role of shape on the biological impact of gold nanoparticles in vitro.

To investigate the influence of gold nanoparticle geometry on the biochemical response of Calu-3 epithelial cells. Spherical, triangular and hexagonal gold nanoparticles (GNPs) were used. The GNP-cell interaction was assessed via atomic absorption spectroscopy (AAS) and transmission electron microscopy (TEM). The biochemical impact of GNPs was determined over 72 h at (0.0001-1 mg/ml). At 1 mg/ml, hexagonal GNPs reduced Calu-3 viability below 60%, showed increased reactive oxygen species production and higher expression of proapoptotic markers. A cell mass burden of 1:2:12 as well as number of GNPs per cell (2:1:3) was observed for spherical:triangular:hexagonal GNPs. These findings do not suggest a direct shape-toxicity effect. However, do highlight the contribution of shape towards the GNP-cell interaction which impacts upon their intracellular number, mass and volume dose.