Seed-mediated Growth Method Research Articles

Optical properties and microstructure of Au nanorods via seed solution amount variation synthesized by seed-mediated growth method

The effect of seed solution amount variation on the aspect ratio and microstructure of gold nanorods (GNRs) using a seed-mediated method has been studied. The ultraviolet–visible (UV–Vis) absorption spectra for all samples shows that the wavelength of transverse surface plasmon resonance (TSPR) peak appeared at around 534 ± 10 nm regardless of the amount of seed solution used. The wavelength of longitudinal surface plasmon resonance (LSPR) of GNRs increased from 750 to 812 nm with seed solution amount being raised from 40 to 320 μl. Then, the wavelength of GNRs slightly decreased from 812 to 789 nm when the seed solution amount increased from 320 to 800 μl. The aspect ratio (AR) value measured from TEM images increased from 3.32 ± 0.07 to 4.03 ± 0.08 when the seed solution amount increased from 40 to 320 μl. Then, the AR value slightly decreased from 4.03 ± 0.08 to 3.95 ± 0.08 when the seed solution amount increased from 320 to 800 μl. The synthesized product of gold nanoparticles included spheres, nanorods and rhombus-shaped particles. The results of NBED and EDS revealed that the rhombus-shaped nanoparticles were bimetallic, containing gold and silver.

Gold nanorods/mesoporous silica-based nanocomposite as theranostic agents for targeting near-infrared imaging and photothermal therapy induced with laser.

Photothermal therapy (PTT) is widely regarded as a promising technology for cancer treatment. Gold nanorods (GNRs), as excellent PTT agent candidates, have shown high-performance photothermal conversion ability under laser irradiation, yet two major obstacles to their clinical application are the lack of selective accumulation in the target site following systemic administration and the greatly reduced photothermal conversion efficiency caused by self-aggregating in aqueous environment. Herein, we demonstrate that tLyp-1 peptide-functionalized, indocyanine green (ICG)-containing mesoporous silica-coated GNRs (I-TMSG) possessed dual-function as tumor cells-targeting near-infrared (NIR) fluorescent probe and PTT agents. The construction of the nanostructure began with synthesis of GNRs by seed-mediated growth method, followed by the coating of mesoporous silica, the chemical conjugation of PEG and tLyp-1 peptide, and the enclosure of ICG as an NIR imaging agent in the mesoporous. The as-prepared nanoparticles could shield the GNRs against their self-aggregation, improve the stability of ICG, and exhibit negligible dark cytotoxicity. More importantly, such a theranostic nanocomposite could realize the combination of GNRs-based photothermal ablation under NIR illumination, ICG-mediated fluorescent imaging, and tLyp-1-enabled more easy endocytosis into breast cancer cells. All in all, I-TMSG nanoparticles, in our opinion, possessed the strong potential to realize the effective diagnosis and PTT treatment of human mammary cancer.

Strong coupling between localized and propagating plasmon polaritons.

We investigate plasmon-plasmon (PP) coupling in the strongly interacting regimes by using a tunable plasmonic platform consisting of triangular Ag nanoprisms placed nanometers away from Ag thin films. The nanoprisms are colloidally synthesized using a seed-mediated growth method and having size-tunable localized surface plasmon polariton (SPP) resonances immobilized on Si(3)N(4) films. The PP coupling between the localized SPPs of metal nanoprisms and the propagating SPPs of the metal film is controlled by the nanoprism concentration and the plasmon damping in the metal film. Results reveal that Rabi splitting energy determining the strength of the coupling can reach up to several hundreds meV, thus demonstrating the ultrastrong coupling occurring between localized and propagating SPPs. The metal nanoparticle-metal thin film hybrid system over the square-centimeter areas presented here provides a unique configuration to study PP coupling all the way from the weak to ultrastrong coupling regimes in a broad range of wavelengths.

Synthesis of Absorption-Dominant Small Gold Nanorods and Their Plasmonic Properties.

Absorption-dominant small Au nanorods with diameters of less than 10 nm are prepared using a facile seed-mediated growth method. The diameters of the small gold nanorods range from 6 to 9 nm, and their lengths vary from 16 to 45 nm. Their aspect ratios can be tailored from 2.7 to 4.7. As a result, the longitudinal plasmon resonance wavelengths are readily tunable from ∼720 nm to ∼830 nm by changing the seed-to-Au(III) molar ratio in the growth solution. The fractions of the scattering in the total extinction of the small Au nanorods are found to be in the range of 0.005 to 0.025 with finite-difference time-domain simulations, confirming that the extinction values of these small Au nanorods are dominantly contributed to by the light absorption. Moreover, the small Au nanorod sample is coated with a dense silica layer for photothermal therapy with three cell lines. It shows improved photothermal therapy performance compared to a large Au nanorod sample for the same cellular Au contents. Our study suggests that small Au nanorods are promising light absorbers and photothermal therapy agents.

Formation of high-density crystalline-shape gold nanoparticles on indium tin oxide surfaces: effects of alcohothermal seeding.

We found that the gold nanoparticles with high-density and crystalline-shape, such as nanocubes, nanobricks, pentahedral nanorods, etc., can be realized on the surface by using a seed-mediated growth method with a unique seeding process, namely alcohothermal. By using a conventional growth solution that contains HAuCl4, cetyltrimethylammonium bromide, NaOH and ascorbic acid, gold nanoparticles with crystalline-morphology (gold nanocrystals) of yield up to ca. 95%, can be prepared. An alcohothermal seeding was carried out by a thermal reduction of gold ions from an alcoholic solution of gold salt on the surface through an annealing process at a moderate temperature, namely 250 degrees C. It is believed that the unique initial characteristic (presumably the structures) of the gold nanoseeds particles as the result of peculiar nanoseeds formation process, prepared using this approach, instead of a simple thermal restructuring of the as prepared nanoseeds as confirmed by the results of annealing treatment on the nanoseed prepared using the normal and in-situ reduction seeding, was as the driving factor for the projected growth of crystalline-shape gold nanoparticles on the surface. The crystalline-shape gold nanoparticles modified-surface should find a potential application in catalysis, sensors and SERS.

Uniform arrays of gold nanoparticles with different surface roughness for surface enhanced Raman scattering

Uniform arrays of coarse and smooth gold nanoparticles with diameter about 130 nm were successfully synthesized through seed-mediated growth method, separately. Scanning and transmission electron microscopy (SEM and TEM) and X-ray diffraction (XRD) have been used to study the formation and structure of the nanocomposites. The high enhancement factor for surface-enhanced Raman scattering of coarse and smooth gold nanoparticles were estimated to be about 3.1 × 106 and 2.0 × 106, respectively. It is evident that the coarse gold nanostructures has higher influence factor than the smooth gold nanostructures. Therefore, these unique properties of the coarse Au nanoparticles appear to be very promising for applications as high-performance SERS substrates.

Near-infrared-absorbing gold nanopopcorns with iron oxide cluster core for magnetically amplified photothermal and photodynamic cancer therapy.

We present the synthesis and application of a new type of dual magnetic and plasmonic nanostructures for magnetic-field-guided drug delivery and combined photothermal and photodynamic cancer therapy. Near-infrared-absorbing gold nanopopcorns containing a self-assembled iron oxide cluster core were prepared via a seed-mediated growth method. The hybrid nanostructures are superparamagnetic and show great photothermal conversion efficiency (η=61%) under near-infrared irradiation. Compact and stable nanocomplexes for photothermal-photodynamic therapy were formed by coating the nanoparticles with near-infrared-absorbing photosensitizer silicon 2,3-naphthalocyannie dihydroxide and stabilization with poly(ethylene glycol) linked with 11-mercaptoundecanoic acid. The nanocomplex showed enhanced release and cellular uptake of the photosensitizer with the use of a gradient magnetic field. In vitro studies using two different cell lines showed that the dual mode photothermal and photodynamic therapy with the assistance of magnetic-field-guided drug delivery dramatically improved the therapeutic efficacy of cancer cells as compared to the combination treatment without using a magnetic field and the two treatments alone. The "three-in-one" nanocomplex has the potential to carry therapeutic agents deep into a tumor through magnetic manipulation and to completely eradicate tumors by subsequent photothermal and photodynamic therapies without systemic toxicity.

Ag-Fe2O3 Heterostructured Nanoparticles as Photocatalysts under Visible Light Irradiation

Due to the synergistic effect between different composites, an increasing number of functional semiconductor-metal hybrid nanomaterials with core-shell or heterostructure geometry has been fabricated and proposed as the preferred form of catalysts. For example, Au@Co3O4 core-shell nanostructures showed higher oxygen evolution reaction activity than a mixture of Au and Co3O4 nanoparticles, or Co3O4 and Au nanoparticles alone. In addition, PbS-Ag heterostructure nanotubes exhibited significantly enhanced photocatalytic activity. Thanks to the controlled syntheses of semiconductor-metal nanocomposites with desired morphologies, it has been feasible to study the nanostructure tuning capacities. Herein, Ag-Fe2O3 core-shell and heteromer nanocomposites were synthesized by a seed-mediated growth method reported previously, and hollow Fe2O3 nanoparticles were obtained by the transformation of Ag-Fe2O3 core-shell nanocomposites. Subsequently, the photocatalytic activity of Ag-Fe2O3 core-shell nanocomposites was directly compared with that of Ag-Fe2O3 heteromer and hollow Fe2O3 nanoparticles, respectively. Finally, we could demonstrate experimentally whether the enhanced photocatalytic activity of Ag-Fe2O3 core-shell arise from its wide absorbance range of visible light and favorable charge separation. This investigation would help us to further understand nanostructure tuning capacity of nanocomposites and control their syntheses for a given application.

Activity of Small Silver Nanocubes as Activators for Electroless Copper Deposition

Small (12nm) Ag nanocubes enclosed by (100) facets were successfully synthesized using Pt seed-mediated growth method for catalyzing electroless copper deposition (ECD). The activities and resulting ECD kinetics were of Ag nanocubes enclosed by (100) planes and Ag nanoparticles (17nm) governed by (111) planes were compared. The deposition kinetics was investigated using an electrochemical quartz crystal microbalance (EQCM). The results showed that the induction period of the nanocubes (observed by a potential-deposition time curve) was 34s, consistent with the incubation time obtained by the curve of frequency change vs. deposition time. The potential at which steady-state deposition occurs was independent of the Ag catalyst facets. At a deposition time of 500s, the mean mass activities (in terms of the weight of the catalyst for the nanocubes and nanoparticles) were determined to be 1.959 and 0.9527, respectively. The smaller Ag nanocubes showed a twofold higher mass activity than the Ag nanoparticles. In a careful comparison based on the same electrochemical surface area (ESA), the specific activity in terms of ESA demonstrated that the Ag nanocubes showed a better ECD activity (5.99×10−2mgcm−2) than the Ag nanoparticles (4.37×10−2mgcm−2); thus, the nanocubes enabled faster ECD. Additionally, the data (supported by Tafel plots and CV curves normalised to the ESA) inferred that the greater specific activity of the nanocubes could be attributed to a higher oxidation power for anodic formaldehyde. The process deposited a Cu film with less CuO via the (100) planes of the nanocubes.

Preparation of Au@Ag Core-Shell Nanoparticles through Seed-Mediated Growth Method

Preparation of Au@Ag Core-Shell Nanoparticles through Seed-Mediated Growth Method

Shape and size controlled synthesis of Au nanorods: H2S gas-sensing characterizations and antibacterial application

Controlling their size and shape is one of the important issues in the fundamental study and application of colloidal metal nanoparticles. In the current study, different sizes and shapes of Au nanorods were fabricated using a seed-mediated growth method. Material characterization by X-ray diffraction and transmission electron microscopy revealed that the obtained products were made of single-crystal Au nanorods with an average diameter and length of 10nm and 40nm, respectively. The Au nanorod-based sensor exhibited significantly high sensitivity and fast response/recovery time to low concentrations (2.5–10ppm) of H2S at temperatures ranging from 300°C to 400°C. Additionally, they exhibited antibacterial effect at low concentration. These results suggested that the fabricated Au nanorods have excellent potential for practical application in air pollution monitoring and biomedicine.

Thermal conversion of core-shell metal-organic frameworks: a new method for selectively functionalized nanoporous hybrid carbon.

Core-shell structured ZIF-8@ZIF-67 crystals are well-designed and prepared through a seed-mediated growth method. After thermal treatment of ZIF-8@ZIF-67 crystals, we obtain selectively functionalized nanoporous hybrid carbon materials consisting of nitrogen-doped carbon (NC) as the cores and highly graphitic carbon (GC) as the shells. This is the first example of the integration of NC and GC in one particle at the nanometer level. Electrochemical data strongly demonstrate that this nanoporous hybrid carbon material integrates the advantageous properties of the individual NC and GC, exhibiting a distinguished specific capacitance (270 F·g(-1)) calculated from the galvanostatic charge-discharge curves at a current density of 2 A·g(-1). Our study not only bridges diverse carbon-based materials with infinite metal-organic frameworks but also opens a new avenue for artificially designed nanoarchitectures with target functionalities.

Preparation of Gold Nanorods and Their Applications in Photothermal Therapy.

Gold nanorods (GNRs) have recently been widely studied due to their unique optical and electronic properties which are dependent on their shape, size, and aspect ratio. Seed-mediated growth method has become the most widely method for the synthesis of GNRs due to its advantages of simplicity of procedure, high yield of nanorods, and ease of aspect ratio controlling. Moreover, GNRs are especially attractive candidates for exploitation in photothermal therapy since they can be readily synthesized with various aspect ratios, which enable GNRs to selectively absorb the near-infrared (NIR) light. This review is focused on summarizing the preparation of GNRs by seed-mediated growth method and their applications in photothermal therapy.

Synthesis of concave gold nanocuboids with high-index facets and their enhanced catalytic activity.

Novel concave gold nanocuboids bounded by 24 high-index {611} facets are synthesized using the seed-mediated growth method via an overgrowth mechanism. The as-synthesized products demonstrated greatly enhanced catalytic activity for the electro-oxidation of glucose and the reduction of 4-nitrothiophenol (4-NTP) under a laser.

Construction of kinked heteronanorods modified by metal nanoparticles with enhanced catalytic performance.

Unique kinked semiconductor-metal Au-Ag2S-ZnS and Au-Ag2S-ZnS-Au heteronanorods have been synthesized for the first time by a seed-mediated growth method. A plausible mechanism for the formation of kinked heteronanorods is proposed. The catalytic activity of such novel kinked semiconductor-metal heteronanorods with selective deposition and uniform morphology is also investigated via a model reaction based on the reduction of 4-nitrophenol by NaBH4.

4MBA-labeled Ag-nanorod aggregates coated with SiO2: synthesis, SERS activity, and biosensing applications

A new nanostructure, silica-coated Ag nanorods (NRs) aggregate with 4-mercaptobenzoic acid molecules (4MBA-Ag NRs@SiO2), was prepared by a seed-mediated growth method and a modified Stöber method.

Synthesis of Cu2SnSe3-Au heteronanostructures with optoelectronic and photocatalytic properties.

Cu2SnSe3-Au heteronanostructures have been successfully synthesized for the first time using a seed-mediated growth method. Such new Cu2SnSe3-Au heteronanostructures demonstrate enhanced and broadened optical absorption in the Vis-NIR region. We have also investigated the optoelectronic and photocatalytic properties of the Cu2SnSe3-Au heteronanostructures and proposed a mechanism to illustrate the improved photocurrent and photocatalytic performance as compared to bare Cu2SnSe3.

3D-gold superstructures grown on a poly(acrylic acid) brush

3D-gold octahedra superstructures are fabricated on a PAA brush using the seed-mediated growth method. The morphologies of the gold micronanostructures can be tuned by a strategy which opens up a new possibility for shape-controlled growth of noble metal structures.

Particle size dependence of the surface-enhanced Raman scattering properties of densely arranged two-dimensional assemblies of Au(core)-Ag(shell) nanospheres.

We investigated the dependence of the surface-enhanced Raman scattering (SERS) activity of densely arranged two-dimensional assemblies of spherical Au(core)-Ag(shell) nanoparticles (Au/AgNSs) on the nanoparticle diameter. The size-controlled Au/AgNSs were synthesized using the Au nanosphere seed-mediated growth method without any bulky stabilizers. The diameters of the Au/AgNSs were 38, 53, and 90 nm and the ratio of the total diameter to the Au core diameter was adjusted to ca. 2.0. Extinction spectra of the colloidal solutions of these nanoparticles exhibited the prominent peak of the localized surface plasmon resonance (LSPR) of Ag and therefore the Au/AgNSs exhibited LSPR properties almost the same as Ag nanospheres. It was confirmed from SEM observation that the organic solvent-mediated liquid-liquid interface assembly technique easily generated densely arranged two-dimensional assemblies of the nanospheres. The extinction spectra of all the assemblies exhibited a prominent broad peak ranging from 500 nm to the near-infrared region, which is assigned to the longitudinal LSPR mode of the coupling nanospheres. The extinction intensity increased with increasing nanosphere diameter. The SERS activities of these assemblies were investigated using p-aminothiophenol as a probe molecule. The result revealed that the enhancement factor (EF) of the Raman signal dramatically increased upon increasing the particle diameter. The maximum EF obtained with a laser excitation wavelength of 785 nm was 1.90 × 10(6) for a nanosphere diameter of 90 nm. This renders the two-dimensional assemblies of the plasmonic Au/AgNSs promising for the development of highly sensitive SERS sensor platforms due to their strong electromagnetic effect.

Kinetic impact of Pt seed morphology on the highly controlled growth of Ni-based nanostructures

A Pt seed-mediated growth method for the synthesis of Ni/NiO and Ni/Ni(OH)2 nanocomposites offers an unprecedented control over the morphological and compositional features of Ni-based nanostructures.