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Plasmonic nanorods exhibit unique optical properties due to their ability to support localized surface plasmon resonances (LSPR). These nanorods are highly valued for applications in sensing, imaging, and medical therapies because of their tunable optical behavior and strong electromagnetic field enhancement. In this study, a seed-mediated approach was utilized to synthesize and purify gold nanorods (GNRs), with a focus on their integration in the LSPR sensor chips. The synthesis was begun with the preparation of small gold nanoparticles as seeds, followed by the growth of nanorods in a carefully controlled environment. UV-visible spectroscopy confirmed the formation of GNRs, revealing two plasmonic peaks, with the transverse peak at 523 nm and the longitudinal peak at 800 nm after 24 hours of aging. Further, the self-assembled monolayer of the GNRs on glass substrate achieved using a thiol-functionalized linker, 3-mercaptopropyltrimethoxysilane (MPTMS), and ionic strength modulation with NaCl. For optimal stabilization and alignment of the nanorods on the glass substrate, the ideal incubation time for the glass substrates in the colloidal gold nanoparticle solution was determined to be 24 hours. This duration was made the most effective configuration of the LSPR sensor chip, with improved stability and sensitivity for plasmonic applications. [ABSTRACT FROM AUTHOR]

Dermatophytes are a group of fungi that cause dermatophytosis, a type of skin infection affecting both humans and animals. While dermatophytosis is typically self-limiting, it can pose significant challenges for individuals with weakened immune systems. Additionally, current treatment options for dermatophytosis have their limitations, including issues of toxicity, inefficacy, and the emergence of drugresistant strains. Recently, nanotechnology-based approaches have emerged as a promising strategy to overcome the drawbacks of conventional antifungal medications. Gold Nanoparticles (GNPs) have demonstrated substantial antifungal activity against various fungal species, including dermatophytes. Among these, Gold Nanobipyramids (GNBPs) exhibit unique physicochemical properties that enhance their effectiveness against dermatophytes. GNBPs were synthesized using the Seed-Mediated Growth Method (SMGM) due to its simplicity. Optically, GNBPs displayed plasmonic peaks at 1.548 (wavelength 561 nm) and 2.372 (wavelength 807 nm). Structurally, intensity peaks at 38.15° (plane 111) and 44.49° (plane 200) were identified. GNBPs have a surface density of ~70.227±0.530. In the dermatophyte treatment process, GNBPs exhibited varying inhibitory effects. At 40% concentration, fungal growth persisted, with a surface density similar to the no control area. At 60%, inhibition occurred, though less efficiently. The most effective inhibition was observed at 80%, and complete inhibition was achieved at 100% concentration. GNBPs proved successful in inhibiting fungal growth, attributed to their curvature and sharp edges interacting with microbial cell membranes, leading to membrane damage and cellular content leakage. [ABSTRACT FROM AUTHOR]

Gold nanorods (GNRs) with exceptional photothermal properties have held promising potential for application in the biomedical field. In this study, the authors achieved photothermal ablation by polyethylene glycol (PEG)‐functionalised GNRs. Well‐dispersed and uniform GNRs were produced through a seed‐mediated growth method. A thermal camera was used to scrutinise the temperature distribution and efficiency of the photothermal properties of the GNRs, which were irradiated by an 808 nm laser on a silicon chip. They observed that the GNRs provided about a 5°C temperature increase and produced hyperthermia efficiently. Since GNRs need to be surface tailored with a biocompatible material rather than cetyltrimethylammonium bromide (CTAB), they chose methoxyl PEG thiol to modify the GNRs. By taking advantage of the alkaline environment that assists this functionalisation, they accomplished about 89% removal of CTAB and identified a PEG layer on the surface of the GNRs. The GNR biocompatibility was considerably improved without any shift of the optical properties. Hepatocellular carcinoma cells were incubated with GNRs for 24 h and then were irradiated with a near‐infrared laser for 3 min. Few cells remained alive, which demonstrated the photothermal ablation ability of the GNRs.

Objective To investigate the antitumor efficacy of near-infrared photothermal therapy (NIPT) at different doses of gold nanorods (GNRs) and near-infrared light on gastric cancer SGC-7901 cells in vitro. Methods GNRs were prepared by seed-mediated growth method, and their morphology, particle size and light absorption were detected. The inhibitory rates of GNRs on the proliferation of SGC-7901 cells were measured by CCK-8. The inhibitory rates of GNRs at different concentrations and NIPT at different powers on the proliferation of SGC-7901 cells were calculated. Meanwhile, the apoptosis of gastric cancer cells was detected by Annexin V-FITC/PI fluorescence method, and the Caspase-3 and Caspase-9 enzyme activities were detected by spectrophotometry. Results The synthesized GNRs had a longitudinal plasmon resonance absorption peak at around 790nm. The cytotoxicity of pure GNRs was really low. However, NIPT had obvious antitumor effects on gastric cancer cells. With the increase of GNRs dose and near-infrared light power, the cell growth inhibition rate increased significantly. After administration of 40μg/ml GNRs for 1h and 3.0W/cm2 near-infrared radiation for 2min, the cell growth inhibition rate reached 93.4%. One hour after treatment, part of the cells were in early apoptotic stage; while three hours after treatment, the cells were in advanced apoptosis or death state, and the Caspase-3, Caspase-9 enzyme activity increased about one fold, compared with those of control group. Conclusion GNRs-mediated NIPT has obvious antitumor and apoptosis induction effects on gastric cancer cells.

A simple technique of seed-mediated growth has been successfully performed to grow anisotropy gold nanoparticles on solid substrates. The growth of the gold nanoparticles has been carried out in the presence of a binary surfactant mixture of hexadecyltrimethylammonium bromide with two different molecular weights of a capping agent, namely polyvinylpyrrolidone: 40,000 and 55,000. In this study, the effect of process parameters, growth time and molecular weight of capping agent was investigated. The growth time shows a significant impact on the shape and size of nanoparticles. The shorter growth time produced small spherical to square-like shape particles, whereas bigger particles including nanorods, nanosquares and nanotriangles were formed with longer growth time. The shape controlling agent, polyvinylpyrrolidone, was used to synthesis gold nanoparticles. It was found that monodisperse gold nanoparticles with uniform shape and size are hardly obtained when polyvinylpyrrolidone 40,000 was used as capping agent. Polyvinylpyrrolidone 55,000 produced more uniform shape and size of gold nanoparticles. Thus, these process parameters were found affected to the size, shape, surface density and uniformity of gold nanoparticles. This sample was further applied as a sensing material in the detection of toxic fungicide, namely chlorothalonil. The sensitivity of the sensor system was determined by the changes in peak positions and intensities of the transverse and longitudinal surface plasmon resonance peaks on different medium, that is, air, deionized water and chlorothalonil solution. The sensor response of gold nanoparticles thin film in 30 mM chlorothalonil showed two resonance peaks in comparison to the control experiment without gold nanoparticle thin film. The gold nanoparticles thin film sensor was successfully synthesized and potentially useful as a sensing material for fungicide detection. [ABSTRACT FROM AUTHOR]

Gold nanorods were synthesized by seed-mediated growth method. The effect of different pH values, hydrogen peroxide concentration and oxidation time on resonance peak position of gold nanorods was studied. The absorption peaks and morphology of gold nanorods with different oxidation time were characterized by UV-Vis absorption spectra and SEM, respectively. The result shows that gold nanorods shortened gradually with increasing oxidation time, while the diameter remained nearly unchanged. Moreover, the longitudinal surface plasmon resonance (SPR) peak of the gold nanorods showed a blue-shift gradually, while transverse SPR peak basically kept constant. The longitudinal SPR peak position changed approximately linearly as a function of the oxidation time. Within the margin of error, the longitudinal SPR peak wavelength of gold nanorods with different sizes was basically consistent with the calculated theoretical value. [ABSTRACT FROM AUTHOR]

Gold nanorods (GNRs) with exceptional photothermal properties have held promising potential for application in the biomedical field. In this study, the authors achieved photothermal ablation by polyethylene glycol (PEG)‐functionalised GNRs. Well‐dispersed and uniform GNRs were produced through a seed‐mediated growth method. A thermal camera was used to scrutinise the temperature distribution and efficiency of the photothermal properties of the GNRs, which were irradiated by an 808 nm laser on a silicon chip. They observed that the GNRs provided about a 5°C temperature increase and produced hyperthermia efficiently. Since GNRs need to be surface tailored with a biocompatible material rather than cetyltrimethylammonium bromide (CTAB), they chose methoxyl PEG thiol to modify the GNRs. By taking advantage of the alkaline environment that assists this functionalisation, they accomplished about 89% removal of CTAB and identified a PEG layer on the surface of the GNRs. The GNR biocompatibility was considerably improved without any shift of the optical properties. Hepatocellular carcinoma cells were incubated with GNRs for 24 h and then were irradiated with a near‐infrared laser for 3 min. Few cells remained alive, which demonstrated the photothermal ablation ability of the GNRs. [ABSTRACT FROM AUTHOR]

Facile preparation of small gold nanorod with controllable and large surface plasmon resonance band is of great value for applications in especially the biomedical and sensing fields. In this work, we propose that without addition of additive to complicate the experimental system catechol of a very weak reducibility can be used as reducing agent for seed-mediated synthesis of gold nanorod. Under a temperature of 40 °C and a catechol concentration of 17.5 mM, monodisperse gold nanorod with a high shape yield, a largest plasmon wavelength of 918 nm, and especially a small diameter of 9.8 nm can be acquired simultaneously. A good tune over the plasmon wavelength is also shown by varying the amount of silver ion. Besides, the effects of experimental parameters including silver ion, cetyltrimethylammonium bromide, gold seed and catechol have also been carefully studied, and the morphological and structural evolutions of the particle have been discussed based on reported growth mechanism. [Display omitted] • Without introduction of additive, catechol is proposed as reducing agent and demonstrated to facilely prepare monodisperse gold nanorod with a small diameter of only 9.8 nm and a silver ion-dependent plasmon wavelength with a largest value of 918 nm. • Effects of synthetic parameters including silver ions, gold seed, reducing agent, and CTAB on the acquired product were studied to discuss the morphological evolution of particle based on reported growth mechanism of gold nanorod. • The successful preparation of gold nanorod by a weakest reducing agent of catechol further demonstrates the significance of synergistic effect shown by experimental parameters in governing the anisotropic evolution of gold nanostructure. [ABSTRACT FROM AUTHOR]

A way of synthesizing bimetallic gold/silver nanoparticles with in situ seeding initiated by the addition of sodium borohydride is proposed. The obtained nanoparticles are studied by means of transmission electron microscopy (TEM). Changes in the optical density spectra of the nanoparticles during their coagulation are investigated. The technique allows the rapid acquisition of nontoxic SERS-active nanoparticles with maximum SERS enhancement factor about 10 in the near infrared range for Raman shifts typical for biological objects such as bacterial cells and spores. [ABSTRACT FROM AUTHOR]

Highlights: [•] ZnO nanocube with (101)-basal plane formed on the substrate via low-frequency ultrasonic-assisted hydrolysis method. [•] A directed-nucleation by the ultrasonic field is the driving factor for nanocube formation. [•] ZnO nanocube show highly efficient heterogenous photocatalytic property. [Copyright &y& Elsevier]

Highlights: [•] Au nanoparticles modified glassy carbon electrodes were prepared by seed mediated growth method. [•] Enhanced electrocatalytic oxidation of glucose was observed at the AuNPs/GC surface. [•] AuNPs/GC exhibits good sensing properties with wide linear range and high sensitivity. [•] Common interfering species have no obvious effects on the oxidation of glucose. [Copyright &y& Elsevier]

In this study, we prepared different shapes of gold nanoparticles by seed-mediated growth method and applied them on the photoelectrodes of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy show that the average diameter of the spherical gold nanoparticles is 45 nm, the average length and width of the short gold nanorods were 55 and 22 nm, respectively, and the average length and width of the long gold nanorods were 55 and 14 nm, respectively. The aspect ratio of the short and long gold nanorods was about 2.5 and 4, respectively. The results of ultraviolet–visible absorption spectra show that the absorption wavelength is about 540 nm for spherical gold nanoparticles, and the absorption of the gold nanorods reveals two peaks. One is about 510 to 520 nm, and the other is about 670 and 710 nm for the short and long gold nanorods, respectively. The best conversion efficiency of the dye-sensitized solar cells with spherical gold nanoparticles and short and long gold nanorods added in is 6.77%, 7.08%, and 7.29%, respectively, and is higher than that of the cells without gold nanoparticles, which is 6.21%. This result indicates that the effect of gold nanoparticles on the photoelectrodes can increase the conductivity and reduce the recombination of charges in the photoelectrodes, resulting in the increase of conversion efficiency for DSSCs. In addition, the long gold nanorods have stronger SPR effect than the spherical gold nanoparticles and short gold nanorods at long wavelength. This may be the reason for the higher conversion efficiency of DSSCs with long gold nanorods than those of the cells with spherical gold nanoparticles and short gold nanorods. [ABSTRACT FROM AUTHOR]

Abstract: Here, we report a new and facile method to prepare silver nanoparticles (Ag NPs) film for surface-enhanced Raman scattering (SERS)-based sensing. The porous Ni foam was used as a template to generate high quality of Ag NPs by seed-mediated growth of metallic nanoparticles. The preparation process is very economic and environment-friendly, can achieve the recovery of the raw materials. We found that the type of silver-plating solution and the growth time are two key factors to determine the magnitude of SERS signal enhancement. Using rhodamine 6G (R6G) and 4-animothiophenol (4-ATP) as probe molecules, the created Ag NP films exhibited relatively high enhancement ability, good stability, and well reproducibility. The synthesized SERS-active substrate was further used to detect melamine molecules, an illegal additive in infant milk powder, and the limitation of detection can reach 1μM. [Copyright &y& Elsevier]

Electrochemical measurements using nonconducting support materials, such as paper and cotton gauze, for modifying glassy carbon (GC) with gold nanoparticles (AuNPs) are described. After a seed-mediated growth modification of AuNPs on Kimwipes, a AuNP-Kimwipes-modified GC electrode that was fabricated by simply fixing a piece of AuNP-modified Kimwipes on a GC electrode surface showed almost reversible cyclic voltammetric responses for the oxidation of Fe(CN)64− in 0.1 M phosphate buffer solution (pH 7.0) even when the GC surface was not polished before fixing. The electrochemical impedance results also indicated the significant effect of the AuNP-modified Kimwipes on reducing the charge transfer resistance. Similar effects were observed for AuNP-modified cotton gauze, whose characteristics were the partial coverage of a GC surface, and, for the electrode in that a piece of untreated Kimwipes was bound between AuNP-modified Kimwipes and a GC electrode surface. On the basis of such partial or remote effects of AuNPs together with other electrochemical results, plausible mechanisms to promote the electron transfer reaction of Fe(CN)64− by AuNPs are discussed. In addition, as a specific phenomenon in the present modified electrodes, the adsorption of Fe(CN)64− with the presence of AuNPs is described. [ABSTRACT FROM AUTHOR]

Seed-mediated growth methods involving reduction of tetrachloroaurate(III) with ascorbic acid are common for the synthesis of gold nanorods. This study shows, however, that simply by appropriate choice of the reducing agent a drastic influence on the aspect ratio can be attained. Weaker reducing agents, such as dihydroxybenzene isomers (hydroquinone, catechol or resorcinol) or glucose can increase the aspect ratio of the nanorods by an order of magnitude, up to values as high as 100 (nanowires). The increase in aspect ratio is mainly a consequence of an increase in length of the particles (up to 1-3 μm). This effect is probably associated with a decrease in the reduction rate of gold(III) species by dihydroxybenzenes or glucose compared to ascorbic acid. The reduction potential of the reducing agents strongly depends on the pH value, and related effects on the dimensions of the nanoparticles are also reflected in this study. The nanorods exhibited penta-twinned nature without noteworthy defects (e.g. stacking faults and dislocations). [ABSTRACT FROM AUTHOR]

This review highlights work from the authors' laboratory on the recent development of seed-mediated growth method for noble metal nanocrystals. The seed-mediated growth method has become one of the most efficient and versatile methods for synthesizing high-quality noble metal nanocrystals. The seed-mediated growth method can separate the nucleation and growth stages of metal nanocrystals, and thus provide better control over the size, size distribution, and crystallographic evolution of metal nanocrystals. Because of its high controllability, the seed-mediated growth method is especially promising in providing mechanistic insights into the growth mechanisms of noble metal nanocrystals. In this review, the thermodynamic and kinetic parameters for the nucleation and growth of noble metal nanocrystals are systematically summarized. Mechanistic understanding of these parameters is provided. These studies provide useful guidelines for the rational design and synthesis of novel noble metal nanocrystals with high quality. [ABSTRACT FROM AUTHOR]

Abstract: Paper surfaces (Whatman filter papers, Kimwipes®, and Japanese Washi papers) were employed as support for gold nanoparticles (AuNPs) deposited by the seed-mediated growth method. The AuNP-modified paper or textile was brought into “weak” (or non-permanent) contact with a glassy carbon electrode and immersed into aqueous electrolyte media. Electrochemical responses for the Fe(CN)6 4−/Fe(CN)6 3− redox system in 0.1M phosphate buffer (pH 7.0) and 1.0M KCl solutions were investigated by voltammetry and impedance methods. Even for weakly contacted AuNP catalysts of relatively low density faster electron transfer was observed. Particle sizes of at least 20nm diameter were required. There was no permanent contact from AuNP catalysts to the electrode and the process was therefore termed “weak contact catalysis”. The method is proposed as a rapid and novel catalyst screening tool with potential applications in fuel cell and sensor technologies. [Copyright &y& Elsevier]

Abstract: A novel nonenzymatic glucose sensor based on flower-shaped (FS) Au@Pd core–shell nanoparticles–ionic liquids (ILs i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide, [P(C6)3C14][Tf2N]) composite film modified glassy carbon electrodes (GCE) was reported. The Au@Pd nanocatalysts were prepared by seed-mediated growth method, forming the three-dimensional FS nanoparticles, where tens of small Pd nanoparticles (∼3nm) aggregated on gold seeds (∼20nm). The FS Au@Pd nanoparticle was a good candidate for the catalytic efficiency of nanometallic surfaces because of its flower-shaped nature, which has greater adsorption capacity. XPS analysis and zeta potential indicated that the surface of Pd atoms is positively charged, profiting the oxidation process of glucose. And ILs acted as bridge connecting Au@Pd one another and bucky gel as platform within the whole nanocomposite. So the modified electrode has higher sensitivity and selectivity owing to intrinsic synergistic effects of this nanocomposite. Amperometric measurements allow observation of the electrochemical oxidation of glucose at 0.0V (vs. Ag/AgCl), the glucose oxidation current is linear to its concentration in the range of 5nM–0.5μM, and the detection limit was found to be 1.0nM (S/N=3). The as-prepared nonenzyme glucose sensor exhibited excellent stability, repeatability, and selectivity. [ABSTRACT FROM AUTHOR]

Abstract: Pt and Pd nanosheaths are successfully synthesized on multi-walled carbon nanotubes (MWCNTs) using the non-covalent poly(diallyldimethylammonium chloride) (PDDA) functionalization and seed-mediated growth methods. In this method, negatively charged Pt or Pd metal precursors are self-assembled with positively charged PDDA-functionalized MWCNTs, forming uniformly distributed Pt or Pd nanoseeds on MWCNTs supports. The contiguous and highly porous Pt and Pd nanosheath structured catalysts are then formed by the seed-mediated growth in corresponding metal precursors using ascorbic acid as the reducing agent. The essential role of uniformly dispersed Pt and Pd nanoseeds on PDDA-MWCNTs is demonstrated. The results indicate that both Pt and Pd nanosheaths show an enhanced catalytic activity for the methanol and formic acid oxidation reaction in acid solution, respectively, as compared with conventional Pt/C and Pd/C catalysts. The enhanced activities are most likely due to the reduced oxophilicity, which results in a weakened chemisorption energy with oxygen-containing species such as COad, and the increased reactive sites due to the large number of grain boundaries of the Pt and Pd nanosheath structured electrocatalysts. [ABSTRACT FROM AUTHOR]

We report the synthesis of gold nanorods (NRs) by seed-mediated growth method. A small amount of different shapes such as triangles, hexagons and a large amount of rods are obtained by varying the proportion of seed to metal salt, adding NaOH to growth solution as well as using the seed solution of CTAB-capped agent. The gold nanorod (NR) formation yield is improved. Meanwhile, the growth mechanism of high yield gold NRs is discussed. The high quality single size NRs can be separated from polydisperse samples using surfactant-assisted nanorod self-assembly. The gold NRs synthesized were characterized by transmission electron microscopy (TEM) and UV-vis spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: An effective approach to attach gold nanoparticles (AuNPs) directly on indium tin oxide (ITO) surface with higher density is reported. The attachment was carried out using a cast seed-mediated growth method, which was revised from our previous seed-mediated growth approach. The cast seeding with three-cycles of the drop of the seed solution containing Au nano-seed particles and the evaporation at 30°C followed by the treatment in the growth solution containing HAuCl4, cetyltrimethylammonium bromide (CTAB) and ascorbic acid was found to be suitable to prepare the AuNPs attached ITO surfaces having higher density and narrower size distribution. The 10-cycles cast seeding formed the connected or networked nanostructures of AuNPs, though the optical properties were different from those of the dispersed AuNP-attached ITO. The present cast seeding approach provides a facile and useful strategy to attach AuNPs on the surface without the use of certain organic binder molecules. [Copyright &y& Elsevier]

Silver nanorods were prepared by seed-mediated growth method, following the procedures recently described by Jana et al. In seed-mediated growth method, small metal particles are prepared first and later used as seeds for the preparation of nanorods. The silver seeds were prepared by reduction of silver ions with sodium borohydride in the presence of sodium citrate dihydrate as stabilizer. These silver seeds were added into the solution containing more silver salt, an ascorbic acid (weak reducing agent) and a cetyltrimethylammonium bromide (CTAB). The effects of temperature and pH of solution on the morphology and uniformity of silver nanorods were investigated by UV-Vis spectroscopy, transmission electron microscopy (TEM). Increase of reaction temperature and pH led to a decrease of aspect ratio of silver nanorods and an increase of monodispersity. Also gold nanoshells have been synthesized by reacting aqueous HAuCl4 solutions with silver nanorods as solid templates. [Copyright &y& Elsevier]