Fabrication Of Gold Nanostructures Research Articles

The Fabrication of Gold Nanostructures as SERS Substrates for the Detection of Contaminants in Water.

Gold nanostructures (AuNSs) were used to fabricate surface-enhanced Raman spectroscopy (SERS) substrates. These AuNSs were produced using the solid-state dewetting method from thin films. The fragmentation process was studied at 300 °C, with durations of thermal treatment of 1, 3, 6, and 12 h. These SERS substrates were then employed to detect Rhodamine B (RhB) as the model analyte, simulating a contaminant in the water at a concentration of 5 ppm. The morphology of the AuNSs was examined using SEM, which revealed a spheroidal shape that began to coalesce at 12 h. The size of the AuNSs was estimated to range from 22 ± 7 to 24 ± 6 nm, depending on the annealing time. The localized surface plasmon resonance of the AuNSs was determined using absorption spectroscopy, showing a shift as the annealing time increased. The SERS signals of RhB adsorbed on the AuNS substrates were validated by performing a 10 × 10 point map scan over each sample surface (1, 3, 6, and 12 h), and a comparative analysis showed no significant differences in the positions of the bands; however, variations in intensity enhancement ranged from 5 to 123 times at 6 and 1 h, respectively.

Fabrication of Gold Nanostructures on Quartz Crystal Microbalance Surface Using Nanoimprint Lithography for Sensing Applications.

A quartz crystal microbalance (QCM) is a sensor that uses the piezoelectric properties of quartz crystals sandwiched between conductive electrodes. Localized surface plasmon resonance (LSPR) is an analytical technique that uses the collective vibration of free electrons on metal surfaces. These measurements are known as analysis techniques that use metal surfaces and have been applied as biosensors because they allow for the label-free monitoring of biomolecular binding reactions. These measurements can be used in combination to analyze the reactions that occur on metal surfaces because different types of information can be obtained from them. However, as different devices are used for these measurements, the results often contain device-to-device errors and are not accurately evaluated. In this study, we directly fabricated gold nanostructures on the surface of a QCM to create a device that can simultaneously measure the mass and refractive index information of the analyte. In addition, the device could be easily fabricated because nanoimprint lithography was used to fabricate gold nanostructures. As a proof of concept, the nanoparticle adsorption on gold nanostructures was evaluated, and it was observed that mass and refractive index information were successfully obtained without device-to-device errors.

Fabrication of gold nanostructures using wet lift-off without adhesion promotion

The use of an intervening adhesion layer is essential in reliable fabrication of noble metallic nanostructures for optical and electronic devices. However, many emerging applications such as plasmonics and transfer printing raise the demand of metallic structures without adhesion layers, either to mitigate the plasmon damping or to facilitate the transfer processes. In this work, we systematically investigate the fabrication reliability of adhesion-free lithographic gold nanostructures on Si wafers and gold-coated substrates using a wet lift-off process. According to a large amount of statistical results, we comprehensively evaluate the patterning behavior of metallic nanostructures without adhesion promotion. Analytical modelling and control experiments are carried out to characterize the mechanics of their failure behaviors as a function of morphology and surface property. Our work provides useful information to the nanofabrication community to obtain adhesion-free gold nanostructures for plasmonic and transfer printing applications.

Flash Ablation of Tunable and Deep-Subwavelength Nanogap by Using a Spatially Modulated Femtosecond Laser Pulse for Plasmonic Application

The fabrication of gold nanostructures on a dielectric substrate with a nanogap between the opposite tips is suitable for the excitation of hot spots. In this study, a novel and efficient one-step ...

Fabrication of gold nanostructures through pulsed laser interference patterning

In this Letter, we report on the experimental development and computational modeling of a simple, one-step method for the fabrication of diverse 2D and 3D periodic nanostructures derived from gold films on silicon substrates and over areas spanning 1 cm2. These nanostructures can be patterned on films of thickness ranging from 50 nm to 500 nm with pulsed interfering laser beams. A finite volume-based inhomogeneous multiphase model of the process shows reasonable agreement with the experimentally obtained topographies and provides insights on the flow physics including normal and radial expansion that results in peeling of film from the substrate.

Building Interfacial Nanostructures by Size-Controlled Chemical Etching

Development of soft chemical processes for the synthesis of interfacial architectures with well-defined structural nano-motifs organized over large areas in two dimensions is an important branch of nanotechnology. The present study deals with the fabrication of gold nanostructures using size-selective chemical etching of continuous gold films on glass support with titanium and chromium adhesive layers. In this process, which is called self-passivated surface etching, a gold film is etched in the presence of citric acid, resulting in gold nanostructures adhering to the metal support. The size-controlled chemical dissolution of gold is driven by a competing reaction between self-organized passivation of surface nano-motifs by citric acid shells and soft etching by a nonoxidative composition containing hydrochloric acid and hydrogen peroxide in water. According to these results, the presence of a chemically stable adhesive layer (titanium), citric acid in solution, and agitation are critical factors to be considered. However, the nature of the adhesive layer is the most influential factor. The following technique presents a simple method for the rapid fabrication of a nanostructured gold substrate that has the ability to support both propagating and localized surface plasmon resonances simultaneously.

Design and fabrication of gold nanostructures with dispersed nanospheres for localized surface plasmon resonance applications

The design and fabrication of gold nanostructures through nanosphere lithography utilizing dispersed nanospheres, on glass substrate for the applications of localized surface plasmon resonance, were investigated in detail. The fabrication of the nanostructures was realized through the gold film deposition onto nanospheres dispersed on a substrate and the subsequent directional gold etching. Depending on the deposition and etching conditions of the gold, a variety of gold nanostructures can be fabricated. So far through this method, only 2D nanocrescents had been reported. However, either 2D or 3D non-conformal nanostructures are formed in this way, and the profiles of the obtainable nanostructures were simulated under various conditions. For nanostructures fabricated on glass, the simulated profiles coincided well with the fabricated ones. These results prove that our profile simulation program can realize the design of 2D and 3D nanostructures obtainable by dispersed nanospheres, and reduce the effort and cost for achieving desired nanostructures by experiments in the trial-and-error stage.

Profile Simulation and Fabrication of Gold Nanostructures by Separated Nanospheres with Oblique Deposition and Perpendicular Etching

This paper investigates in detail the profiles of the nanostructures fabricated by nanosphere lithography through oblique deposition and perpendicular etching. 2D or 3D nanostructures can be achieved by this cost-effective method. Because the optical response of a particular nanoparticle depends on its size and shape, this angle deposition method can produce various shapes of nanostructures, which are suitable for localized surface plasmon resonance biosensor applications. The nanostructure profiles under various deposition and etching conditions are simulated in our work. The calculated 3D profiles are verified by the 3D nanostructures fabricated in our experiments, and the calculated 2D profiles are in good agreement with the fabricated nanocrescents reported by another research group. This paper gives a full theoretical solution of the obtainable nanostructure shapes by nanosphere lithography utilizing oblique deposition and perpendicular etching.

Preparation of gold nanoparticles by arc discharge in water

Gold nanoparticles have been attracting attention due to their extensive application in chemistry, physics, material science, electronics, catalysis and bionanotechnology. Synthesis of gold nanoparticles often involves toxic and expensive physical-chemistry methods. Preparation of gold nanoparticles by arc discharge in water is proposed for the first time. Fabrication of gold nanostructures in deionized water has been successfully established. The evidence of gold particles’ light absorbance reveals a unique surface plasmon resonance for Au nanoparticles suspended in deionized water. Gold nanostructures uniformly dispersed in water, their UV–Vis absorption and crystalline size are shown. Our experimental results demonstrate that fabrication of gold nanoparticles by arc discharge in water is an alternative, cheap, effective and environmentally friendly method.

Fabrication of Gold Nanostructures on Graphite Using Atomic Force Microscope

Various nanostructures are created on graphite in air through the field-induced deposition of gold atoms from the gold-coated tip of atomic force microscope (AFM). The nanolithography controlling system we developed makes it possible to fabricate arbitrary complicated patterns and to optimize the deposition conditions fast and easily. We found that gold mounds can only be created by tip-negative pulses within the pulsed voltage range of ± 20 V, 0.2–300 msec, and the size of gold mounds and the threshold voltages are highly dependent on the geometry of Au-coated tip. Our results support the mechanism of field evaporation of negative gold ions.

Fabrication of gold nanostructures on a vicinal Si(111) 7×7 surface using ultrahigh vacuum scanning tunneling microscope and a gold-coated tungsten tip

We have demonstrated that nanometer-scale gold dots can be deposited on a vicinal Si(111) 7×7 surface using the field-assisted atom transfer from the gold-coated tungsten tip of a scanning tunneling microscope operating in ultrahigh vacuum. With the application of negative voltage pulses to the tip, gold nano-mounds with the size ranging from ∼3 to ∼20 nm across at the base and 0.6–1 nm high can be created on the surface. The deposition is found to be more favored on the step edges than the (111) terraces. Since atomically resolved images of the Si(111) 7×7 structure can be observed even after many cycles of atom transfer using the gold-coated tip, the shape of the tip apex has been kept very stable. The overall findings clearly suggest that the atom-transfer technique proposed here is proven to be a good candidate for fabricating nanometer-scale devices.