Patterning Of Gold Nanoparticles Research Articles

Moving Meniscus-Assisted Template-Free Optothermofluidic Nanoparticle Patterning and Its Application in Optothermoconvective Particle Trapping.

Moving meniscus-assisted vertical lifting is a commonly employed particle assembly technique to realize large-area particle patterning for the easy fabrication of colloidal photonic crystals and sensors. Though great success has been achieved for large-area patterning, inscribing desired patterns over the target substrate with precise control over the morphology remains a challenge. The target substrates need to be functionalized (physically or chemically) to realize desired patterns, which increases the complexity and limits their applicability to specific particle-liquid combinations. We demonstrate a new approach for the precise patterning of gold nanoparticles (Au NPs, diameter ∼60 nm) over solid substrates by the synergy of light-induced Marangoni flow and vertical lifting process (moving meniscus), without the requirement of photomasks or templates. The core idea relies on the particle accumulation due to light-induced Marangoni flow near the liquid meniscus in contact with a solid surface (due to plasmonic absorption of the particles) and the controlled lifting of the substrate. We present both the simulation and experimental results of the developed patterning technique. Various patterns such as continuous lines, intermittent lines with varying lengths, patterns with continuously varying widths, cross patterns, etc. are successfully inscribed. Dynamic control over the three-dimensional morphology of the deposited patterns is achieved by varying the lifting velocity, laser irradiation time, and lifting direction during the inscription process. Finally, we show the applicability of the developed plasmonically active surface for the large-area parallel manipulation of nonabsorbing microparticles based on optothermoconvective flow. The major advantage of the developed method compared to the existing light-controlled patterning techniques is its ability to inscribe patterns over large distances (up to several centimeters). We expect that the results presented in this paper will benefit different applications requiring precise particle patterning, such as optical elements, sensors, plasmonic substrates, microfluidic master templates, and electronic circuits.

Spike Growth on Patterned Gold Nanoparticle Scaffolds.

This work reports a scaffold-templated, bottom-up synthesis of 3D anisotropic nanofeatures on periodic arrays of gold nanoparticles (AuNPs). Our method relies on substrate-bound AuNPs as large seeds with hemispherical shapes and smooth surfaces after the thermal annealing of as-fabricated particles. Spiky features were grown by immersing the patterned AuNPs into a growth solution consisting of a gold salt and Good's buffer; the number and length of spikes could be tuned by changing the solution pH and buffer concentration. Intermediate structures that informed the growth mechanism were characterized as a function of time by correlating the optical properties and spike features. Large-area (cm2) spiky AuNP arrays exhibited surface-enhanced Raman spectroscopy enhancement that was associated with increased numbers of high-aspect-ratio spikes formed on the AuNP seeds.

Synthesis of plasmonic gold nanoparticles on soft materials for biomedical applications

Plasmonic metal nanomaterials are usually supported by rigid substrates, typically made of silicon or glass. Recently, there has been growing interest in developing soft plasmonic devices. Such devices are low weight, low cost, exhibit elevated flexibility and improved mechanical properties. Moreover, they maintain the features of conventional nano-optic structures, such as the ability to enhance the local electromagnetic field. On account of these characteristics, they show promise as efficient biosensors in biological, medical, and bio-engineering applications. Here, we demonstrate the fabrication of soft polydimethylsiloxane (PDMS) plasmonic devices. Using a combination of techniques, including electroless deposition, we patterned thin membranes of PDMS with arrays of gold nanoparticle clusters. Resulting devices show regular patterns of gold nanoparticles extending over several hundreds of microns and are moderately hydrophilic, with a contact angle of about 80°. At the nanoscale, scanning electron and atomic force microscopy of samples reveal an average particle size of ∼50 nm. The nanoscopic size of the particles, along with their random distribution in a cluster, promotes the enhancement of electromagnetic fields, evidenced by numerical simulations and experiments. Mechanical characterization and the stress-strain relationship indicate that the device has a stiffness of 2.8 MPa. In biological immunoassay tests, the device correctly identified and detected anti-human immunoglobulins G (IgG) in solution with a concentration of 25 μg/ml.

Patterning of Hydrophilic and Hydrophobic Gold and Magnetite Nanoparticles by Dip Pen Nanolithography (Small 18/2023)

Dip Pen Nanolithography In article number 2208069, Bart Jan Ravoo and co-workers report the surface patterning of nanoparticles using dip pen nanolithography. Metal and metal oxide nanoparticles functionalized with various organic ligands can be patterned in nanosized clusters. Depending on the polarity of the ligand shell, water or toluene is used as ink solvent. No modification of atomic force microscope (AFM) tip or substrate surface is required.

Patterning of Hydrophilic and Hydrophobic Gold and Magnetite Nanoparticles by Dip Pen Nanolithography.

Nanoparticles offer unique physical and chemical properties. Dip pen nanolithography of nanoparticles enables versatile patterning and nanofabrication with potential application in electronics and sensing, but is not well studied yet. Herein, the patterned deposition of various nanoparticles onto unmodified silicon substrates is presented. It is shown that aqueous solutions of hydrophilic citrate and cyclodextrin functionalized gold nanoparticles as well as poly(acrylic) acid decorated magnetite nanoparticles are feasible for writing nanostructures. Both smaller and larger nanoparticles can be patterned. Hydrophobic oleylamine or n-dodecylamine capped gold nanoparticles and oleic acid decorated magnetite nanoparticles are deposited from toluene. Tip loading is carried out by dip-coating, and writing succeeds fast within 0.1s. Also, coating with longer tip dwell times, at different relative humidity and varying frequency are studied for deposition of nanoparticle clusters. The resulting feature size is between 300 and 1780nm as determined by scanning electron microscopy. Atomic force microscopy confirms that the heights of the deposited structures correspond to a single or double layer of nanoparticles. Higher writing speeds lead to smaller line thicknesses, offering possibilities to more complex structures. Dip pen nanolithography can hence be used to pattern nanoparticles on silicon substrates independent of the surface chemistry.

Templated synthesis of patterned gold nanoparticle assemblies for highly sensitive and reliable SERS substrates

Templated synthesis of patterned gold nanoparticle assemblies for highly sensitive and reliable SERS substrates

Fabrication and Characterization of Novel Silk Fiber-Optic SERS Sensor with Uniform Assembly of Gold Nanoparticles.

Biocompatible optical fibers and waveguides are gaining attention as promising platforms for implantable biophotonic devices. Recently, the distinct properties of silk fibroin were extensively explored because of its unique advantages, including flexibility, process compatibility, long-term biosafety, and controllable biodegradability for in vitro and in vivo biomedical applications. In this study, we developed a novel silk fiber for a sensitive optical sensor based on surface-enhanced Raman spectroscopy (SERS). In contrast to conventional plasmonic nanostructures, which employ expensive and time-consuming fabrication processes, gold nanoparticles were uniformly patterned on the top surface of the fiber employing a simple and cost-effective convective self-assembly technique. The fabricated silk fiber-optic SERS probe presented a good performance in terms of detection limit, sensitivity, and linearity. In particular, the uniform pattern of gold nanoparticles contributed to a highly linear sensing feature compared to the commercial multi-mode fiber sample with an irregular and aggregated distribution of gold nanoparticles. Through further optimization, silk-based fiber-optic probes can function as useful tools for highly sensitive, cost-effective, and easily tailored biophotonic platforms, thereby offering new capabilities for future implantable SERS devices.

DNA Nanostructure-Guided Plasmon Coupling Architectures

DNA Nanostructure-Guided Plasmon Coupling Architectures

A Novel Fabrication of Single Electron Transistor from Patterned Gold Nanoparticle Array Template-Prepared by Polystyrene Nanospheres.

In this paper, polystyrene microspheres were firstly prepared by seeded emulsion polymerization, and the uniform monolayer of polystyrene microspheres was prepared on the substrate by the dipping method. Then, polystyrene monolayer film was used as a mask and a low dimensional array structure of gold was prepared by bottom-up self-assembly process. After that, the method of solution etching and annealing was used, and the gold nanoparticle array was post-processed. As a result, gold nanoparticles were recrystallized, with an average diameter of about 50 nm. Subsequently, the semiconductor process was adopted, with focused ion beams induced deposition and electron beam evaporation, and single electron transistors were fabricated, based on self-assembled gold nanoparticles. Finally, the devices were fixed in a liquid helium cryostat and Coulomb blockade was observed at 320 mK. It is a novel fabrication of a single electron transistor based on gold nanoparticle array template and prepared with polystyrene nanospheres.

DNA-POINT: DNA Patterning of Optical Imprint for Nanomaterials Topography.

Engineering well-defined scale-spanning structures through transfer of diverse biomolecules and materials to a surface is of tremendous interest in life sciences research yet remains profoundly challenging. Here, we report a novel method, termed as DNA patterning of optical imprint for nanomaterials topography (DNA-POINT), for rapid photopatterning of large area, geometrically complex surfaces via light-responsive DNA. Our method employs top-down multiphoton-driven patterning of azobenzene-modified DNA strands, offering precise position control of molecules and nanoparticles along the axial plane and a template for bottom-up self-assembly of multiple layers of different chemical composition along the vertical plane. We demonstrate the surface patterning of plasmonic gold nanoparticles, fluorophore-labeled oligonucleotides, and multiple layers consisting of molecule-nanoparticle hybrid patterns into preconceived shapes without compromising on the functionality of the biomolecules. Furthermore, we exhibit scanning mode operation of DNA-POINT, thereby paving the way for maskless and cleanroom-free fast fabrication of biochips for high-throughput diagnostics and biosensing applications.

Electrospun carbon nanofibre-assisted patterning of metal oxide nanostructures

This work establishes carbon nanofibre-mediated patterning of metal oxide nanostructures, through the combination of electrospinning and vapor-phase transport growth. Electrospinning of a suitable precursor with subsequent carbonization results in the patterning of catalyst gold nanoparticles embedded within carbon nanofibres. During vapor-phase transport growth, these nanofibres allow preferential growth of one-dimensional metal oxide nanostructures, which grow radially outward from the nanofibril axis, yielding a hairy caterpillar-like morphology. The synthesis of metal oxide caterpillars is demonstrated using zinc oxide, indium oxide, and tin oxide. Source and substrate temperatures play the most crucial role in determining the morphology of the metal oxide caterpillars, whereas the distribution of the nanofibres also has a significant impact on the overall morphology. Introducing the current methodology with near-field electrospinning further facilitates user-defined custom patterning of metal oxide caterpillar-like structures.

Patterning of Metallic Nanoparticles over Solid Surfaces from Sessile Droplets by Thermoplasmonically Controlled Liquid Flow.

Optically controlled assembly of suspended particles from evaporating sessile droplets is an emerging method to realize on-demand patterning of particles over solid substrates. Most of the reported strategies rely either on additives or surface texturing to modulate particle deposition. Though dynamic control over the assembly of microparticles is possible, limited success has been achieved in nanoparticle patterning, especially in the case of metallic nanoparticles. This work demonstrates a simple light-directed patterning of gold (Au) nanoparticles based on the thermoplasmonically controlled liquid flow. Excitation at the plasmonic wavelength (532 nm) generates the required temperature gradient, resulting in the particle assembly at the irradiation zone in response to the thermocapillary flow created inside the droplet. Particle streak velocimetry experiments and analysis confirm the existence of a strong thermocapillary flow, which counteracts the naturally occurring evaporative convection flows. By modulating the illumination conditions, we could achieve patterns with various morphologies, including center deposit, off-center deposit, multi-spot deposit, and lines. We successfully applied the developed strategy for realizing closely packed hybrid particle assembly containing different particles: Au and polystyrene particles (PS). We performed optical microscopy, 3D profilometry, and SEM analysis to characterize the particle deposit. We analyzed the periodicity of Au-PS hybrid assembly using fast Fourier transform and radial distribution function analysis. PS particles formed a hexagonal close-packed arrangement at the irradiation zone, with Au NPs residing inside the voids. We believe that the presented strategy could significantly enhance the applicability of the evaporative lithography from sessile droplets for the programmable patterning of metallic nanoparticles.

Gold nanoparticle ring arrays from core-satellite nanostructures made to order by hydrogen bond interactions.

Polyethylene glycol-grafted gold nanoparticles are attached to silica nanoparticle cores via hydrogen bonding in a controlled fashion, forming well-defined core–satellite structures in colloidal solution. For separating these complex structures effectively from the parental nanoparticles, a straightforward and easy protocol using glass beads has been developed. The attached gold nanoparticles show unique surface mobility on the silica core surface, which allows for nanoparticle rearrangement into a 2D ring pattern surrounding the silica nanoparticle template when the core–satellite structures are cast to a planar surface. When etching away the silica core under conditions in which the polymer shell fixes the satellites to the substrate, highly ordered ring-shaped patterns of gold nanoparticles are formed. By variation of the size of the parental particles – 13 to 28 nm for gold nanoparticles and 39 to 62 nm for silica nanoparticles – a great library of different ring-structures regarding size and particle number is accessible with relative ease. The proposed protocol is low-cost and can easily be scaled up. It moreover demonstrates the power of hydrogen bonds in polymers as a dynamic anchoring tool for creating nanoclusters with rearrangement ability. We believe that this concept constitutes a powerful strategy for the development of new and innovative nanostructures.

Engineering surface patterns on nanoparticles: new insights into nano-bio interactions.

The surface properties of nanoparticles affect their fate in biological systems. Based on nanotechnology and its methodology, pioneering studies have explored the effects of chemical surface patterns on the behavior of nanoparticles and provided many new insights into nano-bio interfaces. In this review, we would like to provide a summary of how the nanoparticle surface pattern modulates its biological effects. The relationship between the surface pattern of nanoparticles and the generated interaction with cell membranes, recognition of viruses and adsorption of proteins was discussed. On this basis, we believe that a reasonable design of the surface microstructure will promote the application of artificial nanoparticles in biomedicine and provide a new strategy for improving the design of nano-drug carriers.

Particle size and convergent electron diffraction patterns of triangular prismatic gold nanoparticles

Convergent beam diffraction (CBED) patterns of nanoparticles are possible. CBED of triangular prismatic shaped Au nanoparticle with focus on diffraction pattern symmetry and forbidden reflections observed along [111] and [112] zone axes are reported in this work. It is well known that the CBED patterns of nanoparticles of 30 nm or less in size only show bright kinematical discs. The dynamic contrast with Kikuchi and sharp HOLZ lines within the bright discs, as observed in CBED of volumetric materials, is well observed in particles larger of 500 nm in size. In addition, it is shown that the 1/3[422] and 1/2[311] weak forbidden reflections observed in the [111] and [112] electron diffraction patterns of these particles do not modify the symmetry of the CBED patterns, but they disappear as the size of the particle increases. The symmetry of the CBED patterns are always observed in concordance with the space group Fm3m (No. 225) of the Au unit cell. The possible explanations for observing forbidden reflections are the incomplete ABC stacking due to surface termination and the stacking faults in the fcc structure.

Impressively Printing Patterns of Gold and Silver Nanoparticles.

The optical and chemical properties of gold and silver nanoparticles make them useful for many applications, including surface enhanced spectroscopy-based biosensors, photostable colorants, enhanced photovoltaics, and nanoscale optical elements. We report a simple technique to generate patterns of gold and silver nanoparticles with controlled shape and shape-dependent optical properties using metal stamps to impress them onto a glass substrate or flexible polymers. The pressure flattens the nanoparticles, converting initially spherical nanoparticles into discs with reduced height and increased diameter. This deformation causes their localized surface plasmon resonance wavelength to red-shift. Nanoparticles were characterized by electron microscopy, atomic force microscopy, and dark field optical scattering spectroscopy. The deformed nanoparticle patterns had a lateral resolution limited by the nanoparticle diameter (single particles are partly flattened only where they contact the stamp). The method also (i) transfers the stamp's topography, with smooth stamps generating flattened nanoparticles with uniform height, and small changes in stamp height are evident in the nanoparticle height and scattering wavelength, and (ii) allows facile removal of undeformed nanoparticles using scotch tape, and patterns of deformed nanoparticles can be transferred to a thin polymer-film. The patterning process is simple and inexpensive. It can be performed by hand for demonstrations or artistic applications, with controlled force for plasmonics research, and potentially automated on reel-to-reel presses for large scale production.

Large-Scale Soft-Lithographic Patterning of Plasmonic Nanoparticles.

Micro- and nanoscale patterned monolayers of plasmonic nanoparticles were fabricated by combining concepts from colloidal chemistry, self-assembly, and subtractive soft lithography. Leveraging chemical interactions between the capping ligands of pre-synthesized gold colloids and a polydimethylsiloxane stamp, we demonstrated patterning gold nanoparticles over centimeter-scale areas with a variety of micro- and nanoscale geometries, including islands, lines, and chiral structures (e.g., square spirals). By successfully achieving nanoscale manipulation over a wide range of substrates and patterns, we establish a powerful and straightforward strategy, nanoparticle chemical lift-off lithography (NP-CLL), for the economical and scalable fabrication of functional plasmonic materials with colloidal nanoparticles as building blocks, offering a transformative solution for designing next-generation plasmonic technologies.

Dual modal plasmonic substrates based on a convective self-assembly technique for enhancement in SERS and LSPR detection.

In this study, surface-enhanced Raman scattering (SERS) scheme is combined with localized surface plasmon resonance (LSPR) detection on a thin gold film with stripe patterns of gold nanoparticles (GNPs) via convective self-assembly (CSA) method. The potential of dual modal plasmonic substrates was evaluated by binding 4-ABT and IgG analytes, respectively. SERS experiments presented not only a high sensitivity with a detection limit of 4.7 nM and an enhancement factor of 1.34 × 105, but an excellent reproducibility with relative standard deviation of 5.5%. It was found from plasmonic sensing experiments by immobilizing IgG onto GNP-mediated gold film that detection sensitivity was improved by more than 211%, compared with a conventional bare gold film. Our synergistic SERS-LSPR approach based on a simple and cost-effective CSA method could open a route for sensitive, reliable and reproducible dual modal detection to expand the application areas.

Engineering conductive protein films through nanoscale self-assembly and gold nanoparticles doping.

Protein-based materials are usually considered as insulators, although conductivity has been recently shown in proteins. This fact opens the door to develop new biocompatible conductive materials. While there are emerging efforts in this area, there is an open challenge related to the limited conductivity of protein-based systems. This work shows a novel approach to tune the charge transport properties of protein-based materials by using electron-dense AuNPs. Two strategies are combined in a unique way to generate the conductive solid films: (1) the controlled self-assembly of a protein building block; (2) the templating of AuNPs by the engineered building block. This bottom-up approach allows controlling the structure of the films and the distribution of the AuNPs within, leading to enhanced conductivity. This work illustrates a promising strategy for the development of effective hybrid protein-based bioelectrical materials.

Flexible Photothermal Assemblies with Tunable Gold Patterns for Improved Imaging-Guided Synergistic Therapy.

Self-assembly of gold nanoparticles demonstrates a promising approach to realize enhanced photoacoustic imaging (PAI) and photothermal therapy (PTT) for accurate diagnosis and efficient cancer therapy. Herein, unique photothermal assemblies with tunable patterns of gold nanoparticles (including arcs, rings, ribbons, and vesicles) on poly(lactic-co-glycolic acid) (PLGA) spheres are constructed taking advantage of emulsion-confined and polymer-directed self-assembly strategies. The influencing factors and formation mechanism to produce the assemblies are investigated in details. Both the emulsion structure and migration behaviors of amphiphilic block copolymer tethered gold nanoparticles are found to contribute to the formation of versatile photothermal assemblies. Hyaluronic acid-modified R-PLGA-Au (RPA) exhibits outstanding photothermal performances under NIR laser irradiation, which is induced by strong plasmonic coupling between adjacent gold nanoparticles. It is interesting that secondary assembly of RPA can be triggered by NIR laser irradiation. Prolonged residence time in tumors is achieved after RPA assemblies are fused into superstructures with larger sizes, realizing real-time monitoring of the therapeutic processes via PAI with enhanced photoacoustic signals. Notably, synergistic effect resulting from PTT-enhanced chemotherapy is realized to demonstrate high antitumor performance. This work provides a facile strategy to construct flexible photothermal assemblies with favorable properties for imaging-guided synergistic therapy.