Laser-Induced Transfer of Noble Metal Nanodots with Femtosecond Laser-Interference Processing

Noble metal nanodots have been applied to plasmonic devices, catalysts, and highly sensitive detection in bioinstruments. We have been studying the fabrications of them through a laser-induced dot transfer (LIDT) technique, a type of laser-induced forward transfer (LIFT), in which nanodots several hundred nm in diameter are produced via a solid–liquid–solid (SLS) mechanism. In the previous study, an interference laser processing technique was applied to LIDT, and aligned Au nanodots were successfully deposited onto an acceptor substrate in a single shot of femtosecond laser irradiation. In the present experiment, Pt thin film was applied to this technique, and the deposited nanodots were measured by scanning electron microscopy (SEM) and compared with the Au nanodots. A typical nanodot had a roundness fr=0.98 and circularity fcirc=0.90. Compared to the previous experiment using Au thin film, the size distribution was more diffuse, and it was difficult to see the periodic alignment of the nanodots in the parameter range of this experiment. This method is promising as a method for producing large quantities of Pt particles with diameters of several hundred nm.

Nonenzymatic glucose detection using Au nanodots decorated Cu2O nanooctahedrons

Au nanodots decorated Cu2O nanooctahedrons were fabricated by a facile liquid-phase process combined with a galvanic replacement reaction for nonenzyme glucose detection. A simple rapid test strip based on the nanooctahedrons was proposed to evaluate the possibility of commercial application in nonenzymatic glucose detection. This test strip shows excellent response toward glucose. Linear response was obtained over a concentration ranging from 0.05 mM to 15 mM, and the detection accuracy is 0.05 mM. The good detection performance in selectivity, stability, and feasibility proving the great potential application in human blood glucose monitoring. This study demonstrated the possibility of a high-performance nonenzyme glucose test strip based on metal-oxide nanostructures decorated by catalysts.

Fabrication and Comparison of Self-Organized Ag and Au Nanodots on Ti/MgO(001) Substrates

We analyze and compare the differences in the dewetting phenomena and crystal structure between Ag(5.0 nm) and Au(5.0 nm) layers deposited on a Ti(1.0 nm) seed layer coated onto a MgO(001) substrate. The samples are deposited at room temperature and annealed at 350–450 °C for 5 h. The surfaces of both Ag/Ti and Au/Ti films exhibit a completely separated island structure, subsequently leading to the formation of a nanodot array after annealing. Based on atomic force microscopy (AFM) analysis, we conclude that the dewetting progression speed of Ag/Ti films is higher than that of Au/Ti films. Based on X-ray diffraction (XRD) results, the Ti thin film acts as a seed layer, assisting the epitaxial growth of fcc-Ag(001) nanodots on the MgO(001) substrate, whereas in the case of Au/Ti, the Au layer grows non-epitaxially on the MgO(001) substrate, which is related to the difference in the surface energies of Ag and Au. Furthermore, the optical absorbance spectra of the self-organized Ag and Au nanodots with the Ti seed layer are obtained in the visible light range and the optical properties of Ag and Au nanodots are compared.

Electrochemical biosensing platforms on the basis of reduced graphene oxide and its composites with Au nanodots

rGO and AuNDs-rGO, synthesized by a simple photochemical reduction method, are used for electrochemical biosensors and show good glucose detection.

Shape Dependent EMA Model of Nanostructured Anisotropic Materials

Heterogeneous nanostructures containing nanoparticles of various sizes and shapes have attracted significant attention in the development of nano-biosensors. Especially, plasmonic properties of such materials are advantageously exploited for the detection of biological and chemical substances. Since these media exhibit optical anisotropy, a valid homogenization procedure must be able to describe appropriately the relationship between the geometry of the inclusions and the nature of local field modes. We present a model approach for extension of the effective medium approximation (EMA) and its application to anisotropic nanostructures. The proposed model is based on a “strong-couple-dipole” (SCD) method including a volume-integral correction term in a Green tensor that enables to obtain more accurate representation of polarizability tensor. Derived depolarization factors for discs and bi-cone particles are compared with the early known shapes (spheroids, cylinders) and applied to nanostructures composed of the Fe or Au nanodots in polyacrylate.

Electron Beam Dose and PMMA Thickness Dependent Circularity and Diameter Analysis of Au Nanodots

Background: The electrical and optical properties of nanoparticle-based devices depend on the shape, dimension and uniformity of these particles. Methods: In this work, we fabricated ordered Au nanodots using electron beam lithography and thermal evaporation. Au nanodot diameter and circularity varied with a changed exposure dose and resist thickness. Electron beam dose ranged from 5 fC to 200 fC for single dot patterns. Commonly used PMMA thin films of thicknesses 60 nm and 100 nm coated samples were used for investigating the resist thickness dependency with varying dose exposure. Results: The analyses of patterns show that the diameter and circularity of the Au nanodots ranged from smaller to larger diameters and from lower to higher circularities with increasing dose and resist thickness. Conclusion: The distributions of the nanodot diameter began to show Gaussian behavior at larger electron doses. Besides, single circularity value became dominant up to the medium doses and then a homogeneous distribution was observed with the increasing dose.