Second Harmonic Generation from Coupled Surface‐Plasmon Resonances in Self‐Assembled Gold‐Nanoparticle Monolayers Coated with an Aminosilane

Abstract

BN (hBN) holder. The input microwave power was 1400 W, and the pressure was kept at about 2 10 ±3 torr. Argon and helium were used as plasma-processing gases at flow rates of 10 and 140 sccm (standard cubic centimeters), respectively. Nitrogen, boron trifluoride, and hydrogen were used as reactant gases at gas flow rates of 50, 1.5, and 3 sccm, respectively. A bias voltage ranging from ±10 to ±40 V was applied to the substrate during deposition. The substrate temperature was maintained at about 950 C as measured by an optical pyrometer. The cBN film thickness ranged from 200 nm to 2 lm.The films were characterized by Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM)Ðwith its associated techniques selected area electron diffraction (SAED) and electron energy-loss spectroscopy (EELS)Ðand X-ray diffraction (XRD). The XRD measurements were performed using a Rigaku X-ray diffractometer, the SEM using a Philips FEG XL30, the HRTEM using a Philips FEG CM200 with a point resolution of 0.19 nm. A Gatan GIF 200 spectrometer attached to the HR transmission electron microscope was employed for EELS and elemental scanning measurements. The formation of two-dimensional (2D) arrays of metal nanoparticles on substrates [1±4] is of increasing interest to nanoscale-materials scientists and engineers, and is being continuously investigated for practical applications in optical, electrical, and biological technologies. The phenomenon of single-electron tunneling (SET) [5] with gold (Au) nanoparticles covered with an insulation layer is promising for application in nanoscale memory units working at room temperature, where the 2D nanoparticle array forms the surface of an ultrahigh-density memory disk. In bio-optical science, a 2D monolayer of Au nanoparticles has been applied in an enzyme-based sensor for glucose. [6] With the help of near-field enhancement of the nanoscale roughness of metal surfaces, optical sensors for organic polymers or molecules with high sensitivity have also been developed. [7,8] Furthermore, the near-field effects of the surface of metal nanoparticles is made use of in phosphorescent composites embedded with rareearth ions and Au nanoparticles. [9] Several methods for preparing such 2D arrays are knownÐLangmuir±Blodgett techniques, [10] sputtering, [11] electrochemical deposition, [12] self-assembly, [3,8,13] and so on. Our approach is based on using a self-assembly technique to deposit nanometer-sized Au particles on a chemically modified glass substrate, which can then be stabilized by the application of a layer of silica. This communication reports second harmonic generation (SHG) from monolayers of Au nanoparticles fabricated with a variety of immersion times. It will be shown by optical absorption measurements and atomic force microscopy (AFM) that detectable second harmonic (SH) signals are caused by nonlinear polarization of the longitudinal ªin-phaseº modes of coupled COMMUNICATIONS

Fabrication of 2D ordered structure of self-assembled block copolymers containing gold nanoparticles

“…evaporation [9] and sputtering [10], can be used to fabricate a 2D array of nanoparticles. One of the more efficient methodologies for production of the 2D array of nanoparticles involves the utilization of self-assembling materials, which have an ability to generate spatially regular structures as a result of minimizing their thermodynamic energy [11][12][13][14]. Recently, Mo¨ller and coworkers [15,16] successfully prepared uniform gold nanoparticles and arranged them spatially in 2D arrays by using PS-PVP diblock copolymer micelles.…”

Preparation of γ-APS monolayer with complete coverage via contact printing

“…Among them, aminosilanes such as 3-aminopropyltriethoxysilane (c-APS) have received great attention, as ethoxysilane groups can form covalent bonds with inorganic/organic surfaces, while amino groups can lead to chemical reactions with other organic molecules, or physical interactions with inorganic materials. For this reason, aminosilanes have been extensively investigated in immobilizing or patterning organic and inorganic materials for bio, photonic and electronic applications [3][4][5]. In the process, however, monolayer formation with complete coverage has emerged as a critical concern.…”

Preparation of silver nanoparticle immobilized fibrillar silicate by poly(dopamine) surface functionalization

“…16 Surface functionalization of attapulgite has been extensively carried out to modify their intrinsic properties for the applications in various areas. 17 On the other hand, because of the rich surface-plasmon-related light absorption and scattering properties of noble metal nanoparticles, a large number of efforts have been devoted to the assembly of noble metal nanoparticles in order to enhance the amplification of optical signals, including fluorescence, [18][19][20] Raman scattering, [21][22][23] and second-harmonic generation, 24 which is useful for medical imaging and diagnostic applications. 25,26 Zhang and coworkers fabricated gold and silver nanoparticles on mesostructured silica nanofibers that were synthesized with a structure-directing agent presence.…”