Continuous Flow Electroless Plating Enhances Optical Features of Au Films and Nanoparticles

Abstract

A novel continuous flow (CF) electroless (EL) plating method deposits gold (Au) films which exhibit increased continuity and uniformity relative to batch immersion as measured by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Transmission UV−vis (T-UV) spectra exhibit lower peak heights (PH) and narrower full-width-half-maxima (fwhm), consistent with microscopy measures. Nanoparticles (NPs) obtained by thermal transformation of CF-EL Au film are larger and monodisperse relative to I-EL NPs. Their extinction spectra exhibit higher PH due to enhanced localized surface plasmon resonance (LSPR) and narrower fwhm than NP from I-EL films. Au deposition during CF-EL plating is calculated to be 78.3% higher than during I-EL plating for each 30-s interval. Optical features of T-UV [PH, fwhm, and resonant extinction maxima (λmax)] increase in proportion to time-integrated mass transport coefficient and suggest that increased mass transfer rate and steady higher average local Au concentration during CF improve continuity, uniformity, and overall smoothness of CF plated films.

Reductive spectrophotometry of divalent tin sensitization on soda lime glass

“…Acid etching followed by substrate hydroxylation supports chemisorption of tin (II), improving adherence to the substrate [13]. While the extent of tin (II) interlocking on soda lime glass was not examined directly in this report, previous work showed that nitric acid etching before tin sensitization and subsequent reduction of silver nitrate (AgNO 3 ) followed by galvanic replacement with Au improved Au adhesion to glass substrates [14,39]. Also, Minjer et al used nitric acid treatment of soda lime glass following immersion in sulfuric and chromic acids to remove sodium ions and other impurities [25].…”

“…Tin (II) behaves as a strong stabilizing and reducing agent to create catalytic sites with less than 20 atoms on glass substrates [4]. Control of the equilibrium state and dynamics of the sensitization step could improve uniformity and reproducibility of thin metal films with enhanced optical features [14].…”

Electron optics of nanoplasmonic metamaterials in bio/opto theranostics

“…26 Electroless plating performed using continuous flow of oxidizing metal solutions speeds and normalizes diffusive mass transfer to and from the galvanic interface to enhance continuity and optical properties of Au island films and NP. 42 Real-time spectroscopy of continuous flow electroless plating provides dynamic and equilibrium measures for metal deposition in successive electroless plating steps. 43 Tin chloride sensitization prior to lithography enhances meta-atom uniformity and sphericity 44 .…”

Photothermal response of the plasmonic nanoconglomerates in films assembled by electroless plating

“…40 The electroless lm and lm plus NP lattice were lied off the electron resist and underlying ceramic substrate using adhesive tape. 41 Electroless lms were compared with conventional Au nanolms produced by metal evaporation. The grainy Au morphology resulting from batch ELP increased thermoplasmonic dissipation relative to evaporated lms.…”