Open AccessThickness-dependent humidity sensing by poly(vinyl alcohol) stabilized Au–Ag and Ag–Au core–shell bimetallic nanomorph resistors
Author(s) -
Parag V. Adhyapak,
R. C. Aiyer,
Sreekantha Reddy Dugasani,
HyeongU Kim,
Chung Kil Song,
Ajayan Vinu,
V. Renugopalakrishnan,
Sungha Park,
Taesung Kim,
Haiwon Lee,
Dinesh Amalnerkar
Publication year - 2018
Publication title -
royal society open science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 51
ISSN - 2054-5703
DOI - 10.1098/rsos.171986
Subject(s) - bimetallic strip , vinyl alcohol , shell (structure) , core (optical fiber) , resistor , materials science , humidity , chemical engineering , composite material , physics , engineering , polymer , electrical engineering , metallurgy , meteorology , metal , voltage
We herein report a simple chemical route to prepare Au–Ag and Ag–Au core–shell bimetallic nanostructures by reduction of two kinds of noble metal ions in the presence of a water-soluble polymer such as poly(vinyl alcohol) (PVA). PVA was intentionally chosen as it can play a dual role of a supporting matrix as well as stabilizer. The simultaneous reduction of metal ions leads to an alloy type of structure. Ag(c)–Au(s) core–shell structures display tendency to form prismatic nanostructures in conjunction with nanocubes while Au(c)–Ag(s) core–shell structures show formation of merely nanocubes. Although UV–visible spectroscopy and X-ray photoelectron spectroscopy analyses of the samples typically suggest the formation of both Ag(c)–Au(s) and Au(c)–Ag(s) bimetallic nanostructures, the definitive evidence comes from high-resolution transmission electron microscopy–high-angle annular dark field elemental mapping in the case of Au(c)–Ag(s) nanomorphs only. The resultant nanocomposite materials are used to fabricate resistors on ceramic rods having two electrodes by drop casting technique. These resistors are examined for their relative humidity (RH) response in the range (2–93% RH) and both the bimetallic nanocomposite materials offer optimized sensitivity of about 20 Kohm/% RH and 300 ohm/% RH at low and higher humidity conditions, respectively, which is better than that of individual nanoparticles.