Making strong polyelectrolyte brushes pH-sensitive by incorporation of gold nanoparticles

Abstract

Doping polymer brushes with gold nanoparticles (AuNPs) results in composite materials with colorimetric sensor properties. The present paper addresses the effect of electrostatic particle-particle interaction and the effect of the polymer brush type on particle assembly formation within the polymer matrix. The prospect for long-term use as colorimetric sensors is tested. Therefore, two different types of brushes of pH-insensitive polymers, non-ionic poly(N-isopropylacrylamide) (PNIPAM) and cationic poly-[2-(methacryloyloxy)ethyl] trimethylammonium chloride (PMETAC), are studied. After incubation of the non-ionic PNIPAM brush in an aqueous suspension of AuNPs with a pH-sensitive carboxylic acid capping, hydrogen binding led to attachment of the AuNPs, but they were easily detached at high pH due to loss of the hydrogen binding. In contrast, the anionic AuNPs adhere well to cationic PMETAC brushes even after post-treatment at low pH where the charge density of the AuNPs is strongly reduced. Therefore, the PMETAC/AuNP composites were further tested with respect to their stability against pH variations and their impact for colorimetric sensors. Although the neat PMETAC brush is not pH-sensitive, after embedding pH-sensitive AuNPs, the PMETAC/AuNP composite becomes pH-sensitive in a reversible manner. This is detectable by the reversible shift of the plasmon band and the reversible thickness change of the composites by exposing them to different pH.

Hierarchy of Hybrid Materials—The Place of Inorganics-in-Organics in it, Their Composition and Applications

“…Bringing in inorganic content improved thermal properties of organoclays (Calderon et al, 2008) and mitigated the scaling of calcium carbonate (Sheikhi et al, 2018). A combination of polyelectrolyte polymers and brushes were reportedly enhanced by the addition of gold nanoparticles (Boyaciyan et al, 2018). Some other functionalities include the enhancement of thermal properties (Banjare et al, 2014) including that in LbL layers (Puhr et al, 2014).…”

Functionalization of polymers and nanomaterials for water treatment, food packaging, textile and biomedical applications: a review

“…The former being pH-sensitive on an addition to the insensitive matrix, i.e., polyelectrolyte matrix, made it sensitive to pH alterations and thus helping them in detecting the pH changes in the surrounding environment. The interaction of Au nanoparticles with polyelectrolyte matrix altered with changing pH and in turn altered the surface plasmonic characteristics detected through UV/Vis spectrometer (Boyaciyan et al 2018). In another study, a voltammetric sensor developed using 3-thiophene acetic acid coating Au nanoparticles forming a conductive 3D network film (Fig.…”

“…The shift in surface plasmon response can be detected by using a UV/Vis spectrometer and the possibility of detecting the very low concentration of metal ions, i.e., 1 ppb increases. Boyaciyan et al (2018) prepared a sensor device by embedding the Au nanoparticles in the polyelectrolyte matrix. The former being pH-sensitive on an addition to the insensitive matrix, i.e., polyelectrolyte matrix, made it sensitive to pH alterations and thus helping them in detecting the pH changes in the surrounding environment.…”

Effects of Amino Acid Side-Chain Length and Chemical Structure on Anionic Polyglutamic and Polyaspartic Acid Cellulose-Based Polyelectrolyte Brushes

“…Moreover, the polyelectrolyte nature of the grafted chains makes brush structures tunable by external conditions, e.g., pH and ionic strength of the solution, electromagnetic field, or presence of multivalent salt, allowing for the design of stimuli-responsive materials. Adhesive properties of polyelectrolyte brushes make them usable for a wide range of applications, including water treatment [ 4 ], development of anticorrosion agents [ 5 ], antifouling materials [ 6 ], drug delivery [ 7 ] sensors [ 8 ], and tissue engineering materials [ 9 ].…”