Optical Devices Constructed from Ferrocene-Modified Microgels for H₂O₂ Sensing

Abstract

Ferrocene-modified poly(N-isopropylacrylamide)-based microgels were synthesized, characterized, and used to construct optical devices (etalons). The response of the microgels and etalons to HO was investigated, and we show that both the microgel diameter and the optical properties of the etalons depend on the solution concentration of HO from 0.6 to 35 mM. This behavior is a direct result of the oxidation of ferrocene, which influences the microgel diameter. This was also demonstrated by electrochemical-mediated oxidation/reduction of ferrocene using cyclic voltammetry. We go on to show that these materials could be used to monitor HO that is generated from enzymatic reactions. Specifically, we show that the HO generated from the oxidation of glucose catalyzed by glucose oxidase could be quantified. Finally, the devices can be reused multiple times via a regeneration process. This investigation illustrates the versatility of the etalon system to detect species of broad relevance and how they could potentially be used to quantify products of biological reactions.

Electroactive, Mediating and Thermosensitive Microgel Useful for Covalent Entrapment of Enzymes and Formation of Sensing Layer in Biosensors

“…The more complex situation is seen when a biocatalyst is introduced into the polymer layer and after the electrocatalytic process it must be regenerated. If the enzyme was placed deep in the layer, the shrinking process would depress the electrocatalysis [26][27][28]. In our case the enzyme was bound to the carboxylic groups after the formation of the gel microparticles, therefore it could not penetrate deeply the microgel particles and was located rather close to the surface.…”

“…In the simplest cases the electroactive species find it harder to penetrate the shrunken polymer layer and to reach the electrode surface. If the enzyme was placed deep in the layer, the shrinking process would depress the electrocatalysis [26][27][28]. A more complicated situation takes place when the polymer layer contains catalytic centers (organic or inorganic).…”

Silver nanoparticle-loaded microgel-based etalons for H2O2sensing

“…Furthermore, we observed a change in the intensity of the reectance peaks in response to H 2 O 2 , which is not typically observed from the microgel-based etalons. 4,49 AgNPs are also well known to absorb visible light due to the excitation of plasmons. 50 With the etalons here, we also found that the intensity of reected light increased from 75% to 120%, possibly due to the reduction of AgNP light absorption.…”

“…Photonic crystals have attracted considerable interest due to their low cost, ease of signal readout, simple operation, and their ability to be modied to detect multiple analytes. [1][2][3][4] The Serpe Group pioneered the development of poly(N-isopropylacrylamide) (pNIPAm) microgel-based etalons in 2010. 5,6 Since then, they have been shown to exhibit visual color that can be made to depend on the presence of certain species, or the state of a system, e.g., temperature, pH, 7 Cu 2+ , 8 CO 2 , 9 H 2 O 2 , 4 proteins, 10 and DNA.…”

“…[1][2][3][4] The Serpe Group pioneered the development of poly(N-isopropylacrylamide) (pNIPAm) microgel-based etalons in 2010. 5,6 Since then, they have been shown to exhibit visual color that can be made to depend on the presence of certain species, or the state of a system, e.g., temperature, pH, 7 Cu 2+ , 8 CO 2 , 9 H 2 O 2 , 4 proteins, 10 and DNA. 11 Typically, etalons are constructed by sandwiching a layer of pNIPAm microgels between two thin Au layers.…”