Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection

Abstract

Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.

Sol-Gel Coating Membranes for Optical Fiber Sensors for Concrete Structures Monitoring

“…However, further refinement of the experimental results allowed the sensor to achieve a sensitivity of 2.47 nm/ppm. Kant et al [69] reported the development of an OFS for the detection of caffeine integrating reduced graphene oxide nanohybrid membranes on chitosan modified silica membrane. The sensor features a detection limit of 1.994 nM and operates over a concentration range between 0 and 500 nM with a RT of 16 s. Despite the wide spectrum of applications and publications reported, the development of OFS functionalized with OIH materials is still at an early stage.…”

Comments on the significance and application sphere of SPR based fiber–optic sensors

“…Further, SPR based fiber-optic sensors are used for the sensing and quantification of numerous chemicals and biomolecules of commercial and biomedical significance. 7,8,12,13 The importance of these sensors also stems from the fact that they facilitate multi-channel sensing significant from biological point of view. In that aspect, a cascaded channel fiber-optic SPR sensor has been reported for simultaneous detection of vitamin K 1 and heparin such that vitamin K 1 is sensed on first channel to monitor blood coagulation while the second sensing channel is specific to heparin required for the therapy.…”

Durable Antimicrobial Behaviour from Silver-Graphene Coated Medical Textile Composites

“…Surface plasmons are the in-phase oscillations of free electrons at the interface of a metal and dielectric, as indicated by a strong absorption at the resonance wavelength in a UV-Visible absorption spectrum [110][111][112][113][114][115][116][117]. The SPR band position depends on parameters such as size, shape, and polydispersity of nanostructures, even though it is the ability of rGO to otherwise enhance and control the loading and embedding of AgNPs, due to improved specific surface areas thought to be the reason for the divergence in the signal between the Ag and Ag-rGO samples [56]. Resonance wavelengths strongly depend upon the refractive index of the dielectric medium.…”

“…Treated substrates displayed high air stability and chemical inertia, via a reduced graphene oxide (rGO) protective composite, i.e., the formation of AgNP-rGO composites within substrates for increased loading and enhanced active coating longevity [53,54]. The performance of these composites was compared against solely AgNP-and rGO-impregnated fabrics, with the presence of rGO acting to stabilise and facilitate the loading and adhesion of AgNP nanostructures, which provides them with an improved specific surface area and subsequent improved performance [55,56]. Furthermore, leaching tests indicate enhanced and prolonged adhesion such that, even after accelerated washing cycles, the novel composites still showed high silver loading and high bactericidal efficacy over six hours of treatment, for the optimised composites.…”