Anand M. Shrivastav

Fiber optic profenofos sensor based on surface plasmon resonance technique and molecular imprinting

A successful approach for the fabrication and characterization of an optical fiber sensor for the detection of profenofos based on surface plasmon resonance (SPR) and molecular imprinting is introduced. Molecular imprinting technology is used for the creation of three dimensional binding sites having complementary shape and size of the specific template molecule over a polymer for the recognition of the same. Binding of template molecule with molecularly imprinted polymer (MIP) layer results in the change in the dielectric nature of the sensing surface (polymer) and is identified by SPR technique. Spectral interrogation method is used for the characterization of the sensing probe. The operating profenofos concentration range of the sensor is from 10(-4) to 10(-1)µg/L. A red shift of 18.7 nm in resonance wavelength is recorded for this profenofos concentration range. The maximum sensitivity of the sensor is 12.7 nm/log (µg/L) at 10(-4)µg/L profenofos concentration. Limit of detection (LOD) of the sensor is found to be 2.5×10(-6)µg/L. Selectivity measurements predict the probe highly selective for the profenofos molecule. Besides high sensitivity due to SPR technique and selectivity due to molecular imprinting, proposed sensor has numerous other advantages like immunity to electromagnetic interference, fast response, low cost and capability of online monitoring and remote sensing of analyte due to the fabrication of the probe on optical fiber.

Localized and propagating surface plasmon resonance based fiber optic sensor for the detection of tetracycline using molecular imprinting

In the present study we report a novel approach for the fabrication of localized and propagating surface plasmon resonance based fiber optic sensor for the detection of tetracycline using molecular imprinting (MIP) technique. The sensor is fabricated by coating layers of silver film, silver nanoparticles and MIP film prepared using tetracycline molecule as template over an unclad core of the multimode optical fiber. Nanoparticles of sizes in the range 10–30 nm are synthesized by hydrothermal process. A polychromatic light source is used to launch the light from one end of the fiber and the absorption spectrum for a given concentration of the tetracycline solution around the probe is measured at the other end of the fiber using a spectrometer interfaced with a computer. The absorption spectra are recorded for the concentration range of tetracycline from 10−8 M to 10−5 M. A shift of 102 nm in peak absorbance wavelength is obtained for this concentration range. The sensor works in the promising concentration range of tetracycline found in foods etc. The sensor has various advantages such as high sensitivity, low cost, fast response and capability of online monitoring and remote sensing. Further, the sensitivity of the sensor is about double the sensor based on localized surface plasmon resonance and molecular imprinting.

Surface Plasmon Resonance-Based Fiber Optic Sensors Utilizing Molecular Imprinting

Molecular imprinting is earning worldwide attention from researchers in the field of sensing and diagnostic applications, due to its properties of inevitable specific affinity for the template molecule. The fabrication of complementary template imprints allows this technique to achieve high selectivity for the analyte to be sensed. Sensors incorporating this technique along with surface plasmon or localized surface plasmon resonance (SPR/LSPR) provide highly sensitive real time detection with quick response times. Unfolding these techniques with optical fiber provide the additional advantages of miniaturized probes with ease of handling, online monitoring and remote sensing. In this review a summary of optical fiber sensors using the combined approaches of molecularly imprinted polymer (MIP) and the SPR/LSPR technique is discussed. An overview of the fundamentals of SPR/LSPR implementation on optical fiber is provided. The review also covers the molecular imprinting technology (MIT) with its elementary study, synthesis procedures and its applications for chemical and biological anlayte detection with different sensing methods. In conclusion, we explore the advantages, challenges and the future perspectives of developing highly sensitive and selective methods for the detection of analytes utilizing MIT with the SPR/LSPR phenomenon on optical fiber platforms.

A contemporary approach for design and characterization of fiber-optic-cortisol sensor tailoring LMR and ZnO/PPY molecularly imprinted film

A fiber optic salivary cortisol sensor using a contemporary approach of lossy mode resonance and molecular imprinting of nanocomposites of zinc oxide (ZnO) and polypyrrole (PPY) is structured and depicted for the concentration range of 0-10-6g/ml of cortisol prepared in artificial saliva. Components of polymer preparation and the nanocomposite of polymer with ZnO are optimized for realizing the molecular imprinted layer of the sensor. Nanocomposite having 20% of ZnO in PPY is found to give highest sensitivity of the sensor. The sensor reports the best limit of detection ever reported with better stability, repeatability and response time. Lossy mode resonance based salivary cortisol sensor using nanocomposite molecular imprinted layer reported first time boosts the specificity of the sensor. The implementation of sensor over optical fiber adds up other advantages such as real time and online monitoring along with remote sensing abilities which makes the sensor usable for nonintrusive clinical applications.

Highly sensitive and selective erythromycin nanosensor employing fiber optic SPR/ERY imprinted nanostructure: Application in milk and honey

An erythromycin (ERY) detection method is proposed using the fiber optic core decorated with the coatings of silver and an over layer of ERY imprinted nanoparticles. Synthesis of ERY imprinted nanoparticles is carried out using miniemulsion method. The operating range of the sensor is observed to be from 1.62×10-3 to 100µM while the sensor possesses the linear response for ERY concentration range from 0.1 to 5µM. The sensing method shows a maximum sensitivity of 205nm/µM near ERY concentration of 0.01µM. The detection limit and the quantification limit of the sensor are found to be 1.62×10-3µM and 6.14×10-3µM, respectively. The sensors applicability in real samples is also examined and is found to be in good agreement for the industrial application. The sensor possesses numerous advantages like fast response time (<15s), simple, low cost, highly selective along with abilities towards online monitoring and remote sensing of analyte.

FO-SPR based dextrose sensor using Ag/ZnO nanorods/GOx for insulinoma detection.

In this piece of work, a fiber optic sensor has been fabricated and characterized using surface plasmon resonance for dextrose sensing. The concentration range used in this study is for diagnosing the cases of hypoglycaemia especially in suppression tests of insulinoma. Insulinoma is a medical case in which the person is recognized being hypoglycaemic with the blood dextrose level falling down to 2.2mM or less. Thus, the sensor has been characterized for the dextrose concentration range of 0 mM-10mM including the cases of normal blood dextrose range. Coatings of silver layer and zinc oxide nanorods have been carried out on the bare core fiber with a dual role of zinc oxide followed by immobilization of glucose oxidase. A three stage optimization procedure has been adopted for the best performance of the sensor. Absorbance spectra have been plotted and peak absorbance wavelengths have been extracted for each concentration chosen along with the sensitivities. The results have been made conclusive with control experiments. The probe has also been tested on sample having blood serum to check the reliability of the sensor. The sensor shows better selectivity and response time along with its real time applications, online monitoring, remote sensing and reusability.

SPR and Molecular Imprinting-Based Fiber-Optic Melamine Sensor With High Sensitivity and Low Limit of Detection

We report a fiber-optic surface plasmon resonance (SPR) sensor for the detection of melamine using molecular imprinting and an additional layer of silicon in the probe. To achieve the maximum sensitivity and minimum detection limit of the sensor, the thickness of the silicon layer has been optimized. The proposed sensor has a high sensitivity of 76.0 nm/log M. The limit of detection of the sensor has been found to be 4.3 × 10-11 M, which when compared with the previously reported values for melamine detection has been found to be the least to the best of our knowledge. Selectivity experiments with dissimilar analytes have also been performed and it has been found that the sensor is highly selective. High sensitivity, low limit of detection, and high selectivity are due to a combined approach of SPR, molecular imprinting, and additional layer of silicon used in the probe. The sensor has numerous other advantages like low cost, ease of handling, capability of online monitoring, and remote sensing.

Surface plasmon resonance based fiber optic trichloroacetic acid sensor utilizing layer of silver nanoparticles and chitosan doped hydrogel

In this study, we report a silver nanoparticles/chitosan doped hydrogel-based fiber optic sensor for the detection of trichloroacetic acid (TCA). The sensor is based on the combined phenomenon of localized and propagating surface plasmons. The sensing relies on the interaction of TCA with silver nanoparticles (AgNP) which results in the electron transfer between the negative group of TCA and positive amino group of AgNP stabilizer (chitosan). This alters the mechanical properties/refractive index of the AgNP embedded hydrogel matrix as well as the refractive index of the AgNP. The change in refractive index of both in turn changes the effective refractive index of the nanocomposite hydrogel layer which can be determined using the Maxwell-Garnet Theory. Four stage optimization of the probe fabrication parameters is performed to obtain the best performance of the sensing probe. The sensor operates in the TCA concentration range 0-120 μm which is harmful for the humans and environment. The shift in peak extinction wavelength observed for the same TCA concentration range is 42 nm. The sensor has the linearity range for the TCA concentration range of 40-100 μm. The sensor possesses high sensitivity, selectivity and numerous other advantages such as ease of handling, quick response, modest cost and capability of online monitoring and remote sensing.

Fiber optic SPR nanosensor for erythromycin detection using molecularly imprinted nanoparticles

A fiber optic SPR sensor for erythromycin detection using molecular imprinted nanoparticles has been reported for the concentration range 0 to 50 μM. Its sensitivity and detection limit are 5.32 nm/μM and 6.2×10^-8 M respectively.

Fiber Optic SPR Sensor for Detection of Triclosan Using Molecular Imprinted Polymeric Layer

We report sensing of triclosan using optical fiber configuration with SPR and molecular imprinting techniques. The sensor possesses high sensitivity and selectivity and operates from concentration 0.0001 to 0.1 μg/L of triclosan.