Molecularly Imprinted Polymers in Electrochemical and Optical Sensors

Carbon and graphene quantum dots are prepared using top-down and bottom-up methods. Sustainable synthesis of quantum dots has several advantages such as the use of low-cost and non-toxic raw materials, simple operations, expeditious reactions, renewable resources and straightforward post-processing steps. These nanomaterials are promising for clinical and biomedical sciences, especially in bioimaging, diagnosis, bioanalytical assays and biosensors. Here we review green methods for the fabrication of quantum dots, and biomedical and biotechnological applications.

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Green synthesis, biomedical and biotechnological applications of carbon and graphene quantum dots. A review

Griess reaction-based paper strip for colorimetric/fluorescent/SERS triple sensing of nitrite.

In this work, we report the synthesis of nitrogen (N)-doped carbon nanodots (N-CNDs) with an N doping level of 3.6 at. % by hydrothermal treatment of prawn shell and their application as fluorophores for selective and sensitive fluorescence detection of NO2– in water. The results demonstrate that NO2– detection by directly fluorescent quenching at N-CNDs fluorophores can achieve an analytical detection linear range up to 1.0 mM with a detection limit of 1.0 μM. The obtained detection limit of NO2– using N-CNDs fluorophores is dramatically lower than the maximum limit value of 3.0 mg L–1 (namely, 65 μM) for NO2– in drinking water ruled by the World Health Organization (WHO), which is very important for a practical application of the developed analytical method. The interference experiments indicate that only I– ions among all common anions and cations investigated show very adverse influence on selective detection of NO2– by this developed N-CNDs based fluorescent determination method. Further, the fluores...

Fluorescence Determination of Nitrite in Water Using Prawn-Shell Derived Nitrogen-Doped Carbon Nanodots as Fluorophores

Advances and perspectives in carbon dot-based fluorescent probes: Mechanism, and application

A voltammetric sensor for acetaminophen based on electropolymerized-molecularly imprinted poly(o-aminophenol) modified gold electrode.

Xanthine and its methyl derivatives, theophylline and caffeine are purines which find important roles in biological systems. The simultaneous voltammetric behaviour of these purines has been studied on a glassy carbon electrode modified with an electropolymerised film of para amino benzene sulfonic acid. Well defined and well separated peaks were obtained for the oxidation of xanthine, theophylline and caffeine on the polymer modified electrode in the square wave mode. The experimental requirements to obtain the best results for individual as well as simultaneous determination were optimised. The signal for the electro-oxidation was found to be free of interferences from each other in the range 0.9 – 100 μM in the case of xanthine and from 10–100 μM in the case of theophylline and caffeine with detection limits 0.35 μM, 7.02 μM and 11.95 μM respectively. The simultaneous determination of uric acid, the final metabolic product of xanthine oxidation in biological systems could also be accomplished along with xanthine, theophylline and caffeine atphysiological pH. The mechanistic aspects of the electro-oxidation on the polymer modified electrode was also studied using linear sweep voltammetry. Chronoamperometry was employed to determine the diffusion coefficient of these xanthines. The developed sensor has been successfully demonstrated to be suitable for the determination of these compounds in real samples without much pre-treatment.

Non-enzymatic Electrochemical Sensor for the Simultaneous Determination of Xanthine, its Methyl Derivatives Theophylline and Caffeine as well as its Metabolite Uric Acid

Rapid and sensitive determination of purine bases is vital in clinical analysis. An electrochemical sensor for the determination of the purine bases, guanine, adenine and uric acid, fabricated using a glassy carbon electrode modified with poly(para toluene sulfonic acid), is reported here. In the square wave mode, the modified glassy carbon electrode was able to produce well defined and well separated oxidation peaks for guanine, adenine and uric acid with 0.1 M sodium hydroxide as the supporting electrolyte. The oxidation peak currents for guanine and adenine, showed a dynamic range from 10–100 μM and 20–800 μM with a limit of detection of 0.35 μM and 0.78 μM respectively when determined simultaneously in the presence of uric acid. In simultaneous determination, uric acid also showed a linear increase of oxidation peak current in the concentration range of 10–100 μM, with a limit of detection of 5.88 μM. The variation of peak parameters with scan rate was studied to determine the nature of electro-oxidation and the number of electrons involved in the electrode process. The simultaneous determination of guanine, adenine and uric acid in acid denatured Herring sperm using the fabricated sensor is described. The excellent results obtained indicate that the sensor can be applied for the simultaneous as well as individual determination of guanine, adenine and uric acid in real samples.

Simultaneous determination of guanine and adenine in the presence of uric acid by a poly(para toluene sulfonic acid) mediated electrochemical sensor in alkaline medium

Glutathione is an important antioxidant found in body fluids and tissues, which inhibit damage to essential cellular constituents caused by reactive oxygen species. The analysis of glutathione levels in biological systems is important in early clinical diagnosis. A novel, cost-effective synthetic strategy has been developed for the fluorescent probe ethylenediamine passivated carbon dots. Tissue paper was chosen as the carbon source for this "green one pot" synthesis. Glutathione could induce quenching of the fluorescence intensity of ethylenediamine passivated carbon dots through surface interactions, resulting from their aggregation. Based on this, a novel fluorescence sensor was fabricated for the determination of Glutathione in body fluids. A linear calibration graph was obtained in the range of 6.0 × 10-7 to 5.0 × 10-8 M with a detection limit of 1.74 × 10-9 M. The developed sensor was successfully used for the determination of glutathione in artificial saliva samples.

Fluorescence Determination of Glutathione Using Tissue Paper-derived Carbon Dots as Fluorophores.

Although several methods have been reported for the determination of nitrite, development of simple, rapid,cost-effective, and sensitive sensors still remains a great challenge.Here, a simple yet very sensitive fluorescent method for the rapid determination of nitrite has been developed. The fluorescent assay is based on the aggregation of PEG6000 coated carbon nanoparticles (PCNs) in the presence of NO2(-) ions resulting in fluorescence enhancement. The assay response was linear in a concentration range of 3.84 × 10(-8) M to 4.97 × 10(-9) M with a detection limit of 2.32 × 10(-9) M. The proposed sensor exhibited good selectivity towards NO2(-) and was successfully applied for the determination of nitrite in milk, borewell water and soil samples.

S. Jesny

Papers

A voltammetric sensor for acetaminophen based on electropolymerized-molecularly imprinted poly(o-aminophenol) modified gold electrode.

Non-enzymatic Electrochemical Sensor for the Simultaneous Determination of Xanthine, its Methyl Derivatives Theophylline and Caffeine as well as its Metabolite Uric Acid

Simultaneous determination of guanine and adenine in the presence of uric acid by a poly(para toluene sulfonic acid) mediated electrochemical sensor in alkaline medium

Fluorescence Determination of Glutathione Using Tissue Paper-derived Carbon Dots as Fluorophores.

“Turn On” Fluorescence Determination of Nitrite Using Green Synthesized Carbon Nanoparticles