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Micronutrients are very essential substances required in regulating the normal human growth and development. Since the human body cannot produce sufficient micronutrients, these have to be supplied through the diet. Among the various micronutrients, zinc plays a vital role in regulating cell growth, metabolism, immune response and wound healing. Zinc micronutrient deficiency is common in most of the developing countries and majorly affects children resulting in stunted growth, cognitive impairment, chronic infections and illnesses [1]. The conventional diagnostic assay for zinc detection involves sophisticated instruments and laborious sample processing procedures [2]. In this proposed study, a point of care and label free biosensing technique is demonstrated for detection of zinc utilizing Surface enhanced Raman spectroscopy (SERS) through synergistic Raman signal enhancement from graphene gold nanocomposites. In order to enhance the intensity of Raman spectral peaks, graphene gold nanocomposite based SERS substrates are developed by simple drop casting technique. The Raman signal enhancement due to graphene gold nanocomposites is investigated in our earlier studies using COMSOL by the finite element method [3]. Herein, graphene gold nanocomposites are drop casted onto paper substrates and dried at room temperature to fabricate a flexible SERS substrate. Label free detection of zinc is achieved by coating zinc samples of different concentrations onto these substrates and the Raman measurement is carried out to investigate the characteristic Raman peaks of zinc molecules. Due to the vibration of OH-bond and stretching band of Zn-H2O, the characteristic peaks at 251 cm-1 and 328 cm-1 revealed the presence of zinc and the intensity of the peaks was increased by ~8.9-fold by graphene gold nanocomposites in comparison with the bare analyte. The proposed graphene gold nanocomposite could be employed for detection of zinc with the detection limit of 1 nM. Further, the study could be extended and optimized for automated diagnosis by investigating the inherent Raman spectral peaks and explored for real time detection of zinc in blood samples.
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