Nondestructive detection of the freshness of fruits and vegetables using gold and silver nanoparticle mediated graphene enhanced Raman spectroscopy

Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) are expanding their horizons into widespread applications as analytical tools with immense potentials. In the current work, we demonstrated the use of a portable Raman system conjugated with graphene enhanced Raman spectroscopy (GERS) for assessing the freshness of fruits and vegetables. Dual nano-platforms have been used involving the use of gold/silver nanoparticles seeded graphene sheets (Au@G and Ag@G, respectively) as the SERS system for probing the freshness of fruits and vegetables. The data showed that Au@G offered high sensitivity, high resolution and high biocompatibility. A novel and simple GERS method based on a microdrop of Ag@G or Au@G on the fruit surface was used for the evaluation of the freshness of the fruits/vegetables. Fruits and vegetables like Wax apple, Lemon, Tomato, Red Pepper and Carrot were investigated. Market fresh and refrigerated fruits and vegetables were probed at various time intervals ranging from 1 day to 2 weeks. The results signify that some of the Raman signals increase with storage and certain peaks were found to appear with long term storage in the refrigerator. This study demonstrates that the quality of fruits and vegetables under short term (1 week) and even under cold storage conditions are impacted and should be avoided as much as possible. The changes effected on the fruits and vegetables under refrigeration and the applicability of using Au@G enabled GERS as a successful and novel platform for assessing the freshness of fruits and vegetables is elaborated. (C) 2015 Elsevier B.V. All rights reserved.