Finding a low cost substrate for surface-enhanced Raman spectroscopy (SERS) yielding enhanced, reproducible Raman signal from Raman active samples has been a longstanding goal for researchers for years. Herein, we demonstrate the fabrication of such a SERS substrate from paper. The proposed paper-based SERS substrate was developed by attaching polyvinylpyrrolidone (PVP) capped silver nano-particles (AgNPs) to printing grade paper. The performance of the substrate has been evaluated for paper substrates of various grades (in grams per square meter; GSM). The usability of the developed substrate for detection of two Raman active samples—namely, malachite green (MG) and rhodamine6G (R6G)—is reported. In addition to these samples, the reproducibility of the designed substrate has been evaluated for 1,2-bis(4-pyridyl)ethylene (BPE); a good degree of reproducibility was observed. Finally, applicability of the proposed substrate for reliable detection of Raman signals from two more important samples—namely, glucose and urine—has been successfully demonstrated.

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Surface-enhanced Raman Spectroscopy (SERS) is a unique technique that allows us to detect samples in trace quantities. This nanomaterial assisted phenomenon has been extensively studied over past several decades for sensing various chemical, biological and gaseous samples. Present work demonstrates the working of a paper-based SERS substrate to detect and quantify two pharmaceutical drugs- paracetamol, and aspirin in water. The proposed paper-based SERS substrate has been obtained by drop-casting of silver nanoparticles (AgNPs) over a 100 grams per square meter (GSM) paper. The performance of the designed SERS substrate has been initially evaluated with two Raman active samples - malachite green (MG) and rhodamine-6G (R6G). Upon noticing its reliable performance, the usability of the designed SERS substrate has been demonstrated to detect and quantify paracetamol and aspirin in the water medium. The applicability of the proposed SERS substrate in the real field environment has also been demonstrated through detection of these two drug elements in field collected water samples.

A simple yet effective, handheld and flexible bright-field and fluorescence microscopic platform on a smartphone with varying optical magnifications is reported for morphological analysis and onboard cell counting features.