The synthesis of graphene-like carbon using popcorn kernels as a renewable resource is presented. In a first step popcorn kernels were heated to produce popcorn flakes with a spongy appearance consisting of a polygonal cellular structure. In a second step, the flakes were treated at high temperature in an inert atmosphere to produce carbonization. Raman spectroscopy shows graphene-like structure with a high degree of disorder.

In the present study, we investigated the ability of micro-Raman spectroscopy to identify low concentrations of trimethylamine N-oxide (TMAO) mixed in synthetic urine composed of water, sodium chloride, urea, and creatinine using a support vector machine (SVM) as a discrimination tool to differentiate the Raman spectra of the different concentrations of TMAO. TMAO is a novel biomarker associated with cardiovascular diseases, kidney diseases, and complications of type 2 diabetes. We obtained the Raman spectra of four different concentrations of TMAO. The spectra were filtered before being classified using principal component analysis (PCA) combined with the SVM method. We identify the spectral window that goes from 800 to 870 cm-1 where TMAO presents Raman activity in the synthetic urine mixture without the intervention of Raman activity of another molecule. We predicted the different concentration of TMAO in the synthetic urine until 1ppm (13.21 µM) of TMAO, getting an accuracy of classification greater than 70 percent indicated by the confusion matrix, and area under the receiver operating characteristic curve of 0.86 for 1ppm (13.31 µM) and 10ppm (133.13 µM) concentration. This study showed that Raman spectroscopy combined with SVM has the potential to detect low concentrations of TMAO in urine.

Resumen: En este trabajo hemos usado la técnica de contraste óptico como herramienta de identificación preliminar y sencilla de capas de grafeno, la cual es más simple en comparación con la propuesta de otros autores y es validada con espectroscopia Raman. Para ello obtenemos grafeno y pocas capas de grafeno por exfoliación mecánica de grafito Kish. Adquirimos imágenes digitales, a través de un microscopio óptico, de las diferentes muestras depositadas sobre un sustrato de silicio con una película de óxido de silicio de 306.2 nm. Con un programa de análisis de imágenes adquirimos la componente verde de los números RGB, tanto de la muestra como del sustrato; con ello, calculamos el contraste óptico y determinamos el número de capas de grafeno. Logramos determinar de una a cuatro capas de grafeno.