The aim was to explore the utilization of tea leaf waste fibers (TLWF) as a source for the production of cellulose nanocrystals (CNC). TLWF was first treated with alkaline, followed by bleaching before being hydrolyzed with concentrated sulfuric acid. The materials attained after each step of chemical treatments were characterized and their chemical compositions were studied. The structure analysis was examined by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). From FTIR analysis, two peaks at 1716 and 1207 cm⁻¹—which represent C=O stretching and C–O stretching, respectively—disappeared in the spectra after the alkaline and bleaching treatments indicated that hemicellulose and lignin were almost entirely discarded from the fiber. The surface morphology of TLWF before and after chemical treatments was investigated by scanning electron microscopy (SEM) while the dimension of CNC was determined by transmission electron microscopy (TEM). The extraction of CNC increased the surface roughness and the crystallinity index of fiber from 41.5% to 83.1%. Morphological characterization from TEM revealed the appearance of needle-like shaped CNCs with average diameter of 7.97 nm. The promising results from all the analyses justify TLWF as a principal source of natural materials which can produce CNC.

This article describes chemically modified polyaniline and graphene (PANI/GP) composite nanofibers prepared by self-assembly process using oxidative polymerization of aniline monomer and graphene in the presence of a solution containing poly(methyl vinyl ether-alt-maleic acid) (PMVEA). Characterization of the composite nanofibers was carried out by Fourier transform infrared (FTIR) and Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). SEM images revealed the size of the PANI nanofibers ranged from 90 to 360 nm in diameter and was greatly influenced by the proportion of PMVEA and graphene. The composite nanofibers with an immobilized DNA probe were used for the detection of Mycobacterium tuberculosis by using an electrochemical technique. A photochemical indicator, methylene blue (MB) was used to monitor the hybridization of target DNA by using differential pulse voltammetry (DPV) method. The detection range of DNA biosensor was obtained from of 10⁻⁶–10⁻⁹ M with the detection limit of 7.853 × 10⁻⁷ M under optimum conditions. The results show that the composite nanofibers have a great potential in a range of applications for DNA sensors.

Conducting nanofibers composed of poly(vinyl alcohol) (PVA), graphene oxide (GO) and poly(3,4-ethylenedioxythiophene) (PEDOT) were fabricated via a combined method using electrospinning and electropolymerization techniques. A small amount of GO was dispersed into PVA as the precursor solution for electrospinning, resulting in free-bead nanofiber structures with a diameter range less than 200 nm. SEM images of the obtained nanofiber revealed that PEDOT grew well on the surface of the electrospun nanofibers during the potentiostatic mode of the electropolymerization process. The presence of GO and PEDOT was confirmed by FTIR and Raman spectroscopy analyses. Comparing with the PVA/PEDOT nanofiber, the experimental results indicate that the addition of GO improved the electrochemical performance of the nanofibers. The electrochemical measurements demonstrated that the PVA–GO/PEDOT composite nanofiber could enhance the current response and reduce the charge transfer resistance of the nanofiber.