Graphene Based Electrochemical DNA Biosensor for Detection of False Smut of Rice (Ustilaginoidea virens).

False smut caused by Ustilaginoidea virens is an important rice fungal disease that significantly decreases its production. In the recent past, conventional methods have been developed for its detection that is time-consuming and need high-cost equipments. The research and development in nanotechnology have made it possible to assemble efficient recognition interfaces in biosensors. In this study, we present a simple, sensitive, and selective oxidized graphene-based geno-biosensor for the detection of rice false smut. The biosensor has been developed using a probe DNA as a biological recognition element on paper electrodes, and oxidized graphene to enhance the limit of detection and sensitivity of the sensor. Probe single-stranded DNA (ssDNA) and target ssDNA hybridization on the interface surface has been quantitatively measured with the electrochemical analysis tools namely, cyclic voltammetry, and linear sweep voltammetry. To confirm the selectivity of the device, probe hybridization with non-complementary ssDNA target has been studied. In our study, the developed sensor was able to detect up to 10 fM of target ssDNA. The paper electrodes were employed to produce an effective and cost-effective platform for the immobilization of the DNA and can be extended to design low-cost biosensors for the detection of the other plant pathogens.

Photolysis-Driven, Room Temperature Filling of Single-Wall Carbon Nanotubes.

An alternative process for opening and filling single-wall carbon nanotubes (SWCNTs) based on UV photolysis is proposed. The filling of SWCNTs with MoCl5 and iodine were successfully achieved at room temperature after subjecting SWCNTs with MoCl5 or I2 dissolved in chloroform to UV light for 6 hours. Transmission electron microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS) were used to characterise both the encapsulated materials and the host tube. A mechanism for the related opening and filling events is proposed, along with a possible yet unprecedented structure for the encapsulated MoCl5 material whose the peculiar polymeric configuration could be enforced by the steric constrains resulting from the limited, 1D cavity available in SWCNT core.

Connecting carbon nanotubes using Sn.

Process of Sn coating on mutiwalled carbon nanotubes (MWCNT) and formation of interconnections among nanotubes are studied using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDX). Surface oxidation of nanotubes during heating with HNO3 prior to the SnCl2 treatment and the bonding between functional groups and Sn are found to be responsible for the coating and its stability. Open nanotubes are filled as well as coated during tin chloride treatment. Coating and filling are converted into the coatings on the inner as well as outer walls of the nanotubes during reduction with H2/N2. EDX studies show the formation of intermetallic compounds e.g., Cu6Sn5 and Cu3Sn at the joints between nanotubes. Formation of intermetallic compounds is supposed to be responsible for providing the required strength for bending and twisting of nanotubes joining of nanotubes. Paper presents a detailed mechanism of coating and filling processes, and interconnections among nanotubes.