Nitrogen and Phosphorus Co-Doped Carbon Dots for Selective Detection of Nitro Explosives.

In this work, a highly selective and sensitive method has been developed for the detection of trinitrophenol (TNP), which is a dangerous explosive. For this purpose, N and P co-doped carbon dots (NP-Cdots) have been used. Synthesis of N and P co-doped carbon dots has been carried out by a simple and quick method. X-ray photoelectron spectroscopy analysis was carried out to detect the doping of N and P. These carbon dots are insoluble in water (inNP-Cdots). These carbon dots were functionalized by treating them with conc. HNO3 so that they become water-soluble (wsNP-Cdots). These dots were characterized by different analytical techniques such as IR, UV-vis, and fluorescence spectroscopy. The as-prepared wsNP-Cdots have good fluorescence properties. The average diameter of wsNP-Cdots is found to be 5.7 nm with an interlayer spacing (d-spacing) of 0.16 nm. The as-prepared wsNP-Cdots are highly sensitive and selective toward TNP, as observed using a fluorescence quenching technique. The quenching constant for TNP is found to be very high (8.06 × 104 M-1), which indicates its high quenching ability. The limit of detection is found to be 23 µM.

P2O5 assisted green synthesis of multicolor fluorescent water soluble carbon dots.

A low cost synthesis of multicolor fluorescent carbon dots (C-dots) from edible sugars is described here. Common sugars like dextrose, lactose or maltose in aqueous medium gets dehydrated using phosphorus pentoxide (P2O5). The reaction is facile and completed within few minutes to form insoluble carbon (C-dots) mostly having the graphitic (G-band, Raman) sp2 hybridized carbon atoms (C-atoms). This insoluble carbon on oxidative treatment with nitric acid produced disordered sp3 (D-band retaining G-band, Raman) hybridized C-atoms, originated from the graphitic pool with sp2 hybridized C-atoms. This high density assimilation of self passivated "surfacial defects" become emissive during electronic transitions. Surfacial defects due to high degree of electrophilic carboxylation create the water soluble version of multicolor fluorescent C-dots as "water soluble fluorescent carbon dots" (wsFCDs). wsFCDs being itself self-passivated imposes the tunable multicolor emission throughout the visible spectrum without having any external coating and surface passivation and could be used as multicolor fluorescent probe especially in the emerging field of optical bio-imaging.

Water soluble carbon nano-onions from wood wool as growth promoters for gram plants.

Water-soluble carbon nano-onions (wsCNOs) isolated from wood wool-a wood-based pyrolysis waste product of wood, can enhance the overall growth rate of gram (Cicer arietinum) plants. Treatment of plants with upto 30 µg mL(-1) of wsCNOs for an initial 10 day period in laboratory conditions led to an increase in the overall growth of the plant biomass. In order to examine the growth stimulating effects of wsCNOs under natural conditions, 10 day-old plants treated with and without wsCNOs were transplanted into soil of standard carbon and nitrogen composition. We observed an enhanced growth rate of the wsCNOs pre-treated plants in soil, which finally led to an increased productivity of plants in terms of a larger number of grams. On analyzing the carbon, hydrogen, and nitrogen (CHN) content for the shoot and fruit sections of the plants treated with and without wsCNOs, only a minor difference in the composition was noticed. However, a slight increase in the percentage of carbon and hydrogen in shoots reflects the synthesis of more organic biomass in the case of treated plants. This work shows that wsCNOs are non-toxic to plant cells and can act as efficient growth stimulants which can be used as benign growth promoters.