Green to deep-red emissive carbon dot formation by C+ion implantation on nitrogen beam created self-masked nano-template.

We report the formation of green to red emissive arrays of carbon dot on silicon-nitride nano-templates by successive implantation of nitrogen and carbon broad ion beams. The patterned nano-templates are formed by 14 keV N2+ion-bombardment at grazing incident (70°) on Si. Subsequently, 5 keV C+ions are implanted at the selective sites of the pyramidal nano-template by taking advantage of the self-masking effect. The nano-pyramidal pattern and the implanted carbon dots at the specific sites are confirmed by atomic force microscopy and cross sectional transmission electron microscopy measurements. The developed carbon dots (CDs) are mostly amorphous and consists of SiC and graphitic nitrogen (CN). G-band and D-band carbons are identified by Raman spectroscopy, while the presence of SiC and CN are detected by XPS measurements. A change of band-gap is observed for C-implanted templates by the UV-vis spectroscopy. Excitation wavelength-dependent photoemission from the dots is found in the green to red region. Maximum intense PL is observed in the green-orange region for excitation wavelength of 425 nm and a redshift of PL with decreasing intensity is observed with the increase of excitation wavelength. The observed photoluminescence is described in terms of the combined effects of quantum confinement, graphitic nitrogen and defect induced additional states formation in the carbon dots. The potential applications of CDs are also addressed.

Monolayer Graphene-MoSSe van der Waals Heterostructure for Highly Responsive Gate-Tunable Near-Infrared-Sensitive Broadband Fast Photodetector.

Transition metal dichalcogenides (TMDCs) are potential two-dimentional materials as natural partners of graphene for highly responsive van der Waals (vdW) heterostructure photodetectors. However, the spectral detection range of the detectors is limited by the optical bandgap of the TMDC, which acts as a light-absorbing medium. Bandgap engineering by making alloy TMDC has evolved as a suitable approach for the development of wide-band photodetectors. Here, broadband (visible to near-infrared) photodetection with high sensitivity in the near-infrared region is demonstrated in a MoSSe/graphene heterostructure. In the ambient environment, the photodetector exhibits high responsivity of 0.6 × 102 A/W and detectivity of 7.9 × 1011 Jones at 800 nm excitation with a power density of 17 fW/µm2 and 10 mV source-drain bias. The photodetector shows appreciable responsivity in self-bias mode due to nonuniform distribution of MoSSe flakes on the graphene layer between the source and drain end and the asymmetry between the two electrodes. Time-dependent photocurrent measurements show fast rise/decay times of ∼38 ms/∼48 ms. A significant gate tunability on the efficiency of the detector has been demonstrated. The device is capable of low power detection and exhibits high operational frequency, gain, and bandwidth. Thus, the MoSSe/graphene heterostructure can be a promising candidate as a high-speed and highly sensitive near-infrared photodetector capable of operating at ambient conditions with low energy consumption.

Polymer-Protein Hybrid Network Involving Mucin: A Mineralized Biomimetic Template for Bone Tissue Engineering.

Biomimetic matrices offer a great advantage to understand several biological processes including regeneration. The study involves the development of a hybrid biomimetic scaffold and the uniqueness lies in the use of mucin, as a constituent protein. Through this study, the role of the protein in bone regeneration is deciphered through its development as a 3D model. As a first step towards understanding the protein, the interactions of mucin and collagen are determined by in silico studies considering that collagen is the most abundant protein in the bone microenvironment. Both proteins are reported to be involved in bone biology though the exact role of mucin is a topic of investigation. The in silico studies of collagen-mucin suggest to have a proper affinity toward each other, forming a strong basis for 3D scaffold development. The developed 3D scaffold is a double network system comprising of mucin and collagen and vinyl end functionalized polyethylene glycol. In situ deposition of mineral crystals has been performed enzymatically. Biological evaluation of these mineral deposited scaffolds is done in terms of their bone regeneration potential and a comparison of the two systems with and without mineral deposition is presented.