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Subject: search.filters.subject.Carbon dots

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    Tuning liquid crystal properties with 0D carbon dots: exploring the impact of functionalization of carbon dots
    (RSC, 2025) Manjuladevi, V.; Gupta, Raj Kumar
    Functionalization of nanomaterials is an efficient way to prevent the aggregation of particles and improve the dispersibility in solvents. However, we propose that if unfunctionalized nanoparticles are capable of forming stable dispersions in solvents and miscible in the LC matrix without aggregation or accumulation at interfaces, they could be a better alternative than their functionalized counterparts for improving the physical properties of NLC. In this study, the effect of functionalization of nanomaterials on various physical properties, such as dielectric, electro-optic and conductivity properties, of nematic liquid crystals is investigated. To explore the validity of our hypothesis, we investigated the properties of NLC, 7CB incorporated with carbon dots and octadecylamine-functionalized carbon dots. Dielectric permittivity and elastic constant measurements suggested that quantum dots were rearranged in the nematic matrix in such a way to minimize the free energy of the composite, and functionalization did not significantly affect the global ordering of NLC molecules. We also observed that the conductivity of C-dot composites decreased when compared to pure NLC but increased with the dispersion of ODA C-dot in NLC compared to pure NLC. It was observed that the ligand molecules of the functionalized quantum dots did not add to the conductivity of the dispersions but act as a trap for ionic impurities, and the partial release of these impurities upon interactions of the ligand shell with the uniaxial nematic host could be the source for the increased conductivity. This study is expected to impart substantial insights into designing high-performance nanocomposites of LCs for device applications.
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    CdIn2.2Sy Nanosheet-Based Photoanodes for Photoelectrochemical Water Splitting
    (ACS, 2022-06) Basu, Mrinmoyee
    Photoelectrochemical water splitting is a greener approach to produce hydrogen (H2) as an efficient chemical fuel for the future with high energy density. However, it is extremely challenging to develop suitable semiconductor materials with desired efficiency and stability, which can be applied for practical applications. Looking at the theoretical efficiency and the solar spectrum, it is clear that visible-light-active semiconductors are the most appealing candidates. Herein, CdIn2.2Sy (CIS), a visible light-active semiconductor, is explored as a photoanode for PEC water splitting. The thin nanosheets of CIS are grown vertically through a hydrothermal method. These can efficiently absorb visible light through multiple reflections and scattering of light inside the material and enhance the light–matter interaction. As a result, the developed CIS thin nanosheets produce a maximum photocurrent density of 3.97 mA/cm2 at “1.6” V versus RHE under continuous back illumination. On the other hand, CIS attains a maximum photoconversion efficiency of ∼1.72% at “0.60” V versus RHE. Furthermore, to improve the efficiency and stability, “S” and “N” codoped C-dots (S, N-CDs) are adorned on the CIS photoanode. The “S” and “N” codoped C-dots and CIS form the type-II heterostructure, which efficiently boosts the charge separation and transportation of photogenerated electrons and holes. The transient decay time becomes longer in the case of heterostructure compared to bare CIS. The heterostructure generates 11.2 mA/cm2 photocurrent densities at an applied potential of “1.6” V versus RHE. At the same time, the heterostructure CIS/S, N-CDs-B achieves a ∼2.08-fold higher photoconversion efficiency compared to bare CIS nanosheets and is stable up to 1500 s under continuous back illumination. The present work offers an approach for designing an efficient and stable photoanode for PEC water splitting.
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    FRET and PET paired dual mechanistic carbon dots approach for tyrosinase sensing
    (RSC, 2018-05) Sidhu, Jagpreet Singh
    A dual mechanistic FRET and PET paired ratiometric fluorescence sensor probe has been prepared using carbon dots and naphthalimide fluorophores. The carbon dots are covalently joined with a naphthalimide moiety to develop the FRET phenomenon, which emits at two different wavelengths (i.e., λmax = 440 and 540 nm). However, on catalytic reaction of tyrosinase, the fluorescence emission intensity of the acceptor unit at 540 nm is quenched gradually, owing to the switching on of the PET mechanism; while emission of the donor unit remains significantly unaffected. The probe exhibits high selectivity and specificity towards tyrosinase in complex biological medium with a detection limit of 1.2 U mL−1. Moreover, endogenous images of tyrosinase in B16 cells have been observed under a confocal laser-scanning microscope.
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    Gold conjugated carbon dots nano assembly: FRET paired fluorescence probe for cysteine recognition
    (Elsevier, 2019-03) Sidhu, Jagpreet Singh
    The detection and discrimination of Cys amino acid from numerous other related biomolecules has great importance in clinical field for diagnosis of various diseases. Herein, to detect the Cys, we embedded the carbon dots (CDs), gold, and naphthalimide (L1) into a single ratiometric fluorescence sensor assembly. Sensor assembly works on the principle of FRET mechanism between CDs and naphthalimide when CDs and L1 adhered on gold nanoparticles surface. Gold metal was turned into solid support by in situ reduction of HAuCl4 in the presence of CDs and L1. When the assembly was excited at 360 nm, emission maxima at 568 nm corresponded to naphthalimide emission was emerged that signifies the existence of a FRET between the CDs and naphthalimide fluorophores. With the addition of Cys, the FRET mechanism eliminated and the change in the fluorescence emission at two different wavelengths (450 nm and 568 nm) was recorded. The endogenous images of Cys was recorded by collecting the fluorescence images of HeLa cells under fluorescence microscope and also applied for the assay of Cys in blood serum. Cytotoxicity studies of CDs and sensor assembly were evaluated by performing the MTT assay.