Description:In an embodiment, single-step, the one-pot hydrothermal approach was attempted for the synthesis of water-soluble b-CDs using Beta vulgaris juice as the carbon precursor. Beetroot juice was obtained by thorough grinding of one freshly-peeled beetroot in a mixer grinder without any addition of water. 60 mL of the strained juice was transferred into a Teflon-lined autoclave of 100 mL capacity. The reactant mixture was kept at a constant temperature of 160 oC for eight hours. The autoclave was allowed to attain room temperature. The resultant dark brown colored solution obtained was filtered using a microporous membrane (0.2 µm) and washed thoroughly using ethanol to separate any unreacted organic species. The solution so collected was subjected to centrifugation at 10000 rpm using ethanol followed by double distilled water to remove less-fluorescent particles deposited at the bottom of the tubes. The resultant solution was then subjected to dialysis overnight using a dialysis membrane (Mw=3000) against doubly distilled water. The sample was dried using a vacuum oven at 60 oC for another 24 h.
In another embodiment, quantum yield (φ) calculation was carried out for the b-CDs prepared using quinine sulfate in 0.1 M of H2SO4 as the standard. This was estimated by comparing the intensities of photoluminescence (PL) spectra at an excitation wavelength of 360 nm and its corresponding absorbance values of CDs with that of the quinine sulfate. The equation used is as follows:
φ_CDs= φ_QS × I_CDs/I_QS ×A_Q/A_CDs ×〖ƞ_CDs〗^2/〖ƞ_QS〗^2 (1)
where QS denotes quinine sulfate, I is the integrated intensities of PL emission spectra at 360 nm excitation, A is the absorbance value obtained at 360 nm and ƞ is the refractive index which is 1.33 for both b-CDs and quinine sulfate. In order to reduce the reabsorption effect, we kept the absorbance at 360 nm less than 0.05.
In another embodiment, a DPPH-based reduction assay was used to assess the antioxidant ability of b-CDs derived from beetroot juice with ascorbic acid as the reference. A typical experimental procedure is as follows: 1 mg of the b-CDs synthesized was mixed with 100 ml of methanol to obtain a homogenous stock solution. A series of concentrations ranging from 100 to 1000 µg/ml was prepared in different volumetric flasks from the stock solution. 3 ml of the standard DPPH solution was added to each of the volumetric flasks and kept in the dark for 30 mins. By comparing the absorbance at 517 nm against the blank solution using a UV-Visible spectrophotometer, the unreacted DPPH radical was quantified. Percentage inhibition was calculated using the following equation
Inhibition (%)= ((A_O-A_C ))/A_O X 100 (2)
where A0 and Ac are the absorbance of the sample and that of the control respectively. The concentration of b-CDs required to scavenge 50% of radicals (IC50) was reported using a dose-response curve which was computed using Graph Pad Prism 6 (Graph Pad, SanDiego, CA, USA).
In other embodiment, the hemolysis assay was carried out as per the available report [38]. The blood sample from the chick was collected in a vacutainer containing an EDTA solution of 2 mg/ml concentration. The collected blood samples were centrifuged at 3000 rpm for five minutes at 4 oC to separate plasma and buffy coats. It was washed thrice with 0.85 % sodium saline and then the volume was made up to 20 ml. 1 ml each of a particular concentration of b-CDs in saline was allowed to incubate for two hours at room temperature. After the incubation, the test suspensions were centrifuged at 14000 rpm for five minutes. The supernatant was collected and the optical density was estimated at 540 nm using a UV-Visible spectrophotometer. In this study, 2 % Triton X-100 served as the positive control. Percentage hemolysis was calculated using the following equation
Hemolysis (%)= ((Absorbance of the sample-Absorbance of the blank) )/(Maximum absorbance of the positive control) X 100 (3)

In another embodiment, the cytotoxicity of b-CDs towards MCF-7, HepG2, and HEK-293 cell lines were carried out using 3-[4, 5- dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide or MTT, which is a water-soluble tetrazolium salt showing yellow color in media or salt solutions. The cell culture was trypsinized and the count was adjusted to 5.0 X 105 cells/mL using different media containing 10% FBS. 100 µL solutions of cell suspensions (diluted) were added to each well of 96 well microtiter plate and allowed to grow for 24 h. After that, the supernatant was flicked off and 100 µL of different concentrations of CDs (10, 20, 40, 80, 160, and 320 µg/mL) were added and the plate was incubated for 24 hours in a 5 % CO2 atmosphere at 37 oC. After the incubation, the test solutions in the wells were discarded and the MTT reagent (5mg/ml in PBS) was added to each well. The plates were incubated for another 4 hours at 37 oC in a 5 % CO2 atmosphere. The supernatant was discarded and the purple colored formazan formed was solubilized by the addition of DMSO. The optical density (OD) was measured using a microplate reader at a wavelength of 590 nm. The percentage growth inhibition was calculated using the following formula
Inhibition (%)= ((OD of Control-OD of the Sample))/(OD of the Control) X 100 (4)

Doxorubicin was used as the standard drug for this study. IC50 value is reported.
, Claims:1. The present invention provides a green synthesis of novel carbon dots from Beta vulgaris via a single-step hydrothermal approach
2. A method as claimed in claim 1, wherein quantum yield calculations were evaluated
3. A method as claimed in claim 1, wherein blood compatibility of the novel carbon dots was evaluated using a hemolysis assay
4. A method as claimed in claim 1, wherein the cytotoxicity evaluated using the MTT assay shows significant cell growth-inhibition against the human breast cancer (MCF-7) and hepatocellular carcinoma (HepG2) cell lines were performed
5. A method as claimed in claim 1, wherein 2, 2´-diphenyl-1-picrylhydrazyl (DPPH) assay was performed using maximum scavenging activity of 94.5 % at a concentration of 1000 µg/mL