carbon dots and its applications

A new carbon material carbon dots have myriad applications in Drug delivery, sensing and organic synthesis also.

1. Carbon dots Characterization and Applications Presented By P. Chandrasekaran 1

2. CONTENTS What is Carbon Dots? Properties of Carbon Dots(CD) Synthesis of CDs Characterization of CDs Applications of CDs 2

3. Introduction CDs are small carbon nanoparticle ( less than 10nm in size) with some form of surface passivation. CDs were First discovered by XU et al., in 2004 accidently during the purification of single walled carbon nanotubes. This Discovery triggered extensive studies to exploit the florescence properties of CDs. 3

4. Properties of CDs CDs are Biocompatible small size with large surface area Photoluminescence Photostable properties potential application in sensing, catalysis Biomedicine Heteroatom doped carbon dots are enhance the fluorescent properties 4

5. Excellent water solubility Biocompatibility Good conductivity Photochemical stability Low toxicity Environmental friendly 5

6. Synthesis of CDs Carbonization procedure Microwave synthesis Hydrothermal method Solvothermal method Laser ablation technique Chemical route (thermolysis ) Electrochemical method 6

7. Characterization of Carbon dots UV PL TEM XRD Raman IR XPS 7

8. UV-Visible Principle of ultraviolet–visible absorption. Molecules containing π- electrons or non-bonding electrons (n-electrons) can absorb energy in the form of ultraviolet or visible light to excite these electrons to higher anti-bonding molecular orbitals. 8 π - π * and n- π * transitions associated with C=C and carbonyl/hydroxyl groups respectively

9. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. 9

10. The TEM operates on the same basic principles as the light microscope but uses electrons instead of light. When an electron beam passes through a thin-section specimen of a material, electrons are scattered. The surface morphology of synthesized CDs was obtained using HR-TEM . The synthesized N-CDs were spherical in nature and evenly distributed over the carbon coated Cu grid. Transmission Electron Microscope 10

11. X-ray Diffraction The atomic planes of a crystal causes an incident beam of X-rays to interfere with one another as they come out from the crystal. This phenomenon is called X-ray diffraction. XRD pattern of synthesized N-CDs and this displays a very intense broad peak (002) and a weak peak(001) . From the Bragg's equation the d-spacing value for synthesized N-CDs were calculated. 11

12. Raman spectroscopy Raman spectra arise due to inelastic collision between incident monochromatic radiation and molecules of sample . Spectrum exhibits two distinct Raman bands at ~ 1354 cm -1 and ~1594 cm -1 , which belong to the sp 3 defects (D band) and sp 2 carbon (G band) in the synthesized CDs. D band - vibrations of carbon atoms for distorted graphite G band - two-dimensional hexagonal lattice sp2 carbon atoms. 12

13. Bond Compound Wave number (cm -1 ) Shape/ Intensity -O-H R- O-H (alcohol)  3200 - 3600 broad, strong -C-H (alkane) R- C-H 3  2850 - 2950 sharp, strong -N-H R- NH 2 (Primary amine – two peaks) R 2 NH (secondary amine – single peak )  3350 - 3500 broad, medium Bond Compound Wave number (cm -1 ) Shape/ Intensity -C-N R-H 2 C -N R 2 ( amine)  1180 - 1360 sharp, strong C=C R- C=C - C=C - R 1620-1640 sharp, strong -C=O R- C(=O) R/H  1640 - 1740 Sharp, strong 13 Infrared spectroscopy Group Frequencies

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15. XPS spectra are obtained by irradiating a material with a beam of X-rays. XPS survey scan spectrum of the synthesized NCDs and high resolution XPS spectra of their three elements: C (1s ), N (1s) and O (1s ). The deconvolution spectrum of C1s revealed four peaks at 283.5, 284.4 , 287.1 and 294.5 eV and they are attributed to C-H, C=C (sp2 ),C-N/O-C=O and p-p* transitions. The XPS results confirmed that the synthesized N-CDs were functionalized by hydroxyl, amine and carboxyl groups. 15

16. Applications of CDs Catalysis (Reduction of Dyes, HER, ORR, Oxidation of Organic molecules( paracetamol , toluene,…) Bio imaging Drug Delivery Bio sensing 16

17. Cancer Drugs Carbon dots passivated Folic acid ( Vit B9) and Functionalized with Niclosamide, Curcumin , Quercetin, Doxorubicin. 17

18. Graphical mechanism 18

19. Drug delivery is transportation of a pharmaceutical compound in the body to safely achieve the desired effect via use of system or technology . It concerns with both quantity and duration of drug presence. 19

20. An efficient approach for targeting and detecting cancer cells has been developed through the design of the assembly of fluorescent CDs and folic acid (C-dots–FA), which is endocytosible by the overexpressed folate receptor (FR) molecule. 20 C-dots–FA

21. Laser Scanning Confocal Microscopy 21 LSCM images of SiHa cells incubated with CDs- DOX and DOX only for 5 h observed under different wavelengths

22. Sharp decrease in peak intensity of the CDs-DOX DOX molecules probably quenched the CDs fluorescence The zeta potential (CDs) = − 5.12 mV The value increased up to 1.03 mV, indicate successful preparation of the CDs-DOX complexes via electrostatic interaction 22

23. SEM images of CDs , DOX and CDs-DOX 23 SEM Images

24. Bio imaging 24

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27. Carbon dots catalyze the coupling reaction 27

28. Suzuki– Miyaura coupling - Mechanism and Reaction 28

29. Alkenylation of Chromones 29

30. Characterize the Pd@CQD@Fe 3 O 4 NPs 30

31. UV-Visible spectrum 31

32. carbon in the structure of Pd@Cdots@Fe3O4 confirmed by XPS analysis BE = 335.6 and 340.8 eV (related to Pd ) BE=338 and 343 eV (related to Pd II ) indicate that most of the Pd is present in the reduced form , which confirms the capability of C-dots@Fe3O4 in the efficient reduction of Pd II to Pd NPs. 32 XPS Spectrum

33. TGA Spectrum The first weight loss - water and physically adsorbed solvents . The second weight loss- C-dots on the Fe3O4 NPs 33

34. SEM and TEM Images for the Pd@CQD@Fe 3 O 4 NPs 34 SEM images of the Pd@C-dots@Fe 3 O 4 showed the formation of uniform spherical particles and the energy-dispersive spectrum (EDS) obtained from SEM confirmed the presence of Pd, Fe, and C species in the structure of the material.

35. TEM image TEM image of Pd@C-dots@Fe3O4 at different magnifications. 35

36. 36 XRD pattern of Pd@C-dots@Fe 3 O 4 XRD Pattern

37. Conclusions Finally Organic coupling reaction catalyzed by Pd@CQD@Fe 3 O 4 NPs. CDs catalyst the reduction of Dyes, oxidation of Organic molecules using glassy carbon electrode Bio imaging and drug delivery easily done by CDs 37

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