C H a R a C T E R I Z a T I

Optical properties of Graphene Quantum Dots Himadri Sekhar Tripathi1,, Rajesh Mukherjee *2 , T.P. Sinha1 1Department of Physics, Bose Institute, 93/1, APC Road, Kolkata, India – 700009 2Department of Physics, Ramananda College, Bishnupur, Bankura, India –722122 *Corresponding author: [email protected] ABSTRACT: Graphene quantum dots (GQDs) exhibit interesting chemical and physical properties due to the quantum confinement and edge effect. GQDs were prepared by simple pyrolysis of citric acid. Room temperature X-ray diffraction (XRD) pattern of the sample is carried out from 0 0 Bragg angle 2θ = 5 to 80 with the Rigaku Miniflex II diffractometer having Cu Kα radiation (λ = 0.1542 nm). The UV–Visible spectrum of the materials was collected using UV–Vis spectrophotometer (Shimadzu UV 2401Pc). The photoluminescence (PL) spectra of GQDs were taken by JASCO FP-8500. INTRODUCTION: Semiconductor nanocrystal or quantum dots are Nano particles of ten of atoms but confined in a very small region. These are zero dimensional materials and are gaining attention to the researchers because of their interesting optical, electronic and opto-electronic properties compared to bulk. Quantum mechanical confinement plays a key role in determining the peculiar behaviour compared to bulk. GQDs exhibit interesting chemical and physical properties due to the quantum confinement and edge effect. As the number of carbon atoms in edge is more than in basal plane, GQDs are more reactive. SYNTHESIS: Five grams of citric acid was heated and melted at 650C-700C temperature. This melted citric acid was converted into dark orange color within 25 – 30 min. Then this dark citric acid solution was kept at room temperature. 2 M solution of NaOH was added drop wise in the melted dense solution of citric acid at room temperature. PH of the solution was tested for several times. Finally, the GQDs are prepared at PH level 11. The temperature of the solution was increased slowly and was dried at temperature ~ 500C to get in powder form. C X-ray diffraction peak at Bragg angle 2θ=18.420 corresponds to the inter layer H spacing 0.468 nm. Again another diffraction peak at 2θ=30.420, corresponding A the d spacing 0.293 nm. The inter layer spacing of GQDs is broader than graphite which suggests more oxygen containing functional group attached to R GQDs. A 3 251 nm Bandgap of GQD C 440 nm 2000 460 nm 470 nm 10 T 2 (a.u) 480 nm 0.5 ) 66.82 nm h 100 E ( 1000 R 80 1 0 2.7 3.6 4.5 Absorbance (a.u) I Absorbance (a.u) h (eV) 60 Z 0 40 0 A 500 600 700 200 300 400 500 600 700 800 900 Intensity (%) wavelength (nm) wavelength (nm) 20 T (a) (b) 0 0 50 100 150 I Size (nm) O The emission peaks in the UV-Visible spectra confirm that Dynamic light scattering (DLS) analysis N photoluminescence spectra are red shifted GQDs show optical absorption with the increase of excitation wavelength. shows that average size of the particles is in the visible region. found to be ~ 65 nm. CONCLUSION: GQD can be synthesized by a simple process. Room temperature XRD data confirm the formation of the material. Optical property shows that the material can be a good candidates for optical applications. REFERENCES: 1. Rajesh Mukherjee. Quantum dots: Properties, Synthesis and Applications. Research & Reviews: Journal of Physics. 2020; 9(1): 1–4p. 2. Himadri Sekhar Tripathi, Rajesh Mukherjee, Moumin Rudra, Ranjan Sutradhar, R. A. Kumar, T. P. Sinha, AIP Conference Proceedings, 2019: 2162(1):020088 Molecular Dynamics simulation of human rennin Abhik Chatterjee, Biswajit Das, Uttam Kumar Mondal Insilico Chemical Laboratory, Department of Chemistry, Raiganj University,Raiganj-733134. [email protected] Introduction: Renin is a hormone enzyme produced from the inactive protein prorenin. Renin initiates renin-angiotensin system (RAS) producing the angiotensin peptides that control blood pressure, cell growth, apoptosis and electrolyte balanced. Renin is highly specific aspartic proteinases and mainly produced by Juxtaglomerular cell in the kidney. The Secretion of renin from Juxtaglomrular cell is controlled by several mechanisms, including the sympathetic nervous system, salt and fluid balance, and blood pressure. It cleaves angiotensinogen to form the decapeptide angiotensin I. Then inactive decapeptide converted to active octapeptide angiotensin II by the angiotensin converting enzyme (ACE). Next the angiotensin II binds to the type 1 angiotensin II receptors (AT1). Stimulation of type 1 angiotensin II receptor increases arterial tone and also the secretion of aldosterone. Therefore angiotensin II plays a key role in blood pressure, fluid and electrolyte homeostasis. In this study MD simulation was performed to consider the flexibility of protein. The MD simulation was carried out using GROMACS software. The 2.00 A° resolution x-ray structure of Human renin (PDB code 3GW5) was used as a starting structure. The overall structural stability of the free protein during the simulation has been monitored using several parameters likes the radius of gyration (Rg), RMSF etc., were calculated over the course of the simulation. Methodology: The MD simulation was carried out using GROMACS. The 2.00 A° resolution x-ray structure of Human renin (PDB code 3GW5) was used as a starting structure. We have carried out MD simulation of free protein not the complex. The protein was solvated with SPC water molecules in a cubic box, having an edge length of 3.5 A°. The LINCS algorithm was employed to constrain all bond lengths. The simulation was conducted at a constant temperature (300K) and the Berendsen coupling method was used for coupling each component separately to a temperature bath. MD simulation was performed for 6 ns. Before running simulation, an energy minimization was performed by steepest descent (sd) method. After that the positional restraints were released and simulation is performed for 6ns with time step 2 fs. Finally the end of the simulation the respective trajectory files were examined with different tools of GROMACS. Results and Discussions: The overall structural stability of the free protein during the simulation has been monitored using several parameters likes the radius of gyration (Rg), RMSF and RMSD of individual residues were calculated over the course of the simulation.. The variation of radius of gyration (Rg) as a function of time is presented in Figure 2 and from this figure it is clear that the initial Rg value is 2.68172 and then Rg value decreases up to 437ps with Rg value 2.6126, after that Rg slightly increases up to 5261ps(2.69299). The overall plot of Rg during the simulation shows a periodical nature. The flexibility of different segments of the protein is also revealed by looking at the root mean-square fluctuation (RMSF) of each residue from its time-averaged position is presented in Figure3.. Among the secondary structure beta strand has higher fluctuation than alphahelix. There is ten Helix in both chains (A&B) within the protein in which Helix, H2 in chain B has highest fluctuations and Helix H10 in chain A has lowest fluctuations. Heilix H2, H4, H6 and H8, in chain A and H13, H14, H16, H17and H18 in chain B shows considerable fluctuations. Acknowledgement: Authors are thankful to Late Prof. Asim kumar Bothra. Figure 1. Protein 3GW5 Figure 2. Radius of gyration (Rg) as a function of time with respect to starting structure during the MD simulations. Figure 3. Root mean square fluctuations (RMSF) during the MD simulations. Dr. Amit Kumar Dutta, Assistant Professor,Department of Chemistry, Bangabasi Morning College Substitution of A by T Mutation is define as a change in nucleotide sequence of DNA (Thalassemia) Premature termination (during synthesis) of protein, functional activity may be destroyed. Some Viral vectors (carrier )(a modified Virus)) are used in gene therapy to deliver genetic material into cells, to restore the function of the protein., as vaccines, and for cancer therapy Virus has been modified in a laboratory so they can't cause disease when used in people for gene therapy, as vaccines Adenovirus vectors (most commonly employed vector, target and destroy cancer cells while leaving normal cells unharmed. Anti-leishmanial activities of palladium(II) and platinum(II) complexes of glyoxalbis(N-aryl)osazone ligand Dr. Amit Saha Roy Assistant Professor, New Alipore College, Kolkata-53 E-mail: [email protected] NHPhH2 NH(ClPh)H2 NHPhH2 Abstract: These work report the synthesis and characterisation of four Pd(II) and Pt(II) complexes [Pd(L )Cl2] (1), [Pd(L )Cl2] (2), [Pt(L )Cl2] (3) and NH(ClPh) [Pt(L H2)Cl2] (4) containing osazone ligands including single crystal X-ray diffraction of 2 and 4. All the complexes 1-4 were characterized by different spectral study (IR, UV-vis, NMR, and Mass). Complexes 3 and 4 can be reversibly reduced and the electro-generated anions [3]•‒ and [4]•‒ show EPR parameters indicative for the localization of the unpaired electron on the osazone ligand. DFT calculations support this. Cell viability experiments (MTT assay) show that the complexes are potent anti-leishmaniasis agents while their anti-bacterial and anti-fungal activities are low. In cyclic voltammetry 3 and 4 display quasi-reversible (ipc/ipa ≈ 1.2) waves at –1.28 (0.22) and –1.11 (0.21) V whereas the anodic waves of both 3 and 4 are NH(ClPh) • irreversible and appear at +0.97 and +0.75 V, respectively (L H2 = osazone anion radical). (3) (4) Fig. 2 Cyclic voltammograms NHPh of [Pt(L H2)Cl2](3)and NH(ClPh) [Pt(L H2)Cl2] (4) (scan rate:100) in CH2Cl2 NHPh NHPh Fig. 1 Molecular geometries of cis-[Pd(L H2)Cl2] (2 )and cis-[Pt(L H2)Cl2] (4) solvent at 298K. EPR spectra of the electro-generated [3] and [4] (a) (b) Fig.4 Spin density plot of (a) [3] and (b) [4] ions were recorded in CH2Cl2 solution at 298 K.

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