Chitosan-grafted thymol (CST) coated on gold nanoparticles has been synthesized and characterized for the design of antimicrobial materials. CST was synthesized via adapting the Mannich reaction, and it acted as the capping agent for the synthesis of gold nanoparticles (AuNPs). The grafting of thymol onto the side chain of chitosan has provided a degree of substitution value (%DS NMR ) of 10.0%, calculated by nuclear magnetic resonance spectroscopy. UV–visible spectrometry and elemental analysis were used to confirm the successful synthesis of CST through adapting the Mannich reaction. The appropriate concentration of CST for AuNP synthesis was found to be 0.020%w/v. A red-wine colloidal AuNP solution of 2.41–3.30 nM particle size exhibits a strong surface plasmon resonance at 502 nm, which shows negative charges at pH = 9 of −36.37 mV. This result evidenced that the AuNPs showed electrostatic repulsion and CST played a role as a capping agent to provide a good dispersion and stability state. CST coated on the AuNP surface was successfully utilized for the control of cariogenic bacteria in the oral cavity. The results obtained from this study show that the tuning of the capping agent used in the synthesis step strongly influences the latter antimicrobial activity of the nanoparticles against Streptococcus mutans ATCC 25175 and Streptococcus sobrinus ATCC 33402 activity, with an inhibition zone of 15.90 and 14.25 mm, respectively. The average minimum inhibitory concentration values against S. mutans ATCC 25175 and S. sobrinus ATCC 33402 were found to be 25 and 100 mg/L, respectively, whereas the minimum bactericidal concentration values were 100 and 200 mg/L, respectively.

Triphenylamine-base organic dyes were designed and investigated for dye-sensitized solar cells (DSSCs). The dye molecules consist of three parts, an electron-donor connected by the π-conjugated linker (benzene and thiophene) as an electron spacer and an acceptor/anchoring (cyanoacrylic acid). In this study, quantum chemical calculations were used to study the electronic properties, optical properties and density of electron in the linker of dye molecule by using the density functional theory. The results present that thiophene is the most appropriate to use as electron linker between triphenylamine donor and acrylic acceptor due to the wide of absorption band and π-conjugate bond effect on exhibiting red-shifted absorption spectra.

A chemosensor based on a cyanoacrylic (DTP-C) consists of dithieno[3,2-b;2’,3’-d]pyrrole(DTP) as a chromophore and a cyanoacrylic moiety as an ionophore which linked by aromatic system. DTP-C demonstrates the response of complex with Fe(II) in dimethylformamide (DMF) solution. The binding mode of Fe(II)/DTP-C complex was characterized using UV-Visible and fluorescence spectroscopy. In addition, the effect of various MES buffer was then studied at 5%, 10%, 15% and 20% v/v in Fe(II)/DTP-C complex which the appropriate ratiomatric of MES buffer is 10%. The enhancement of Fe(II) concentration indicate a decrease emission intensity while the addition of buffer concentrations found to increase in the intensity. Moreover, quantum chemical calculations were used to study the electronic and optical properties of the molecular structure of DTP-C under the density functional theory.

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