Quinaldine and Indole based pH Sensitive Colorimetric Chemosensor and their application of nanofiber J.S. Bae, S.H. Kim, Y.A. Son * and D.H. Lee ** Kyungpook National University, Daegu, S.Korea, jbae@knu.ac.kr * Chungnam National University, Daejeon, S.Korea, yason@cnu.ac.kr ** Korea Dyeing Technology Center, Daegu, S.Korea, lee@dyetec.or.kr ABSTRACT Colorimetric chemosensors are now considered as one of the most effective analytical method used in the environment monitoring. Colorimetric chemosensors for pH sensing can easily detect the primary danger or change of the surrounding environment pollution and source of infection and can prevent danger in the various fields. Quinaldine and Indole based colorants having the function of colorimetric chemosensors were synthesized. Synthesized colorants were characterized by 1H NMR, GC- Mass, EA and UV-Vis spectroscopy. Especially UV-Vis spectroscopy revealed that the color of each colorant solution was changed in basic conditions while no changes were observed in acidic condition. And then synthesized colorants were mixed with poly-acrylonitrile for electrospinning. Electrospun fibers containing each colorant were used as pH textile sensors and they were analyzed by Spectrophotometer. Keywords: quinaldine, indole, nanofiber, chemosensor, pH sensor 1 INTRODUCTION Colorimetric chemosensors are now considered as one of the most effective analytical method used in the environment monitoring [1-3]. Among lots of dangers threatening our environment, pH is a very important factor not only in the research area such as environmental, medical, and industrial area but also in our daily life. Many studies using some appliances have been conducted to detect pH but those methods have disadvantages such as complex procedure or high price. In this regard, colorimetric chemosensors for pH detection which make up for this disadvantage have received attention. Colorimetric chemosensors for pH sensing can easily detect the primary dangers or changes of the surrounding environmental pollution and source of infection. They also can prevent danger in the various fields [4-6]. In this study, Quinaldine and Indole based colorants were synthesized to detect pH changes easily with naked eyes and evaluated as pH sensors. Synthesized colorants were characterized by 1H NMR, GC-Mass, Elementary Analysis (EA) and UV-Vis spectroscopy. UV-Vis spectroscopy was measured to evaluate the synthesized colorants as pH sensing chemosensors. This change was considered that the color changes are due to the change of arrangement of electron in the colorants with regard to acidic or basic conditions. And then nanofiber containing each colorant were prepared as pH textile sensors. Electrospun fibers were obtained by electrospinning method with poly-acrylonitrile and analyzed by a variety of methods such as Scanning Electron Microscope (SEM), and Spectrophotometer. So, it was anticipated that they can be applied in many fields because they have advantages environmentally and economically. 2 EXPERIMENTAL 2.1 Materials Iodomethane, 2-methylquinoline, Indole-3- carboxaldehyde, 2-methyl benzothiazol and Piperidine were purchased from Sigma-Aldrich chemical. Acetonitrile was purchased from Burdick & Jackson chemical. Chloroform, 1-propanol and Hexane were supplied by Duksan. Poly- acrylonitrile with a molecular weight of 150,000 g/mol was supplied by Sigma-Aldrich. All the chemicals were used without further purification. 2.2 Synthesis of Quinaldine based dye 4.5g of Iodomethane and 5g of 2-methylquinoline was refluxed with acetonitrile solvent in round flask for 7hr. After reflux, quinaldinium salt was obtained by removing solvent in evaporator followed by washing using chloroform and drying. 0.5g of quinaldium salt was put in flask with 0.225g of indole-3-carboxaldehyde and 20ml of 1-propanol. By adding 2-5 drop of piperidine, color change was observed immediately. The solution was refluxed for 7 hours in ambient temperature and cooled for 1 day. The colorant was obtained after filter and washed with hexane followed by drying. Yield: 81%; mass (m/z): 284.1(M + ). 1 H NMR (400MHz, chloroform-d 6 ): δ 4.47(s, 3H, -NCH 3 ), 7.29(m, 2H), 7.54(m, 2H), 7.82(t, 1H, J=7.84), 8.06(t, 1H, J=8.84), 8.20(m, 1H), 8.23(d, 1H, J=8.12), 8.39(s, 1H), 8.43(d, 1H, J=8.84), 8.59(d, 1H, J=9.08), 8.63(d, 1H, NSTI-Nanotech 2013, www.nsti.org, ISBN 978-1-4822-0586-2 Vol. 3, 2013 758