Delivered by Ingenta to: Nanyang Technological University IP: 37.9.46.40 On: Fri, 10 Jun 2016 17:58:17 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2012 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 12, 4199–4202, 2012 Detection of Nitroaromatic Compounds Based on Phenylethylene-Derivatized Porous Silicon Sungyong Um 1 , Minwoo Hwang 1 , Hyun Cho 1 , Hee-Gweon Woo 2 , and Honglae Sohn 1 ∗ 1 Department of Chemistry, Chosun University, 375 Seosuk-Dong, Dong-Gu, Gwangju 501-759, Korea 2 Department of Chemistry, Chonnam National University, 300 Yongbong-Dong, Buk-Gu, Gwangju 500-757, Korea Nanocrystalline porous silicon (PSi) surfaces have been used to detect nitroaromatic compounds in vapor phase. The mode of photoluminescence (PL) is emphasized as a sensing attitude or detec- tion technique. Quenching of PL from nanocrystalline porous surfaces as a transduction mode is measured upon the exposure of nitroaromatic compounds. To verify the detection of explosives, the surface of PSi is functionalized with different groups. The quenching mechanism of PL is attributed to the electron transfer behaviors of quantum-sized nano-crystallites in the PSi matrix to the analytes (nitroaromatics). An attempt has been done to prove that the surface-derivatized photoluminescent PSi surfaces can act as versatile substrates for sensing behaviors due to having a large surface area and highly sensitive transduction mode. Keywords: Porous Silicon, Photoluminescence, Quenching Efficiency, Chemical Sensor. 1. INTRODUCTION The identification and quantification of traces of nitroaro- matic explosives, 1 which offer new approaches to the rapid detection of ultra-trace anaytes from explosives, have attracted attention because explosives are important chem- ical species to detect in mine fields, 2 military applica- tions, munitions remediation sites, homeland security, 3 and forensic application. 4 Consequently a great number of ana- lytical methods have been developed for monitoring these compounds, for example, mass spectrometry, 5 ion mobil- ity spectrometry, 6 fluorescence, 7 chemiluminescence, 8 sur- face enhanced Raman spectroscopy, 9 nuclear quadrupole resonance, 10 energy-dispersive X-ray diffraction, 11 neutron activation analysis, electron capture detection, 2 and cyclic voltammetry. 12 These techniques are highly selective, but some are expensive and others are not easily fielded in a small, low-power package. Organic polymers 1 13 14 and optical fibers 15 have been previously studied to detect vapors of explosive ana- lytes. Other materials such as Zn complex, 16 pyrene, 17 nanofibril film, 18 gold nanoparticles, 19 and porous sili- con microcavity. 20 The transduction methods used include absorption, fluorescence, conductivity, and so forth. Such simple techniques are promising, because they can be incorporated into inexpensive and portable microelectronic devices. ∗ Author to whom correspondence should be addressed. Compared to other analytical techniques, fluorescence is more attractive because of its high sensitivity and high selectivity. Photoluminescent porous silicon (PSi) has a high surface area network of silicon nanocrystallites and exhibit quantum confinement effects. PSi based on PL quenching of nanocrystalline silicon might be an alterna- tive candidate for the detection of nitroaromatics. However PSi is limited by its chemical stability for many applica- tions due to the oxidation. For sensor applications, attachment of chemical species is highly desired to prevent the surface oxidation of PSi. The attachment of organic group to silicon surfaces by for- mation of Si–C bonds has been shown to provide greater stability toward oxidation and to significantly impede the rate of surface oxidation of the silicon. The work described herein represents an attempt to develop an inexpensive PSi sensor that can provide a stability toward oxidation and sensitive response to nitroaromatic compounds. 2. EXPERIMENTAL DETAILS 2.1. Materials and Methods Silicon wafer (silicon sense, n-type, 100 orientation, P -doped, 1–10 ohm) were purchased from Siltron Inc. Aquous HF (49%) and absolute ethanol (95%) were brought from Scientific Fisher. phenyl acetylene were ordered from Aldrich, sparged with dry argon and used. Out of the nitroaromatics here used for sensing, DNT J. Nanosci. Nanotechnol. 2012, Vol. 12, No. 5 1533-4880/2012/12/4199/004 doi:10.1166/jnn.2012.5922 4199