Advances in Environmental Biology

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1 AENSI Journals Advances in Environmental Biology ISSN EISSN Journal home page: Room Temperature Synthesis of Water-Soluble Starch-Stabilized CdSe Quantum Dots for Latent Fingerprints Detection 1 Tanutkun Palakawong Na Ayudhaya, 2 Panida Viwattana, 2 Kheamrutai Thamaphat, 1 Khemika Lomthaisong 1 Program of Forensic Science, Faculty of Science, Khon Kaen University, Khon Kaen 40000, Thailand. 2 Green Synthesis and Applications Laboratory, Department of Physics, Faculty of Science, King Mongkut s University of Technology Thonburi, Bangmod, Thungkru, Bangkok 10140, Thailand. A R T I C L E I N FO Article history: Received 25 June 2014 Received in revised form 8 July 2014 Accepted 14 September 2014 Available online 27 September 2014 Keywords: CdSe QDs Green synthesis Latent fingerprint Forensic science A B S T R A C T Detection of latent fingerprint on porous and non-porous surfaces using cadmium selenide nanoparticles (CdSeNPs) has been described in this work. CdSeNPs, which is quantum dot, has high photoluminescence quantum efficiency. The luminescent wavelength of CdSeNP is dependent on its particle size. Starch-stabilized CdSeNPs were synthesized at room temperature by chemical reaction between Na 2SeSO 3 and CdCl 2. In this work, the size and shape of CdSeNPs, band gap energy, and emission wavelength and intensity under 450 nm excitation was determined using transmission electron microscope, UV-vis spectrophotometer, and fluorescence spectrophotometer, respectively. The synthesized CdSeNPs were used to detect the sebaceous latent fingerprint on surface of aluminium foil, tile, brass sheet, stainless steel sheet, sticky side of yellow sealing tape and cloth tape. The results showed that the fingerprints were developed on substrates surface after immersion of substrates in CdSeNPs colloid for 3 min. These developed fingerprints can be observed by naked eye under daylight AENSI Publisher All rights reserved. To Cite This Article: Tanutkun Palakawong Na Ayudhaya, Panida Viwattana, Kheamrutai Thamaphat, Khemika Lomthaisong., Room Temperature Synthesis of Water-Soluble Starch-Stabilized CdSe Quantum Dots for Latent Fingerprints Detection. Adv. Environ. Biol., 8(14), 44-49, 2014 INTRODUCTION Despite the rapid growth in DNA profiling, fingerprints (FPs) that consist of line patterns formed on the finger tips, named as ridges, have been mostly used as an important physical evidence in criminal investigation purposes since FPs are unique to each person and immutable [1, 2]. When a finger touches a surface, it leaves marks on the surface. Generally, there are found to be three main types of FPs evidence presented at a crime scene: visible, indented or plastic, and latent FPs (LFPs) [3]. The visible FPs can be made by fingers contaminated with blood, grease, ink, paint, or dirt. The indented or plastic FPs are a three-dimensional fingertip impression and can be produced by pressing fingers on malleable substances such as soap, candle wax, fresh paint, and tar. The visible and plastic FPs are straightforwardly observed by naked eye without any development. Whereas the observation of LFPs is the most problematic because they are present but largely invisible. They extremely require optical, physical, physico-chemical, or chemical methods to enhance their visualization. The LFPs are the most common form of fingerprints evidence. They are produced by natural secretions from three types of body glands (eccrine, apocrine, and sebaceous) deposited and left the finger s ridge patterns on a substrate surface [1]. Among different types of glands, the sebaceous secretions that are organic compounds of glycerides (30-40%), fatty acid (15-25%), wax esters (20-25%), squalene (10-12%), sterol esters (2-3%), and sterols (1-3%), associated with hair roots and located throughout the body are often found in LFPs [3]. Over the last 20 years, a number of forensic science laboratories around the world [3-8] has developed a variety of techniques to differentiate the LFPs from the different types of substrate material. The general characteristics of the substrate surface are porous, non-porous smooth, and non-porous rough. Usually, powdering, vacuum metal deposition, aqueous electrolytes, iodine fuming, ninhydrin, and cyanoacrylate fuming are widespread used for detection of LFPs on various substrates [1, 4, 6, 9]. However, each technique can be Corresponding Author: Kheamrutai Thamaphat, Department of Physics, Faculty of Science, King Mongkut s University of Technology Thonburi, Bangmod, Bangkok 10140, Thailand. Tel: ; s903607@yahoo.com

2 45 Tanutkun Palakawong Na Ayudhaya et al, 2014 applied for LFPs development with limitation depending on the substrate characteristic, there are no methods adequate for all substrates. Therefore, the new and more efficient methods still need for detection of LFPs. In recent years, nanostructured materials possess several distinctive physical and chemical properties such as noble metal nanoparticles (NPs) and quantum dots (QDs) have been interested by researchers and industry because they can be employed in a broad spectrum of application fields including forensic FPs detection [10]. The first use of metal NPs for FPs detection was proposed in the late 1989 by Sauders [11]. His method called multimetal deposition (MMD) is a well-known FPs detection technique based on the use of gold NPs in solution followed by a silver physical developer. The MMD accomplishes for visualizing LFPs on a wide range of substrate surfaces including porous, non-porous, wet, colored, colorless surfaces [3]. Nevertheless, several drawbacks of the MMD obviously appear: dark-brown patterns on an unstrained substrate and as light patterns on dark substrate, requiring several rinsing and immersion baths, time consuming, and poor repeatability [1,3, 7]. The QDs or semiconductor NPs with a diameter of 1-10 nm have been interested intensively from worldwide researchers due to their several unique intrinsic optical and electronic properties. The properties include size-dependent band gap, broad absorption spectra with high extinction coefficient, along with a narrow emission with a full width at half maximum (FWHM) of nm, and tunable emission spectra [10, 12-14]. The intrinsic optical properties of QDs as previously described lead them promising the strong candidate for optical detection. In 2000, Manzel suggested CdS QDs to be the first kind of QDs to develop the LFPs [15]. After Manzel discovery up to now, many type of QDs have been explored for forensic science application. Among other QDs, CdSe classified as a II-VI semiconductor of the n-type is mainly focused because of their tunable emission in the visible range [16]. This work therefore focuses on synthesis of the CdSe QDs and their application for detection of LFPs deposited on porous and non-porous substrates. Many synthetic methods have been developed for producing CdSe QDs such as electrochemical method, solid-state reaction, solid-state metathesis, and self-propagating high temperature synthesis [17]. Some processes require high temperature, high pressure, difficult and complicated steps, extended reaction time, expensive equipment, using high toxic H 2 Se as selenium source and common toxic substances such as thiolphenol, thiourea, mercaptoacetic acid, trioctylphosphine oxide, ethyl hexanoate, and so on [14, 18, 19] as a stabilizer. In order to minimize complicated processes, hazard to synthesizer/user s health, and pollution to environment, the green synthesis of the water soluble starch-stabilized CdSe QDs at room temperature was carried out herein. The effect of ph solution (ph = 4, 6, 8, and 11) on size and band gap energy of CdSe QDs was investigated. Furthermore, the as-synthesized CdSe QDs were utilized for visualizing LFPs under daylight. MATERIALS AND METHODS Reagents and Equipments: Commercial analytical grade of selenium metal powder (Se), sodium sulfite (Na 2 SO 3 ), cadmium chloride (CdCl 2 2.5H 2 O) and soluble starch were obtained from Ajax Finechem. All the chemicals were used as received without any further purification. Deionized (DI) water was used for prepared aqueous solutions. Prior to use, all glassware were cleaned with aqua regia and thoroughly rinsed with DI water. Synthesis and Characterization of Starch-Stabilized CdSe QDs: The synthetic method proposed herein is simple and does not require any high-cost equipment. The method involves an addition of selenide ion solution to an aqueous solution of soluble starch and cadmium precursor. A stock solution of 0.5 M sodium selenosulfate (Na 2 SeSO 3 ), selenium source, was prepared by refluxing the aqueous solution containing 1 M Na 2 SO 3 and 0.5 M elemental Se under constant stirring at approximately 75 C for 5 h until the black color disappeared. Then, the stock solution of Na 2 SeSO 3 was filtered and collected for further step. In a typical room temperature reaction, 1 ml of 0.1 M CdCl 2 solution was added to an aqueous solution of soluble starch (100 ml, 0.05 wt %) with constant stirring at 37 C. After stirring for 30 min, 1 ml of as-prepared Na 2 SeSO 3 colorless solution was slowly added into a mixture. At this stage, the ph value of mixture was adjusted by adding acetic acid or ammonia to obtain acidic or basic solution, respectively. Then, the mixture was stirred at 37 C for 2 h to achieve a red transparent solution. The red transparent solution was taken to measure absorption spectrum and fluorescence emission spectrum by an Avantes AvaSpec fiber optic spectrometer and a F-2500 fluorescence spectrophotometer (Hitachi, Japan), respectively. To determine the crystal structure and particle size of as-synthesized CdSe QDs, the red transparent solution was extracted with acetone to obtain a red precipitate of CdSe QDs. The precipitate was washed several times with acetone and dried in air at room temperature. The XRD measurement of the CdSe powders was performed using a Bruker D8 Advance X-ray diffractometer with CuK α radiation (λ = Å) operated at 40 kv and 40 ma. A FEI

3 46 Tanutkun Palakawong Na Ayudhaya et al, 2014 Tecnai G2 20 TWIN TEM was used to carry out an average particle size of achieved starch-capped CdSe QDs colloid solution. Preparation of the substrates for LPFs detection application: A several of substrate materials were selected for the LFPs experiment. These includes (1) non-porous surfaces such as brass sheet, stainless steel sheet, aluminium foil and rough cream tile, and (2) porous surfaces such as yellow sealing tape and green cloth tape. The brass sheet, stainless steel sheet, aluminium foil and tile were washed in acetone, ethanol, DI water, and left to dry in the air at room temperature. Application of as-synthesized starch-stabilized CdSe QDs for development of LFPs: Prior to produce LFPs on substrates, the hands were washed thoroughly with soap, rinsed with water, and dried. The sebaceous LFPs were prepared by wiped the fingertip over forehead and nose and stamping onto the substrates surface slightly. Then, all samples were immersed into the as-synthesized starch-stabilized CdSe suspension until the LFPs appeared. The LFPs image was captured using digital camera, Canon EOS 400D, under daylight. RESULTS AND DISCUSSION Effect of ph on physical and optical properties of starch-stabilized CdSe QDs: The chemical reactions involved in the production of CdSe QDs are shown by the following equations: Na 2 SO 3 + Se Na 2 SeSO 3 (1) andcd 2+ + SeSO OH - CdSe + SO H 2 O. (2) The color of mixture solution changed from colorless to red indicated the fabrication of CdSe QDs. In aqueous solution, the hydroxyl groups of the starch acts as the coordination site of cadmium ions and passivating centres for dispersion, stabilization, and solubility of the as-synthesized CdSe QDs in water. Furthermore, the free aldehyde group on one end of the starch polymer could also act as conjugation site for other biomolecules [20]. The XRD pattern of as-synthesized CdSe was illustrated in Figure 1. It showed a good agreement with the JCPDF file No Three clear diffraction peaks appeared at 2θ = 25.6, 42.6, and 49.8 that are corresponding to the (111), (220), and (311) planes of bulk cubic CdSe, respectively. The broad peaks imply that the particle size is nanometer size. TEM was employed to characterize the morphology and size of assynthesized CdSe QDs. In Figure 2, TEM image showed that the CdSe QDs were spherical morphology and the diameters estimated from TEM image were approximately 7.5 ± 2.3, 5.5 ± 0.1, 5.1 ± 2.2, and 4.6 ± 1.1 nm for CdSe QDs synthesized under ph 4, 6, 8, and 11, respectively. Fig. 1: XRD pattern of as-synthesized CdSe QDs. The optical properties of CdSE QDs were characterized using UV-vis absorption spectroscopy and fluorescent spectroscopy. Figure 3 exhibits the UV-vis absorption spectra from our experiment. The blue shifted was observed when the ph value increased. In comparison with that of bulk CdSe, the blue shifted from the optical absorption onset of bulk CdSe (730 nm, 1.70 ev) [20] was observed as well. It indicated the decrease of particle size that was in good agreement with TEM results. This clearly indicates the quantum confinement effect. Figure 3 gave the information on the optical absorption onset and band gap energy as summarized in Table 1.

4 47 Tanutkun Palakawong Na Ayudhaya et al, 2014 Fig. 2: TEM image of starch-stabilized CdSe nanoparticles synthesized under different ph values. Fig. 3: Absorption spectrum of the starch- stabilized CdSe QDs in aqueous solution obtained at different ph values. Table 1: Summary data obtained from TEM and UV-vis absorption analysis. ph Particle size (nm) λ onset (nm) Band gap energy (ev) ± ± ± ± Fig. 4: The florescent spectrum of the starch- stabilized CdSe QDs in aqueous solution. The excitation wavelength is 450 nm: The typical fluorescent spectrum of as-synthesized CdSe QDs taken at ph 11 was shown in Figure 4. A strong emission peak was observed at around 569 nm with the excitation wavelength 450 nm. In comparison with that of bulk CdSe at 730 nm [20], there is a blue-shift in fluorescent spectrum of as-synthesized CdSe QDs. This effect might be also related to the quantum effects. The as-synthesized starch-stabilized CdSe QDs in weak basic condition can be stored more than 2 months without agglomeration, whereas the as-synthesized CdSe QDs without addition of starch precipitated within 3 days. LFPs Development using as-synthesized starch-stabilized CdSe QDs: The as-synthesized starch-stabilized CdSe QDs could work for detection of LFPs on all substrates. The taken images were shown in Figure 5. In Figure 5, it is clear that the LPFs pattern can be observed by naked eye

5 48 Tanutkun Palakawong Na Ayudhaya et al, 2014 under daylight. It worked pretty well on conductive surfaces. The necessary time of immersion in CdSe QDs suspension was different depending on kind of substrate. The least time for development of ridge pattern on substrate was 3 min. Fig. 5: Fingerprints developed on different substrates. Left: before development; right: after development. Conclusion: This work has shown the success in the preparation of monodispersed CdSe QDs using soluble starch as a capping agent at room temperature. The diameter of as-prepared spherical CdSe QDs was less than 10 nm. They emitted light in the green region. This proposed method is a simple, low-cost, environmentally benign solution growth method without additional another stabilizers. Thus, this method may be applicable to synthesize other selenide nanostructures and also large-scale productions. Additionally, the as-synthesized CdSe QDs in aqueous phase successfully developed LFPs on porous and non-porous substrates. However, the suitable condition for synthesis of CdSe QDs to achieve the shorter detection time should be studied in the next task. ACKNOWLEDGEMENTS This work was financial supported by a grant from Khon Kaen University. The authors would like to thank Department of Chemistry, Faculty of Science, King Mongkut s University of Technology Thonburi for providing the fluorescent spectrophotometer and also thank Department of Chemistry, Faculty of Science, Mahidol University for XRD measurement. REFERENCES [1] Qin, G., M, Zhang, Y. Zhang, Y. Zhu, S. Liu, W. Wu and X. Zhang, Visualizing Latent Fingerprints by Electrodeposition of Metal Nanoparticles. Journal of Electroanalytical Chemistry, 693: [2] Liu, M., Fingerprint Classification based on Adaboost Learning from Singularity Features. Pattern Recognition, 43: [3] Choi, M.J., A.M. McDonagh, P. Maynard and C. Roux, Metal-Containing Nanoparticles and Nano- Structured Particles in Fingermark Detection. Forensic Science International, 179: [4] Sodhi, G.S. and J. Kaur, A Novel Fluorescent Small Particle Reagent for Detecting Latent Fingerprints on Wet Non-Porous Items. Egyptian Journal of Forensic Science, 2: [5] Dilag, J., H. Kobus and A.V. Ellis, Cadmium Sulfide Quantum Dot/Chitosan Nanocomposites for Latent Fingermark Detection. Forensic Science International, 187: [6] Sodhi, G.S. and J. Kaur, Powder Method for Detecting Latent Fingerprints: a Review. Forensic Science International, 120: [7] Becue, A., A. Scoundrianos and S. Moret, Detection of Fingermarks by Colloidal Gold (MMD/SMD)-beyond the ph 3 Limit. Forensic Science International, 219: [8] Ferguson, S., L. Nicholson, K. Farrugia, D. Bremner and D. Gentles, A Preliminary Investigation into the Acquisition of Fingerprints on Food. Science and Justice, 53: [9] Ramos, A.S. and M.T. Vieira, An efficient Strategy to Detect Latent Fingermarks on Metallic Surfaces. Forensic Science International, 217: [10] Agasti, S.S., S. Rana, M.H. Park, C.K. Kim, C.C. You and V.M. Rotello, Nanoparticles for Detection and Diagnosis. Advanced Drug Delivery Reviews, 62:

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