Browsing by Subject "Volatile organic compounds"

Now showing 1 - 8 of 8

Open Access
Binary coded identification of industrial chemical vapors with an optofluidic nose
(OSA - The Optical Society, 2016) Adamu, A. I.; Ozturk, F. E.; Bayındır, Mehmet
An artificial nose system for the recognition and classification of gas-phase analytes and its application in identifying common industrial gases is reported. The sensing mechanism of the device comprises the measurement of infrared absorption of volatile analytes inside the hollow cores of optofluidic Bragg fibers. An array of six fibers is used, where each fiber targets a different region of the mid-infrared in the range of 2-14 ìm with transmission bandwidths of about 1-3 μm. The quenching in the transmission of each fiber due to the presence of analyte molecules in the hollow core is measured separately and the cross response of the array allows the identification of virtually any volatile organic compound (VOC). The device was used for the identification of seven industrial VOC vapors with high selectivity using a standard blackbody source and an infrared detector. The array response is registered as a unique six digit binary code for each analyte by assigning a threshold value to the fiber transmissions. The developed prototype is a comprehensive and versatile artificial nose that is applicable to a wide range of analytes.
Open Access
Bio-insprired optoelectronic digital nose for breath analysis
(2011) Bayındır, Mehmet; Yıldırım, Adem; Yaman, Mecit; Vural, Mert
A novel electronic nose device is presented that can be used in disease diagnostics by exhaled breath analysis. Exhaled breath contains more than a thousand organic compounds that can be analysed to insect various diseases and metabolic activity. The novel device is an electronic nose, based on photonic bandgap fibers that can selectively guide infrared radition inside a hollow core plastic fiber. Instead of a laser line source, a broadband balackbody source is used that exploits the filtering/ guiding properties of the fibers to scan the whole mid-infrared region, making it high selectivity of volatile organic compounds possible. In addition waveguiding inside the fiber enhances the electromagnetic radiation intensity, resulting in improved infrared absorption cross-section. The fiber electronic nose can be integrated and deployed as a portable electronics device to point-of-care institutes.
Open Access
Electrospinning of polymer-free cyclodextrin/geraniol-inclusion complex nanofibers: enhanced shelf-life of geraniol with antibacterial and antioxidant properties
(Royal Society of Chemistry, 2016) Aytac Z.; Yildiz, Z. I.; Kayaci-Senirmak, F.; Keskin, S. N. O.; Tekinay, T.; Uyar, Tamer
Free-standing nanofibrous webs of cyclodextrin/geraniol-inclusion complex (CD/geraniol-IC-NF) showing antibacterial, antioxidant activity and slow release of geraniol were developed as flavour/fragrance releasing materials via electrospinning. The electrospinning of CD/geraniol-IC-NFs with uniform and bead-free morphology was achieved without using a polymer matrix. Three types of CDs modified with hydroxypropyl and methyl groups (HPβCD, MβCD, and HPγCD) were used to obtain CD/geraniol-IC-NFs. The polymer-free CD/geraniol-IC-NFs allow us to attain much higher geraniol loading (∼11%, w/w) when compared to electrospun polymeric nanofibers containing CD/geraniol-IC (∼5%, w/w). Geraniol has a volatile nature, yet, a significant amount of geraniol (∼60-90%) was preserved in CD/geraniol-IC-NFs due to the complexation, whereas evaporation of geraniol was unavoidable for polymeric nanofibers incorporating geraniol without cyclodextrin. Short-term (3 h) temperature dependent release (37 °C, 50 °C, and 75 °C) and long-term open air (50 days, at RT) release tests revealed that MβCD/geraniol-IC-NF released less geraniol compared to HPβCD/geraniol-IC-NF and HPγCD/geraniol-IC-NF, indicating that much stronger inclusion complexation was formed between MβCD and geraniol. The release of geraniol from CD/geraniol-IC-NFs prevented the colonization of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria to a great extent, as observed in the antibacterial activity results. It was observed that CD/geraniol-IC-NFs had higher antioxidant activity compared to pure geraniol due to the solubility increase. In brief, the results reported here may open a new door to enhance the performance of essential oils and flavour/fragrances, to preserve volatile compounds from evaporation and to better understand the potential of CD/IC-NFs as carrier systems for guest compounds in the food, cosmetic and household cleaning industries.
Open Access
Molecular entrapment of volatile organic compounds (VOCs) by electrospun cyclodextrin nanofibers
(Elsevier, 2016-02) Celebioglu A.; Sen, H. S.; Durgun, Engin; Uyar, Tamer
In this paper, we reported the molecular entrapment performance of hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD) electrospun nanofibers (NF) for two common volatile organic compounds (VOCs); aniline and benzene. The encapsulation efficiency of CD samples were investigated depending on the various factors such as; CD form (NF and powder), electrospinning solvent (DMF and water), CD (HPβCD and HPγCD) and VOCs (aniline and benzene) types. BET analysis indicated that, electrospun CD NF have higher surface area compared to their powder form. In addition DMA measurement provided information about the mechanical properties of CD NF. The encapsulation capability of CD NF and CD powder was investigated by 1H-NMR and HPLC techniques. The observed results suggested that, CD NF can entrap higher amount of VOCs from surroundings compared to their powder forms. Besides, molecular entrapment efficiency of CD NF also depends on CD, solvent and VOCs types. The inclusion complexation between CD and VOCs was determined by using TGA technique, from the higher decomposition temperature of VOCs. Finally, our results were fortified by the modeling studies which indicated the complexation efficiency variations between CD and VOC types. Here, the inclusion complexation ability of CD molecules was combined with very high surface area and versatile features of CD NF. So these findings revealed that, electrospun CD NF can serve as useful filtering material for air filtration purposes due to their molecular entrapment capability of VOCs.
Open Access
Photonic bandgap infrared spectrometer
(Optical Society of America, 2010) Kondakci, H.E.; Yaman, M.; Dana, A.; Bayındır, Mehmet
We propose and demonstrate an infrared (IR) absorption spectrometer, made with a spatially variable photonic bandgap (PBG) structure, a blackbody source, and a simple IR detector, to identify the IR molecular fingerprints of analyte molecules. The PBG-based structure consists of thermally evaporated, IR transparent, high-refractive-index chalcogenide quarter-wave stacks (QWS) with a cavity layer. Spatial variation of the very sharp transmission peak due to the QWS cavity mode allows the structure to be used as a variable IR filter. Our proposed IR-PBG spectrometer can be used for detection and identification of volatile organic compounds.
Open Access
Selective and efficient removal of volatile organic compounds by channel-type gamma-cyclodextrin assembly through inclusion complexation
(American Chemical Society, 2017) Celebioglu A.; Ipek, S.; Durgun, Engin; Uyar, Tamer
Cyclodextrins (CD), produced from enzymatic degradation of starch, are a form of biorenewable cyclic oligosaccharide which has an outstanding capability to form inclusion complexes with a variety of molecules including pollutants due to their toroid-shaped molecular structure. In this study, by a simple reprecipitation method, we obtained "channel-type" packing from γ-CD where CD molecules are stacked on top of each other to form long cylindrical channels. The γ-CD "channel-type" crystals have shown very effective removal of organic volatile compounds (VOCs; aniline and toluene) from the surroundings, whereas cage-type γ-CD could not entrap VOCs from the same environment. Encapsulation capability of channel-type γ-CD is at a ∼2:1 and ∼1:1 molar ratio for aniline/CD and toluene/CD, respectively. Thus, channel-type γ-CD crystals have shown higher removal efficiency for aniline compared to toluene. Channel-type γ-CD is also able to remove aniline selectively from surroundings. Additionally, computational modeling studies suggested that single γ-CD cavity can host two molecules of aniline or toluene for the complexation, yet, aniline is more insistent to make a complex with the γ-CD cavity when compared to toluene. We show that channel-type γ-CD can remove VOCs molecules (aniline and toluene) as efficiently as activated carbon. Hence, being a starch-based biorenewable cyclic oligosaccharide in the form of white powder, the use of "channel-type" γ-CD crystals could be a competitive alternative to activated carbon as an adsorbent for the VOC removal/filtering.
Open Access
VOC gas leak detection using pyro-electric infrared sensors
(IEEE, 2010) Erden, Fatih; Soyer, E. B.; Toreyin, B. U.; Çetin, A. Enis
In this paper, we propose a novel method for detecting and monitoring Volatile Organic Compounds (VOC) gas leaks by using a Pyro-electric (or Passive) Infrared (PIR) sensor whose spectral range intersects with the absorption bands of VOC gases. A continuous time analog signal is obtained from the PIR sensor. This signal is discretized and analyzed in real time. Feature parameters are extracted in wavelet domain and classified using a Markov Model (MM) based classifier. Experimental results are presented. ©2010 IEEE.
Open Access
Volatile organic compound plume detection using wavelet analysis of video
(IEEE, 2008-10) Töreyin, B. Uğur; Çetin, A. Enis
A video based method to detect volatile organic compounds (VOC) leaking out of process equipments used in petrochemical refineries is developed. Leaking VOC plume from a damaged component causes edges present in image frames loose their sharpness. This leads to a decrease in the high frequency content of the image. The background of the scene is estimated and decrease of high frequency energy of the scene is monitored using the spatial wavelet transforms of the current and the background images. Plume regions in image frames are analyzed in low-band sub-images, as well. Image frames are compared with their corresponding low-band images. A maximum likelihood estimator (MLE) for adaptive threshold estimation is also developed in this paper. © 2008 IEEE.