• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.963-968
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• 2002

In this work, porous silicon (PS) layer is investigated as a sensing material to detect organic vapors such as ethanol (called alcohol), methanol, and acetone in low concentrations. To do this, PS sensors were fabricated. They have a membrane structure and comb-type electrodes were used to detect the change of electrical resistance effectively. PS layer on Si substrates was formed by anodization in HF solution of 25%. From fabricated sensors, current-voltage (Ⅰ-Ⅴ) curves were measured for gases evaporated from 0.1 to 0.5% organic solution concentrations at 36$\^{C}$. As the result, all curves showed rectifying behavior due to a diode structure between Si and the PS layer. The conductance of most sensors increased largely at high voltage of 5V, but the built-in potential on the measured Ⅰ-Ⅴ curve was lowered inversely by the adsorption effect of the organic vapors with high dipole moment.

• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1555-1559
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• 2005

High-performance fluorescent probes which exhibit either on/off or dual color fluorescence switching in response to the presence of organic vapors with a rapid response, a high sensitivity and a high-contrast on/off signaling ratio were demonstrated on the basis of the vapor-controlled AIEE phenomenon.

• Preventive Nutrition and Food Science
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• v.6 no.4
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• pp.247-252
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• 2001

The need to determine the permeability of organic vapors to polymeric films such as aromas, flavors, etc. has significantly increased in the food industry because of preservation and safety issues along with migration problems. However, due to the complex nature of the permeation process, there have been few investigations compared to nonorganic compounds. In this paper, we review the history of permeability studies and typical methods of permeability measurement such as the isostatic method and quasi-isostatic method for organic vapors. New instrumental developments and significant findings are also introduced and discussed.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.55-66
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• 1996

This study was conducted to evaluate breakthrough characteristics of respirator cartridge using multi-organic vapors, including carbon tetrachloride, trichloroethylene, and toluene. The organic vapors were used as single phase, binary system, and ternary system. The results are summarized as follows. 1. Organic vapors studied were 1,000 ppm, 750 ppm, 500 ppm and 250 ppm in single phase. Carbon tetrachloride having the highest molecular weight showed the breakthrough first, and breakthrough sequency by organic vapor was dependent on its molecular weight. The 10% breakthrough times at 1,000 ppm of organic vapor were 97 minutes for carbon tetrachloride, 129 minutes for trichloroethylene and 135 minutes for toluene. 2. When concentrations of organic vapors were at levels of the Threshold Limit Values, the lives of the respirator cartridges were 122 hours in carbon tetrachloride, 18 hours in trichloroethylene and 28 hours in toluene. 3. In the binary system at a total concentration of 1,000 ppm with carbon tetrachloride and trichloroethylene, breakthrough times ranged from 104 minutes to 125 minutes, which were longer than 97 minutes in a single phase (1,000 ppm) for carbon tetrachloride, but shorter than breakthrough times for TCE and Toluene. 4. Breakthrough times in the binary system with carbon tetrachloride and toluene were 131~132 minutes. 5. Breakthrough times in the ternary system with carbon tetrachloride, toluene, and trichloroethyl ene were $120{\pm}8$ minutes, which were longer than 97 minutes in the single phase (1,000 ppm) for carbon tetrachloride, equal to 129 minutes for trichloroethylene, and shorter than 135 minutes for toluene. Those were almost similar to $124{\pm}9$ minutes of breakthrough times in the binary systems.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.97-108
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• 1996

A new type of passive samplers were designed and produced by authors. After evaluating the quality of activated carbon by measuring recovery rate of organic vapors and steadiness of sampling rate, activated carbon with 30 - 35 mesh produced by Company S in Korea was selected. In each passive sampler, an amount of 400 mg of the activated carbon was filled in 25-mm cassette and covered by fixed screen (or wire screen with 100 mesh). In addition to the fixed screen, a wind screen (or wire screen with 300 mesh) was also attached at outer face. The sampling rate of the new Korean passive samplers was estimated Conclusions obtained in the study are as follows. 1. Sampling rates of the newly developed Korean passive samplers were affected by sampling time. For n-hexane, sampling rates of 15- and 60-minute samples were 70.92 and 37.45 ml/min, respectively. Sampling rate of both 200- and 450-minute samples was 25.96 ml/min. It is concluded that, when passive samplers are used for measuring organic vapors, samples be collected longer than 60 minutes. 2. Sampling rate of the passive samplers was also affected by airborne concentration of organic vapors. Lower sampling rates were determined at level of 1/2 threshold limit values (TLVs) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). It is recommended that sampling rate of the passive samplers be obtained at site by measuring concentrations using both the NIOSH Method and passive samplers simultaneously. 3. When the passive samplers, which collected organic vapors, were exposed to clean air for five hours, there was no significant loss of organic vapors due to reverse diffusion. 4. When samples were stored at room temperature ($21.8{\pm}0.7^{\circ}C$) and refrigerator ($3.8{\pm}0.7^{\circ}C$), there was no significant difference in the accuracy of results. For trichloroethylene and n-hexane, accuracies were within 25 % at both temperatures until seven days. However, poor accuracy exceeding 25 % was indicated in toluene from the first day. It is recommended that samples be stored at freezing temperature below $0^{\circ}C$. 5. Sampling efficiency was significantly affected by direction of the passive samplers. Results of samplers facing wind and down, respectively, were compared. Lower amount of organic vapors were collected when the sampler was oriented down. It is recommended that, when air velocity is low in plants, the passive samplers be oriented to the wind. However, when air velocity is high, the passive samplers be oriented down.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.461-464
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• 1997

In this paper, the response characteristics for organic vapors has been studied using both itaconate copolymer and maleate copolymer, which have different hydrophilic group and same hydrophilic group. The conductivity of sensitive LB films was decreased in the range of 18 layers and maintained over 30 layers, which can describe the behaviors of urganic vapors such as penetration and surface absorption. It was thought that the organic vapors was penetrated into sensitive 13 films below 18 layer and the electrode was covered with sensitive LB film over 30 layers.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.1
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• pp.33-48
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• 1997

Korean diffusive sampler (KDS) and charcoal tube (CT) were used for sampling n-hexane, trichloroethylene and toluene in air KDS was made by Department of Environmental Health, SNU-SPH in 1995. Surveys were conducted at ten industrial plants with organic solvents. The relationship between two sampling methods was examined by linear regression analysis, and concentrations by two sampling methods were compared using paired t-test. The results are as follows: 1. The geometric means by CT and KDS methods were 3.26ppm and 3.32ppm for n-hexane, 5.07ppm and 6.34ppm for toluene, and 7.18ppm and 7.90ppm for toluene, respectively. There was no significant difference between results by CT and KDS methods in three organic vapors (p>0.05). When linear regression analysis was performed, two sampling methods were highly related ; correlation coefficients were 0.98, 0.90 and 0.96 for n-hexane, toluene and trichloroethylene, respectively. 2. Airborne concentrations of n-hexane (n=21) were below 0.5 TLV level. The GM by two methods were almost same (3.09 ppm). And there was no significant difference between results by two methods (p>0.05). 3. Since toluene and trichloroethylene concentrations showed several levels, appropriate sampling rates were applied for each level. The GM of toluene concentrations by two methods at 0.5 TLV level were 3.75ppm and 5.48ppm. The KDS method overestimated the toluene concentrations at 0.5 TLV level (p<0.05). The GM values of toluene concentrations at 1 TLV level were 31.80ppm and 25.38ppm and at 2 TLV level were 64.13 ppm and 51.37 ppm. The KDS method underestimated concentration at both level (p<0.05). For trichloroethylene, the GM at 0.5 TLV level were 4.97 ppm and 7.11ppm. The KDS method overestimated the concentration of trichloroethylene (p<0.05). In conclusion, concentrations of three organic vapors measured by CT and KDS were not significantly different and results by two methods were highly related. But at contain concentrations, the levels by method were significantly different. Therefore, it is suggested that sampling rate of KDS should be studied simultaneously using CT method for organic vapors.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.2
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• pp.200-211
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• 1995

This study was designed to evaluate the effects of temperature and humidity on the sampling efficiency of mixed organic vapors of l,2-DCE, benzene, and MIBK by 3 different types of diffusion monitors. Independent variables used for the study were temperatures ($25^{\circ}C$, $35^{\circ}C$), humidities (30%, 80%), and vapor concentrations (low, medium, and high). In addition, vapor concentrations measured by the traditional charcoal tube method were used as reference values and were compared with those of by diffusion monitors. The results were as follows: 1. The desorption efficiencies(DE) of 1,2-DCE and benzene from charcoal tubes and from diffusion monitors ranged from 98% to 105%. In contrast, the DEs of MIBK from charcoal tubes and diffusion monitors except DM1 ranged from 71% to 85%. The DE of MIBK from DM1 was 98%. 2. No statistically significant differences of 1,2-DCE concentrations and the sampling efficiencies regardless of temperatures and humidities studied between charcoal tube and 3 diffusion monitors were found. 3. At 80% humidity, increasing frequencies of 1,2-DCE breakthrough at higher temperature and higher vapor concentration measured by charcoal tubes were observed. 4. No statistically significant difference of benzene concentrations were found between charcoal tube and diffusion monitors except DM3. The sampling efficiencies of DM3 were statistically significantly lower at all experimental conditions except the $35^{\circ}C$ and 30% humidity condition. 5. No statistically significant difference of MIBK concentrations were found between charcoal tube and diffusion monitors except DM3. The sampling efficiencies of DM3 were statistically significantly higher at higher humidity conditions regardless of temperature. Although statistically not significant, sampling efficiency of MIBK showed positive correlation with humidity while negative correlation with concentration was observed. 6. For sampling 1,2-DCE and benzene, no significant variations of concentrations among three diffusion monitors regardless of temperature and humidity conditions were found. For MIBK sampling, however, wide variations with increasing humidity among diffusion monitors were obtained. In conclusion, this study suggests that diffusion monitors will be a reasonables substitute for the traditional charcoal tubes for sampling non-polar organic vapors at temperature and humidity conditions studied. For polar organic vapors, use of an alternative desorption solution other than CS2 is recommended because of its low desorption efficiency. In addition, since variable among diffusion monitors for polar organic vapors particularly at higher humidity conditions were observed, further study is recommended of the effects of humidity on the performance of diffusion monitors.

• Analytical Science and Technology
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• v.8 no.4
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• pp.745-751
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• 1995

In this paper, several simulated devices were constructed for determining components of organic vapors emitting from decorative materials, daily use chemicals and from common behavior of human beings, such as smoking and cooking. The VOCs were preconcentrated on activated carbon and then desorbed by carbon disulphide. The results were obtained by GC/MS analysis and computer searching. It can be concluded that the categories of the sources and the components of organic vapors in indoor air are very complicated, and different sources of VOCs in indoor air have their own emission characteristics.

• Journal of Integrative Natural Science
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• v.8 no.1
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• pp.67-74
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• 2015

Sensing characteristics for porous smart particle based on DBR smart particles were reported. Optically encoded porous silicon smart particles were successfully fabricated from the free-standing porous silicon thin films using ultrasono-method. DBR PSi was prepared by an electrochemical etch of heavily doped $p^{++}$-type silicon wafer. DBR PSi was prepared by using a periodic pseudo-square wave current. The surface-modified DBR PSi was prepared by either thermal oxidation or thermal hydrosilylation. Free-standing DBR PSi films were generated by lift-off from the silicon wafer substrate using an electropolishing current. Free-standing DBR PSi films were ultrasonicated to create DBR-structured porous smart particles. Three different surface-modified DBR smart particles have been prepared and used for sensing volatile organic vapors. For different types of surface-modified DBR smart particles, the shift of reflectivity mainly depends on the vapor pressure of analyte even though the surfaces of DBR smart particles are different. However huge difference in the shift of reflectivity depending on the different types of surface-modified DBR smart particles was obtained when the vapor pressures are quite similar which demonstrate a possible sensing application to specify the volatile organic vapors.