Fabrication and Characterization of Chemical Vapor Deposition Buckypapers for Use in Air Sampling of Volatile Organic Compounds Jacob S. Shedd, Jonghwa Oh, Claudiu T. Lungu Department of Environmental Health Sciences, School of Public Health, University of Alabama at Birmingham Air sampling is important for assessing exposure to volatile organic compounds (VOCs), a group of chemicals with recognized adverse health effects VOC samples are traditionally collected through active sampling using a pump and sorbent media; however, diffusive sampling is rising as a popular alternative Diffusive samplers are compact and do not require a pump, but their low mass-uptake rate limits usability for short term and/or low concentration samples The limitations of diffusive samplers can be avoided by adopting a modified analytical technique, such as photothermal desorption (PTD), which quickly (>1 sec) desorbs analytes by exposing thermally conductive sorbent to pulses of light, and analyzes the sample using a photoionization detector (PID)1 In this study, the applicability of chemical vapor deposition (CVD) single-walled carbon nanotubes (SWNT) as a sorbent for the photothermal desorption (PTD) technique was investigated for use in air sampling. INTRODUCTION RESULTS Figure 1: Toluene adsorption isotherm generated by diffusive adsorption isotherm chamber; Inset image – Diagram of DAIC Figure 2: TGA curves for two BP samples (CV108 and CV110); Inset image – CVD BP Summary of results: BET surface area ranged between 316.8 - 360.5 m2/g (n = 3) Pore size ranged between 7.4 - 13.2 nm (n=3) Toluene adsorption capacity was found to be 64.7 mg/g (n = 1) at 800 ppm Thermogravimetric analysis showed that CVD BPs 10% mass loss between 497 - 505°C (n = 2) Table 1: Analytical Data Characterization Data BET Surface Area 346 ± 6 m2/g Pore Size 9.2 ± 0.6 nm Toluene Adsorption Capacity 64.7 mg/g Thermogravimetry 10% mass loss @ 501℃ Fabrication of Buckypaper (BP)2: 50 mg CVD SWNTs was suspended in 400 mL methanol via sonication (2 h) Suspension was vacuum filtered using a 47 mm diameter PTFE membrane filter (5 µm pore size) Resulting BP was allowed to vacuum dry for 30 minutes followed by turning the vacuum off and allowing for 2 h of rest BP is delaminated from PTFE filter and stored at 100°C in an oven oven BP samples are named CV###; numbers are assigned in order of fabrication (as seen in Figures 1 and 2) Characterization: CVD BPs were characterized to determine their efficacy as sorbents to be used in conjunction with the PTD technique. The following methods were used to quantify the adsorptive properties and thermal stability of the material. Brunauer-Emmitt-Teller (BET) surface area and pore size were determined to characterize the adsorption efficiency of BPs Performed by physisorption analysis with N2 adsorption at 77K Toluene adsorption capacity at 800 ppm was obtained from adsorption isotherms at 30­°C Toluene adsorption isotherms were generated using a diffusive adsorption isotherm chamber (DAIC) system by diffusing toluene onto BP and constantly measuring toluene flux via photoionization detector Toluene capacity is determined from the mass adsorbed at the saturation concentration on the adsorption isotherm (Figure 1) Thermogravimetric analysis was conducted to determine the material’s pattern of decomposition Degassed at 120°C for 20 min then heated to 800°C (ramping rate: 10°C/min) for 45 min in air environment (Figure 2) METHODS Average BET surface area was lower than activated charcoal (AC) and 3M OVM 3500/3520 pad (charcoal pad) by 72% and 61% respectively3 Average pore size is 5.4 times larger than that AC and charcoal pad3 Though AC and the 3M charcoal pad were seen to have better adsorbent properties, there is promise of improving CVD BPs by heat treating to remove amorphous carbons and suspension solvents from BP adsorption sites Future works will explore the use of BPs, made from different SWNTs, for adsorption of VOCs with varying polarities. CONCLUSION ACKNOWLEDGEMENTS This study was supported by The Deep South Center for Occupational Health and Safety (Grant #2T42OH008436-13 from NIOSH). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of NIOSH. Special thanks to Clint Anderson (Safeware inc.) for donation of PPE, and to Virginia A. Davis, Phd (Auburn University) for use of thermogravimetry instrumentation. References 4 4 Floyd, E. L., Sapag, K., Oh, J. & Lungu, C. T. Photothermal desorption of single-walled carbon nanotubes and coconut shell-activated carbons using a continuous light source for application in air sampling. Ann. Occup. Hyg. 58, 877–888 (2014). Oh, J., Floyd, E. L., Watson, T. C. & Lungu, C. T. Fabrication and adsorption characterization of single-walled carbon nanotubes (SWNT) buckypaper (BP) for use in air samples. Anal. Methods 8, 4197–4203 (2016). Oh, J. Fabrication and Characterization of Buckypapers for Use in Air Sampling. (Thesis, University of Alabama at Birmingham, 2016).