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Quantifying Surface Area of Nanosheet Graphene Oxide Colloid Using a Gas-Phase Electrostatic Approach Wei-Chang Chang, Shiuh-Cherng Cheng, Wei-Hung Chiang, JiaLiang Liao, Rong-Ming Ho, Ta-Chih Hsiao, and De-Hao Tsai Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.7b02969 • Publication Date (Web): 31 Oct 2017 Downloaded from http://pubs.acs.org on November 3, 2017
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Analytical Chemistry
Quantifying Surface Area of Nanosheet Graphene Oxide Colloid Using a Gas-Phase Electrostatic Approach Wei-Chang Chang,1 Shiuh-Cherng Cheng,1 Wei-Hung Chiang,2 Jia-Liang Liao,2 Rong-Ming Ho,1 Ta-Chih Hsiao,3 De-Hao Tsai1,* 1
Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.
2
Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, Republic of China.
3
Graduate Institute of Environmental Engineering, National Central University, Zhoung-Li, Taiwan, Republic of China. ABSTRACT We demonstrate a new, facile gas-phase electrostatic approach to successfully quantify equivalent surface area of graphene oxide (GO) colloid on a number basis. Mobility diameter (dp,m)-based distribution and the corresponding equivalent surface area (SA) of GO colloids (i.e., with different lateral aspect ratios) were able to be identified by electrospray-differential mobility analysis (ES-DMA) coupled to an condensation particle counter (CPC) and an aerosol surface area analyzer (ASAA). A correlation of SA ∝ dp,m2.0 was established using the ES-DMA-CPC/ASAA, which is consistent with the observation by the 2-dimensional image analysis of size-selected GOs. An ultrafast surface area measurement of GO colloid was achieved via a direct coupling of ES with a combination of ASAA and CPC (i.e., measurement time was 2 minutes per sample; without size classification). The measured equivalent surface area of GO was ≈(202±7) m2g-1, which is comparable to Brunauer-Emmett-Teller (BET) surface area, ≈ (240±59) m2g-1. The gas-phase electrostatic approach proposed in this study has the superior advantages of fast, no elaborate drying process and requiring only very small amount of sample (i.e., below 0.01 mg). To the best of our knowledge, this is the first study of using an aerosol-based electrostatic coupling technique to obtain the equivalent surface area of graphene oxide on a number basis with a high precision of measurement.
Graphene oxide (GO), especially in the form of colloidal dispersion with a lateral size of < 100 nm, has attracted a substantial interest based on their superior physical and chemical properties.1-5 The convenience in formation leads to important advances to a variety of nanomaterial-manufactured products for a range of innovative applications including energy generation and storage, chemical and biosensors, catalysis, nanocomposites, and nanoelectronics.1,4,6-13 In addition, GO can be prepared via a direct exfoliation from a variety of carbon materials (i.e., graphite, carbon nanotube) and then distributed rapidly onto any surface and/or interior of composite material, showing the promise for a large-scale production for emerging industrial applications. Apart from the thickness and the extent of reduction, surface area of GO is one of the most important properties of GO-based products. Brunauer-EmmettTeller (BET) surface area analysis has shown to be a dominant and widely used method in the field of surface area characterization.3,14-16 However, the requirement of large amount of sample and an elaborate drying process in BET analysis is still an issue. In addition, BET analysis does not provide the information of surface area of GO on a number basis. Hence there is an urgent need is to develop a
suitable approach to directly characterize surface area of GO colloids on a quantitative basis. In this study, we propose an aerosol-based electrostatic approach for quantifying surface area of GO. Firstly, an electrospray-differential mobility analysis (ES-DMACPC) in combination with an aerosol surface area analyzer (ASAA), is employed to quantitatively characterize the mobility size distribution and the corresponding equivalent surface area of GO colloids. In comparison to the BET method, the developed ES-DMA-CPC/ASSA method possesses superior advantages in: (1) the high speed of a single measurement, (2) the direct probing of multi-modal, number-based distributions; (3) the low detection limit based on the amount of sample required,
