A POLYSACCHARIDE BIOPROTONIC FIELD EFFECT TRANSISTOR

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1 Supplementary Information A POLYSACCHARIDE BIOPROTONIC FIELD EFFECT TRANSISTOR Chao Zhong, 1 Yingxin Deng, 1 Anita Fadavi Roudsari, 3 Adnan Kapetanovic, 1 M.P. Anantram 2 & Marco Rolandi 1 1 Department of Materials Science and Engineering 2 Department of Electrical Engineering University of Washington, Seattle, WA (USA) 3 Department of Electrical Engineering University of Waterloo, Waterloo (Canada) 1

2 Supplementary Figures a 4.0 b 0.2 M-chitosan, PdH x, H 2 Current (µa) - Current (µa) 0.1 M-chitosan, Pd contact,n 2 M-chitosan, Au contact H 2 Chitin, Pd contact, H c Bias (V) d Bias (V) Current (µa) - Current (µa) Bias (V) Bias (V) Supplementary Figure S1 Current voltage characteristics of nanofiber polysaccharide thin films (1x1 cm 2, 300 µm thick) measured as a function of contact material, polysaccharide composition. (a,b) Maleic chitosan measured at 75% RH with Au contacts (orange), Pd contacts in N 2 atmosphere (blue), PdH x contact in 5% H 2 atmosphere (red). (c,d) Chitin (green) and maleic Chitosan (red) measured at 75% RH with PdH x contacts in 5% H 2 atmosphere. Note: b, d is magnified curve from a, c, respectively. 2

3 a I ds (na) V -5 V -2 V 0 V 2 V 5 V 10 V b n H + ( cm -3 ) V ds (V) V gs (V) Supplementary Figure S2 Protonic transistors transfer characteristics for device 2 (a) Plot of I ds as a function of V ds for different V gs (RH 75%). For device with PdH x contacts shown in figure S2. Device dimensions: length 5.0 µm, width 12 µm, height 120 nm. (b) Plot of channel proton density as function of gate voltage. Points are the values of n derived from the IV transfer data and assuming n= 8.9 x cm -3 at V gs =0, which in this device results a mobility of (3.4 ± 0.3) 10-3 cm 2 V -1 s -1. Line represents the values of n derived from Q/ V from simulations and estimated channel volume from AFM data. 3

4 Supplementary Figure S3 2D log plot of simulated current density different V gs for device 1 shown in figure 1. (Device dimensions: length 8.6 µm, width 3.5 µm, height 82 nm). (a) V gs = -15 V, (b) V gs = 0 V, (c) V gs = 15 V. The X and Y axis represents the direction along the length and height of the devices, respectively. 4

5 a I ds (na) V ds (V) -15 V -10 V -5 V -2 V 0 V 2 V 5 V 10 V 15 V Supplementary Figure S4 Hysteresis curves for device shown in Fig 3. 5

6 Supplementary Table S1. The average dimensions of the films on two different three-terminal devices determined based on AFM height images Devices Length (µm) Width (µm) Height (nm) Cross section Area ( m 2) ± ± ± ±

7 Supplementary Methods Maleic Chitosan Proton Concentration Estimate In order to calculate the proton concentration, we first derive the concentration of carboxyl functional groups. The hydration level for maleic chitosan at 75% is 20.2 ± 1.3 wt%. Here we use 20 wt%. The degree of substitution (DS) of maleic chitosan=0.85. The average molecular weight for each repeating unit for maleic chitosan = The carboxyl group concentration C (COOH ) can be calculated by the following equation: C (COOH ) = 0.85 C (repeat unit) = 0.85 n(repeat unit)/v Total = 0.85 n(repeat unit)/[v ( H 2 O ) + V ( maleic chitosan ) ] =0.85 (0.8/250.6)/ [0.2/ρ ( H 2 O ) + 0.8/ ρ ( maleic chitosan ) ] Because ρ ( H 2 O ) =1.0 g/cm 3, ρ (maleic chitosan ) = 1.4 g/cm 3 (based on the density of chitin= g/cm 3 ) 1 We obtain C ( COOH ) = 0.35*10 4 mol/m 3 The free protons can be considered to mainly come from dissociation of carboxyl groups on the polysaccharide molecules. The reported pka of carboxylmethyl chitosan ( CH 2 COOH) is The maleoyl group ( COCH=CHCOOH) in maleic chitosan is a relatively stronger electron withdrawing group (EWG) compared with carboxylmethyl group, and thus afford maleic chitosan a stronger acid with a relatively lower pka_enref_4. For this consideration, we used the pka of maleic chitosan

8 The initial concentration of carboxyl group is A 0 and after dissociation, the concentration becomes (A 0 - A) After dissociation: RCOOH RCOO - + H + A A 0 -A A A pka = - log 10 Ka = - log 10 ([RCOO - ] [H + ]/[RCOOH]) = - log 10 {[RCOO - ] [H + ]/([RCOOH] 0 - [RCOO - ]) } = - log 10 [A 2 /(A 0 - A)] A 0 = 0.35*10 4 mol/m 3, pka = 3.2, then we obtain A = 1.48 mol/m 3 = m -3 or 8.9 x cm -3. Note: C (H 2 O ) : Concentration of water molecules in the system C (COOH ) : Concentration of carboxyl molecules in the system N ( H 2 O ) : Total amount of water molecules in the system (in moles) N (COOH ) : Total amount of carboxyl molecules in the system (in moles) V Total : The total volume of the system V ( H 2 O ) : the volume of water molecules V ( maleic chitosan ) : the volume of maleic chitosan molecules Calculation of proton mobility and proton concentration Based on the dimensional data, device 1 has the following parameters (Supplementary Table S1): Length (L) = 8.6 µm, Width (W) = 3.5 µm, Height (H) = 82 ± 1 nm; and Area of cross-section (A) = 232 ± m 2. 8

9 We also define at V g = 0, Proton Concentrations (n 0 ) = cm -3, and based on slope of I/V curve at V g = 0, 1/R 0 = (1.90 ± 3) 10-9 Ω -1 from two equation, σ 0 = L/(R 0 *A), µ = σ 0 /(N 0 * e) We obtain µ= (4.9 ± 0.5) 10-3 cm 2 V -1 s -1 Device 2 has: Length (L) = 5 µm, Width (W) = 12 µm, Height (H) = 120 ± 3 nm; and Area of cross-section (A) = 1110 ± m 2. Using a similar approach described above, we obtain µ = (3.4 ± 0.3) 10-3 cm 2 V -1 s -1 for device 2. Supplementary References 35 Li, J., Revol, J. F., Naranjo, E. & Marchessault, R. H. Effect of Electrostatic Interaction on Phase Separation Behaviour of Chitin Crystallite Suspensions. International Journal of Biological Macromolecules 18, ,(1996). 36 Chen, L. Y., Tian, Z. G. & Du, Y. M. Synthesis and Ph Sensitivity of Carboxymethyl Chitosan-Based Polyampholyte Hydrogels for Protein Carrier Matrices. Biomaterials 25, ,(2004). 9