Supporting Information

Transcription

1 Supporting Information Tip-enhanced Photoinduced Electron Transfer and Ionization on Vertical Silicon Nanowires Xiaoming Chen, a Tao Wang, a Leimiao Lin, a Fangjie Wo, a Yaqin Liu, a Xiao Liang, b Hui Ye, c Jianmin Wu a * a Institute of Analytical Chemistry, Department of Chemistry, Zhejiang University, Hangzhou 3158, P. R. China, wjm-st1@zju.edu.cn b Department of General Surgery, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou 3116, P. R. China c College of Optical Science and Engineering, Zhejiang University, Hangzhou 3127, P. R. China S-1

2 Supplementary Experimental Procedures Table of Contents FDTD simulation of light absorption and electromagnetic field in the vertical SiNWs array UV-assisted field emission of SiNWs characterization Imprinting and transfer of metabolites from mouse tissues onto SiNWs substrate Sample treatment and extraction of agrochemicals from fruits and pool water Matrix-free LDI-MS detection of pure analytes Supplementary Figures and Tables Supplemental Figure S1 SEM of thermal-treated SiNWs-1 and SiNWs-2 Supplemental Figure S2 Reflective spectra of two types of SiNWs and Si wafer under the irradiation of UV-LED and absorption distribution simulation along SiNWs by FDTD software Supplemental Figure S3 Scheme and actual object of the field emission characterization Supplemental Figure S4 SEM image and LDI mass spectra of SiNWs-1 after 8 o C oxidation and HF treatment Supplemental Figure S5 UV-vis absorption spectra of indigo and isatin Supplemental Figure S6 LDI mass spectra of isatin detected on six material surfaces Supplemental Figure S7 SEM and EDS comparison of SiNWs-1 before and after contact sampling of fingerprint Supplemental Figure S8 Negative ion-mode LDI-MS spectra of standard free fatty acids (FFAs) mixture and DPPE (16:/16:) detected on the SiNWs-1-APTES chip Supplemental Figure S9 Negative ion-mode LDI-MS spectra of sweat originated in fingers after making a fist detected on the SiNWs-2-APTES, thermal treated SiNWs-1-APTES and Si wafer Supplemental Figure S1 LDI-MS spectrum and standard calibration curve of pure TNT solution in negative ion mode and its possible dissociation process Supplemental Figure S11 LDI mass spectra of metabolites in kidney tissue sections mounted on the SiNWs-1-APTES chips with different section thickness Supplemental Figure S12 LDI mass spectrum and MSI results of metabolites in kidney tissue section imprint Supplemental Figure S13 Typical LDI mass spectrum of the thiabendazole molecule detected on SiNWs-1 S-2

3 Supplemental Figure S14 LDI mass spectra of background signals on the orange pericarp extracted with the SiNWs-1 chips Supplemental Figure S15 Dynamic curves of thiabendazole extraction process from pool water sample by SiNWs-1 chips and their LDI mass spectra Supplemental Table S1 Signal/noise values of thiabendazole transferred from orange pericarp to SiNWs-1 chip S-3

4 Supplementary Experimental Procedures FDTD simulation of light absorption and electromagnetic field in the vertical SiNWs array The electromagnetic field and light absorption distribution were simulated by the Finite Difference Time Domain (FDTD) solution software (Lumerical Solutions Co.). To simplify the simulation, periodic boundary conditions were used to model the periodic nature of the arrays while perfectly matched layer (PML) boundary conditions were used for the upper and lower boundary of the simulation cell. The SiNWs were considered as a periodic cylinder array with a length of 15 nm, a diameter of 75 nm and a center-to-center distance of 15 nm. A uniform mesh of 2 nm 2 nm 2 nm was utilized in the simulation. A plane wave with a wavelength of 355 nm was applied as the incident light, activating the energy absorption and electro-magnetic field distribution along the SiNWs. After solving the Maxwell s equations by FDTD, two-dimensional distribution of the electro-magnetic field ( E 2 ) was calculated and visualized as colormaps. For the light absorption power calculation, an internal equation, L =.5 eps W E 2 Imag (eps) was used to measure the absorption value in each mesh position. The parameters are electric field intensity E 2, the meshgrid4d W which was created as a 4D matrix composed of x, y, z and field f. UV-Assisted field emission of SiNWs characterization A home-built setup for field emission measurement was assembled (Figure S3). The SiNWs (SiNWs-1) chip was set as the negative electrode while an indium tin oxide (ITO) coated glass slide was used as the positive electrode. A black tape with a thickness of 1 μm was adhered on the upper edge position of the SiNWs. After assembling the ITO glass and the SiNWs chip face to face in the PTFE chamber, there would be a 1 μm space between positive and negative electrodes. During the field emission measurement, a UV lamp (Uvata Co.) with a maximal emission wavelength of 367 nm was immobilized on top of the ITO glass and can be irradiated on the surface of the SiNWs. A vacuum pump was connected with the chamber to maintain a vacuum circumstance. A bias voltage scanning from to 5 V with a step of 2 V was applied between these two electrodes, while the bias current flowing through the ITO-SiNWs array was acquired with a Keithley 6487 picoammeter (Keithley Instruments Co.) operated with Labview 8.6 software (National Instruments Co.). To demonstrate the tip-enhancement effect of the nanowires as well as the conductivity influence, the un-etched Si wafer and SiNWs after thermal treatment at 8 o C were also applied for the field emission. Three replicates were applied for each condition or each chip of the materials. Imprinting and transfer of metabolites from mouse tissues onto SiNWs substrate A two-month old nude mouse was sacrificed for the kidney tissue removal. The collected tissue sample was immediately frozen in liquid nitrogen and stored at -8 o C. For metabolites collection, the SiNWs chip was directly touched at the surface of tissue solid on ice for 1 s. Then the chip was washed with pure water thoroughly and waited to be dry. To gain the spatial distribution imaging of detected metabolites on the kidney tissue, an alternative imprint-transfer method was also applied. Firstly, the sample was cut into 25 µm sections using a Leica CM353 cryostat (Leica Microsystems, Germany). The tissue slices were transferred on the SiNWs chip, which was placed in the cryostat at -2 o C in advance. The SiNWs substrate was heated from its other side by the operator s finger. The quick heating and thaw mounting process resulted in an imprint of the section onto the underlying SiNWs. The tissue was then carefully torn off by a stream of water, while the imprints of nonpolar lipids were left on the surface of the SiNWs. Following the imprinting process, the SiNWs chips were stored in the desiccator before matrix-free MS detection. Experiments related to animal studies were performed in accordance with the guidelines of the S-4

5 Laboratory Animal Center of Zhejiang University (License Number: SYXK ). And all animal experimental protocols were approved by the the Laboratory Animal Centre of Zhejiang University. Sample treatment and extraction of agrochemicals from fruits and pool water The orange samples were purchased from a local supermarket and washed thoroughly with DI water before agrochemical spraying. To obtain a fruit sample polluted with the agrochemicals, a series of gradient thiabendazole solutions diluted from 1 mg/ml (~ 5 mm) stock solution dissolved in 5% EtOH were sprayed onto the surface of an orange. To semi-quantify the thiabendazole amount on the orange pericarp, pieces of pericarps with surface area = 1 cm 2 and average mass = 5 g were teared off for thiabendazole spraying. The volume of spraying solutions was about 4 μl once. After drying naturally, in order to extract the residual thiabendazole, a chip of vertical SiNWs was touched at the surface of the orange for 3 s. Furthermore, the polluted orange was washed with water only or with water and detergent for 1 s in succession. Another two SiNWs chips were also applied for the agrochemical extraction after the washing treatment, respectively. The natural water sample was collected from a pool in the campus and used without any treatment. Thiabendazole was added into the pool water samples, obtaining solutions with final agrochemical concentrations of 1 ng/ml, 2 μg/ml and.1 mg/ml, respectively. SiNWs-1 chips (2 mm 2 mm) were immersed into the thiabendazole spiked solutions and shaken on the vibrator (VXR B S25, IKA Co., Germany) at 1 rpm/min for 1 s to 18 s. The chips after extraction were dried naturally and preserved in desiccator until LDI-MS detection. Matrix-free LDI-MS detection of pure analytes For LDI-MS detection of standard analytes, FFAs mixture (C12:, C16:, C18:, C2:, C24:) and DPPE were dissolved in CHCl 3 to a final concentration = 1 mg/ml. Indigo, isatin and TNT were dissolved in a mixture of MeOH and H 2 O (v/v = 1:1) while thiabendazole was dissolved in a mixture of EtOH and H 2 O (v/v = 1:1). 2 μl of each standard solution droplet was deposited onto the SiNWs or Si wafer and waited to be dry in air. To maintain the hydrophilicity of Si wafer like SiNWs, Si wafers applied in the LDI-MS were treated with O 2 plasma for 6 s before analyte deposition, which would not influence its conductivity. To avoid the excessive diffusion of droplet, a circular hydrophobic hydrosphere with D = 3 mm was generated on the substrates with a crayon. When the FFAs mixture and DPPE were detected by the MALDI, 2 μl liquid was deposited onto the MALDI steel plate. 2 μl CHCA saturated solutions or 2 μl 1 mg/ml DHB solutions dissolved in a mixture of H 2 O:ACN:TFA = 5:5:.1 were thereafter dropped onto the spot and waited to be dry naturally. S-5

6 Y (nm) Y (nm) Y (nm) Reflectivity (%) Y (nm) Y (nm) Y (nm) Supplementary Figures and Tables (b) 1. μm 3. μm Figure S1. 45 o -tilted SEM images of 8 o C thermal-treated SiNWs-1 and (b) SiNWs Accident light 8 o Sample location Receiving optical fiber Si wafer SiNWs-1 SiNWs Wavelength (nm) (b) (c) (d) Z=75 nm Z=74 nm Z=7 nm X (nm) X (nm) X (nm) (e) (f) (g) Z=5 nm Z= nm Z= -75 nm X (nm) X (nm) X (nm) Figure S2. Reflective spectra of two types of SiNWs and Si wafer under the irradiation of UV-LED (λmax = 367 nm) when non-etched Si wafer was considered as the total reflection material without any absorption. Inset in is the schematic diagram for the reflectivity measurement. (b-g) Absorption distribution simulation along SiNWs by FDTD software. The simulation conditions: Diameter = 75 nm, Length = 1.5 μm. UV (b) A SiNWs Figure S3. Scheme and (b) actual object of the field emission characterization. S-6

7 Absorption 1. μm (b) Indigo on SiNWs-1-8 o C-HF M M-2 M-1 M Figure S4. 45 o -tilted SEM image and (b) Negative ion-mode LDI mass spectrum of SiNWs-1 after 8 o C oxidation and HF treatment for removal of oxide layer nm Wavelength (nm) Indigo Isatin Figure S5. UV-vis absorption spectra of.25 mg/ml indigo and.25 mg/ml isatin dissolved in 5% MeOH. S-7

8 Total Ion 82% laser energy 76% laser energy Isatin Exact MS: (1%) (8.7%) M-1: Isatin M: M+1: (b) 12 (e) Isatin on SiNWs-1 negative mode M M M+1 Isatin on SiNWs-1-8 o C negative mode M-1 (c) (f) Isatin on SiNWs-2 negative mode M Isatin on SiNWs-2-8 o C negative mode M-1 (d) (g) Isatin on Si negative mode Isatin on Si-8 o C negative mode M-1 M M M (h) 8 6 SiNWs-1 SiNWs-2 Si SiNWs-1-8 o C SiNWs-2-8 o C Si-8 o C Relative laser energy (%) Figure S6. Molecular information of the isatin molecule and its molecular ions detected in the negative ion-mode LDI-MS. (b-g) LDI mass spectra of indigo detected on six material surface. (b) SiNWs-1, (c) SiNWs-2, (d) Si wafer, (e) SiNWs-1 after thermal oxidation for 2 min, (f) SiNWs-2 after thermal oxidation for 2 min, (g) Si wafer after thermal oxidation for 2 min. The relative laser energy was set at 76% in (b, c, d) while 82% in (e, f, g). (h) Total ion intensity curves of M-1, M and M+1 on different substrates with promotion of relative laser energy (from 68% to 88% of maximum laser energy) in negative ion mode. For each condition, three replicates were done. Inset image in (h) is the magnified curve. S-8

9 Relative intenisity (a.u.) (c) 1μm 1μm (b) Element. Intensity (c/s) Atomic % Atomic Ratio Conc Units Error 2-sig C.... wt.%. N wt.%.315 O wt.%.24 Si 6, wt.%.442 P wt.%.13 (d) Element. Intensity (c/s) Atomic % Atomic Ratio Conc Units Error 2-sig C wt.%.923 N.... wt.%. O wt.%.191 Si 5, wt.%.311 P wt.%.68 (e) (f) (g) 8 C distribution before fingerprint touching C distribution after fingerprint touching μm 1μm 1.5 m Figure S7. SEM and EDS comparison of as-prepared SiNWs-1 (a, b, e, black curve in g) before and (c, d, f, red curve in g) after contact-sampling of fingerprint. The conditions of fabricating SiNWs-1 and metabolites transfer are referred to the Experimental Section. The concentrations of the elements C, N, O, Si, P on the top surface of SiNWs-1 were calculated by 2D scanning within the red boxes of and (c) and shown in tables (b) and (d). Compared with SiNWs-1 before metabolites transfer, the C ratio obviously increased after fingertip contact sampling. Since more FFAs and lipids were left over on the SiNWs-1 after sebum-rich fingertip contact, the linear elemental distribution along nanowires (g) shows a distinctive C accumulation near the tip and relative low concentration at the bottom location. To actually demonstrate the C element change after contact-sampling of fingerprint, materials used in Figure S5 were newly prepared SiNWs-1 without any modification. S-9

10 Normalized Normalized Normalized [C12:-H] [DPPE-H] [C16:-H] [C18:-H] [C2:-H] [C24:-H] FFAs+DPPE on SiNWs-1-APTES (b) FFAs+DPPE +CHCA on MALDI plate (c).6 FFAs+DPPE +DHB on MALDI plate Figure S8. Negative ion-mode LDI-MS spectra of standard free fatty acids (FFAs) mixture (C12:, C16:, C18:, C2:, C24:) and DPPE (16:/16:) detected on the SiNWs-1-APTES chip, (b) MALDI plate with CHCA, (c) MALDI plate with DHB. The exact of C12:, C16:, C18:,C2:, C24:, DPPE after deprotonation are , , , , and , respectively. Insets in (b) are the molecular structure of DPPE and the magnified mass spectra of. The applied relative laser energy of was set at 81.1%. Figure S9. Negative ion-mode LDI-MS spectra of sweat originated from fingers contacted on SiNWs-2-APTES, (b) thermal treated SiNWs-1-APTES and (c) Si wafer. S-1

11 SN (Signal/Noise) Value Normalized intensity TNT (c) (b) % Intensity of I = % Intensity of I = y =.168x R 2 =.9989 (direct weighting) Concentration of TNT (ng/ml) Figure S1. Typical LDI-MS spectrum of pure TNT solution in negative ion mode. (b) Standard calibration curve of TNT with different concentrations in 5% MeOH solutions (SN value is the sum of the two molecular ion and three fragments). (c) Possible dissociation process of TNT molecules. The relative laser energy was set at 87.9%. Figure S11 LDI mass spectra of metabolites in kidney tissue sections mounted on the SiNWs-1-APTES chips with different section thickness. S-11

12 (b) (c) (d) Kidney section imprint (e) (f) (g) Figure S12. LDI mass spectrum and (b) MSI results of metabolites in kidney tissue imprints detected on the APTES-terminated SiNWs-1 chip. The scale bar in the images is 2 mm Thiabendazole on SiNWs =2.28 SN = Figure S13. Typical LDI mass spectrum of the thiabendazole molecule detected on SiNWs-1. S-12

13 SN (Signal/Noise) Value Intensity (a. u.) Intensity (a. u.) SiNWs after touching the orange (b) 5 4 SiNWs after touching the orange (washed by water) (c) 2 15 SiNWs after touching the orange (washed by detegent) Figure S14. LDI mass spectra of background signals on the orange pericarp extracted with the SiNWs-1 chips through touching the SiNWs chip at the surface of the orange for 3 s. The orange sample in was sprayed with 5% EtOH solution and waited to be dry before SiNWs extraction. Inset in is the magnified mass spectrum of Figure 7b. The sample in (b) was washed with water for 1 s after the same treatment with (b). Sample in (c) was washed with water and detergent for 1 s in succession after the same treatment with (b). The relative laser energy was set at 81.1%. 12 (b) 15.1 mg/ml(c) 15 1 g/ml g/ml g/ml ng/ml Background Extraction time (s) Figure S15. Dynamic curves of thiabendazole extraction process from pool water sample by SiNWs chips. The pool water was spiked in with 2 μg/ml and 1 μg/ml thiabendazole, respectively. Inset in is the photo of pool water. (b, c) LDI mass spectra of thiabendazole-spiked river water extracted by SiNWs chips for 18 s. The spiked concentrations of thiabendazole were.1 mg/ml, 2 μg/ml, 1 ng/ml and (background of river water sample without thiabendazole). Mass spectra in (c) are the magnified spectra of (b) at = mg/ml 2 g/ml 1 ng/ml 4 Background 2 = 2.17, Isotope peak of ~I (=2.17) = 13% I (=199.17) S-13

14 Table S1. Signal/noise values of thiabendazole transferred from orange pericarp to SiNWs-1 Initial conc. (Thiabendazole) SN1 a Error SN2 b Error SN3 c Error.8 ng/cm 2 (.16 μg/kg) 4 ng/cm 2 (8 μg/kg) 4 ng/cm 2 (8 μg/kg) 8 ng/cm 2 (16 μg/kg) 4 ng/cm 2 (8 μg/kg) 4 ng/cm 2 (8 μg/kg) 3.8 / 3.5 / 2.4 / / 4.2 / / a SN1: the orange pericarp was not washed before residual thiabendazole extraction b SN2: the orange pericarp was washed with DI water before residual thiabendazole extraction c SN3: the orange pericarp was washed with DI water and detergent before residual thiabendazole extraction S-14