SECM and SI 扫描电化学显微镜 表面询问模式.ppt

1、1,Scanning Electrochemical Microscopy (SECM) and Surface Interrogation Mode(SI),Department of Chemistry, School of Science C. Gu 2011.4.19,CONTESTS,1. Principles of SECM 2. Applications 2.1 Imaging surface reactivity 2.2 Solid/liquid interface 2.3 Liquid/liquid interface 3. SI-SECM 3.1 Principles 3.

2、2 Advantages 3.2 Latest informations 4. References,2,1. Principles of SECM,3,A.J.Bard SECM, 1989,4,Fig 1Block diagram of the SECM apparatus,5,2. Applications,2.1 Imaging surface reactivity An important advantage of SECM is the capability to image the surface topography or reactivity by using amperom

3、etric and potentiometric probes 1. Two modes are used to map the surfaces of targets by SECM: the constant height mode and the constant distance mode 2.,6,the constant height mode,the constant distance mode,2.2 Solid/liquid interface 2.2.1 ET (Electron transfer),7,Fig 2 Pathway of general electrode

4、reaction,2.2.2 Biological systems In particular, SECM has been devoted to studying the activity of immobilized enzymes on patterned interfaces in order to attempt to structure biosensors ,chip-based assay and enzyme immunoassays (EIAs).,8,2.3 Liquid/liquid interface 2.3.1 ET (Electron transfer),9,Fi

5、g 3 Schematic diagram of the feedback mode SECM measurements of the kinetics of ET between organic and aqueous redox species. Electroneutrality was maintained by transfer of common ions shown as negative charges.,2.3.2 Ion transfer (IT) at the ITIES Heterogeneous IT reactions are essential for many

6、biological and technological systems . Especially, simple IT reactions are numerous and of great importance for biological systems.,10,2.3.3 Molecular transfer Studies of molecular transfer processes of non-charged species at the L/L interfaces can be performed by SECM.,Accurately measuring respirat

7、ory activity of single living cells by SECM 3,Fig 5,First, cells are immobilized on a glass substrate modied with collagen. Then, a Pt ultramicroelectrode tip of SECM held at 0.50V is scanned along the central line across a living cell and a SECM scan curve, i.e., the relationship of the tip current

8、 versus the displacement (the rst scan curve) is recorded with a negative peak. The peak current ip on this rst scan curve is composed of ip1, which corresponds to the cell respiratory activity and ip2, which corresponds to the cell topography.,Third,In order to isolate the ip2 component, the cell i

9、s killed by exposing it to 1.010-3 mol/L KCN for 10min. The tip is then scanned again with the same trace over the dead cell, and a second SECM scan curve is recorded. Thus, ip2is obtained from the second SECM scan curve. Finally, ip1 corresponding to the respiratory activity of the living cell can

10、be accurately calculated using ip1 = ip ip2. This method can be used to monitor real-time change in the respiratory activity of single cells after exposing them to KBr,NaN3 and KCN.,15,Reduction of Ru(NH3)63+,Reduction of O2 and Oxidation of H2 at Pt electrode in water,Electrode,Electrode,Solvent,So

11、lvent,Ligand,Ligand,Fig 6 Schematic diagram of outer/inner-sphere electrontransfer reactions,3. Surface Interrogation (SI),A.J.Bard , 2008 outer-sphere electrontransfer reactions inner-sphere electrontransfer reactions their greater complexity and the difculty in obtaining reliable quantitative data

12、 about intermediates and products on electrode surfaces. SI is an in situ electrochemical technique based on the scanning electrochemical microscope (SECM)for the quantication of adsorbed species at electrodes.4,16,17,3.1 Principles,Fig 7 Schematics of the proposed mechanism for the surface interrog

13、ation.,3.2 Advantages The proposed technique allows quantication of the adsorbed species generated at the substrate at a given potential under open circuit conditions, a feature not attainable with conventional electrochemical methods. The feedback mode allows the tip to be both the titrant generato

14、r and detector, simplifying notably the experimental setup. Upon subtraction of the negative feedback curve to these tip responses and integration of the current with time, the collection efciency (dened as the ratio of the charge recovered by the tip to the input charge used in the initial charging

15、 of the substrate) is found to be larger than 98%. 4,18,3.3 Latest informations （1）,Fig 8 Representative result of the surface interrogation, showing the differences between the first and second cycles, = 50 mV/s. The Au tip was oxidized for 30 s in 0.3 M TRIS buffer, pH=7, at 1.4 V.,19,experiments

16、with the Ru(NH3)63+ /2+ to evaluate the feasibility of the reduced form (Ru(NH3)62+) being able to reduce an electrogenerated oxide on a gold electrode.4,20,Fit quite well with simulations and the results obtained by CV,(2) Reaction of Br2 with Adsorbed CO on Pt, Studied by SI-SECM 5,21,Fig 11 SI-SE

17、CM detection of COads on a Pt UME substrate.,（3） the Open Circuit CatalyticDecomposition of Formic Acid at Platinum6,Figure 9 Depiction of the mode of operation of the surface interrogation technique for the oxidation of adsorbed hydrogen on Pt .,22,23,Fig 10 (A) SI scans using 0.5 mM TMPD in 1 M HC

18、lO4 with different doses of Hads delivered to the Pt substrate by a linear sweep at 50 mV/s from 0.42 V to the potential limit indicated for each curve, interrogator electrode =5 mV/s. The inset shows representation of the potential limits on the Pt substrate sweep used during the Hads dosage. (B) Representative SI measurements at various OCP of