Monitoring surface charge migration in the spectral dynamics of singleCdSe∕CdSnanodot/nanorod heterostructures

2005 ◽  
Vol 72 (20) ◽  
Author(s):  
J. Müller ◽  
J. M. Lupton ◽  
A. L. Rogach ◽  
J. Feldmann ◽  
D. V. Talapin ◽  
...  
Keyword(s):  
Surface Charge ◽  
Charge Migration ◽  
Spectral Dynamics

Surface charge migration and dc surface flashover of surface-modified epoxy-based insulators

2017 ◽  
Vol 50 (6) ◽  
pp. 065301 ◽  
Author(s):  
Chuanyang Li ◽  
Jun Hu ◽  
Chuanjie Lin ◽  
Boya Zhang ◽  
Guixin Zhang ◽  
...  
Keyword(s):  
Surface Charge ◽  
Charge Migration ◽  
Surface Flashover ◽  
Surface Modified ◽  
Modified Epoxy

Imaging molecules adsorbed onto electrodes under potential control by scanning probe microscopy

1991 ◽  
Vol 49 ◽  
pp. 376-377 ◽  
Author(s):  
N.J. Tao ◽  
J.A. DeRose ◽  
P.I. Oden ◽  
S.M. Lindsay
Keyword(s):  
Surface Charge ◽  
Environmental Effects ◽  
Scanning Probe Microscopy ◽  
Statistical Significance ◽  
Electrochemical Methods ◽  
Surface Structures ◽  
Scanning Probe ◽  
Potential Control ◽  
Afm Imaging ◽  
Special Circumstances

Clemmer and Beebe have pointed out that surface structures on graphite substrates can be misinterpreted as biopolymer images in STM experiments. We have been using electrochemical methods to react DNA fragments onto gold electrodes for STM and AFM imaging. The adsorbates produced in this way are only homogeneous in special circumstances. Searching an inhomogeneous substrate for ‘desired’ images limits the value of the data. Here, we report on a reversible method for imaging adsorbates. The molecules can be lifted onto and off the substrate during imaging. This leaves no doubt about the validity or statistical significance of the images. Furthermore, environmental effects (such as changes in electrolyte or surface charge) can be investigated easily.

Molecular Characterization of the Surface Excess Charge Layer in Droplets

2020 ◽  
Author(s):  
Victor Kwan ◽  
Styliani Consta
Keyword(s):  
Hydrogen Bonds ◽  
Surface Charge ◽  
Droplet Size ◽  
Chloride Ions ◽  
Total Charge ◽  
Excess Charge ◽  
Surface Excess ◽  
High Concentration ◽  
Dipole Orientation ◽  
Charge Layer

<div>Charged droplets play a central role in native mass spectrometry, atmospheric aerosols and in serving as micro-reactors for accelerating chemical reactions. The surface excess charge layer in droplets has often been associated with distinct chemistry. Using molecular simulations for droplets with Na+ and Cl- ions we have found that this layer is ≈ 1.5−1.7 nm thick and depending on the droplet size it includes 33%-55% of the total number of ions. Here, we examine the effect of droplet size and nature of ions in the structure of the surface excess charge layer by using molecular dynamics. We find that in the presence of simple ions the thickness of the surface excess charge layer is invariant not only with respect to droplet size but also with respect to the nature of the simple ions and it is not sensitive to fine details of different force fields used in our simulations.</div><div> In the presence of macroions the excess surface charge layer may extend to 2.0. nm. For the same droplet size, iodide and model hydronium ions show considerably higher concentration than the sodium and chloride ions. <br></div><div>We also find that differences in the average water dipole orientation in the presence of cations and anions in this layer are reflected in the charge distributions. Within the surface charge layer, the number of hydrogen bonds reduces gradually relative to the droplet interior where the number of hydrogen bonds is on the average 2.9 for droplets of diameter < 4 nm and 3.5 for larger droplets. The decrease in the number of hydrogen bonds from the interior to the surface is less pronounced in larger droplets. In droplets with diameter < 4 nm and high concentration of ions the charge of the ions is not compensated only by the solvent polarization charge but by the total charge that also includes the other free charge. This finding shows exceptions to the commonly made assumption that the solvent compensates the charge of the ions in solvents with very high dielectric constant. The study provides molecular insight into the bi-layer droplet structure assumed in the equilibrium partitioning model of C. Enke and assesses critical assumptions of the Iribarne-Thomson model for the ion-evaporation mechanism. <br></div>

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