A review of understanding electrocatalytic reactions in energy conversion and energy storage systems via scanning electrochemical microscopy

To address climate change and promote environmental sustainability,electrochemical energy conversion and storage systems emerge as promising alternative to fossil fuels,catering to the escalating demand for energy.Achieving optimal energy efficiency and cost competitiveness in these systems requires the strategic design of electrocatalysts,coupled with a thorough comprehension of the underlying mechanisms and degradation behavior occurring during the electrocatalysis processes.Scanning electrochemical microscopy(SECM),an analytical technique for studying surface electrochemically,stands out as a powerful tool offering electrochemical insights.It possesses remarkable spatiotemporal resolution,enabling the visualization of the localized electrochemical activity and surface topography.This review compiles crucial research findings and recent breakthroughs in electrocatalytic processes utilizing the SECM methodology,specifically focusing on applications in electrolysis,fuel cells,and metal–oxygen batteries within the realm of energy conversion and storage systems.Commencing with an overview of each energy system,the review introduces the fundamental principles of SECM,and aiming to provide new perspectives and broadening the scope of applied research by describing the major research categories within SECM.

Investigation of reflection anisotropy induced by micropipe defects on the surface of a 4H-SiC single crystal using scanning anisotropy microscopy

Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy(SAM)system.The reflection anisotropy(RA)image with a'butterfly pattern'is obtained around the micropipes by SAM.The RA image of the edge dislocations is theoretically simulated based on dislocation theory and the photoelastic principle.By comparing with the Raman spectrum,it is verified that the micropipes consist of edge dislocations.The different patterns of the RA images are due to the different orientations of the Burgers vectors.Besides,the strain distribution of the micropipes is also deduced.One can identify the dislocation type,the direction of the Burgers vector and the optical anisotropy from the RA image by using SAM.Therefore,SAM is an ideal tool to measure the optical anisotropy induced by the strain field around a defect.

Correlating the Interfacial Polar-Phase Structure to the Local Chemistry in Ferroelectric Polymer Nanocomposites by Combined Scanning Probe Microscopy

Ferroelectric polymer nanocomposites possess exceptional electric properties with respect to the two otherwise uniform phases,which is commonly attributed to the critical role of the matrix-particle interfacial region.However,the structure-property correlation of the interface remains unestablished,and thus,the design of ferroelectric polymer nanocompos-ite has largely relied on the trial-and-error method.Here,a strategy that combines multi-mode scanning probe microscopy-based electrical charac-terization and nano-infrared spectroscopy is developed to unveil the local structure-property correlation of the interface in ferroelectric polymer nano-composites.The results show that the type of surface modifiers decorated on the nanoparticles can significantly influence the local polar-phase content and the piezoelectric effect of the polymer matrix surrounding the nano-particles.The strongly coupled polar-phase content and piezoelectric effect measured directly in the interfacial region as well as the computed bonding energy suggest that the property enhancement originates from the formation of hydrogen bond between the surface modifiers and the ferroelectric polymer.It is also directly detected that the local domain size of the ferroelectric polymer can impact the energy level and distribution of charge traps in the interfacial region and eventually influence the local dielectric strength.

Single Particle-Based Confocal Laser Scanning Microscopy for Visual Detection of Copper Ions in Confined Space

Main observation and conclusion A single particle-based confocal laser scanning microscopy was developed for the visual detection of copper ions in confined space.A fluorescence microparticle,named AuNCs/ZIF-8,was synthesized by coating gold nanoclusters(AuNCs)onto the outer surface of zeolitic imidazolate framework-8(ZIF-8).

Corrosion behavior of aluminum alloys in Na_2SO_4 solution using the scanning electrochemical microscopy technique

The corrosion behavior of aluminum alloys 1060 and 2A12 in a 10 mM Na2SO4＋5 mM KI solution was investigated by scanning electrochemical microscopy （SECM） and scanning electron microscopy （SEM）. The potential topography and corrosion morphology results show that the potential of the sample surface over the same area changes with the increase of immersion time. The corrosion area becomes large, and the potential becomes more negative. The corrosion potential of the 2A12 alloy surface is lower than that of 1060 aluminum, and 2A12 alloy becomes easily corrosive. This is the reason that preferential dissolution in the boundary region of some intermetallic particles （IMPs） occurs and different dissolution behaviors are associated with different types of IMPs because of different potentials.

Imaging of Activity of Horseradish Peroxidase at β-Cyclodextrin Polymer by Scanning Electrochemical Microscopy

The activity of horseradish peroxidase at b-cyclodextrin polymer was imaged by scanning electrochemical microscopy using 3, 3', 5, 5'-tetramethylbenzide and H2O2 as the substrates.

Multi-objective Optimal Design of High Frequency Probe for Scanning Ion Conductance Microscopy

Scanning ion conductance microscopy（SICM） is an emerging non-destructive surface topography characterization apparatus with nanoscale resolution. However, the low regulating frequency of probe in most existing modulated current based SICM systems increases the system noise, and has difficulty in imaging sample surface with steep height changes. In order to enable SICM to have the capability of imaging surfaces with steep height changes, a novel probe that can be used in the modulated current based bopping mode is designed. The design relies on two piezoelectric ceramics with different travels to separate position adjustment and probe frequency regulation in the Z direction. To fiarther improve the resonant frequency of the probe, the material and the key dimensions for each component of the probe are optimized based on the multi-objective optimization method and the finite element analysis. The optimal design has a resonant frequency of above 10 kHz. To validate the rationality of the designed probe, microstructured grating samples are imaged using the homebuilt modulated current based SICM system. The experimental results indicate that the designed high frequency probe can effectively reduce the spike noise by 26% in the average number of spike noise. The proposed design provides a feasible solution for improving the imaging quality of the existing SICM systems which normally use ordinary probes with relatively low regulating frequency.

Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study

The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate（MTA） was studied by scanning electron microscopy（SEM）. Single-rooted human premolars（n560） were instrumented to an apical size #50/0.06 using ProF ile and treated as follows： Group 1（n510） was filled with phosphate buffered saline（PBS）; Group 2（n510） was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3（n520） was obturated orthograde with a paste of OrthoM TA（BioM TA, Seoul, Korea） and PBS; and Group 4（n520） was incubated with E. faecalis for 3 weeks and then obturated with OrthoM TA–PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material（IRM）, and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoM TA-filled roots（Groups 3 and 4）. Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots（Group 4）. Therefore, the orthograde obturation of root canals with OrthoM TA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization.

Non-invasive and low-artifact in vivo brain imaging by using a scanning acoustic-photoacoustic dual mode microscopy

Photoacoustic imaging is a potential candidate for in vivo brain imaging,whereas,its imaging performance could be degraded by inhomogeneous multi-layered media,consisted of scalp and skull.In this work,we propose a low-artifact photoacoustic microscopy(LAPAM)scheme,which combines conventional acoustic-resolution photoacoustic microscopy with scanning acoustic microscopy to suppress the reflection artifacts induced by multi-layers.Based on similar propagation characteristics of photoacoustic signals and ultrasonic echoes,the ultrasonic echoes can be employed as the filters to suppress the reflection artifacts to obtain low-artifact photoacoustic images.Phantom experiment is used to validate the effectiveness of this method.Furthermore,LAPAM is applied for in-vivo imaging mouse brain without removing the scalp and the skull.Experimental results show that the proposed method successfully achieves the low-artifact brain image,which demonstrates the practical applicability of LAPAM.This work might improve the photoacoustic imaging quality in many biomedical applications which involve tissues with complex acoustic properties,such as brain imaging through scalp and skull.

Comparison of scanning electron microscopy findings regarding biofilm colonization with microbiological results in nasolacrimal stents for external, endoscopic and transcanalicular dacryocystorhinostomy

AIM:To compare bacterial biofilm colonization in lacrimal stents following external dacryocystorhinostomy(EX-DCR),endoscopic dacryocystorhinostomy(EN-DCR),and transcanalicular dacryocystorhinostomy(TC-DCR)with multidiode laser.METHODS:This prospective study included 30consecutive patients with nasolacrimal duct obstruction who underwent EXT-,EN-,or TC-DCR.Thirty removed lacrimal stent fragments and conjunctival samples were cultured.The lacrimal stent biofilms were examined by scanning electron microscopy(SEM).RESULTS:Eleven(36.7%)of the 30 lacrimal stent cultures were positive for aerobic bacteria(most commonly Staphylococcus epidermidis and Pseudomonas aeruginosa).However anaerobic bacteria and fungi were not identified in the lacrimal stent cultures.Twenty-seven(90%)patients had biofilmpositive lacrimal stents.The conjunctival culture positivity after the DCR,biofilm positivity on stents,the grade of biofilm colonization,and the presence of mucus and coccoid and rod-shaped organisms did not significantly differ between any of the groups(P】0.05).However,a significant difference was found when the SEM results were compared to the results of the lacrimal stent and conjunctival cultures(P【0.001).CONCLUSION:Type of dacryocystorhinostomy(DCR)surgery did not affect the biofilm colonization of the lacrimal stents.SEM also appears to be more precise than microbiological culture for evaluating the presence of biofilms on lacrimal stents.

EFFECT OF THE TOTAL SAPONIN OF DIPSACUS ASPER ON INTRACELLULAR FREE CALCIUM CONCENTRATION IN THE CELLULAR MODEL OF ALZHEIMER'S DISEASE-SCANNING CONFOCAL MICROSCOPY

Objective To study the effect of ginsenoside Rb1 and total saponin of dipsacus asper on intracellular free calcium concentration mediated by β amyloid protein.So as to lay a foundation for developing effective Chinese traditional medicine to treat Alzheimer’s disease.Methods The technique of laser scanning confocal microscopy combining primary cultured neurons was adopted to quantitatively analyze the change of [Ca 2+ ] i.Results The [Ca 2+ ] i of primary cultured hippocampal neurons was nmol·L -1 on basal levels.Control group showed obvious change of calcium vibration,[Ca 2+ ] i was elevated to nmol·L -1 .The peak of [Ca 2+ ] i of Rb1 group reached nmol·L -1 and was lower than that of control group .The tSDA group displayed distinct change of calcium vibration too,and [Ca 2+ ] i reached nmol·L -1 .There was a significant difference in [Ca 2+ ] i between control and tSDA group .Conclusion The research indicated that one of mechanisms by which Rb1 and tSDA protected the neurons was to maintain the balance of [Ca 2+ ] i.

The scanning tunneling microscopy and spectroscopy of GaSb_(1-x)Bi_(x) films of a few-nanometer thickness grown by molecular beam epitaxy

The ultrahigh vacuum scanning tunneling microscope(STM)was used to characterize the GaSb_(1-x)Bi_(x) films of a few nanometers thickness grown by the molecular beam epitaxy(MBE)on the GaSb buffer layer of 100 nm with the GaSb(100)substrates.The thickness of the GaSb_(1-x)Bi_(x) layers of the samples are 5 and 10 nm,respectively.For comparison,the GaSb buffer was also characterized and its STM image displays terraces whose surfaces are basically atomically flat and their roughness is generally less than 1 monolayer(ML).The surface of 5 nm GaSb_(1-x)Bi_(x) film reserves the same terraced morphology as the buffer layer.In contrast,the morphology of the 10 nm GaSb_(1-x)Bi_(x) film changes to the mound-like island structures with a height of a few MLs.The result implies the growth mode transition from the two-dimensional mode as displayed by the 5 nm film to the Stranski-Krastinov mode as displayed by the 10 nm film.The statistical analysis with the scanning tunneling spectroscopy(STS)measurements indicates that both the incorporation and the inhomogeneity of Bi atoms increase with the thickness of the GaSb_(1-x)Bi_(x) layer.

Scanning transmission electron microscopy: A review of high angle annular dark field and annular bright field imaging and applications in lithium-ion batteries

Scanning transmission electron microscopy（STEM） has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field（HAADF） and annular bright field（ABF） imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries（LIBs）. The future prospects of the STEM are also discussed.

SCANNING TUNNELING MICROSCOPY OF （CrFe）7C3

The microstructure of(CrFe)_7C_3 has been studied with scanning tunneling microscopy.It shows that a carbide consists of colonies which are full of stacking faults. The stacking faults in one colony are parallel while those in different colonies lie at angle with each other.

Graphene/Rh(111) Structure Studied Using In-Situ Scanning Tunneling Microscopy

Scanning tunnel microscopy （STM） is performed to verify if an Rh ＇nails＇ structure is formed accompanying the graphene growing during chemical vapor deposition. A structure of a graphene island in an Rh vacancy island is used as the start. While the graphene island is removed by oxygenation, the variations of the Rh vacancy island are imaged with an in-situ high-temperature STM. By fitting with our model and calculations, we conclude that the best fit is obtained for 0% Rh, i.e., for the complete absence of nails below graphene on Rh（111）. That is, when graphene is formed on Rh（111）, the substrate remains fiat and does not develop a SUPPorting nail structure.

The Study on the Self-assembled Monolayer(SAMs)of Porphyrin with Different Chain Length by Scanning Electrochemical Microscopy(SECM)

The thiol-porphyrins were prepared to investigate the effect of spacer length on the gold electrode. These measurements showed that as the length of the spacers increases, the SAMs tend to form highly ordered structures on the gold electrodes. In addition, the structures of the monoalyers vary depending on the even and odd number of the methylene spacers （n）.

Scanning tunneling microscopy study of molecular growth structures of Gd@C_(82) on Cu(111)

The coverage and temperature-dependent nucleation behaviors of the Gd@C82 metallofullerenes on Cu（111） have been studied by low-temperature scanning tunneling microscopy （LT-STM） in detail. Upon molecular deposition at low temperature, Gd@C82 molecules preferentially decorate the steps and nucleate into single layer islands with increasing coverage. Further annealing treatment leads some of the Gd@C82 molecules to assemble into bright and dim patches, which are correlated to the adsorption induced substrate reconstruction. Upon sufficient thermal activation, Gd@C82 molecules sink into the Cu（111） surface one-copper-layer-deep, forming hexagonal close-packed molecular islands with intra-molecular details observed as striped patterns. By considering the commensurability between the Gd@C82 nearest-neighbor distance and the lattice of the underlying Cu（111）, we clearly identified two kinds of in-plane molecular arrangements as （19（1/2）×19（1/2））R23.4°and （19（1/2）×19（1/2））R36.6°with respect to Cu（111）. Within the assembled Gd@C82 molecular, island molecules with dim–bright contrast are spatially distributed, which may be modulated by the preexisted species on Cu（111）.

Combination of Instrumented Nanoindentation and Scanning Probe Microscopy for Adequate Mechanical Surface Testing

The elastic indentation modulus and hardness of standard bulk materials and advanced thin films were determined by using the nanoindentation technique followed by the Oliver- Pharr post-treatment. After measurements with different loading/unloading schemes on chemically polished bulk titanium a substantial decrease of both modulus and hardness vs an increasing loading time was found. Then, hard nanostructured TiBN and TiCrBN thin films deposited by magnetron sputtering （using multiphase targets） on substrates of high roughness （sintered hard metal） and low roughness （silicon） were studied. Experimental modulus and hardness characterized by using two different nanoindenter tools were within the limits of standard deviation. However, a strong effect of roughness on the spread of the experimental values was observed and it was found that hardness and elastic indentation modulus obeyed a Gaussian distribution. The experimental data were discussed together with scanning probe microscopy （SPM） images of typical imprints taken after the nanoindentation tests and the local topographyls strong correlation with the results of nanoindentation was described.

Clustering study in Eu(DBM)_3Phen-doped polymer optical fibers by optical properties and near-field scanning microscopy

The clusters of Eu^3＋ ion in Eu（DBM）3Phen-doped polymethyl methacrylate （PMMA） have been studied by three means. The relative fluorescence intensity ratio of the ^5D0 → ^7F2 to ^5D0 → ^7F1 transitions with different concentrations of Eu^3＋ in Eu（DBM）3Phen-doped PMMA and metastable-state （^5D0） lifetime dependence on Eu^3＋ concentration axe analyzed. The analysis indicates that there axe no clustering effects in Eu^3＋ ions of Eu（DBM）3Phen-doped PMMA when the Eu^3＋ doping concentration is up to 1.0 wt.-%. At the same time, the clustering effect has not been observed by the scanning neax-field optical microscopy （SNOM） in Eu（DBM）3Phen-doped PMMA with 1.0 wt.-% of Eu^3＋ ions. The analysis reveals that a high concentration of Eu^3＋ can be incorporated into polymer optical fiber （POF） without clustering effect.

Electronic phase diagram of NaFe_(1-x)Co_xAs investigated by scanning tunneling microscopy

Our recent scanning tunneling microscopy （STM） studies of the NaFelxCoxAs phase diagram over a wide range of dopings and temperatures are reviewed. Similar to the high-Tc cuprates, the iron-based superconductors lie in close proximity to a magnetically ordered phase. Therefore, it is widely believed that magnetic interactions or fluctuations play an important role in triggering their Cooper pairings. Among the key issues regarding the electronic phase diagram are the properties of the parent spin density wave （SDW） phase and the superconducting （SC） phase, as well as the interplay between them. The NaFe l-xCoxAs is an ideal system for resolving these issues due to its rich electronic phases and the charge-neutral cleaved surface. In our recent work, we directly observed the SDW gap in the parent state, and it exhibits unconventional features that are incompatible with the simple Fermi surface nesting picture. The optimally doped sample has a single SC gap, but in the underdoped regime we directly viewed the microscopic coexistence of the SDW and SC orders, which compete with each other. In the overdoped regime we observed a novel pseudogap-like feature that coexists with supercon- ductivity in the ground state, persists well into the normal state, and shows great spatial variations. The rich electronic structures across the phase diagram of NaFel_xCoxAs revealed here shed important new light for defining microscopic models of the iron-based superconductors. In particular, we argue that both the itinerant electrons and local moments should be considered on an equal footing in a realistic model.