Electrochemically probing exciton transport in monolayers of two-dimensional semiconductors

Tolbert, Chloe L.; Hill, Caleb M.

doi:10.1039/d1fd00052g

Cited by 21 publications

(20 citation statements)

References 45 publications

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“…Here, we demonstrate that scanning electrochemical cell microscopy (SECCM) − can be utilized to form well-ordered NP arrays in a powerful, instantly reconfigurable manner. In SECCM, electrolyte-filled pipets are utilized to define nanometer-scale electrochemical interfaces which enable the high-resolution analysis of chemical processes spanning electrocatalysis, − anodic dissolution, , photoelectrochemistry, − ionic transport, and crystallization …”

Section: Introductionmentioning

confidence: 99%

On-Demand Electrochemical Fabrication of Ordered Nanoparticle Arrays using Scanning Electrochemical Cell Microscopy

et al. 2022

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Well-ordered nanoparticle arrays are attractive platforms for a variety of analytical applications, but the fabrication of such arrays is generally challenging. Here, it is demonstrated that scanning electrochemical cell microscopy (SECCM) can be used as a powerful, instantly reconfigurable tool for the fabrication of ordered nanoparticle arrays. Using SECCM, Ag nanoparticle arrays were straightforwardly fabricated via electrodeposition at the interface between a substrate electrode and an electrolyte-filled pipet. By dynamically monitoring the currents flowing in an SECCM cell, individual nucleation and growth events could be detected and controlled to yield individual nanoparticles of controlled size. Characterization of the resulting arrays demonstrate that this SECCM-based approach enables spatial control of nanoparticle location comparable with the terminal diameter of the pipet employed and straightforward control over the volume of material deposited at each site within an array. These results provide further evidence for the utility of probe-based electrochemical techniques such as SECCM as tools for surface modification in addition to analysis.

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Section: Introductionmentioning

confidence: 99%

On-Demand Electrochemical Fabrication of Ordered Nanoparticle Arrays using Scanning Electrochemical Cell Microscopy

et al. 2022

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“…The i–E curves from the natural SPI-MoS 2 varied significantly from domain to domain, yielding a large distribution of E on values (open red circles in Figure b). The differences between the individual i-E curves are likely due to spatial variations in doping density as well as bulk or surface defects that can influence charge recombination in the space charge region or interfacial charge transfer rates. , The average E on value from the p-type domains was 0.831 ± 0.021 V. Importantly, none of the single domain i–E curves from SPI-MoS 2 exhibited a photocurrent switching effect that was apparent in the ensemble-level measurement in Figure c. Therefore, the photocurrent switching effect observed at the ensemble-level in Figure c is likely caused by summing n- and p-type domain currents, which will be discussed below.…”

Section: Resultsmentioning

confidence: 94%

“…One possible explanation for PEC performance variation among apparently smooth basal planes is doping heterogeneity. Hill and co-workers observed anodic to cathodic photocurrent switching behavior for different basal planes of single nanoflakes, , suggesting doping heterogeneity exists within the flake. In the early 1980s, Menezes and Lewerenz reported doping heterogeneity limits the photoelectrochemical efficiency of synthetic bulk TMD crystals. , Similarly, Kline and Parkinson provided some evidence that bulk MoS 2 and WSe 2 photoelectrodes with ideal stoichiometry exhibited better photovoltage, open-circuit potential, and fill factor than crystals with nonideal stoichiometry .…”

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Single Nanoflake Photoelectrochemistry Reveals Intrananoflake Doping Heterogeneity That Explains Ensemble-Level Photoelectrochemical Behavior

Erdewyk

Sambur

2021

ACS Appl. Mater. Interfaces

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Transition metal dichalcogenide (TMD) nanoflake thin films are attractive electrode materials for photoelectrochemical (PEC) solar energy conversion and sensing applications, but their photocurrent quantum yields are generally lower than those of bulk TMD electrodes. The poor PEC performance has been primarily attributed to enhanced charge carrier recombination at exposed defect and edge sites introduced by the exfoliation process. Here, a single nanoflake PEC approach reveals how an alternative effect, doping heterogeneity, limits ensemble-level PEC performance. Photocurrent mapping and local photocurrent–potential (i–E) measurements of MoS2 nanoflakes exfoliated from naturally occurring bulk crystals revealed the presence of n- and p-type domains within the same nanoflake. Interestingly, the n- and p-type domains in the natural MoS2 nanoflakes were equally efficient for iodide oxidation and tri-iodide reduction (IQE values exceed 80%). At the single domain-level, the natural MoS2 nanoflakes were nearly as efficient as nanoflakes exfoliated from synthetic n-type MoS2 crystals. Single domain-level i–E measurements explain why natural MoS2 nanoflakes exhibit an n-type to p-type photocurrent switching effect in ensemble-level measurements: the n- and p-type diode currents from individual domains oppose each other upon illuminating the entire nanoflake, resulting in zero photocurrent at the switching potential. The doping heterogeneity effect is likely due to nonideal stoichiometry, where p-type domains are S-rich according to XPS measurements. Although this doping heterogeneity effect limits photoanode or photocathode performance, these findings open the possibility to synthesize efficient TMD nanoflake photocatalysts with well-defined lateral p- and n-type domains for enhanced charge separation.

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“…Benefiting from unique structures and electronic properties, two-dimensional (2D) materials, including transition metal dichalcogenides (TMDCs, e.g., WS2, MoS2 and WSe2), 229,[280][281][282][283][284] graphene and graphene derivatives, 223,285,286 hexagonal boron nitride (h-BN) etc., 287 have generated great interest in catalysis applications, especially in the area of photocatalysis and electrocatalysis. SECCM is ideally suited for studying the electrochemistry of such materials, as small flakes or regions of a 2D material can be targeted directly and the properties of those regions can be deduced by a range of co-located complementary techniques, e.g., Raman microscopy, AFM etc.…”

Section: Two-dimensional Materialsmentioning

confidence: 99%

The new era of high throughput nanoelectrochemistry

Valavanis

Ciocci

et al. 2022

Preprint

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Scanning electrochemical probe microscopies (SEPMs) have played a key role in advancing small-scale electrochemistry. SEPMs use an electrochemical probe (micro/nanoelectrode or pipet) to quantify and map local interfacial fluxes of electroactive species and have found increasingly wide applications. Our contribution to the Fundamental and Applied Reviews in Analytical Chemistry 2019 discussed how advances in SEPMs converged towards nanoscale electrochemical mapping. This inflection in experimental capability has opened up myriad opportunities for SEPMs in many types of systems, from material and energy sciences to the life sciences. The enhancement in the spatial resolution of imaging techniques, and instrumental developments, have resulted in significant increases in the size of electrochemical datasets from a typical experiment and served to speed up measurement throughput. Next generation nanoelectrochemistry will thus see an emphasis on “big data”, its analysis, storage and curation, high throughput analysis and parallelization, “intelligent” instruments and experiments, active control of nanoscale systems, and the integration of nanoelectrochemistry and nanoscale micro(spectro)scopy. For this review article, we focus on recent advances in frontier nanoscale electrochemistry, analysis and imaging techniques that are already addressing some of these key targets, and are well-placed to embrace other aspects in the near future. Our goal is to provide an overview of the present state-of-the-art in high throughput nanoelectrochemistry and imaging, and signpost promising new avenues for nanoscale electrochemical methods.

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Electrochemically probing exciton transport in monolayers of two-dimensional semiconductors

Abstract: Two-dimensional semiconductors (2DSCs) are attractive for a variety of optoelectronic and catalytic applications due to their ability to be fabricated as wide-area, monolayer-thick films and their unique optical and electronic...

Cited by 21 publications

References 45 publications

On-Demand Electrochemical Fabrication of Ordered Nanoparticle Arrays using Scanning Electrochemical Cell Microscopy

On-Demand Electrochemical Fabrication of Ordered Nanoparticle Arrays using Scanning Electrochemical Cell Microscopy

Single Nanoflake Photoelectrochemistry Reveals Intrananoflake Doping Heterogeneity That Explains Ensemble-Level Photoelectrochemical Behavior

The new era of high throughput nanoelectrochemistry

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