Pith. sign in

REVIEW 4 major objections 5 minor 48 references

MoS$_{2}$ pixel arrays for real-time photoluminescence imaging of redox molecules

T0 review · 4 major / 5 minor · reviewed 2026-08-14 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read A monolayer MoS2 pixel array images redox molecule concentrations optically, in real time, down to nanomolar levels.

desk verdict A genuinely new MoS2 pixel-array imaging modality with solid physics, but the headline sensitivity claims are internally inconsistent and the nM-at-100ms readout is an extrapolation. read the letter →

arxiv 1908.03471 v1 pith:OF7JRQIM submitted 2019-08-09 physics.app-ph cond-mat.mes-hall

M. F. Reynolds , M. H. D. Guimaraes , H. Gao , K. Kang , A. J. Cortese , D. C. Ralph , J. Park , P. L. McEuen This is my paper · ORCID
classification physics.app-phcond-mat.mes-hall
keywords MoS2photoluminescenceredoxsensingchemicalpotentialNernstequation2Dmaterialsreal-timeimagingferrocene
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper claims that a patterned array of small, electrically floating monolayer MoS2 squares can act as an optical redox sensor, imaging the concentration of redox-active molecules in space and time. The photoluminescence of each pixel follows the local chemical potential of the solution, which is set by the ratio of oxidized to reduced molecules through the Nernst equation, so redox chemistry effectively acts as a gate voltage on the semiconductor. Because the readout is light rather than wires, the sensor can combine micrometer-scale spatial resolution with millisecond temporal response, and the noise is close to the shot-noise floor. The authors report a voltage-equivalent sensitivity of $0.9\,\mathrm{mV}/\sqrt{\mathrm{Hz}}$ on a $5\,\mu\mathrm{m}\times5\,\mu\mathrm{m}$ pixel, a resolution of about 10% in the redox ratio at a 25 Hz bandwidth, and a first detectable ferrocene response at 10 nM.

What carries the argument

The mechanism is the coupling of the Nernst equation for the solution to the doping-dependent emission of monolayer MoS2. The ratio $[\mathrm{Fc}^+]/[\mathrm{Fc}]$ fixes the solution chemical potential, ferrocenium withdraws electrons from MoS2, and the resulting shift in Fermi level changes the photoluminescence intensity in the same way an applied ionic-liquid gate voltage does. A gate curve from a neighboring contacted transistor converts pixel photoluminescence into an effective voltage, while the shot-noise-limited photon count sets the detection floor.

What would settle it

Place a floating pixel and a contacted transistor side by side in the same solution, sweep the ferrocene/ferrocenium ratio, and compare the two photoluminescence-versus-chemical-potential curves: an offset, hysteresis, or dependence of the pixel curve on illumination intensity would invalidate the gate-curve conversion and the reported $\mathrm{mV}/\sqrt{\mathrm{Hz}}$ sensitivity. A second check is to change the excitation power and see whether the apparent solution potential shifts, which would reveal a light-driven charging path rather than an equilibrium Nernst response.

Watch

Extended reading notes

Core claim

The central discovery is that the photoluminescence of a floating MoS2 pixel is determined by the electrochemical potential of the surrounding solution, so redox chemistry acts as an effective gate voltage on the semiconductor. The paper demonstrates a one-to-one correspondence, with no rescaling, between the photoluminescence response of pixels as the ferrocene/ferrocenium ratio is changed and the photoluminescence response of contacted MoS2 transistors as an ionic-liquid gate voltage is swept. Oxidized ferrocenium extracts electrons from the MoS2, changing its doping and therefore its emission. This allows a pixel array to record the diffusion of ferrocenium from a working electrode, yielding a measured diffusion constant of $(1.76 \pm 0.02) \times 10^{-9}\,\mathrm{m}^2/\mathrm{s}$, and to track oxidized molecules carried by laminar or electroosmotic flow. The photoluminescence noise lies close to the shot-noise floor, giving the stated voltage-equivalent sensitivity and making the sensor a wireless, real-time redox imaging platform.

Load-bearing premise

The calibration and the stated nanomolar sensitivity assume that a floating MoS2 pixel's photoluminescence responds to the solution's chemical potential exactly like a contacted MoS2 transistor responds to an applied ionic-liquid gate voltage, with no offset, kinetic lag, or illumination-induced charge transfer.

Editorial extensions

If this is right

  • Patterned MoS2 arrays can image the diffusion of oxidized molecules from a working electrode without any electrical connection to the sensing pixels.
  • Because the signal tracks the oxidized-to-reduced ratio, detection sensitivity holds at low absolute concentrations, with first response observed at 10 nM ferrocene.
  • The arrays can be embedded in microfluidic channels and on optical fibers, so redox activity can be read out in flows and confined geometries.
  • The same approach responds to other redox-active species, including ruthenocene and dopamine, indicating the sensing mechanism is not specific to ferrocene.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Beyond the paper's demonstrations, the same calibration logic should apply to any redox couple that exchanges electrons quickly with the MoS2 surface; slow couples would appear as a lag or offset between the photoluminescence signal and the true solution potential.
  • Since the noise floor is set by photon shot noise, further sensitivity would come mainly from brighter MoS2 films: a tenfold quantum-efficiency gain could push the same voltage-equivalent noise down to smaller pixels or faster frame rates.
  • If the equilibrium response survives in physiological media, a wireless photoluminescence readout could map neurotransmitter efflux from cells, though the paper's dopamine data is an initial step rather than a demonstration in tissue.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 5 minor

Summary. The manuscript reports a new optical redox-imaging platform based on arrays of electrically floating monolayer MoS2 pixels. The central claim is that the photoluminescence (PL) of a MoS2 pixel is set by the local electrochemical potential of the solution, which is determined by the ratio of oxidized to reduced redox species through the Nernst equation. The authors support this with three main experimental pillars: (i) the PL of MoS2 pixels at different ferrocene/ferrocenium ratios overlays, without rescaling, the PL of an ionically gated MoS2 transistor as a function of gate voltage (Fig. 2C); (ii) imaging ferrocenium diffusion from a microelectrode yields a diffusion coefficient D = (1.76 ± 0.02) × 10^-9 m^2/s, consistent with literature (Fig. 3); and (iii) cyclic voltammetry data collapse onto a single Nernst curve with kBT/e = (21 ± 5) mV (Fig. 5C). The paper further claims shot-noise-limited sensitivity of 0.9 mV/√Hz on a 5×5 µm^2 pixel, parts-per-hundred concentration resolution, and nanomolar detection limits at 100 ms frame rates. The Supplementary Information includes additional control experiments (ruthenocene, dopamine, microfluidic flow) and, importantly, a section documenting the concentration-dependent PL equilibration time after breaking electrical contact (SI §8).

Significance. If the quantitative chemical-potential readout holds, this would be a genuinely new, wire-free optical method for spatially and temporally resolved redox imaging, with clear applications in electrochemistry, microfluidics, and biological sensing. The paper is notable for including multiple independent external benchmarks: the measured diffusion constant matches literature values, the CV data collapse onto a Nernst form, and the PL-versus-chemical-potential response is compared directly to ionic-liquid gating. These checks lend credibility to the core sensing mechanism. However, the central quantitative claims—0.9 mV/√Hz, parts-per-hundred resolution at 25 Hz, and nanomolar detection at 100 ms frame rates—are not yet supported by the presented data. The voltage calibration relies on a nearby transistor rather than the imaged pixel itself, the sensitivity arithmetic is internally inconsistent, and the SI's own equilibration measurements raise a kinetic concern that directly affects the real-time claim. These issues are addressable with additional measurements and a careful recalculation, so the paper merits revision rather than rejection.

major comments (4)
  1. [Abstract and SI §8] The claim of real-time imaging at 100 ms frame rates is not supported by the equilibration data in SI §8. After breaking electrical contact, the PL relaxes to the value set by the solution with a double-exponential time course whose width decreases with ferrocene concentration; no time constant is quoted for nanomolar concentrations, but the trend in Fig. S5C implies that equilibration can take seconds. The diffusion experiment (Fig. 3) and the CV-sweep experiment (Fig. 5D) were performed at millimolar concentrations or on slow voltage sweeps, respectively, so they cannot validate a 100 ms response at the claimed nanomolar detection limit. The authors should either provide direct time-resolved PL response data at low concentrations or temper the temporal-resolution claim accordingly.
  2. [Fig. 2C and Fig. 4] The voltage calibration of the floating pixels is not established for the imaged pixels themselves. Fig. 2C compares the PL of pixels to a gate curve taken from a nearby contacted transistor, and Fig. 4 converts pixel PL noise into voltage noise using that same gate curve. This assumes that a floating MoS2 pixel and a contacted MoS2 transistor have identical dPL/dV and that the pixel is in electrochemical equilibrium with the solution on the measurement timescale. The first assumption is plausible but unverified; the second is contradicted by the slow equilibration documented in SI §8. A direct calibration of the same pixel—for example, by stepping the solution potential through a known redox couple and measuring PL—would remove this ambiguity. Without it, the quoted mV/√Hz sensitivity and the derived δr/r values are not firmly grounded.
  3. [Fig. 4 and Discussion] The sensitivity numbers are internally inconsistent. The text states a redox detection resolution of δr/r = 0.03 Hz^-1/2 or 10% at a 25 Hz bandwidth on a 5×5 µm^2 pixel. With a voltage noise density of 0.9 mV/√Hz, the rms voltage noise over 25 Hz is 0.9 × 5 = 4.5 mV, giving δr/r = 4.5/25.7 ≈ 17%, not 10%. The Discussion states '10% in a 30 Hz bandwidth,' which gives δr/r ≈ 19%, and the abstract emphasizes '100 ms frame rates,' corresponding to a 10 Hz bandwidth, which gives δr/r ≈ 11%. The three statements are mutually incompatible. Moreover, the measured 0.9 mV/√Hz is 1.5× above the plotted shot-noise floor of 0.6 mV/√Hz, so the 'shot-noise-limited' label is an overstatement. The authors should recalculate the resolution for a clearly defined bandwidth and report an honest comparison to the shot-noise floor.
  4. [Fig. 5D and 'nanomolar at 100 ms' claim] The claim of nanomolar detection limits at 100 ms frame rates conflates two distinct observations. Fig. 5D shows that the PL response during slow cyclic voltammetry begins at 10 nM ferrocene, but it also states that the response 'begins to shift at 100 and 10 nM concentrations, perhaps due to comparable concentrations of contaminant redox molecules.' The latter statement acknowledges that the apparent nM response may be limited by background contaminants, and the measurement is not time-resolved. No data are shown demonstrating that a 10 nM concentration change can be detected within 100 ms. The abstract and introduction should be reworded to distinguish the concentration sensitivity measured under quasi-static conditions from the temporal resolution measured at millimolar concentrations.
minor comments (5)
  1. [Abstract vs. Discussion] The temporal resolution is quoted inconsistently: the abstract says '100 ms frame rates,' the main text says '10% at a 25 Hz bandwidth,' and the Discussion says '10% in a 30 Hz bandwidth.' These should be harmonized after the sensitivity calculation is corrected.
  2. [Fig. 4 text] The main text reports a voltage noise density of '2 /mV Hz' for the 2×2 µm^2 pixel, while the Fig. 4 caption lists the shot-noise floor as 1.5 mV/√Hz for that same pixel. One of these numbers appears to be a typo; please check and correct.
  3. [Eq. (1)] Equation (1) is garbled in the typeset text; the standard Nernst form should be written clearly as μ_s = eE0 + kBT ln([Fc+]/[Fc]) (or the equivalent potential form). The current rendering is difficult to parse.
  4. [Fig. 5C fit] The Nernst fit in Fig. 5C includes two adjustable parameters (E' and a current offset of -1 nA/mM) and reports kBT/e = (21 ± 5) mV. This is a weak quantitative confirmation because the uncertainty is large; the authors should state the fit range and the sensitivity of the result to the offset choice.
  5. [SI §8] SI §8 presents a double-exponential fit but does not quote the extracted time constants. A table or plot of τ1 and τ2 versus concentration would make the kinetic limitation quantitative and would directly support (or bound) the real-time claim.

Circularity Check

0 steps flagged · score 0.0 of 10

No material circularity: the PL-to-voltage calibration and Nernst analysis are independent consistency checks, and the key outputs are benchmarked externally.

full rationale

The paper's central derivation is that MoS2 PL is set by the solution chemical potential, tested by overlaying PL-versus-chemical potential (from the Nernst equation with prepared Fc+/Fc ratios) on PL-versus-ionic-liquid-gate-voltage for a contacted transistor (Fig. 2C). This is an empirical comparison of two independent perturbations, not a definitional identity. The noise sensitivity in Fig. 4 is a unit conversion using a measured gate curve, not a fitted parameter renamed as a prediction. The Fig. 5C Nernst collapse uses the PL-to-voltage slope as a calibration and then compares with electrode current; the fitted slope kBT/e = 21±5 mV is compared with the independent thermal value 25.7 mV, so it is a consistency check rather than circular. The diffusion-constant measurement (Fig. 3D) is benchmarked against literature values (1.6–2.2×10^-9 m^2/s). The only author-overlap citation (ref. 25 for MOCVD growth) is a fabrication method, not a load-bearing theoretical premise. Concerns about redox equilibration kinetics and the assumption that floating pixels share the transistor's dPL/dV are assumptions affecting validity of the quantitative sensitivity, but they do not reduce the derivation to its inputs by construction.

Assumptions & free parameters 2 free parameters · 6 assumptions · 0 invented entities

No new particles, fields, or material phases are introduced. The only new element is the patterned MoS2 pixel array geometry, which is a fabricated structure rather than a postulated entity. The central claims rest on standard electrochemistry (Nernst), an equilibrium charge-transfer assumption between solution and MoS2, and an empirical calibration of PL to voltage using a neighboring transistor. The headline sensitivity numbers depend on this calibration and on the stated but inconsistent noise-to-percent conversion.

free parameters (2)
  • PL-to-voltage conversion slope = not quoted numerically; taken from the linear region of the PL vs VLG curve of a nearby transistor (Fig. 2B, 2C)
    This conversion is load-bearing for the reported 0.9 mV/√Hz voltage noise and the concentration resolution derived from it, as well as for the CV collapse in Fig. 5C.
  • E' and current offset in Fig. 5C Nernst fit = E' = 0.53 ± 0.01 V; current offset = -1 nA/mM
    Fit parameters in a validation plot showing the data collapse onto the Nernst form; they do not set the sensor's detection limits but are fitted quantities used for the consistency check.
assumptions (6)
  • domain assumption Nernst equation (Eq. 1) relates solution chemical potential to the ferrocenium/ferrocene ratio.
    Invoked throughout to convert measured concentration ratios to chemical potentials; assumes ideal dilute solution and that the surface ratio equals the bulk ratio.
  • domain assumption The MoS2 Fermi level follows the solution chemical potential via charge transfer, with no significant kinetic or contact barrier.
    Stated after Eq. 1; the entire potentiometric readout depends on this equilibrium assumption.
  • domain assumption The PL versus doping relationship is the same for floating MoS2 pixels and for contacted transistor devices on the same chip.
    Used to calibrate pixel PL against gate voltage in Fig. 2C, to convert PL noise to voltage noise in Fig. 4, and to collapse CV data in Fig. 5C; verified only by the single overlay in Fig. 2C.
  • domain assumption MoS2 doping is linear in chemical potential in the operating window (Supplementary section 4).
    Justifies linear conversion between PL changes and voltage changes; relies on estimated double-layer and quantum capacitances.
  • domain assumption Ferrocenium concentration at a fixed position is proportional to the working electrode current in steady state (Supplementary section 7).
    Underlies the CV comparison and the Nernst collapse in Fig. 5C.
  • standard math Diffusion from the microelectrode follows the point-source erfc profile (Fig. 3C).
    Standard solution to the diffusion equation; the extracted D matches literature, supporting its validity.

how reviews work

0 comments
Cite this review

Pith. "Pith review of MoS$_{2}$ pixel arrays for real-time photoluminescence imaging of redox molecules." pith.science (2026). https://pith.science/paper/OF7JRQIM

@misc{pith2026190803471,
  author       = {Pith},
  title        = {Pith review of: MoS$_2$ pixel arrays for real-time photoluminescence imaging of redox molecules},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/OF7JRQIM}},
  note         = {Machine review of arXiv:1908.03471}
}
abstract

Measuring the behavior of redox-active molecules in space and time is crucial for better understanding of chemical and biological systems and for the development of new technologies. Optical schemes are non-invasive, scalable and can be applied to many different systems, but usually have a slow response compared to electrical detection methods. Furthermore, many fluorescent molecules for redox detection degrade in brightness over long exposure times. Here we show that the photoluminescence of pixel arrays of an atomically thin two-dimensional (2D) material, a monolayer of MoS$_{2}$, can image spatial and temporal changes in redox molecule concentration in real time. Because of the strong dependence of MoS$_{2}$ photoluminescence on doping and sensitivity to surface changes characteristic of 2D materials, changes in the local chemical potential significantly modulate the photoluminescence of MoS$_{2}$, with a sensitivity of 0.9 mV/$\sqrt{Hz}$ on a 5 $\mu$m by 5 $\mu$m pixel, corresponding to better than parts-per-hundred changes in redox molecule concentration down to nanomolar concentrations at 100 ms frame rates. The real-time imaging of electrochemical potentials with a fast response time provides a new strategy for visualizing chemical reactions and biomolecules with a 2D material screen.

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

48 extracted references · 48 canonical work pages

  1. [1]

    K. F. Mak, C. Lee, J. Hone, J. Shan, T. F. Heinz, Atomically Thin MoS 2 : A New Direct-Gap Semiconductor. Phys. Rev. Lett. 105, 136805 (2010)

    work page 2010

  2. [2]

    Splendiani et al., Emerging Photoluminescence in Monolayer MoS 2

    A. Splendiani et al., Emerging Photoluminescence in Monolayer MoS 2. Nano Lett. 10, 1271–1275 (2010)

    work page 2010

  3. [3]

    K. F. Mak et al., Tightly bound trions in monolayer MoS2. Nat. Mater. 12, 207–211 (2013)

    work page 2013

  4. [4]

    The devices thus operate as redox sensors, with orders of magnitude changes in PL seen when changing the Ox/Red ratio

    when electrons are added to the conduction band. The devices thus operate as redox sensors, with orders of magnitude changes in PL seen when changing the Ox/Red ratio. The mechanism can be understood by considering the chemical potential of the solution s set by the ferrocene/ferrocenium ratio. This chemical potential is given by the Nernst equation: 0 [...

    work page

  5. [5]

    A. K. M. Newaz et al., Electrical control of optical properties of monolayer MoS2. Solid State Commun. 155, 49–52 (2013)

    work page 2013

  6. [6]

    Peimyoo et al., Chemically Driven Tunable Light Emission of Charged and Neutral Excitons in Monolayer WS 2

    N. Peimyoo et al., Chemically Driven Tunable Light Emission of Charged and Neutral Excitons in Monolayer WS 2. ACS Nano. 8, 11320–11329 (2014)

    work page 2014

  7. [7]

    Mouri, Y

    S. Mouri, Y. Miyauchi, K. Matsuda, Tunable Photoluminescence of Monolayer MoS2 via Chemical Doping. Nano Lett. 13, 5944–5948 (2013). 8 of 28

    work page 2013

  8. [8]

    Zhang, K

    W. Zhang, K. Matsuda, Y. Miyauchi, pH-Dependent Photoluminescence Properties of Monolayer Transition-Metal Dichalcogenides Immersed in an Aqueous Solution. J. Phys. Chem. C. 122, 13175–13181 (2018)

    work page 2018

Show all 48 references
  1. [9]

    Nan et al., Strong Photoluminescence Enhancement of MoS2 through Defect Engineering and Oxygen Bonding

    H. Nan et al., Strong Photoluminescence Enhancement of MoS2 through Defect Engineering and Oxygen Bonding. ACS Nano. 8, 5738–5745 (2014)

    2014

  2. [10]

    N. Kang, H. P. Paudel, M. N. Leuenberger, L. Tetard, S. I. Khondaker, Photoluminescence Quenching in Single-Layer MoS2 via Oxygen Plasma Treatment. J. Phys. Chem. C. 118, 21258–21263 (2014)

    2014

  3. [11]

    Wang et al., Electrochemical Control of Photoluminescence in Two-Dimensional MoS 2 Nanoflakes

    Y. Wang et al., Electrochemical Control of Photoluminescence in Two-Dimensional MoS 2 Nanoflakes. ACS Nano. 7, 10083–10093 (2013)

    2013

  4. [12]

    J. Z. Ou et al., Ion-Driven Photoluminescence Modulation of Quasi-Two-Dimensional MoS 2 Nanoflakes for Applications in Biological Systems. Nano Lett. 14, 857–863 (2014)

    2014

  5. [13]

    Velický et al., Photoelectrochemistry of Pristine Mono- and Few-Layer MoS 2

    M. Velický et al., Photoelectrochemistry of Pristine Mono- and Few-Layer MoS 2. Nano Lett. 16, 2023–2032 (2016)

    2016

  6. [14]

    Wang, C.-H

    Y. Wang, C.-H. Kim, Y. Yoo, J. E. Johns, C. D. Frisbie, Field Effect Modulation of Heterogeneous Charge Transfer Kinetics at Back-Gated Two-Dimensional MoS 2 Electrodes. Nano Lett. 17, 7586–7592 (2017)

    2017

  7. [15]

    J. Wang, R. Trouillon, Y. Lin, M. I. Svensson, A. G. Ewing, Individually Addressable Thin-Film Ultramicroelectrode Array for Spatial Measurements of Single Vesicle Release. Anal. Chem. 85, 5600–5608 (2013)

    2013

  8. [16]

    Hafez et al., Electrochemical imaging of fusion pore openings by electrochemical detector arrays

    I. Hafez et al., Electrochemical imaging of fusion pore openings by electrochemical detector arrays. Proc. Natl. Acad. Sci. U. S. A. 102, 13879–13884 (2005)

    2005

  9. [17]

    D. L. Bellin et al., Electrochemical camera chip for simultaneous imaging of multiple metabolites in biofilms. Nat. Commun. 7, 10535 (2016)

    2016

  10. [18]

    Shields, B

    P. Shields, B. Nemeth, R. B. Green, M. O. Riehle, D. R. S. Cumming, High-Speed Imaging of 2-D Ionic Diffusion Using a 16x16 Pixel CMOS ISFET Array on the Microfluidic Scale. IEEE Sens. J. 12, 2744–2749 (2012)

    2012

  11. [19]

    A. J. Bard et al., Chemical imaging of surfaces with the scanning electrochemical microscope. Science. 254, 68–74 (1991)

    1991

  12. [20]

    D. G. Hafeman, J. W. Parce, H. M. McConnell, Light-adressable potentiometric sensor for biochemical systems. Science (80-. ). 240, 1182–1185 (1988)

    1988

  13. [21]

    A. Jane, R. Dronov, A. Hodges, N. H. Voelcker, Porous silicon biosensors on the advance. Trends Biotechnol. 27, 230–239 (2009)

    2009

  14. [22]

    X. Shan, U. Patel, S. Wang, R. Iglesias, N. Tao, Imaging local electrochemical current via surface plasmon resonance. Science. 327, 1363–6 (2010)

    2010

  15. [23]

    K. M. Mayer, J. H. Hafner, Localized Surface Plasmon Resonance Sensors. Chem. Rev. 111, 3828–3857 (2011)

    2011

  16. [24]

    M. P. Landry et al., Single-molecule detection of protein efflux from microorganisms using fluorescent single-walled carbon nanotube sensor arrays. Nat. Nanotechnol. 12, 368–377 (2017)

    2017

  17. [25]

    Kruss et al., High-resolution imaging of cellular dopamine efflux using a fluorescent nanosensor array

    S. Kruss et al., High-resolution imaging of cellular dopamine efflux using a fluorescent nanosensor array. Proc. Natl. Acad. Sci. U. S. A. 114, 1789–1794 (2017)

    2017

  18. [26]

    Kang et al., High-mobility three-atom-thick semiconducting films with wafer-scale homogeneity

    K. Kang et al., High-mobility three-atom-thick semiconducting films with wafer-scale homogeneity. Nature. 520, 656–660 (2015)

    2015

  19. [27]

    Amani et al., High Luminescence Efficiency in MoS2 Grown by Chemical Vapor Deposition

    M. Amani et al., High Luminescence Efficiency in MoS2 Grown by Chemical Vapor Deposition. ACS Nano. 10, 6535–6541 (2016)

    2016

  20. [28]

    A. J. Bard, L. R. Faulkner, ELECTROCHEMICAL METHODS Fundamentals and Applications (2001)

    2001

  21. [29]

    Y. Wang, E. I. Rogers, R. G. Compton, The measurement of the diffusion coefficients of ferrocene and ferrocenium and their temperature dependence in acetonitrile using double 9 of 28 potential step microdisk electrode chronoamperometry. J. Electroanal. Chem. 648, 15–19 (2010)

    2010

  22. [30]

    I. F. Cheng, L. D. Whiteley, C. R. Martin, Ultramicroelectrode Ensembles, and Theoretical Responses and Detection Limits Comparison of Experimental Evaluation of Electroanalytical. Anal. Chem. J. Phys. Rev. C Earth Planet. Sci. Lett. Geochim. Cosmochim. Acta N.; Masuda, A. Mem...

    1989

  23. [31]

    pixel array

    P. Hernández, I. Sánchez, F. Patón, L. Hernández, Cyclic voltammetry determination of epinephrine with a carbon fiber ultramicroelectrode. Talanta. 46, 985–991 (1998). Acknowledgments General: We thank H. Abruña, M. Velicky, and M. Lee for fruitful discussions, and M. Ramaswam...

    1998

  24. [32]

    MoS2 Characterization

  25. [33]

    Relationship between carrier density and chemical potential

  26. [34]

    Ionic current plots in diffusion experiments

  27. [35]

    Experiments in Ruthenocene and Ruthenocene/Ferrocene mixtures

  28. [36]

    Linear relationship between ferrocenium concentration and current

  29. [37]

    Decay time of MoS2 PL as a function of concentration

  30. [38]

    Dopamine Detection 18 of 28

  31. [39]

    The homogeneous coverage of monolayer MoS 2 was confirmed by atomic force microscopy and photoluminescence imaging

    Sample Fabrication The monolayer MoS 2 films are directly grown on 1” transparent fused silica substrates using the Metal-Organic Chemical Vapor Deposition described in reference S (25). The homogeneous coverage of monolayer MoS 2 was confirmed by atomic force microscopy and p...

  32. [40]

    S1A shows continuous, monolayer MoS2

    MoS2 Characterization A representative atomic force microscopy (AFM) image, Fig. S1A shows continuous, monolayer MoS2. The photoluminescence (PL) spectrum (Fig. S1B) gives a peak at approximately 660 nm, consistent with previous results for MoS 2 on SiO2 (1, 25, 26). The Raman...

  33. [41]

    Experimental Setup The devices were measured using a probe -station with automated micromanipulators (Sensapex). The samples were mounted with the MoS 2 side pointing up on an inverted microscope and imaged with a water immersion 60x objective with numerical aperture 1.25 and ...

  34. [42]

    Relationship between carrier density and chemical potential In general, the equation describing the potentials in the fluid can be written as: ( ) ( )cir e eeV s m=− , [1] where Vcir is an applied potential between the solution and the MoS 2, and µe(s) and µe(m) are the elec...

  35. [43]

    In order to demonstrate this, we performed similar experiments as described in the main text with ruthenocene (C 10H10Ru) in place of ferrocene

    Experiments in Ruthenocene and Ruthenocene/Ferrocene mixtures The detection of the electrochemical potential using the MoS 2 PL is not limited to ferrocene ions. In order to demonstrate this, we performed similar experiments as described in the main text with ruthenocene (C 10...

  36. [44]

    Using the same video shown in Fig

    Ionic current plots in diffusion experiments PL measurements during diffusion can be used to plot concent ration gradients by taking local gradients of PL. Using the same video shown in Fig. 3 of the main text, the PL of each pixel is plotted in a grid. Gradients are calculate...

  37. [45]

    Linear relationship between ferrocenium concentration and current For simplicity, we model our ultramicroelectrode as a sphere, with a radius of approximately 10 µm. For oxidation of a molecule at a spherical ultramicroelectrode due to a potential step, steady state is reached...

  38. [46]

    Decay time of MoS2 PL as a function of concentration 24 of 28 While the PL of MoS 2 responds to redox molecules down to low (nan omolar) concentrations, the timescale of that response changes as a function of concentration. To demonstrate this, we set the potential of MoS 2 by...

  39. [47]

    6A, B, we place two platinum wires on either side of the channel (Fig S6A)

    Electroosmotic Flow In the same experimental setup as in Fig. 6A, B, we place two platinum wires on either side of the channel (Fig S6A). By applying 50 V across the approximately 1 mm channel, we drive an electroosmotic flow. This flow is imaged with the MoS2 PL in the same m...

  40. [48]

    Dopamine detection We demonstrate that our detection scheme also works for redox biomolecules in aqueous solution by measuring PL versus dopamine concentration in a pH buffered solution, shown in Fig. S7. Without any dopamine in the solution, the MoS2 is in a bright state at p...

Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.