Research ArticleMATERIALS SCIENCE

Switchable counterion gradients around charged metallic nanoparticles enable reception of radio waves

See allHide authors and affiliations

Science Advances  12 Oct 2018:
Vol. 4, no. 10, eaau3546
DOI: 10.1126/sciadv.aau3546
  • Fig. 1 Device architecture and its current rectification characteristics at steady state.

    (A) Scheme of the device in which a ~1-μm-thick layer of AuNPs functionalized with charged HS-(CH2)11-N(CH3)3+Cl (TMA) ligands is flanked by a gold electrode and a porous CNT/graphene electrode. The SEM image shows the microstructure of the CNT/graphene electrode. The scheme of the NP and of the individual thiol (along with the mobile counterion) is also shown. (B) Typical current-voltage characteristics of the device collected at a sweep rate of 0.01 V/s. With a positive bias placed on the CNT/graphene electrode, the current increases rapidly and the rectification ratio (r = I+ 1 V/I− 1 V) reaches ~30. (C) Linear current-voltage characteristics recorded for TMA AuNPs flanked by symmetric electrodes (Au-Au and CNT/graphene-CNT/graphene) and for protonated, electrically neutral MUA AuNPs flanked with asymmetric, Au-CNT/graphene electrodes. (D) Current-voltage characteristics for devices varying in the thickness of the CNT/graphene electrode (from ~20 to ~80 nm). Error bars are based on six independent devices. The curves were normalized to have the same current at −1 V. (E) Plotted corresponding rectification ratios.

  • Fig. 2 Time-dependent performance characteristics of AuNP-based rectifiers.

    (A) Current transients monitored upon inverting the bias from +1 to −1 V at frequencies of 1, 10, and 50 Hz (square wave, light blue curve). Rectification ratios increase to steady-state values within tens of millseconds (red curve, right axis). (B) Current monitored for 300 s upon stepping the bias from 0 to +1 or −1 V. The rectification ratio is plotted by dividing the currents at +1 and −1 V (red curve, right axis). (C) Rectification ratio quantified over much longer times, up to ~50 days. (D) Diagram of a half-wave rectifier circuit composed of a NP-based rectifier, a resistor, and an AC signal generator. (E) Performance of this half-wave rectifier circuit (R = 1 megohm) with sinusoidal voltage signals with varying frequencies as inputs (Vinput, black curve). As frequency increases from 1 to 5000 Hz, the rectification ability diminishes and |Vmax/Vmin| decreases from ~11 to ~5 (Voutput, red curve). (F) The rectification ratio decreases exponentially with increasing frequency, although it is still present at 500 kHz (r = 1.6). The thickness of CNT/graphene electrodes used in (A), (B), (C), and (E) is ~60 nm.

  • Fig. 3 NP-based radio receiver.

    (A) Diagram of a radio wave receiving circuit composed of a NP-based diode, an antenna, a varactor, an electromagnetic coil, and an earphone. A one-tube medium-wave continuous wave (CW)/AM transmitter was assembled in-house to generate carrying waves. (B) A photograph of an actual experimental setup in which audio signals carried by a 510-kHz AM radio wave (produced by the transmitting circuit) were intercepted, demodulated, and finally converted into sound by the receiving circuit. (C and D) Examples of two audio waveforms (Mozart’s Turkish March and Symphony No. 40) recorded by the NP-based receiving circuit with an ~80-nm-thick CNT/graphene composite electrode. Audio files are included in the supplementary materials. Photo credit: Y. Yan, National Center for Nanoscience and Technology, Chinese Academy of Sciences.

  • Fig. 4 Theoretical description of the NP-based rectifiers.

    Time-dependent distribution of Cl counterions under positive bias placed on (A) CNT/graphene and (B) Au electrodes. Left: Black, CNT/graphene electrode. Right: dark yellow, Au electrode. Yellow lines, dimensionless concentration profiles of Cl as a function of time (from top to bottom, t = 0, 2 × 105, 1 × 106, and 2 × 107). Concentration scale bars are plotted on the Au electrodes. When a positive bias is placed on CNT/graphene, counterions can migrate into this electrode because of its porous and capacitive characteristics. In contrast, with positive bias placed on the Au electrode, counterions cannot enter bulk gold and only accumulate at the electrode’s surface. (C) Steady-state distributions of conduction electrons (ne), (D) electric potential (u), and (E) electric field (E) across the NP layer under positive bias on CNT/graphene (black curves) or Au (red curves) electrodes. Within the NP layer, ions and electrons move in concert to maintain local charge neutrality. (F) Dimensionless steady-state I-V characteristics of the rectifier. (G) Dimensionless time-dependent current characteristics with constant bias placed on either CNT/graphene or Au electrodes. (H) Modeled dependence of the rectification ratio on the thickness of the CNT/graphene electrode. The rectification ratios are quantified by dividing steady-state currents at dimensionless potentials +10 and −10. The dimensionless thickness indicated on the horizontal axis (80 to 320) corresponds to experimental thickness varying from 20 to 80 nm. For further details of the model, see section S2.

  • Fig. 5 KFM potential scans over planar AuTMA films.

    (A) Scheme of the experimental arrangement and (B) actual experimental scans over the 50-μm gap between the CNT/graphene and Au electrodes. (C) Potential profiles over the gap under no bias (0 V, blue line), +1V bias placed on the CNT/graphene electrode (black line), and −1 V bias on the CNT/graphene electrode (red line). (D) Internal fields derived from the linearly fitted slopes of the profiles in (C). The magnitude of the field established when Cl counterions migrate toward and into the CNT/graphene electrode is larger. KFM measurements were performed on a Bruker Multimode-8 in the tapping mode with constant bias applied on CNT/graphene or Au electrodes.

  • Fig. 6 EDS elemental distribution mapped over planar AuTMA films.

    The arrangement used for these measurements is the same as in Fig. 5A for KFM. The distribution of Au, S, and Cl under no bias (A), +2-V (100 s) bias applied on the CNT/graphene electrode (B), and +2-V (100 s) bias applied on the Au electrode (C). The intense Au signal at the right parts of Au maps is due to the Au electrode under the NPs. The most pronounced concentration gradient is observed when Cl counterions move toward the CNT/graphene electrode [rightmost image in (B)]. Measurements were performed on a Hitachi SU8220 SEM using a Horiba EMAX x-ray detector.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/10/eaau3546/DC1

    Section S1. Experimental

    Section S2. Theoretical details

    Fig. S1. Characterization of the structure, thickness, and electrochemical performance of CNT/graphene electrodes.

    Fig. S2. Current-voltage characteristics of a control device and stability test of a NP-based rectifier.

    Fig. S3. Current-voltage characteristics of the device upon bending.

    Fig. S4. Comparison of the frequency performance of TMA and TMA/MUA AuNP diodes.

    Fig. S5. Time-dependent distributions of electrons, electric potentials, and fields.

    Fig. S6. Thickness-dependent characteristics of AuNP-based rectifiers.

    Fig. S7. Comparisons of theoretically predicted versus experimentally observed characteristics of the diodes.

    Fig. S8. Distribution of counterions under bias as a function of time and voltage.

    Fig. S9. AuNP film and the energy diagrams of two adjacent NPs.

    Table S1. Electrical characteristics of CNT/graphene electrodes.

    Audio file S1. Turkish March.

    Audio file S2. Symphony No. 40.

    References (3037)

  • Supplementary Materials

    The PDF file includes:

    • Section S1. Experimental
    • Section S2. Theoretical details
    • Fig. S1. Characterization of the structure, thickness, and electrochemical performance of CNT/graphene electrodes.
    • Fig. S2. Current-voltage characteristics of a control device and stability test of a NP-based rectifier.
    • Fig. S3. Current-voltage characteristics of the device upon bending.
    • Fig. S4. Comparison of the frequency performance of TMA and TMA/MUA AuNP diodes.
    • Fig. S5. Time-dependent distributions of electrons, electric potentials, and fields.
    • Fig. S6. Thickness-dependent characteristics of AuNP-based rectifiers.
    • Fig. S7. Comparisons of theoretically predicted versus experimentally observed characteristics of the diodes.
    • Fig. S8. Distribution of counterions under bias as a function of time and voltage.
    • Fig. S9. AuNP film and the energy diagrams of two adjacent NPs.
    • Table S1. Electrical characteristics of CNT/graphene electrodes.
    • References (3037)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article