Large work function difference driven electron transfer from electrides to single-walled carbon nanotubes.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Work function differences are crucial for charge transfer between materials.
• Inorganic electrides possess unique properties, including very low work functions (2.4-2.6 eV) due to interstitial anionic electrons.
• Single-walled carbon nanotubes (SWNTs) have work functions ranging from 4.73-5.05 eV.

Purpose of the Study:

• To investigate charge transfer between two distinct inorganic electrides, [Ca(2)N](+)·e(-) and [Ca(24)Al(28)O(64)](4+)·4e(-), and SWNTs.
• To evaluate the impact of electride structure on electron donation efficiency to SWNTs.
• To assess the resulting changes in SWNT properties, including fluorescence and field emission.

Main Methods:

• Comparative study of electron transfer from two types of inorganic electrides ([Ca(2)N](+)·e(-) and [Ca(24)Al(28)O(64)](4+)·4e(-)) to SWNTs.
• Characterization of electron concentration and mobility in the electrides.
• Measurement of near-infrared fluorescence enhancement in SWNTs.
• Evaluation of field emission properties of electride-SWNT composites.

Main Results:

• [Ca(2)N](+)·e(-), with its open 2D electron layers, demonstrated more effective electron donation to SWNTs compared to the closed cage structure of [Ca(24)Al(28)O(64)](4+)·4e(-).
• This enhanced donation is attributed to the higher electron concentration (1.3 × 10^22 cm^-3) and mobility (∼200 cm^2 V^-1 s^-1 at RT) of [Ca(2)N](+)·e(-).
• Non-covalent conjugation with electrides resulted in up to a 52% enhancement in SWNT near-infrared fluorescence.
• Field emission current density of electride-SWNT-silver paste increased dramatically by a factor of 46,000, reaching 14.8 mA cm^-2 at 2 V μm^-1, with a low turn-on voltage of 0.85 V μm^-1.

Conclusions:

• The structure of inorganic electrides significantly influences their electron-donating capability.
• [Ca(2)N](+)·e(-) is a highly effective electron donor for modifying SWNT properties.
• Electride-SWNT composites show promising applications in enhanced fluorescence and field emission devices.