Electronically Coupled, Two-Dimensional Assembly of Cu_1.1S Nanodiscs for Selective Vapor Sensing Applications

Abstract

We study temperature-dependent charge transport in two-dimensional assemblies of copper sulfide nanodiscs in the covellite crystal phase (Cu1.1S). To enhance interparticle coupling, we cross-link the nanocrystals with the organic π-system Cu-4,4′,4″,4‴-tetraaminophthalocyanine and observe an increase in the conductivity by 6 orders of magnitude. The electrical properties of monolayers of this hybrid ensemble are consistent with a two-dimensional semiconductor and exhibit two abrupt changes at discrete temperatures (120 and 210 K), which may be interpreted as phase changes. X-ray scattering experiments serve to study the importance of electronic conjugation in the organic π-system vs interparticle spacing for efficient charge transport. Applying the hybrid ensemble as a chemiresistor in organic vapor sensing experiments reveals a strong selectivity between polar and nonpolar analytes, which we discuss in light of the role of the organic π-system and its metal center.

Dye-Sensitized Ternary Copper Chalcogenide Nanocrystals: Optoelectronic Properties, Air Stability, and Photosensitivity

“…The fabrication process and ligand exchange were carried out in a home-built Teflon chamber according to our previously reported method. 5 2.4. Instrumentation: Scanning transmission electron microscopy (STEM, Hitachi SU 8030 microscope operating at 30 kV) is employed to determine the particle size and shape.…”

“…In view of a recent report on electric transport in similar Cu1.1S 12 NC ensembles, the Cu2SeyS1-y NCs investigated here resemble much more that of the binary sulphides than the selenides. 5 To further understand the electronic properties of CoTAPc-capped Cu2SeyS1-y NCs, we perform temperature-dependent resistivity measurements under high vacuum (Figure 4a). Throughout the entire temperature regime of 20-300 K, we observe monotonically increasing resistance with temperature, reminiscent of metallic behavior.…”

“…Copper chalcogenide nanocrystals (NCs) have become a subject of intense research as possible alternatives to the more toxic Cd or Pb-based counterparts for optoelectronic applications such as solar cells or photocatalysts, but also as thermoelectric converters, gas sensors, optical filters, superionic conductors and electro-optical devices. [1][2][3][4][5][6][7][8][9][10][11][12][13] A majority of these investigations focused on the binary compounds copper selenide (Cu2Se) and copper sulphide (Cu2S) with variable Cu(I) deficiency (e.g., Cu2-xSe, 0.00 ≤ x ≤ 0.6) and tailored charge carrier concentration as well as charge carrier concentration dependent localized plasmon resonance frequency (LSPR). 11,[14][15][16][17][18][19][20][21][22][23] Introducing Cu(I) vacancies is readily afforded by oxidizing parts of the chalcogenide sublattice into the (-I)-state, which leads to a loss of Cu(I)-ions and the release of free holes in the NC core.…”

“…31,32 For the binary, copper-deficient copper chalcogenide NCs, Cu2-xSe and Cu2-xS, several studies have been conducted to increase electronic coupling in thin films of these materials, for instance by removing the native ligand with smaller molecules or anions, by thermal decomposition of the insulating ligand sphere or by thermal doping. 3,5,19,20,[33][34][35][36][37][38][39][40] Specifically for Cu2-xSe NCs, several groups have reported that high electric conductivities (up to 25 Scm -1 ) may also be obtained without such post-synthetic ligand exchange, indicating that charge carrier transport in these NCs potentially follows a different mechanism than in copper sulphide where ligand exchange is usually necessary. [41][42][43][44] From the perspective of tailoring the optoelectronic properties of copper chalcogenide NCs by their surface chemistry, such ligand-independent transport characteristics are undesirable.…”

Chemiresistive Properties of a Novel Composite Comprised of ITO-Nanoparticles and 1,8-Diaminooctane

“…Nearly all composites use gold nanoparticles stabilized or linked with thiol based molecules. A replacement of the expensive noble metal nanoparticles with nanoparticles comprised of conductive oxides [2] or semiconductors [3] could reduce the cost of the sensor, enable transparent sensitive films, allow larger material variations for sensor arrays and may prevent long-term materials degradation.…”