Nanomechanical properties of ordered phthalocyanine Langmuir–Blodgett layers

Abstract

The mechanical properties of monolayer and multilayer structures of several symmetrically substituted alkoxy copper phthalocyanine, CuPc(OR)8, Langmuir–Blodgett (LB) films were evaluated. One-dimensional compliance of the monolayers was determined from the slopes of the surface pressure–area isotherms. Multilayers were examined using a SPM and a commercial nanoindentation system. The nanomechanical studies show a distinct relationship between the position and length of alkoxy substituents on the Pc macrocycle and the LB film elasticity and hardness. The phthalocyanine complexes with peripheral octabutoxy and octaoctyloxy substituents form stiff LB monolayers and multilayers. The nonperipheral alkoxy derivetized CuPc films were less stiff. For monolayer films, it appears that the extent of π-π interaction determines the strength of the film. In multilayers, significant additional stability can be imparted through interdigitation of long paraffinic chains which play a significant role in determining the interlayer structure of the LB layers.

Electron affinity states of metal supported phthalocyanines measured by tunneling spectroscopy

“…Monolayers and submonolayers of vapor deposited CuPc [30] on Au(111), as well as other metallophthalocyanines (CoPc, ZnPc, NiPc, and FePc) [25,30] all form beautiful close packed 2D structures where the molecules lie flat on the substrate surface. TSPc [31,53], CuTSPc [52], and pCuPc(OBu) 8 [28,29] on the other hand, all form cofacially packed Pc assemblies facilitated by strong p-p interaction between the adjacent chromophores. In highly acidic solutions, TSPc exhibits coherent columnar architecture with the phthalocyanine macrocycle planes aligned parallel to the substrate surface forming stacks [31,53], while the Pc chromophores in pCuPc(OBu) 8 [28,29] and CuTSPc [52] are aligned nearly vertical to the surface normal [28,29].…”

“…TSPc [31,53], CuTSPc [52], and pCuPc(OBu) 8 [28,29] on the other hand, all form cofacially packed Pc assemblies facilitated by strong p-p interaction between the adjacent chromophores. In highly acidic solutions, TSPc exhibits coherent columnar architecture with the phthalocyanine macrocycle planes aligned parallel to the substrate surface forming stacks [31,53], while the Pc chromophores in pCuPc(OBu) 8 [28,29] and CuTSPc [52] are aligned nearly vertical to the surface normal [28,29]. The detailed analysis of the Pc structures was reported by us in other publications and will not be presented here [28,29,31,53].…”

“…Copper(II) 2,3,9,10,16,17,23,24-octabuloxyphthalocyanine, pCuPc(OBu) 8 , was prepared using the synthetic method reported elsewhere [28,29]. The compound was recrystallized from THF and ethanol prior to use.…”

“…The pCuPc(OBu) 8 LB layer was prepared using the KSV 5000 LB double trough system by a procedure described earlier [28,29]. Aliquots (200-900 mL) of 1 × 10 -4 M to 2 × 10 -4 M solution of the complex dissolved in chloroform were spread on a MilliPore purified water subphase typically kept at approximately 20 °C.…”

Evaporation induced two-dimensional buckling within liquid droplet

“…7 Essentially, not only do surfactant and PS share similar atomic compositions but their similar molecular packing at the nanometer scale has downplayed their original difference in molecular weight to the observed mechanical properties. 13 Moreover, this aforementioned buckling model is suitable for all two dimensional problems. For a herringbonetype buckling, Audoly and Boudaoud have had an asymptotic solution.…”