Abstract
Tuneable pressure effects associated with changing interlayer distances in two-dimensional graphene oxide (GO)/reduced GO (rGO) layers are demonstrated through monitoring the changes in the spin-crossover (SCO) temperature (T1/2) of [Fe(Htrz)2(trz)](BF4) nanoparticles (NPs) incorporated in the interlayer spaces of the GO/rGO layers. The interlayer separation along the GO to GO/rGO-NP composites to rGO series decreases smoothly from 9.00 Å (for GO) to 3.50 Å (for rGO) as the temperature employed for the thermal reduction treatments of the GO-NP composites is increased. At the same time, T1/2 increases from 351 K to 362 K along the series. This T1/2 increment of 11 K corresponds to that observed for pristine [Fe(Htrz)2(trz)](BF4) NPs under a hydrostatic pressure of 38 MPa. The influence of the stacked layer structures on the pseudo-pressure effects has been further probed by investigating the differences in T1/2 for [Fe(Htrz)2(trz)](BF4) that is present in the composite as larger bulk particles rather than as NPs.
Highlights
Van der Waals interactions in the pores of micro-porous materials are known to generate a confinement effect for guest species[1,2,3,4]
In order to demonstrate the presence of pressure effects in graphene oxide (GO)/reduced graphene oxide (rGO) layer structures, we have focused on spin-crossover (SCO) phenomena that occurs for [Fe(Htrz)2(trz)](BF4) nanoparticles (NPs) confined in the interlayer spaces
The transformations from GO to rGO in these composites were corroborated by investigating their current-voltage (IV) properties, X-ray photo-electron spectroscopy (XPS) spectra, thermogravimetric (TG) behaviour and Raman spectra (Supplementary Figures [3, 4, 5] and 6)
Summary
Van der Waals interactions in the pores of micro-porous materials are known to generate a confinement effect for guest species[1,2,3,4]. In the graphene sheet case, an extended H-bond network forms between water and methanol, giving rise to the formation of such a stable 2D structure In these cases, the relationship between the resulting pressure (P) and the interlayer distance (d) is given by P ≈ Ew/d, where Ew is the adhesion energy[8,9,10]. In order to demonstrate the presence of pressure effects in GO/rGO layer structures, we have focused on spin-crossover (SCO) phenomena that occurs for [Fe(Htrz)2(trz)](BF4) nanoparticles (NPs) confined in the interlayer spaces. We demonstrate that pseudo-pressure effects, generated by transformation of GO to rGO, leads to changes in T1/2 for [Fe(Htrz)2(trz)](BF4) NPs that are accommodated between the GO/rGO layers. T1/2 shows a smooth increase as the interlayer distance is decreased, demonstrating the presence of tuneable pressure effects in the GO/rGO layers
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