Single Crystal Organic Nanoflowers

Abstract

Nano-flowers reported so far were mostly constituted of inorganic or hybrid materials. We have synthesized and crystallized a new organic compound, 1, 2-bis(tritylthio)ethane forming an organic nano-flower consisting of single crystalline petals. Crystal structure at nano and micro level indicates that π-π stacking interactions between aromatic systems is the principal factor governing molecular recognition and assembly. Single crystal X-ray Diffraction (S-XRD) supported by Selective Area Electron Diffraction (SAED) experiments indicate the single crystalline nature of the flower-like assembly even at the nanoscale. In order to fabricate the nanoflower as a potential stimulus responsive material; the 'petals' were coated with magnetite nanoparticles, verified by Energy-dispersive X-ray spectroscopic (EDX) analysis. Herein, we have further tested the potential utility of the hybrid material in water remediation as a nano-based adsorbent for removal of heavy metals like chromium.

Figure 1

Synthesis, crystallization and nano-assembly of 1, 2-bis(tritylthio)ethane. (a) Scheme illustrating the reaction conditions for the synthesis and crystallization of 1, 2-bis(tritylthio)ethane. (b) ORTEP diagram of 1,2-bis(tritylthio)ethane. (c) The schematic unit cell of 1, 2-bis(tritylthio)ethane, showing the type of interactions in phenyl embraces (The green dashed line indicates T shaped edge to face interaction, and the red dotted line indicates parallel displaced orientation). (d) False-colored FE-SEM image showing flower like assembly.

Figure 2

Morphological and structural characterization of 1, 2-bis(tritylthio)ethane assemblies. (a,b) FE-SEM images of different structural morphologies formed by 1, 2-bis(tritylthio)ethane; (a) plate-like assemblies and (b) nanoflower (False coloured in blue). (c,d) TEM images showing (d) nanoflowers made from (c) individual plate-like morphologies. (e) P-XRD of plate-like structures. (f) SAED pattern of the flower with a diffraction spot indexed as (008), verify the constitution and single crystalline nature of the flower at nano-level.

Figure 3

Characterization of magnetite coated 1, 2-bis(tritylthio)ethane assemblies. TEM analysis (a) showing the impregnation of magnetite on to the nano-assembled plate-like structure, and its EDX confirming the attachment of magnetite. FE-SEM micrograph of the magnetite coated plate (b) and flower-like morphologies (c) with insets showing the enlarged view of the coated areas. Magnetite nanoparticles in the insets are false-colored (green) for better understanding. Elemental mapping of the highlighted areas in the nanoassemblies (d,e) further confirms the dispersion of magnetite on the entire surface.

Figure 4

Elemental distribution on the surface of nanoassemblies probed by EDS-mapping. TEM and EDX spectra of chromium (Cr) sequestered hybrid material (a). Backscattered electron image shown in the top left panel of figure b, to verify elemental composition. Elemental spot maps of C, S, Fe and Cr, measured by STEM-EDX, are shown in the following panels of (b), confirming the Cr sequestration on to the hybrid nano assembly.