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In this work, an easy, reliable, effective approach for preparation of modified Boron Nitride (BN) from h-BN (Hexagonal boron nitride) was developed via liquid-phase exfoliation using a dopamine chemistry. Supramolecular interactions of the polydopamine (PDA) with h-BN has been used to achieve the facile surface modification of h-BN by forming a PDA shell on its surface. The successful and effective preparation of different h-BN-PDA hybrids has been confirmed by Scanning Electron Microscopy (SEM), Raman spectroscopy, XRD, IR and TGA investigations. The PDA coating increases the dispersibility of these hybrids as filler in polymers. Since polymer-based thermal interface materials (TIMs) with excellent thermal conductivity and electrical resistivity are in high demand, epoxy composites filled with h-BN, BBN (Ball milled Boron Nitride), MBN (Modified Boron Nitride) and MBBN (Modified Ball milled Boron Nitride) were processed. The thermal conductivity is as high as 4 W/mK for MBBN as compared with 0.2 W/mK of neat epoxy. This method of producing multifunctional exfoliated h-BN provides eco-friendly, easy handling, and suitable as a unique paradigm for developing the next generation of thermal conductive devices and solution-processed semiconductors.

Photochromic molecules derived from bioresources and their hybrids with various carbon nanomaterials always resulted in devices with outstanding performance. Among different carbon nanomaterials su...

Carbon is an elite element when coming to the material research field [1]. Carbon has delivered numerous useful nanostructures including carbon nanotube [2], graphene, etc. [3]. The history of carbon nanomaterials began with the synthesis of graphene oxide from graphite, and it was named as ‘graphon’ in the older time [4]. Then a large number modified synthetic procedures were developed for the production of graphene oxide in bulk quantity [5]. Along with these developments, the invention of fullerene, an important allotrope of carbon, occurred [6], and it was followed by the discovery of one-dimensional carbon nanotubes [7]. At the same time, the existence of single sheet of graphite was a hot topic of debate, and its existence was only theoretical until in 2011 the monolayer graphene through scotch-tape technique was synthesized [8]. The other important carbon nanomaterials invented include nano-horns [9], nano-onions [10], etc. Thus, the carbon nanomaterial family included members in various dimensions ranging from zero to three.

The process of utilizing organic molecules for tuning carbon nanomaterials has paved the way to a tremendous revolution in organic electronics, especially in developing field effect transistors, memory devices etc. Here we report the influence of insulating photochromic molecules on the conductance behaviour of carbon nanomaterials. Azobenzene derived from cardanol was functionalized with reduced graphene oxide and this combination showed a phototunable conductance behaviour with the light induced trans–cis isomerisation of an azo moiety. The difference in the mode of interaction between the two moieties, i.e. covalent and non-covalent functionalization, influences the photoconductance behaviour of reduced graphene oxide. The rate constant of photoisomerisation for the covalent hybrid is 0.04259 and for the non-covalent hybrid is 0.04687. Similarly, the photoresponse ratio calculated for the covalent hybrid system is 0.178 and the same for the non-covalent hybrid is 0.571. This clearly implies that the non-covalent mode offers better tuning of photoconductance than the covalent mode as the latter can cause a larger restriction in the photo-isomerisation activity of the azosystem. This finding will lead to more development in the area of sustainable molecular electronics.

Emerging Graphene Quantum Dots (GQDs)—a new member of the carbon family—have attracted a tremendous research interest in the scientific community due to their small size and tunable photoluminescence properties. Even though a plethora of reports discuss the synthesis of GQDs using various methods, this study introduces the reader to the most recent and important progress regarding the synthesis of GQDs from different bioresources and highlights their applications in various fields.

Hexa-peri-hexabenzocoronene (HBC) substituted by six benzothiadiazole (BTZ) units with ethynylene bridges was synthesized as a new donor-acceptor (D-A) motif. The C≡C bridges significantly reduce the dihedral angles between HBC and BTZ, and thus lead to a planar molecular conformation as predicted by density functional theory (DFT) calculations. The optoelectronic properties were investigated by UV-vis absorption and emission spectroscopies with absorption and emission maxima at 424 and 650 nm, respectively, indicating tunable electronic structures of HBC by attaching electron-withdrawing BTZ units . Two-dimensional wide-angle X-ray scattering (2D-WAXS) analysis manifested that the molecules self-assembled into liquid crystalline columns with high stability over a wide temperature range. Scanning tunneling microscopy (STM) revealed the formation of ordered bilayers of the D-A molecules with star-shaped structures.

Herein, we describe the role of end functional groups in the self-assembly of amide-functionalized oligo(p-phenylenevinylene) (OPV) gelators with different end-groups. The interplay between hydrogen-bonding and π-stacking interactions was controlled by the bulkiness of the end functional groups, thereby resulting in aggregates of different types, which led to the gelation of a wide range of solvents. The variable-temperature UV/Vis absorption and fluorescence spectroscopic features of gelators with small end-groups revealed the formation of 1D H-type aggregates in CHCl(3). However, under fast cooling in toluene, 1D H-type aggregates were formed, whereas slow cooling resulted in 2D H-type aggregates. OPV amide with bulky dendritic end-group formed hydrogen-bonded random aggregates in toluene and a morphology transition from vesicles into fibrous aggregates was observed in THF. Interestingly, the presence of bulky end-group enhanced fluorescence in the xerogel state and aggregation in polar solvents. The difference between the aggregation properties of OPV amides with small and bulky end-groups allowed the preparation of self-assembled structures with distinct morphological and optical features.

The development of soft nanomaterials by the controlled self-assembly of molecules derived from renewable sources has become a major area of interest for scientists across the world. Our attempt in this paper is to report the self-assembly of a cardanol based photoswitchable molecule in non polar solvents such as cyclohexane. The self-assembly of molecule 1 leads to the formation of nanospheres and it is transformed under UV light. This could be seen as an example of light induced size variation at the nanoscale.

Tuning the microstructure, conductance, band gap of a single molecule with an external stimuli such as light have vital importance in nanoscale molecular electronics. Azobenzene systems are inimitable light responsive molecules suitable for the development of optically modulated materials. In this work we have demonstrated the development of an optically active Multiwalled Carbon Nanotube (MWCNT)-hybrid material by the noncovalent functionalization of azo based chromophore derived from cardanol, a bioresource material. This photoresponsive noncovalent hybrid shows trans–cis photoisomerization induced switching of conductance. We report this as the first example in which the photochromic assembly developed from a bioresource material exhibited tunable conductivity. We expect that this novel photoswitchable hybrid with reversible conductance may have potential applications in nanoscale molecular electronics, solar cells, OLEDs, etc.

The properties of graphene nanoribbons (GNRs) make them good candidates for next-generation electronic materials. Whereas 'top-down' methods, such as the lithographical patterning of graphene and the unzipping of carbon nanotubes, give mixtures of different GNRs, structurally well-defined GNRs can be made using a 'bottom-up' organic synthesis approach through solution-mediated or surface-assisted cyclodehydrogenation reactions. Specifically, non-planar polyphenylene precursors were first 'built up' from small molecules, and then 'graphitized' and 'planarized' to yield GNRs. However, fabrication of processable and longitudinally well-extended GNRs has remained a major challenge. Here we report a bottom-up solution synthesis of long (>200 nm) liquid-phase-processable GNRs with a well-defined structure and a large optical bandgap of 1.88 eV. Self-assembled monolayers of GNRs can be observed by scanning probe microscopy, and non-contact time-resolved terahertz conductivity measurements reveal excellent charge-carrier mobility within individual GNRs. Such structurally well-defined GNRs may prove useful for fundamental studies of graphene nanostructures, as well as the development of GNR-based nanoelectronics.

Ostwald ripening allows the synthesis of 1D nanorods of metal and semiconductor nanoparticles. However, this phenomenon is unsuccessful with organic π-systems due to their spontaneous self-assembly to elongated fibers or tapes. Here we demonstrate the uses of light as a versatile tool to control the ripening of amorphous organic nanodots (ca. 15 nm) of an azobenzene-derived molecular assembly to micrometer-sized supramolecular rods. A surface-confined dipole variation associated with a low-yield (13-14%) trans-cis isomerization of the azobenzene moiety and the consequent dipole-dipole interaction in a nonpolar solvent is believed to be the driving force for the ripening of the nanodots to rods.

Morphology variation: The Boc-alanine linked OPV exhibits an unprecedented formation of periodic macroporous honeycomb structures in chloroform and aligned fiber bundles in toluene (see SEM images). This represents a unique example for a distinct morphology change of an organogelator from macroporous honeycomb to aligned fiber bundles upon changing the solvent.

Nanodonuts: A hydrogen-bonded cyclic assembly (rosette, left) of a melamine featuring π-conjugated oligo(p-phenyleneethynylene) hierarchically self-organizes with a cyanurate in decane under dilute conditions to form toroidal nanostructures (right) with a diameter of 40 nm.

Coassembly of short molecular wires OPE1 with chiral analogues OPE2, both of which are CD silent, exhibited a sergeant-and-soldiers effect that resulted in transformation of vesicular aggregates of OPE1 into CD-active helical nanotubes (see schematic picture), as revealed by CD, dynamic light scattering, and atomic force and transmission electron microscopies (TEM). OPE=oligo(p-phenyleneethynylene).

Wires to particles: A subtle balance of H-bonding, π-stacking, and van der waals interactions facilitates the concentration-controlled self-assembly of a short molecular wire (see figure) into nanoparticles and fluorescent microspheres in nonpolar hydrocarbon solvents. Above a critical concentration, a blue-light emitting organogel is formed.

A simple protocol to create nanofibers and -rings through a rational self-assembly approach is described. Whereas the melamine-oligo(p-phenylenevinylene) conjugate 1a self-aggregates to form ill-defined nanostructures, conjugate 1b, which possesses an amide group as an additional interactive site, self-aggregates to form 1D nanofibers that induce gelation of the solvent. AFM and XRD studies have shown that dimerization through the melamine-melamine hydrogen-bonding interaction occurs only for 1b. Upon complexation with 1/3 equivalents of cyanuric acid (CA), conjugate 1a provides well-defined, ring-shaped nanostructures at micromolar concentrations, which open to form fibrous assemblies at submillimolar concentrations and organogels in the millimolar concentration range. Apparently, the enhanced aggregation ability of 1a by CA is a consequence of columnar organization of the resulting discotic complex 1a(3).CA. In contrast, coaggregation of 1b with CA does not provide well-defined nanostructures, probably due to the interference of complementary hydrogen-bonding interactions by the amide group.

The reversible shift of emission in fluorescent molecular gelators has been explored for the preparation of a composite polymer film useful for erasable thermal imaging and secret documentation. A gelation-assisted photopolymerization of styrene allowed the entrapment of the fluorescent gelator molecules within a polystyrene matrix with a weak green fluorescence, which upon heating above the T(g) of the polymer resulted in high-contrast fluorescence images due to the strong blue fluorescence of the individual molecules. The blue emission from the disassembled oligo(p-phenylenevinylene) molecules (OPVs) could be reversed to the green emission of the self-assembled OPVs by exposing the polymer film to chloroform vapors. The thermally written images are visible only under UV light and cannot be photocopied. A solvent-vapor-controlled recreation of the self-assembly of a fluorescent organogelator within a polymer matrix and its application in erasable secret documentation has not been reported previously.

Melamine-functionalized tri(p-phenyleneethynylene) 1 self-assembles to form opaque and weak gels in aliphatic solvents which turned transparent and stable upon addition of a cyanurate, affording supramolecular nanostructures with distinct physical properties.