Synthesis of N-Heteroarenemethyl Esters via C–C Bond Cleavage of Acyl Cyanides Under Transition Metal-Free Conditions

A practical method to synthesize N-heteroaryl esters from N-heteroaryl methanols with acyl cyanides via C–C bond cleavage without using any transition metal is demonstrated here. The use of Na₂CO₃/15-crown-5 couple enables access to a series of N-heteroaryl esters in high efficiency. This protocol is operationally simple and highly environmentally benign producing only cyanides as byproducts.

Calixarene-mediated assembly of water-soluble C60-attached ultrathin graphite hybrids for efficient activation of reactive oxygen species to treat neuroblastoma cells

Unprecedented nano-carbon hybrids consisting of exfoliated ultrathin graphite (or single-walled carbon nanotubes) with pristine C₆₀ molecules attached on the surfaces have been produced in water in the presence of p-phosphonic acid calix[8]arene. The amphiphilic calixarene plays multiple roles in these processes to provide water dispersibility and π-π interactions with flexible conformations complementing curvatures of the carbon surfaces. The significantly increased water solubility and area of exposure of C₆₀ enable efficient activation of reactive oxygen species for enhanced phototoxicity to SH-SY5Y human neuroblastoma cell line under laser irradiation.

Vortex fluidic mediated synthesis of polysulfone

Polysulfone (PSF) was prepared under high shear in a vortex fluidic device (VFD) operating in confined mode, and its properties compared with that prepared using batch processing. This involved reacting the pre-prepared disodium salt of bisphenol A (BPA) with a 4,4'-dihalodiphenylsulfone under anhydrous conditions. Scanning electron microscopy (SEM) established that in the thin film microfluidic platform, the PSF particles are sheet-like, for short reaction times, and fibrous for long reaction times, in contrast to spherical like particles for the polymer prepared using the conventional batch synthesis. The operating parameters of the VFD (rotational speed of the glass tube, its tilt angle and temperature) were systematically varied for establishing their effect on the molecular weight (M w), glass transition temperature (T g) and decomposition temperature, featuring gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) respectively. The optimal VFD prepared PSF was obtained at 6000 rpm rotational speed, 45° tilt angle and 160 °C, for 1 h of processing with M w ∼10 000 g mol-1, T g ∼158 °C and decomposition temperature ∼530 °C, which is comparable to the conventionally prepared PSF.

Vertically aligned laser sliced MWCNTs

Applications of multi-walled carbon nanotubes (MWCNTs) benefit from the availability of specific lengths of the material while keeping the outer walls pristine, for example, for applications requiring vertically aligned tubes. To this end, a simple and effective continuous flow 'top down' process to control the length of sliced MWCNTs has been developed using a vortex fluidic device (VFD) coupled with a 1064 nm pulse laser, with the process in the absence of chemicals and any auxiliary substances. Three different length distributions of the sliced MWCNTs, centered at 75 ± 2.1 nm, 300 ± 1.8 nm and 550 ± 1.4 nm, have been generated with the length depending on the VFD operating parameters and laser energy, with the processing resulting in a decrease in side wall defects of the material. We also show the ability to vertically self assemble short MWCNTs on a silicon substrate with control of the surface density coverage using a simple dipping and rinsing method.

High-Yield Continuous-Flow Synthesis of Spheroidal C60@Graphene Composites as Supercapacitors

Graphene spheres confining fullerene C60 are quantitatively formed under high-shear and continuous-flow processing using a vortex fluidic device (VFD). This involves intense micromixing a colloidal suspension of graphite in DMF and an o-xylene solution of C60 at room temperature in the absence of surfactants and other auxiliary substances. The diameters of the composite spheres, C60@graphene, can be controlled with size distributions ranging from 1.5 to 3.5 μm, depending on the VFD operating parameters, including rotational speed, flow rate, relative ratio of C60 to graphite, and the concentration of fullerene. An electrode of the composite material has high cycle stability, with a high areal capacitance of 103.4 mF cm-2, maintaining its capacitances to 24.7 F g-1 and 86.4 mF cm-2 (83.5%) at a high scan rate of 100 mV s-1.

Three-step-in-one synthesis of supercapacitor MWCNT superparamagnetic magnetite composite material under flow

Composites of multi-walled carbon nanotubes (MWCNTs) and superparamagnetic magnetite nanoparticles, Fe3O4@MWCNT, were synthesized in DMF in a vortex fluidic device (VFD). This involved in situ generation of the iron oxide nanoparticles by laser ablation of bulk iron metal at 1064 nm using a pulsed laser, over the dynamic thin film in the microfluidic platform. The overall processing is a three-step in one operation: (i) slicing MWCNTs, (ii) generating the superparamagnetic nanoparticles and (iii) decorating them on the surface of the MWCNTs. The Fe3O4@MWCNT composites were characterized by transmission electron microscopy, scanning transmission electron microscope, TG analysis, X-ray diffraction and X-ray photoelectron spectroscopy. They were used as an active electrode for supercapacitor measurements, establishing high gravimetric and areal capacitances of 834 F g-1 and 1317.7 mF cm-2 at a scan rate of 10 mV s-1, respectively, which are higher values than those reported using similar materials. In addition, the designer material has a significantly higher specific energy of 115.84 W h kg-1 at a specific power of 2085 W kg-1, thereby showing promise for the material in next-generation energy storage devices.

p-Phosphonic acid calix[8]arene mediated synthesis of ultra-large, ultra-thin, single-crystal gold nanoplatelets

Large, ultrathin, single-crystal gold platelets are produced in the presence of p-phosphonic acid calix[8]arene as both a catalyst and stabiliser.

Controlling the growth of fullerene C60 cones under continuous flow

Micromixing of an o-xylene solution of C60 with N-N-dimethylformamide (DMF) at room temperature under continuous flow in a vortex fluidic device (VFD) results in the formation of symmetrical right cones in high yield with diameters 0.5 to 2.5 μm, pitch angle 25° to 55° and wall thickness 120 to 310 nm. Their formation is in the absence of surfactants and any other reagents, and is scalable. The cones are formed at specific operating parameters of the VFD, including rotational speed, flow rate and concentration, and varying these results in other structures such as grooved fractals. Other aromatic solvents in place of o-xylene results in the formation of rods, spicules and prisms, respectively for m-xylene, p-xylene and mesitylene.

Facile sonochemical synthesis of highly dispersed ultrafine Pd nanoparticle decorated carbon nano-onions with high metal loading and enhanced electrocatalytic activity

Highly dispersed, ultrafine Pd nanoparticle decorated carbon nano-onions (CNO) were prepared by a facile, one-step sonochemical method.

Towards aryl C-N bond formation in dynamic thin films

C-N bond forming reactions are important in organic chemistry. A thin film microfluidic vortex fluidic device (VFD) operating under confined mode affords N-aryl compounds from 2-chloropyrazine and the corresponding amine, without the need for a transition metal catalyst.

Shear induced fabrication of intertwined single walled carbon nanotube rings

Thin film microfluidic shearing of a mixture of toluene dispersed single walled carbon nanotubes (SWCNTs) and water in a vortex fluidic device results in SWCNT nanorings (and related structures), diameters 100 to 200 nm or 300 to 700 nm, for respectively 10 mm or 20 mm diameter rotating tubes.

Room temperature vortex fluidic synthesis of monodispersed amorphous proto-vaterite

Monodispersed particles of amorphous calcium carbonate (ACC) 90 to 200 nm in diameter are accessible at room temperature in ethylene glycol and water using a vortex fluidic device (VFD). The ACC material is stable for at least two weeks under ambient conditions.

Microencapsulation of bacterial strains in graphene oxide nano-sheets using vortex fluidics

Microencapsulation of bacterial cells with different shapes in graphene oxide (GO) layers is effective using a vortex fluidic device, with the bacterial cells showing restricted cellular growth with their biological activity sustained.

Continuous flow vortex fluidic synthesis of silica xerogel as a delivery vehicle for curcumin

Sol–gel synthesis of silica xerogel using a continuous flow vortex fluidic device at room temperature is effective in direct incorporation of preformed curcumin particles, which has antimicrobial activity against Staphylococcus aureus.

Facile synthesis of electrochemically active Pt nanoparticle decorated carbon nano onions

Well dispersed platinum nanoparticles (∼2 nm) on carbon nano-onions are accessible using a simple and scalable one-step batch method.

Carbon nanofibres from fructose using a light-driven high-temperature spinning disc processor

A novel high flux bright light-driven high temperature spinning disc processor operating at ∼720 °C can effectively synthesise carbon nanofibres from fructose, a natural feedstock, in polyethylene glycol-200, within minutes and with multiple reactor passes being a pivotal operating parameter in controlling the growth of the fibres.

Stereospecific synthesis of resorcin[4]arenes and pyrogallol[4]arenes in dynamic thin films

Acid catalysed condensation of resorcinol and pyrogallol with aromatic aldehydes using a microfluidic vortex fluidic device (VFD) under continuous flow conditions results in the selective formation of resorcin[4]arenes and pyrogallol[4]arenes as predominantly their C(4v) isomers. Notably C(2v) isomers and C(2h) isomers can be also prepared with the latter being converted to the C(4v) isomer when the VFD operates in confined mode.

Optimising a vortex fluidic device for controlling chemical reactivity and selectivity

A vortex fluidic device (VFD) involving a rapidly rotating tube open at one end forms dynamic thin films at high rotational speed for finite sub-millilitre volumes of liquid, with shear within the films depending on the speed and orientation of the tube. Continuous flow operation of the VFD where jet feeds of solutions are directed to the closed end of the tube provide additional tuneable shear from the viscous drag as the liquid whirls along the tube. The versatility of this simple, low cost microfluidic device, which can operate under confined mode or continuous flow is demonstrated in accelerating organic reactions, for model Diels-Alder dimerization of cyclopentadienes, and sequential aldol and Michael addition reactions, in accessing unusual 2,4,6-triarylpyridines. Residence times are controllable for continuous flow processing with the viscous drag dominating the shear for flow rates >0.1 mL/min in a 10 mm diameter tube rotating at >2000 rpm.

Spinning up the polymorphs of calcium carbonate

Controlling the growth of the polymorphs of calcium carbonate is important in understanding the changing environmental conditions in the oceans. Aragonite is the main polymorph in the inner shells of marine organisms, and can be readily converted to calcite, which is the most stable polymorph of calcium carbonate. Both of these polymorphs are significantly more stable than vaterite, which is the other naturally occurring polymorph of calcium carbonate, and this is reflected in its limited distribution in nature. We have investigated the effect of high shear forces on the phase behaviour of calcium carbonate using a vortex fluidic device (VFD), with experimental parameters varied to explore calcium carbonate mineralisation. Variation of tilt angle, rotation speed and temperature allow for control over the size, shape and phase of the resulting calcium carbonate.

Shear flow assisted decoration of carbon nano-onions with platinum nanoparticles

Aqueous based controlled decoration of platinum nanoparticles on plasma treated carbon nano-onions (CNOs) occurs within the shear flow generated by a vortex fluidic device (VFD), using ascorbic acid as the reducing agent, with the electrocatalytic potential of the resulting Pt-NPs@CNOs nano-composites demonstrated.

Lab-on-a-chip synthesis of inorganic nanomaterials and quantum dots for biomedical applications

The past two decades have seen a dramatic raise in the number of investigations leading to the development of Lab-on-a-Chip (LOC) devices for synthesis of nanomaterials. A majority of these investigations were focused on inorganic nanomaterials comprising of metals, metal oxides, nanocomposites and quantum dots. Herein, we provide an analysis of these findings, especially, considering the more recent developments in this new decade. We made an attempt to bring out the differences between chip-based as well as tubular continuous flow systems. We also cover, for the first time, various opportunities the tools from the field of computational fluid dynamics provide in designing LOC systems for synthesis inorganic nanomaterials. Particularly, we provide unique examples to demonstrate that there is a need for concerted effort to utilize LOC devices not only for synthesis of inorganic nanomaterials but also for carrying out superior in vitro studies thereby, paving the way for faster clinical translation. Even though LOC devices with the possibility to carry out multi-step syntheses have been designed, surprisingly, such systems have not been utilized for carrying out simultaneous synthesis and bio-functionalization of nanomaterials. While traditionally, LOC devices are primarily based on microfluidic systems, in this review article, we make a case for utilizing millifluidic systems for more efficient synthesis, bio-functionalization and in vitro studies of inorganic nanomaterials tailor-made for biomedical applications. Finally, recent advances in the field clearly point out the possibility for pushing the boundaries of current medical practices towards personalized health care with a vision to develop automated LOC-based instrumentation for carrying out simultaneous synthesis, bio-functionalization and in vitro evaluation of inorganic nanomaterials for biomedical applications.

High-yield synthesis of silicon carbide nanowires by solar and lamp ablation

We report a reasonably high yield (~50%) synthesis of silicon carbide (SiC) nanowires from silicon oxides and carbon in vacuum, by novel solar and lamp photothermal ablation methods that obviate the need for catalysis, and allow relatively short reaction times (~10 min) in a nominally one-step process that does not involve toxic reagents. The one-dimensional core/shell β-SiC/SiOx nanostructures-characterized by SEM, TEM, HRTEM, SAED, XRD and EDS-are typically several microns long, with core and outer diameters of about 10 and 30 nm, respectively. HRTEM revealed additional distinctive nanoscale structures that also shed light on the formation pathways.

Vortex fluidic entrapment of functional microalgal cells in a magnetic polymer matrix

Composite materials based on superparamagnetic magnetite nanoparticles embedded in polyvinylpyrrolidone (PVP) are generated in a continuous flow vortex fluidic device (VFD). The same device is effective in entrapping microalgal cells within this material, such that the functional cells can be retrieved from aqueous dispersions using an external magnet.