Suela Kellici

Instant nano-hydroxyapatite: a continuous and rapid hydrothermal synthesis

Nano-particle hydroxyapatite (HA) rods, were rapidly synthesised using a three pump continuous hydrothermal process (using a water feed at up to 400 degrees C and at 24 MPa): the product was obtained as a highly crystalline and phase pure material, without the need for an ageing step or subsequent heat treatment.

High-throughput continuous hydrothermal flow synthesis of Zn-Ce oxides: unprecedented solubility of Zn in the nanoparticle fluorite lattice

High-throughput continuous hydrothermal flow synthesis has been used as a rapid and efficient synthetic route to produce a range of crystalline nanopowders in the Ce–Zn oxide binary system. High-resolution powder X-ray diffraction data were obtained for both as-prepared and heat-treated (850°C for 10 h in air) samples using the new robotic beamline I11, located at Diamond Light Source. The influence of the sample composition on the crystal structure and on the optical and physical properties was studied. All the nanomaterials were characterized using Raman spectroscopy, UV–visible spectrophotometry, Brunauer–Emmett–Teller surface area and elemental analysis (via energy-dispersive X-ray spectroscopy). Initially, for ‘as-prepared’ Ce1−xZnxOy, a phase-pure cerium oxide (fluorite) structure was obtained for nominal values of x=0.1 and 0.2. Biphasic mixtures were obtained for nominal values of x in the range of 0.3–0.9 (inclusive). High-resolution transmission electron microscopy images revealed that the phase-pure nano-CeO2 (x=0) consisted of ca 3.7 nm well-defined nanoparticles. The nanomaterials produced herein generally had high surface areas (greater than 150 m2 g−1) and possessed combinations of particle properties (e.g. bandgap, crystallinity, size, etc.) that were unobtainable or difficult to achieve by other more conventional synthetic methods.

Optical and photocatalytic behaviours of nanoparticles in the Ti–Zn–O binary system

Continuous hydrothermal flow synthesis (CHFS) has been used as a rapid and clean, synthetic method to produce a range of crystalline nanoparticles in the Ti–Zn–O binary system. The nanopowders were prepared from aqueous solutions of titanium(IV) bis(ammonium lactato)dihydroxide (TIBALD) and hydrated zinc nitrate, respectively, using a CHFS reactor which uses superheated water (at 400 °C and 24.1 MPa) as a reagent and crystallizing medium. The resulting nanopowders were heat-treated at 850 °C for five hours in air to give photoactive semiconductor mixtures of rutile and zinc oxide and/or zinc titanates. The as-prepared powders and their corresponding heat-treated mixed phase photocatalysts were characterized using powder X-ray synchrotron diffraction, transmission electron microscopy, BET surface area measurement, X-ray photoelectron spectroscopy and UV-Vis spectrophotometry. Because of the interest for these materials in UVA and UVB attenuating materials, the UV-Vis profiles of the nanocomposites and solid solutions were studied. Photocatalytic activity of the samples towards the decolourisation of methylene blue dye was also assessed.

Calixarene Assisted Rapid Synthesis of Silver-Graphene Nanocomposites with Enhanced Antibacterial Activity

Demonstrated herein is a single rapid approach employed for synthesis of Ag-graphene nanocomposites, with excellent antibacterial properties and low cytotoxicity, by utilizing a continuous hydrothermal flow synthesis (CHFS) process in combination with p-hexasulfonic acid calix[6]arene (SCX6) as an effective particle stabilizer. The nanocomposites showed high activity against E. coli (Gram-negative) and S. aureus (Gram-positive) bacteria. The materials were characterized using a range of techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis spectrophotometry, FT-IR, and X-ray powder diffraction (XRD). This rapid, single step synthetic approach not only provides a facile means of enabling and controlling graphene reduction (under alkaline conditions) but also offers an optimal route for homogeneously producing and depositing highly crystalline Ag nanostructures into reduced graphene oxide substrate.

Selective calixarene directed synthesis of MXene plates, crumpled sheets, spheres and scrolls

Fully exploiting the electronic and mechanical properties of 2D laminar materials not only requires efficient and effective means of their exfoliation into low dimensional layers, but also necessitates a means of changing their morphology so as to explore any enhancement that this may offer. MXenes are a rapidly emerging new class of such laminar materials with unique properties. However, access to other morphologies of MXenes has not yet been fully realised. To this end we have developed the synthesis of MXenes (Ti2 C) as plates, crumpled sheets, spheres and scrolls, which involves selective intercalation of p-phosphonic calix[n]arenes, with control in morphology arising from the choice of the size of the macrocycle, n=4, 5, 6, or 8. This opens up wider avenues of discovery/design for new morphologies from the wider family of MXenes beyond Ti2 C, along with opportunities to exploit any new physico-chemical properties proffered.

Controlled growth of titania nanospheres in supercritical carbon dioxide using a novel surfactant stabilised precursor

Titania nanospheres have been synthesised via the controlled hydrolysis of a mixture of novel precursor [Ti(OPri)3(Krytox)]n and titanium (IV) isopropoxide, [Ti(OPri)4], in supercritical carbon dioxide (sc-CO2). The use of sc-CO2 in the reaction, eliminates the need for organic solvents, optimises manufacturing efficiency and produces materials with tailored properties; additionally the use of the functionalised precursor [Ti(OPri)3(Krytox)]n, during co-hydrolysis with [Ti(OPri)4], gave a significantly narrower particle size distribution for the products than when the functionalised compound was not present.

Rapid synthesis of graphene quantum dots using a continuous hydrothermal flow synthesis approach.

A rapid, continuous, environmentally benign and innovative approach is employed for the synthesis of green fluorescent graphene quantum dots (GQD) with low cytotoxicity by utilising a Continuous Hydrothermal Flow Synthesis (CHFS) process as an efficient cutting tool in combination with calix[4]arene tetrasulfonic acid (SCX4) as an effective particle size limiting agent.

The Rapid Automated Materials Synthesis Instrument (RAMSI): A High Throughput Combinatorial Robot for Nanoceramics Discovery

A high throughput combinatorial robot RAMSI (Rapid Automated Materials Synthesis Instrument) has been developed for nanoceramics synthesis. It can rapidly produce nanoparticle libraries that can be used for new materials discovery. The RAMSI robot has 3 motor-driven axes moving in X-Y-Z space and linking the synthesis, cleanup and printing sections. A High Throughput Continuous Hydrothermal (HiTCH) flow synthesis reactor is contained within RAMSI, and reaches significant production capability of 48 tubes of 50mL samples in 8 hours. Supported by the high throughput hardware design, the control system adopts parallel operations and multi-task assignments. Key strategies include intelligent supernatant detection, dot printing protocols and robot arm route schedule etc. The commissioning of RAMSI showed its high efficiency by producing samples of yttrium hydroxide doped with europium. In a 6-hour experiment, 8 unique 100mL samples were synthesized then cleaned and printed into 96 dots (100 minutes only for synthesis time). The ceramic dots were heat-treated at different temperatures up to 1200°C and affixed into a well-plate library. The brightest phosphors could be readily identified by illumination under UV light.

New Pathways in the Synthesis of 2-Dimensional Materials

Our research focuses on designing and discovering new 2D and other (3D, 1D, 0D) advanced functional nanomaterials (utilizing a target-oriented approach) and technologies that provide effective solutions in the energy, biomedical and environmental applications.