Surface Charge Manipulation on Diamond and its Applications in Water Filtration
Lead Research Organisation:
Cardiff University
Department Name: School of Physics and Astronomy
Abstract
Initial work will focus on the manipulation of diamond nanoparticle surface chemistry, in order to drive guided self-assembly on defined surfaces. This technique will allow control over the positioning of nanodiamond particles with nanoscale resolution.
Following this, Chemical Vapour Deposition (CVD) will be used to grow diamond on these nanoparticles, with the addition of Silicon or Nitrogen precursors, in order to create single photon sources.
Finally, the design and construction of a novel CVD system is proposed, for the incorporation of new materials into diamond. Elements including Ni, Cr, W, Al will be introduced into diamond, and investigations into the defects they create will be carried out, as possible new single photon sources.
Following this, Chemical Vapour Deposition (CVD) will be used to grow diamond on these nanoparticles, with the addition of Silicon or Nitrogen precursors, in order to create single photon sources.
Finally, the design and construction of a novel CVD system is proposed, for the incorporation of new materials into diamond. Elements including Ni, Cr, W, Al will be introduced into diamond, and investigations into the defects they create will be carried out, as possible new single photon sources.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509449/1 | 01/10/2016 | 30/09/2021 | |||
| 1938439 | Studentship | EP/N509449/1 | 01/10/2017 | 31/07/2021 | Henry Bland |
| Description | Relating to the published work, 'Superconducting diamond on silicon nitride for device applications' - Chemical vapour deposition (CVD) grown nanocrystalline diamond is an attractive material for the fabrication of devices. For some device architectures, optimisation of its growth on silicon nitride is essential. Here, the effects of three pre-growth surface treatments, often employed as cleaning methods, were investigated. Such treatments provide control over the surface charge of the silicon nitride substrate through modification of the surface functionality, allowing for the optimisation of electrostatic diamond seeding densities. Zeta potential measurements and X-ray photoelectron spectroscopy (XPS) were used to analyse the silicon nitride surface following each treatment. Exposing silicon nitride to an oxygen plasma offered optimal surface conditions for the electrostatic self-assembly of a hydrogen-terminated diamond nanoparticle monolayer. The subsequent growth of boron-doped nanocrystalline diamond thin films on modified silicon nitride, under CVD conditions, produced coalesced films for oxygen plasma and solvent treatments, whilst pin-holing of the diamond film was observed following RCA-1 treatment. The sharpest superconducting transition was observed for diamond grown on oxygen plasma treated silicon nitride, demonstrating it to be of the least structural disorder. Modifications to the substrate surface optimise the seeding and growth processes for the fabrication of diamond on silicon nitride devices. Relating to the patent application 'filter element for liquid filtration GB1916744.4' - The filtration of nanoscale contaminants like viruses from the water supply is a critical problem for clean drinking water worldwide. Filtration based on size offers up clear logistical and cost related limitations. Filtration based instead on charge offers a mechanism that bypasses the limitations of size exclusion filtration. However, most filter elements are negatively charged, making them ineffective in removing negatively charged contaminants, like viruses. We switch the zeta potential (surface charge) of a quartz fibre filter by loading with positively charged diamond nanoparticles. The resulting filters are able to effectively filter negatively charged nano-contaminants from the water supply. These filters were robust to continuous filtration. Relating to the unpublished work, 'Electropositive Nanodiamond-Coated Quartz Microfiber Membranes for Targeted Water Filtration' - Electropositive membranes demonstrating high flux at low pressure differentials show great promise as universal separation platforms for viruses and other charged entities when centralized systems of water and power are scarce. However, the fabrication of a suitably stable membrane with optimal electrostatic characteristics remains a challenge. Here, hydrogenated detonation nanodiamond was loaded onto a quartz microfiber support membrane and coupled to the membrane surface under a high vacuum annealing process. The fabricated membranes display a zeta potential of +45 mV at pH 7 and an isoelectric point around pH 11; to our knowledge it is the highest zeta potential observed for any separation platform in the literature. We show that the nanodiamond coating is robust to prolonged periods of water flow by performing extensive membrane zeta potential measurements, and water filtration tests demonstrated excellent retention of the electronegative probe molecule acid black 2 and at least a 6.2 log10 reduction in MS2 bacteriophage (>99.9999%). Relating to unpublished work on the occurrence of positive surface charge (basic surface properties) of carbon based species following annealing under hydrogen - Diamond particles assume a positive surface charge, or zeta potential, when annealed in hydrogen. Several explanations have been given for the phenomenon, however, the most widely accepted points towards the need for a non-pristine, sp2 carbon rich, diamond surface. Under these conditions, an interaction between graphitic ring systems and hydronium ions, at the solid-liquid interface, is proposed to be the cause of the positive charge. Nevertheless, the relationship between sp2 carbon at the diamond surface and a positive shift in zeta potential has not been examined experimentally. Using bulk pCVD diamond as a model surface, we expose the diamond to successive graphitisation and hydrogenation conditions in order to establish sp2 at the surface. Yet following such procedures, we were unable to detect a positive surface change on the diamond material, and so the source of the positive charge is still unknown. We new seek to use a modified Boehm titration to quantify specific oxygen based functional groups that are present on positively charged diamond particles, and high vacuum FTIR. |
| Exploitation Route | Relating to the published work, 'Superconducting diamond on silicon nitride for device applications' - Oxidation of a substrate surface under an oxygen plasma should find regular use prior to the growth of CVD diamond on silicon nitride, especially for device applications where control over the nature of the film is critical. Applications include diamond based bolometers and microcalorimeters. Relating to the patent application 'filter element for liquid filtration GB1916744.4' - The outcomes are clear and obvious. The work has shown a proof of principle that diamond can be used to filter negatively charged entities such as viruses, bacteria, and by-products of industry, from a water supply without any need for electrical input. The filter material may be developed into a commercial filter, or added to existing filtration systems. |
| Sectors | Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Electronics,Environment,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology |