Nanotechnology for Smart Materials in Water Treatment

Transcription

1 Nanotechnology for Smart Materials in Water Treatment Ivan Maximov Lund Nano Lab, Division of Solid State Physics Nanometer Structure Consortium, Lund University

2 Talk outline Introduction What is nanotechnology? Examples of nanostructures. Research at Nanometer Structure Consortium at Lund University Nanotechnology in water treatment Smart materials for water transport Conclusions

3 Introduction Nanotechnology: area of science and technology dealing with objects below 100 nm (1 nanometer=10-9 m 10 atoms). Typical size of those objects (nanostructures) is nm, i.e. few hundred atoms! National Nanotechnology Initiative (US) definition of nanotechnology: Research and technology development at the 1 to 100 nm range Create and uses structures with novel properties due to small size Nanotechnology builds on the ability to control at the atomic scale Semiconductor nanotechnology focuses on research on semiconductor (e.g. Si, GaAs etc) nanostructures.

4 DNA-molekyl What is nanotechnology? Influensavirus Atom Lus Transistor idag Ur-transistorn 1947

5 Nanoparticles TEM images of Ru/BN nanoparticles Hansen et al. Science 294, 1508 (2001) Shrinkage in size leads to larger number of atoms are on the surface surface/volume ratio increases. Practical significance for e.g. catalysis.

6 Nanoparticles in concrete: self-cleaning Dives in Misericordia church in Rome, Italy. TiO 2 nanoparticles + UV light: self-cleaning effects

7 CNT and fullerenes Carbon Nanotubes (CNT) and fullerenes are: Mechanically very strong Metallic or semiconducting Have good thermal conductivity Single- or multiple-wall Used in composite materials, electronics etc Easy to produce

8 Nanoelectronics Nanowire of InAs with two barriers of InP Physical size of nanostructures electron wavelength leads to quantum mechanical effects (tunnelling). Results in new controllable properties.

9 Nanophotonics Two-dimensional periodic stucture controls light of a specific wavelength Physical size of nanostructures wavelength of light. New possibilities to produce advanced optical devices.

10 How to make nanostructures? Top-down approach Key technology: highresolution lithography and pattern transfer Examples: "Nano-guitar" and an array of nanopillars made by electon beam and nanoimprint lithography. The scale bar is 1 µm.

11 How to make nanostructures? Bottom-up approach SEM images of epitaxial InP/InAs nanowires grown using Au seed particles (above) and self-organized domains of block-copolymers (right).

12 The Nanometer Structure Consortium at Lund University is Sweden's most modern and comprehensive research facility for nanoscale research. Founded in Material science and nanofabrication platform for: physics, chemistry, electronics and life-sciences. Engaging more than 200 scientists (PhD students and up) at 10% of their time or more. Three faculties: engineering (60%), natural sciences (30%), medical (10%) Participants from 26 Divisions, e.g. in Physics, Chemistry, Biology, Electrical Engineering, and the Medical faculty. Spin-off companies (GLO, Sol Voltaics, NEMS etc)

13 Research: semiconductor nanowires Long, crystalline needles, typically nm diameter and several micrometers long. Heterostructure, InAs/InP nanowire Björk et al., Nano Lett. 2002

14 Lund Nano Lab Lund Nano Lab (LNL) and cleanroom class ISO 5 (100)

15 How nanotechnology can help in water treatment and distribution? Worldwide some 780 million people still lack access to good quality water (WHO, 2012) Several aspects of water supply and treatment: Water purification, including organic substances and heavy metals removal, Disinfection and microbial control, Water quality monitoring and sensing, Transportation of water

16 Nanotechnology in water purification Size-dependent properties of nanomaterials for water treatment: High specific surface area, Strong sorption, High reactivity, Fast dissolution Carbon- and metal-based nanoparticles (<20 nm in size) can be used for water purification. Magnetic (metal-oxide) nanoadsorbents to remove As, Pb, Cu, Cd, Cr, Ni contaminants. Membranes for water purification.

17 Water purification: adsorption Adsorption is used for removal of organic and inorganic contminants in water. CNTs show higher efficiency compared to activated carbon due to a large specific area. Oxidized CNTs can be used for heavy metal removal. Metal-based nanoadsorbents Fe 2 O 3, TiO 2, Al 2 O 3 effective for heavy metals and radionuclides. Decrease of particle size from 300 to 11 nm results in improvement As adsorption capacity by a factor of 100.

18 Water purification: adsorption Iron oxide nanoparticles: single domain with high magnetic susceptibility (<40 nm), smaller particles are superparamagnetic. Can easily be separated in a low-gradient magnetic field. Core-shell nanoparticles (above) the shell provides the desired function. (X. Qu, P. J. J. Alvarez, Q. Li, Water research, 47 (2013) 3931)

19 Water purification: membranes Membranes provide a physical barrier for contaminants to separate them from water. Major challenges: A tradeoff between membrane sepectivity and permeability, High energy consumption to push the water through membrane Functional nanomaterials (e.g. metal oxide nanoparticles, TiO 2 or Al 2 O 3 ) in membranes improve their properties (permeability, fouling resistance, mechanical stability etc). Antimicrobial nanoparticles (nano-ag) and CNTs reduce polymer membrane fouling.

20 Water purification: (photo)catalysis Photocatalytic oxidation is used efficiently to remove trace contaminants and microbial pathogens. Typically: nanoparticles of TiO 2 or ZnO. Processes: Generation of e-h pair after UV-light absorption, Electron-hole pair produces reactive oxygen species (ROS) or recombines, ROS results in oxidation of contaminants (or/and disinfection)

21 M. J. Hanus, A. T. Harris, Progress in Materials Science, 58 (2013) 1056 Mechanism of (photo)catalysis and disinfection Reactive Oxygen Species Limiting factor of kinetics Can be reduced by a noble metal doping

22 Microbial control in water by nanomaterials Challenge in water industry: effective disinfection vs formation of toxic disinfection by-products (DBPs). Cl 2 and O 3 can form toxic DBPs, UV-disinfection require high exposure dosis for some viruses (e.g. adenoviruses) Nanomaterials can be use efficiently to deal with bacterial contamination, e.g. the most commonly used is nano-ag or nanoparticles of TiO 2.

23 M. J. Hanus, A. T. Harris, Progress in Materials Science, 58 (2013) 1056 Mechanisms of antimicrobial control Nano-Ag: release of Ag +, protein and membrane damage, Nano TiO 2 : generation of ROS, CNTs: membrane damage

24 M. J. Hanus, A. T. Harris, Progress in Materials Science, 58 (2013) 1056 Antimicrobial properties of Cu nanoparticles a) SEM image of Cu nanoparticles on SiO 2 (Cu/SiO 2 ), b) algae did not grow on a surface with Cu/SiO 2, c) algae grew on a surface without Cu/SiO 2.

25 Sensing and monitoring bacterias in water Pathogen detection is of critical importance public health Most commonly used nanomaterials in pathogen detection: Quantum dots (QDs), Magnetic nanoparticles, CNTs, Noble metals (Surface Enhanced Raman Scattering SERS) QDs (e.g. CdSe) are nanocrystals with a well-defined size, can be excited by a light source. Give narrow emission spectra which depend on detected species. SERS extreme sensitivity, detection of single molecules

26 Nanomaterials in water transport applications How can we control properties of materials used in water distribution system? Can we get information about status (T, stress, water leakage etc) of the material on-line? "Health" monitoring of the material? "Self-healing" materials can nanotechnology be of any help?

27 A simple example: "nano-concrete" Addition of TiO 2, SiO 2 or Al 2 O 3 nanoparticles (several wt.%) to concrete improves it mechanical properties and reduce the permeability of concrete to ions thereby improving durability. Strength of concrete with and without addition of 4 wt.% of SiO 2 nanoparticles. M. J. Hanus, A. T. Harris, Progress in Materials Science, 58 (2013) 1056

28 A smart nano-material? Nanotechnology can gramatically improve the properties of materials, but how can be monitor the material "on-line"? One possibility is to embed a suitable nanomaterial into the main construction material (concrete, plastic etc). The nanomaterial will change its electrical, optical or other properties as a function of temperature, stress or another parameter of interest. Nanoparticles of Fe 2 O 3 or CNT added to concrete may affect conductivity of the material depending on applied compressive stress. Potentially this effect may be used for "self-diagnostic" purposes.

29 A smart nano-material? Another option: embedded MEMS (microelectromechanical systems) sensors, which can monitor temperature, moisture, stress, ph etc. Challenge: the MEMS sensors are too expensive to produce. CNT-based sensor for structural health monitoring. M. J. Hanus, A. T. Harris, Progress in Materials Science, 58 (2013) 1056

30 Control of corrosion Example of self-healing coating with nanoencapsulated corrosion inhibitor. M. J. Hanus, A. T. Harris, Progress in Materials Science, 58 (2013) 1056

31 Conclusions Nanotechnology deals with sub-100 nm structures Those structures have unique properties due to their small size There is a great potential of nanotechnology in water purification and in construction of smart materials Thank you!