Dr. Mohammad Amdad Ali

I am fortunate enough to have worked in different areas in chemistry, and in multidisciplinary environments. My research interests are focused on the things that happen at surfaces and interfaces to understand the structure-property relationship of molecules. To study the interfacial dynamics and thermodynamics of materials, I have combined chemical synthesis with advanced spectroscopic methods to probe the underlying physics with nanoscale resolution. I have then used this fundamental insight to engineer smart/intelligent materials, which respond to their environment by reversibly changing their physical and/or chemical properties and adapt to the external cues via reconfiguration. Such materials are potential candidates in emerging industrial applications, such as wearable electronics, biosensors, actuators, soft robotics, smart coating (self-healing, tunable surface), smart textile design, etc. I have published eighteen papers (eleven as first author and five as a corresponding author) in prestigious journals, including Nature Communications, Angewandte Chemie, Chemical Communications, Sensors and Actuator B: Chemical, Carbon, Synthetic Metals. Below is a summary of my research endeavors.

a) Information Transport via Chemical Wave:

My colleagues and I have developed materials which transport chemical information via travelling ionic wave.1,2 The traveling ionic wave is triggered by the introduction of spatially localized ions which, through an ion exchange process, converts quaternary ammonium groups in the hydrogel from hydrophilic to hydrophobic (Fig. 1). Through a reaction-diffusion process, the hydrophobic region expands with a sharp transition at the leading edge. Key is that the reaction-diffusion mechanism accelerates chemical transport relative to a purely diffusive mechanism, and thus offers a way to propagate the chemical information. The travelling wave propagates 100 μm in 1 min, over 10 times faster than if the chemical wave was moving via diffusion. The travelling waves were characterized using confocal Raman imaging microscope and inverted fluorescence light microscope. Furthermore, to understand ion exchange reaction and transport in hydrogel media, I employed COMSOL multiphysics program (ver. 5.1) to model the system.

b) Chemical Force Enhanced Signal Amplification:

My supervisor (Prof. Paul Braun) and I invented a novel chemical force enhanced amplified detection of chemical agent and we also filed an “US Patent” (Fig. 2a).3,4 Companies have already expressed interest in buying this device. The method uses a gel comprised of at least one agent capable of fragmenting the analytes into two or more fragments, as well as gradients of functional groups to concentrate the fragments for detection. For example, when an aerosol-deposited sarin simulant, diisopropyl fluorophosphate, absorbs into a hydrogel it subsequently hydrolyzes upon contact with water, producing F-. The F- is then concentrated via an ionic chemical gradient to a fluoride ion selective electrochemical sensor, leading to an amplified response (Fig. 2b). A 30-fold increase of F- concentration was achieved within 5 min with a theoretical upper bound of 1000-fold (Fig. 2c,d). I synthesized a polyacrylamide-based hydrogel as the host media by radical polymerization. The chemical gradient was then formed through localized hydrolysis within the gel to create carboxylic acid groups, followed by a coupling reaction of the carboxylic acid groups with amine-appended molecules. I also fabricated a miniature electrochemical sensor for fluoride ion. To better understand the mechanism, I used COMSOL multiphysics program (ver. 5.1) to model the system.

c) Fluorescence-Based Sensors for Explosive Detection:

My PhD project focused on understanding the diffusion of analyte vapors into conjugated fluorescent sensing films and subsequent interaction with the fluorophore to guide the design of new sensing molecules that are selective and sensitive to the targeted analyte. Studies reported in literature had performed in solution to understand selectivity and sensing mechanism, with no reports in the literature about the diffusion kinetics of the analyte into thin films of the sensors, or how the analytes interact with the chromophores in the sensors. Since this is not a trivial measurement, I built an experimental setup integrating quartz crystal microbalance (QCM), fluorescence spectroscopy, excitation sources, and an analyte chemical vapor unit. The QCM quantified mass uptake in the film that allowed for determination of the diffusion mechanism. Correlating the analyte mass uptake to fluorescence intensity in the film provided the basis for exploring the impact of exciton diffusion from the chromophore to analyte and binding strength between them on the sensing mechanism. 5-8 While the QCM technique can measure mass uptake it cannot provide any information about the distribution of analyte molecules in the sensing films. Therefore, I performed a second method, neutron reflectometry, to investigate the distribution of the analyte molecules and structural changes occurring in the film as the sorption proceeded. I also characterized the optical properties of the sensing molecules using fluorescence spectroscopy, UV spectroscopy, ellipsometry, and transient absorption spectroscopy (Fig. 3). I used Wolfram Mathematica to model molecular diffusion and excitation diffusion. The work presented in my doctoral thesis led to a much better understanding of the structure-property relationship for the diffusion of analyte molecules into the sensing films and the factors affecting the sensing mechanism. The project was a remarkable success and our developed sensor device was shortlisted for the 2015 Defense Science and Technology Group Eureka Prize for Outstanding Science for Safeguarding Australia.

d) Wearable Biosensors and Electronics:

Advances in materials science have begun to establish the foundations for a next generation of wearable electronic technologies, where sensors and other functional components reside not in conventional rigid packages mounted on straps or bands but instead directly on the skin. Materials for this application should be soft, stretchable, robust, non-irritating, and form long-lived interfaces with the human epidermis. Polymers and hydrogels are perfect materials for such applications. This developing field involves innovative ideas in both organic and composite functional materials, where chemical, mechanical and manufacturing science play important roles.

Hydrogel-Based Colorimetric Biosensors: The development of noninvasive and rapid diagnostic devices for analyzing biofluid (such as sweat) has been limited over the last two decades because the devices require electrical components (such as wires, battery etc.). Those devices are uncomfortable to wear and tend to have a short lifetime. To overcome this constraint, colorimetric detection continues to become increasingly popular since the technology does not require any energy input and quantitative detection can be done using a smart phone or even the naked eye. Over the last decade significant research has been done to invent colorimetric dyes (ions: H+, Na+, K+ etc., small molecules: glucose, urea, lactate etc., and biomolecules: proteins, bacteria, virus etc.). However, most of the dye molecules are toxic and could not be used on/in the human body. To solve this issue, I have been synthesizing a carboxylic acid functional dye, so that it can form covalent chemical bonds with an amine functional hydrogel. Covalently-bonded dyes stay within the gel and are safer to use. One of my recently developed sensing gels is shown in Fig. 4. The structure of the dye molecule has been characterized by NMR (H, C), FTIR, and mass spectroscopy. The thermomechanical properties of the sensing gel were characterized by differential scanning calorimetry and thermogravimetric analysis.

Wearable Tactile Devices: There is a growing demand for low-voltage-driven electromechanical transducers because of their wide use in emerging fields such as soft robotics, electronic skin and wearable health monitors. A promising candidate is the ionic polymer actuator, which is capable of large displacement under low operation voltages of only a few volts. Most of the low voltage polymer actuators in the literature consist of the commercial polymer Nafion. However, the limitation of Nafion is that it should be loaded with solvent or ionic liquid. To overcome this limitation, my research goal is to synthesize new material containing bulky ionic charges in a polymer network which can be tuned to a much greater degree than Nafion in terms of thermal and mechanical properties (Fig. 5.). Crucially, this device can be operated without solvent or ionic liquid.

Conductive Polymer: Flexible, stretchable and biocompatible electrically conducting layers are crucial to use as an electrode in bioelectronics. Conventionally, electrodes including carbon nanotube (CNT) paper or metals are being used. Their rigidity decreases the performance of tactile devices. Electrically-conducting polymers are excellent candidates for such applications. A polymer known as PEDOT, or poly (3,4-ethylenedioxythiophene) has received a great amount of attention owing to several useful properties, such as high conductivity, chemical stability and excellent transparency in the visible range. Vapor phase polymerization of PEDOT allows direct deposition of a conducting layer onto a variety of substrates and nanostructures. While there are many studies on the chemical reaction dynamics during the film formation, there is insufficient information into how the oxidant and monomer interact in the solid state and lead to chain growth. Understanding the film growth mechanism is thus a critical subject, due to this knowledge being required to precisely tailor the film properties (such as, electrical, optical and mechanical). I investigated the film growth mechanism by probing the initial film growth profile and the diffusing species at the nucleation stage and correlated the growth mode with the physical properties of the PEDOT film.10-15 I used atomic force microscopy (AFM) and scanning electron microscopy (SEM) images to observe the initial growth mechanism and utilized Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) to investigate the diffusion of monomer into the oxidant layer. Electrical properties were investigated using four-point probe, Hall measurement and semiconductor parameter analyzer. With this knowledge, I developed a self-assembled monolayer-directed polymer layer patterning technique and fabricated organic field effect transistors.14

e) Agrochemicals and Environmental Chemistry:

Before starting my PhD degree, I worked in Bangladesh Agricultural University for a year and investigated nanostructure ZnO for catalytic applications. ZnO nanoparticles (NPs) were fabricated by simple combustion process (Fig. 7a).16 To see the effectiveness of the fabricated ZnO NPs, it was employed as photocatalytic agent to degrade the organic dyes, and catalytic activities under both sunlight and UV light were analyzed and compared with respect to the commercially available ZnO (Fluka) (Fig. 7b). I worked on a project to extract food colorant from natural products (Fig. 7c).17 In another project, I developed a method to separate heavy metal ions utilizing EDTA-grafted anion exchange resin Amberlite IRA-420 in Cl- form.18 With the incorporation of EDTA, distribution coefficients of the metal ions increased significantly and the mixtures of the metal ions viz. Cu-Pd-Cd were successfully separated (Fig. 7d). I also collaborated with professors in the department of poultry science (BAU) to investigate the possibility of potato and cassava as carbohydrate source in poultry meal to lower the cost of poultry feed (70–80% of total production cost). Potato is an extensively cultivated annual crop in Bangladesh and its price is one third of maize. In some years, when the production of potato is surplus, tons of potatoes are damped due to insufficient storage facilities. I investigated the nutrient content of cassava and potato at different stage of processing.19-21 Findings from the research conducted at the BAU were published in several journals16-21.

My working knowledge of polymer synthesis, characterization, and processing, experience in molecular diffusion, along with strong analytical problem-solving, and communication skills allow me to gain a strong understanding of materials and their characterization. Furthermore, I have gained strong project and time management skills through the preparation of project reports and collaboratively working with colleagues across multiple disciplines. I believe my experience and knowledge in polymer science, molecular diffusion, and instrumentation will be useful to solve chemical- and material-related problems and to innovate new approaches to solve technical problems.

References:

1. M. A. Ali, T. H. Tsai, and P. V. Braun. “Chemical information transport in organogel” submitted to ACS Applied Materials and Interfaces.
2. T. H. Tsai, M. A. Ali, Z. Jiang and P. V. Braun. “Dynamic gradient directed molecular transport and concentration in hydrogel films” Angewandte Chemie International Edition 56 (2017) 5001
3. P. V. Braun and M. A. Ali “Chemical Force Driven Concentration for Amplified Detection of Chemical Agents". U.S. Provisional Patent Application No. 62/451,389, January 2017
4. M. A. Ali, T. H. Tsai, and P. V. Braun “Amplified Detection of Chemical Warfare Agents using 2D Chemical Potential Gradients” accepted in ACS Omega.
5. M. A. Ali, S. Shoaee, S. Q. Fan, P. L. Burn, I. R. Gentle, P. Meredith, P. E. Shaw “Detection of explosive vapours with a porous polymer film: the roles of vapour and exciton diffusion” ChemPhysChem 17:3350 (2016).
6. M. A. Ali, Y. Geng, H. Cavaye, P. L. Burn, I. R. Gentle, P. Meredith, P. E. Shaw “Molecular versus exciton diffusion in fluorescence-based explosive vapour sensors” Chemical Communications 51:17406 (2015).
7. Y. Geng, M. A. Ali, A. J. Clulow, S. Q. Fan, P. L Burn, I. R. Gentle, P. Meredith, P. E. Shaw “Selectively detection of explosives using fluorescent dendrimer” Nature Communications 6:8240 (2015).
8. M. A. Ali, S. S. Y. Chen, H. Cavaye, A. R. G Smith, P. L. Burn, I. R. Gentle, P. Meredith, P. E. Shaw. Diffusion of nitroaromatic vapours (explosive) into fluorescent dendrimer films for explosives detection. Sensors and Actuators B: Chemical 210:550 (2015).
9. Christopher Even, M. A. Ali, Pengcheng Sun, Paul Braun, Conductive polymer electrode electroactive artificial muscles. (in preparation).
10. M. A. Ali, K. H. Wu, J. E. McEwan, J. G. Lee. Translated structural morphology of conductive polymer nanofilms synthesized by vapor phase polymerization. Synthetic Metals 244 (2018) 113–119.
11. K. H. Wu, H. H. Cheng, M. A. Ali, I. Blakey, K. Jack, I. R. Gentle, D. W. Wang “Electron-beam writing of deoxygenated micro-patterns on graphene oxide film” Carbon 9 (2015) 738.
12. M. A. Ali, H. H. Kim, C. Y. Lee, H. S. Nam, J. G. Lee. Effects of iron(III) p-toluenesulfonate hexahydrate oxidant on the growth of conductive poly(3,4-ethylenedioxythiophene) (PEDOT) nanofilms by vapor phase polymerization. Synthetic Metals 161 (2011) 1347.
13. M. A. Ali, H. H. Kim, K. H. Jeong, H. S. Soh, J. G. Lee. Effects of solvents on poly(3,4- Ethylenedioxythiophene) (PEDOT) thin films deposited on a (3-aminopropyl) trimethoxysilane (APS) monolayer by vapor phase polymerization. Electronic Materials Letters 6 (2010) 17.
14. M. A. Ali, H. H. Kim, K. H. Jeong, H. S. Soh, H. S. Nam, J. G. Lee, E. G. Lee. Application of tosylatedoped poly(3,4-ethylenedioxythiophene) (PEDOT) films into bottom contact pentacene organic thin film transistors (OTFTs). Thin Solid Films 518 (2010) 6315.
15. M. A. Ali, H. H Kim, C. H. Lee, H. S Soh, J. B Lee. Effects of the FeCl3 concentration on the polymerization of conductive poly(3,4-ethylenedioxythiophene) thin films on (3-aminopropyl) trimethoxysilane monolayer-coated SiO2 surface. Metals and Materials International 15 (2009) 977.
16. M. A. Ali, M. R. Idris, M. E. Quayum. Fabrication of ZnO nanoparticles by solution-combustion method for the photocatalytic degradation of organic dye. Journal of Nanostructure in Chemistry 3:36 (2013) 1.
17. H. P. Seal, M. A. Ali, M. U. Ali, M. H. Akhter, F. Sultana. Thin layer chromatographic analysis of food colorants from three morphotypes of Annatto (Bixa orellana L.). International Journal of Agricultural Research, Innovation and Technology 2 (2012) 7
18. M. A. Ali, M. R. Rahman, and A. M. S. Alam. Use of EDTA-grafted anion-exchange resin for the separation of selective heavy metal ions. Analytical Chemistry Letters 3:3 (2013) 199
19. F. Sultana, H. Khatun, M. A. Ali. Use of potato as carbohydrate source in poultry ration. Chemical and Biological Technologies in Agriculture 3 (2016) 30
20. F. Sultana, M. A. Ali, and I. Jahan. Growth Performance Meat Yield and Profitability of Broiler Chickens Fed Diets Incorporating Cassava Tuber Meal. J. Environ. Sci. & Natural Resources. 5:1 (2012) 47
21. F. Sultana, M.F. Khatun, M. A. Ali. Effects of Dietary Cassava Tuber Meal on Egg Production and Egg Quality of Laying Hen. International Journal of BioResearch 2:1 (2011) 1