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- Phal, Sereilakhena, 1984-
(författare)
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Development of electrochemical sensor and biosensor platforms : detection of therapeutic drugs and heavy metal ions
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrochemical sensors and biosensors combine the sensitivity of electroanalytical methods with the selectivity of a sensor or biosensor surface. The chemical or biochemical component (receptor) in the sensor recognizes an analyte and produces an electrical signal which is proportional to the analyte concentration. Some of these sensors are routinely used in clinical applications and are known for their simplicity, portability, cost-effective, and miniaturization. The glucose sensor used in the management of diabetes is a good example of such biosensors.This thesis deals with the development of electrochemical biosensor and sensor platforms for the detection of therapeutic drugs, demonstrated using methotrexate (MTX) which is the most common drug used for the treatment of cancer patients, and heavy metal ions (Pb2+ and Cd2+).The biosensor surfaces were generated by immobilization of antibody (anti-MTX) on chemically modified gold electrodes using different surface modification protocols. Self-assemble monolayer (SAM) using alkanethiol (cysteamine) or electrografting with diazonium salt (4- carboxybenzenediaonium tetrafluoroborate, 4-CBD) was used for surface modification. The surface modification was monitored and characterized using electrochemical immittance spectroscopy (EIS) and cyclic voltammetry (CV) along with other complementary technique such as X-ray photoelectron spectroscopy (XPS). The biosensing surfaces were used for the detection of MTX in an electrochemical flow cell (paper I) and in a batch system (paper II). The detection was based on non-faradaic electrochemical immittance spectroscopy (EIS) and singular value decomposition (SVD) for data evaluation. Both electrochemical biosensors provided the lowest limit of detection, LOD (at picomolar level) compared to earlier reports.The electrografting of 4-CBD on glassy carbon electrode (GCE) using CV and the parameters that influence the number of monolayers that can be grafted on the surface are demonstrated (paper III). The CVs obtained during grafting showed one or two reduction peaks, and this was found to be related to the number of monolayers deposited on the electrode. One can increase the number of monolayers by increasing the concentration of 4-CBD or decreasing the scan rate. The GCE, grafted using 4-CBD, was incorporated with Bi by an in situ electrodeposition of Bi3+ and used as an electrochemical sensor for detection of Pb2+ and Cd2+ using square wave anodic stripping voltammetry, SWASV (paper IV). The sensor resulted in LOD of 10 μg L-1 for Pb2+ and 25 μg L-1 for Cd2+. The applicability of the sensor was tested for detection of Pb2+ and Cd2+ in tap water and compared with ICP-OES. The results were comparable, demonstrating the potential of the sensor as an alternative to ICP-OES for the detection of metal ions in water samples.
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| 2. |
- Bui, Thai Q., 1989-
(författare)
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Development of nitrogen-containing materials for capture and catalytic conversion of carbon dioxide to value-added chemicals
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Anthropogenic carbon dioxide (CO2) emissions have become a critical environmental issue because a large amount of CO2 releasing into the atmosphere, particularly from the massive use of fossil fuels, is the major factor promoting the global warming and climate change. To mitigate the CO2 emissions, Carbon Capture, Utilization and Storage (CCUS) can be one of important solutions. Inspired by the CCUS approach, the aims of this thesis are to develop materials for CO2 capture (Papers I, II) and conversion of CO2 to value-added chemicals (Papers III, IV) such as dimethyl carbonate (DMC) and cyclic carbonates (CCs). The main idea is to focus on nitrogen-containing materials because basic nitrogen sites can increase the chemical affinity towards CO2, which is a weak Lewis acid gas.In practice, aqueous monoethanolamine (aq MEA) is widely used to capture CO2 from flue gases in CCUS projects. However, this solvent suffers from several major drawbacks such as high energy consumption for regeneration of MEA, degradation and evaporation. In Paper I, aq pentaethylenehexamine (PEHA) was proposed as an alternative solvent for chemical absorption of CO2. A comprehensive study was performed, including the influence of water content on CO2 capacity, chemical composition of absorption products, viscosities before and after absorption, regeneration of PEHA, correlation between CO2 capacity with Kamlet-Taft parameters, comparison with aq MEA. In Paper II, aq PEHA was further studied for CO2 capture from bio-syngas resulting from pilot-scale gasification of biomass to investigate the influence of other compositions on the capture performance. Additionally, this solvent was simultaneously used as a reagent for chemical pretreatment of biomass to investigate the influence of pretreatment on biomass gasification and CO2 capture.The conversion of captured CO2 to value-added chemicals gains increasing attentions in both academia and industry because CO2 represents a renewable, virtually inexhaustible, and nontoxic building block. In addition, this approach can provide economic incentives for CO2 capture facilities by selling their captured CO2 to other interested users or by benefiting from their own additional facilities using the CO2. In Paper III, 1,8-diazabicyclo[2.2.2]undec-7-ene (DBU) was used to capture and subsequent conversion of CO2 to DMC at ambient conditions. In Paper IV, mesoporous melamine-formaldehyde resins were prepared, characterized and studied as heterogeneous catalysts for synthesis of CCs from epoxides and CO2. These low-cost polymeric catalysts were reusable and demonstrated excellent performance in a flow reactor under industrially relevant conditions (120 °C, 13 bar, solvent-free/co-catalyst-free).Applications of ionic liquids (ILs) in capture and conversion of CO2 to organic carbonates were briefly reviewed in Paper V (mini review). The viscosity of ILs for CO2 capture and the mechanism involved in the CO2 binding were also discussed.In conclusion, this thesis will hopefully contribute to the sustainable development of society in the fields of reducing anthropogenic CO2 emissions and production of chemicals.
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