Browsing by Author "Baig, Mirza Muhammad Fahad"

Now showing 1 - 5 of 5

Bright carbon dots as fluorescence sensing agents for bacteria and curcumin
(2017-09-01)
Baig, Mirza Muhammad Fahad
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Carbon dots (C-dots) are fluorescent nanomaterials that possess good photostability and low toxicity. They have been used as sensing probes and bioimaging agents for a variety of biological species. Numerous methods are available to generate C-dots. Nevertheless, simple and straightforward synthesis methods must be explored for the synthesis of C-dots from inexpensive, natural sources. In this study, we developed a simple method to generate C-dots from inexpensive chicken egg whites through a one-step heating reaction. The size of the generated C-dots was 3.3 +/- 0.4 nm, and the quantum yield of the C-dots was as high as similar to 43%. The as-prepared C-dots can be used as multicolor labeling agents for bacteria such as Staphylococcus aureus and Escherichia coli. Furthermore, the generated C-dots can be used as Forster resonance energy transfer sensing probes for curcumin, which is an active ingredient of turmeric and medicinal pigment. The feasibility of using the C-dots as selective sensing probes to determine the amount of curcumin from complex turmeric powder and condensed turmeric tablets is also demonstrated. (C) 2017 Elsevier Inc. All rights reserved.
Carbon fiber ionization mass spectrometry coupled with solid phase microextraction for analysis of Benzo[a]pyrene
(2019-02-21)
Wu, Min-Li
;
Chen, Te-Yu
;
Chen, Wen-Jie
;
Baig, Mirza Muhammad Fahad
;
Wu, Yi-Cheng
Solid phase micro-extraction (SPME) is an effective technique that can be used to selectively enrich trace analytes of interest from complex samples. Owing to its high sensitivity and high selectivity, mass spectrometry (MS) has been widely used as the detection tool to confirm the analytes enriched on SPME fibers. Generally, thermal desorption or solvent desorption is used to desorb analytes from SPME fibers for MS analysis. A straightforward ionization method called carbon fiber ionization (CFI), which uses a single carbon fiber (diameter: similar to 10 mu m) as ionization emitter in MS, has been demonstrated lately. Analytes adsorbed on the carbon fiber, which is placed close (similar to 5 mm) to the inlet of a mass spectrometer, can be readily ionized through corona discharge and detected by the mass spectrometer. One unique feature regarding this approach over other existing ambient ionization methods is that no additional electric contact is applied directly on the carbon fiber. Nevertheless, on the basis of the electric field provided by the mass spectrometer, corona discharge can readily occur for ionizing analytes on the carbon fiber. Carbon fiber has high affinity toward polycyclic aromatic hydrocarbons due to its graphite-like surface structure. We herein explore a hyphenated-technique by combining carbon-fiber based SPME with CFI-MS for extraction of benzo[a]pyrene (BaP), a carcinogen, from aqueous samples. After BaP are adsorbed on a carbon fiber through SPME, the SPME carbon fiber can be readily placed in front of the mass spectrometer for MS analysis. The ions at m/z 252 derived from BaP adsorbed on the carbon fiber can be immediately acquired by the mass spectrometer without the requirement of applying heating or solvent. The limit of detection of BaP using the developed method was as low as similar to 60 pM. It is also feasible to detect BaP from complex serum sample. The feasibility of using the approach for quantitative analysis of BaP was also demonstrated. The linear dynamic range toward BaP was 0.2-5 nM. The extraction efficiency using this approach for aqueous samples was similar to 91%. (C) 2018 Elsevier B.V. All rights reserved.
Gold nanocluster-based fluorescence sensing probes for detection of dipicolinic acid
(2019-05-21)
Baig, Mirza Muhammad Fahad
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Bacillus spp. are spore-forming bacteria, and some of them, including Bacillus cereus and Bacillus anthracis, are pathogens. Dipicolinic acid (DPA) has been recognized as a biomarker for spore-forming bacteria. Thus, developing rapid sensing methods to spot the presence of DPA in suspicious samples is significant. In this study, we employ complexes of glutathione-capped gold nanoclusters (Au@GSH NCs) with Cu2+ as sensing probes against DPA. Au@GSH NCs possess orange-reddish fluorescence. However, their fluorescence is significantly quenched in the presence of Cu2+. In the presence of DPA, the fluorescence of Au@GSH NCs can be restored because DPA can easily remove Cu2+ on the NCs through chelation based on the high formation constant (log K = 7.97) between Cu2+ and DPA. Therefore, on the basis of this fact, Au@GSH NC-Cu2+ complexes are used as turn-on fluorescence probes against DPA. Unlike most of the existing sensing methods, the developed Au@GSH-Cu2+-based sensing method is not affected by the presence of phosphates, which can be commonly found in real samples. The limit of detection of using the developed sensing method toward DPA can reach as low as -19nM. In addition, we also demonstrate the feasibility of using the developed sensing method for detection and quantification of DPA in soil samples and B. cereus spore lysates.
Gold nanoparticle-based colorimetric sensing of dipicolinic acid from complex samples
(2018-02-01)
Baig, Mirza Muhammad Fahad
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Dipicolinic acid (DPA) can cause neurotoxicity and is abundant in bacterial spores. Although analytical methods have been reported for DPA detection with high sensitivity, their selectivity toward DPA is declined greatly in the presence of phosphates in the samples. In this study, we developed an approach for DPA detection that is not affected by the presence of phosphates. A colorimetric method based on the use of gold nanoparticles (AuNP) complexed with Ca2+ as sensing agents was explored for DPA detection. Calcium ions and glutathione-capped gold nanoparticles (AuNPs@GSH) can easily form complexes (Ca2+-AuNP@GSH) through GSH-Ca2+ chelation, leading to the aggregation of AuNPs@GSH. The aggregation resulting from the complexes of AuNPs@GSH and Ca2+ can be reversed with the addition of DPA owing to the high formation constant (log K (f) = 4.4) between DPA and Ca2+. Furthermore, the color of AuNPs@GSH changes from red to purple when complexed with Ca2+, returning to red upon addition of DPA. The limit of detection of this sensing method toward DPA was estimated to be as low as similar to 2 mu M. The feasibility of using the sensing method for quantitative detection of DPA in soil and Bacillus cereus spore samples was also demonstrated.
Photoluminescence Determination of Aluminum Using Glutathione-Capped Gold Nanoclusters
(2016)
Baig, Mirza Muhammad Fahad
;
Chen, Cheng-Tai
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Aluminum is a common metal that is used extensively in daily life. However, over-exposure to aluminum may result in nervous systemrelated diseases. Thus, it is important to develop a rapid sensing method that can be used to screen samples. In this study, glutathione-capped gold nanoclusters with bright photoluminescence were demonstrated to be effective sensing probes for aluminum ions. The photoluminescence of glutathione-capped gold nanoclusters was enhanced in the presence of aluminum ions. The results show that glutathione-capped gold nanoclusters selectively determined aluminum ions in samples prepared in aqueous ammonium acetate buffer (pH 5.5). The acetate maintains the pH and serves as a chelating agent to interact with non-analyte metal ions. Therefore, other metal ions have little effect on the photoluminescence of the glutathione-capped gold nanoclusters. The photoluminescence of the glutathione-capped gold nanoclusters was switched on in samples containing aluminum ions. The selective sensing was based on chelation between the aluminum ions and ligands on the surface of the glutathione-capped gold nanoclusters. The limit of detection was estimated to be as low as approximately 100 nM. The method was used to determine the concentration of aluminum ions in lake water and soil extracts.