Papers by Keyword: Fluorescence

Abstract: Solar cells are a promising technology for energy production, and they provide a sustainable and environmentally friendly alternative to traditional energy sources based on fossil fuels. This study aims to improve the efficiency (E)of the solar cell using Triglyceride for Oleic Acid. Crystal Triglyceride for Oleic Acid is a compound of two components (Triglyceride and Oleic Acid), Each compound has a structural formula and physical and chemical properties. The prepared samples (1, 1.4, 1.5, 1.6, and 2) mol/l. The required data were collected and analyzed through (a UV/visible spectrophotometer, Spectrofluorometer, and Solar Module Analyzer), The data obtained were wavelength for absorption, wavelength for fluorescence, Stokes shift (the difference between fluorescence and absorption wavelengths), practical and theoretical efficiency, current and voltage values, and power factor. Luminescent solar concentrators were used to test the efficiency of the PV. The results showed that the E improved well, as the efficiency was (21.57) before using the solar concentrator, and after using the concentrator, it became (26.61) at a concentration of 1.5 mol/l.

Abstract: Protein-stabilized gold nanoclusters have been intensively studied due to their excellent fluorescent properties and potential biomedical applications. Human Serum Albumin is abundant in human blood. Here, we synthesized human serum albumin-stabilized gold nanoclusters. The gold nanoclusters were characterized and used for glucose sensing. It is found that the human serum albumin encapsulated gold nanoclusters emit bright red fluorescent with a long fluorescence lifetime in the range of microseconds. The fluorescence intensity for gold nanoclusters decreased as the concentration of added glucose increased. The fluorescence intensity decreases due to the by-product (H₂O₂) from the enzymatic reaction of glucose oxidase. The Au-S bond can be destroyed by Hydrogen Peroxidase (H₂O₂). The fluorescence lifetime value of gold nanoclusters is unchanged in the presence and absence of glucose. This unchanged fluorescence lifetime obeyed a simple static quenching mechanism and indicated the destruction in the structure of gold nanoclusters, leading to the quenching of fluorescence intensity. This work suggests that human serum albumin-encapsulated gold nanoclusters can be used for glucose detection with a detection limit of 0.5×10^-6 mol/L.

Abstract: The hydrothermal synthesis of amikacin modified carbon dots-doped nitrogen and zinc- (N,Zn-CDs) and its capacity to detect Escherichia coli (E. coli) have been investigated. Amikacin is one of the aminoglycoside antibiotics utilized in this study as a ligand of N,Zn-CDs to attach to E. coli. This study also examined the effect of nitrogen (N) and zinc (Zn) dopant content on enhancing N,Zn-CDs fluorescence emission intensity. N,Zn-CDs were characterized using a spectrofluorometer, UV-Vis spectrophotometer, FTIR, EDX, XRD, and TEM, which revealed their amorphous nature and average particle size of 3 nm. The emergence of bond vibrations of C=O, CN, and ZnO indicates the success of N and Zn dopants. Amikacin was then included in the structure of N,Zn-CDs to enhance their ability to detect E. coli. The maximum fluorescence intensity was seen in N,Zn-CDs with a mole ratio of 1:4:4 mmol for the carbon precursor, N, and Zn dopants, and a volume of 0.1 mL amikacin. Based on the fluorescence response of amikacin-modified N,Zn-CDs against E. coli, a limit of detection 1,490 cfu mL^-1 was obtained.

Abstract: Green synthesized surface passivated carbon dots for detection of Citrate as biomarker for prostate cancer. The carbon sources of CQDs are passivated with L-cysteine via a one-pot hydrothermal route. The quenching in emission intensity of the synthesized carbon dots (CQDs) is observed for Citrate samples. The hydroxyl and carboxylic functional groups of Citrate showed a binding affinity with amino and free carboxyl cysteine passivated over the surface of carbon dots. The CQDs showed a high sensitivity for detection of Citrate in a continuous range of 1.0 μM–500 μM. The CQDs showed good level of selectivity, repeatability, and stability for the detection of Citrate. We successfully detected the Citrate content for prostate cancer cells using an L-cysteine passivated carbon quantum dots various incubation durations. As a result, quenching in fluorescence intensity CQDs are noted to analyze extent of cancer cells in biological samples.

Abstract: The 2-Dimennsionnal nanocomposites are applied for the ennhannced fluorescence sensor for analysing heavy metal ions is explored using a simple novel technique based on green manufactured (CQDs@MoS₂) nanocomposite. The emission intensity of CQDs have a better dispersibility, and MoS₂ nanosheets have an excellent exfoliation, allowing the CQDs to adhere to the surface and form a label-free sensors. The emission peak of CQDs was quenched by transferring non-radiative energy as of CQDs to MoS₂ sheets in an excited state. However, when metal ions are included in the CQDs@MoS₂ nanocomposite, it develops a solid surface combined with the carbon dots nanosheets, that might aid in CD recovery. More intriguingly, the sensing performance of MoS₂ nanosheets were examined at various pH levels to better recognize the change in surface charge, which resulted in significantly improved responsiveness for identification of Pb (II) ions with LODs of 0.9 nM. Furthermore, it is suggested that present method are intended to be quick, easy, cost effective, environmental friendly for sensing heavy metal ions.

Abstract: A CdTe quantum dot modified with thioglycolic acid as stabilizer was prepared. The structure of CdTe quantum dots was characterized by IR, UV and fluorescence spectra, transmission electron microscopy (TEM) scanning and X-ray diffraction (XRD). The effects of reactants, temperature, time and PH on the luminescence properties of the quantum dots were investigated. It is found that the quantum dots have strong fluorescence intensity. The synthesized QDS have small and uniform particle size and high crystallinity. The optimum conditions were determined as follows: n (Cd²⁺): n (Te^2-): n (TGA) = 2:1:4, heating temperature 140°C, reaction time 60min, pH 11.

Abstract: Recently, Far-infrared Light Emitting Diodes have attracted considerable interest in the research field worldwide. Emerging light therapy requires effective red/far-infrared light resources in clinical and plant photomorphogenesis to target or promote the interaction of light with living organisms. Here, Gd₃Al₄GaO₁₂:Cr³⁺ (hereinafter referred to as: GAGG:Cr³⁺) phosphor was synthesized by high-temperature solid-phase method, and the crystal structure, morphology, and luminescence properties of this series of phosphor samples were studied. Through X-ray powder diffraction to obtain pure phase GAGG:Cr³⁺ series phosphor. Under the excitation of 420nm blue light, a broad band emission from 640 to 850nm is obtained, which is the result of the transition of Cr^{3+ 4}T₂→⁴A₂ level. A sharp emission peak at 693nm is the R line belonging to Cr³⁺ in Gd₃Al₄GaO₁₂ garnet. R line is assigned to the spin-forbidden ²E→⁴A₂ transitions of Cr³⁺ ions that occupy the ideal octahedral sites. As the Cr³⁺ doping concentration increases, the luminous intensity of the sample increases first and then decreases. When the doping concentration of Cr³⁺ is 0.1mol phosphor,the luminous intensity is strongest at one single broad peak at about 712nm. At 440k, the R sharp line (693nm) and broad band (712nm) emission intensity maintained 78.6% and 71.8% , compared to room temperature intensity, respectively. The change of fluorescence lifetime at different temperatures gives the mechanism of fluorescence change with temperature. The current exploration will pave a promising way to engineer GAGG:Cr³⁺ activated optoelectronic devices for all kinds of photobiological applications.

Abstract: Photodynamic therapy (PDT) is a promising modern method for treatment of oncological, bacterial, fungal and viral diseases. However, its application is limited to diseases with superficial localization since the body tissues are not transparent for visible light. To address this problem and extend PDT application to abdominal diseases, an enhanced method of X-ray photodynamic therapy (XRPDT) is suggested, involving X-ray radiation easily penetrating the body tissues. The implementation of this approach requires the development of a pharmacological drug including a photosensitizer stimulated by visible light to yield active oxygen and a nanosized phosphor converting X-ray radiation into visible light with the wavelength required for the photosensitizer activation. This study is aimed at obtaining X-ray stimulated phosphors with nanosized particles suitable for XRPDT application. For this purpose, Y₂O₃:Eu phosphors were synthesized via hydrothermal processing of the corresponding mixed acetate followed by annealing. To prevent from the undesirable agglomeration of the particles in the course of hydrothermal synthesis and subsequent annealing, different techniques were used, including rapid thermal annealing (RTA), microwave annealing and addition of finely dispersed pyrogenic silica (aerosil) to the phosphor. The microwave annealing was carried out using a special installation including a resonance chamber for maintaining a standing wave of microwave radiation. The performed research allowed the determination of hydrothermal processing optimal duration affording the synthesis of phosphors with the highest luminescence brightness. The application of microwave annealing is found to provide phosphors with a more perfect crystal structure compared with RTA. The developed method of Y₂O₃:Eu phosphor synthesis involving pyrogenic silica addition to the autoclave allowed the preparation of samples with the amorphous structure and significantly reduced the particle size without a considerable decrease in the luminescence brightness. The particle size of the phosphor synthesized with aerosil addition is less than 100 nm that allows its implementation in pharmacological drugs for XRPDT.

Abstract: In order to explore more functional supported probe material, the ultraviolet absorbance together with fluorescence properties of a probe with the structure of salicylaldehyde Schiff-base in various solvents and pHs were investigated after its synthesis. When the concentration of Cr³⁺ ion was in the range of 3~7×10^-5 mol•L^-1, the complex reaction between the probe and Cr³⁺ could be used for quantitation of the latter, which was developed by UV absorbance intensity of the complex and the concentration of Cr³⁺ ion. Ultraviolet analytic results determined that they were complexed in the molar ratio of 1:1. Finally, the MOF-supported probe material was successfully synthesized for further application, which realized the immobilization of the probe through simple operations.

Abstract: Nowadays some types of polymer are being developed as Polymer Light Emitting Diode (PLED) materials because they have some advantages compared to small molecule organic light emitting diode (SM-OLED). Polymers which have numerous conjugated double bonds can be used as PLED materials, such as the polyethersulfone (PES) and its derivatives. Therefore, further research on the synthesis of PES and its derivatives is needed to explore their potential as PLED materials. In this research, the synthesis of polyethersulfone has been performed utilizing Microwave Assisted Organic Synthesis (MAOS) method and subsequently the synthesized PES was being transformed into the nitrated PES (PES-NO₂) and the aminated PES (PES-NH₂) utilizing the conventional method (reflux). Polymer structure is elucidated through FT-IR and ¹H-NMR spectrum. Polymer application as PLED material is characterized by fluorescence emission spectrum. The maximum wavelengths in the fluorecence emission spectra of polymer in NMP were 444 nm for PES, 356 nm and 444 nm for PES-NO₂, also 440 nm for PES-NH₂.Based on the various analyses of data, the synthesis of PES, PES-NO₂, and PES-NH₂ has been successfully performed and all of polymers have the potent to be used as PLED materials because of its ability to emit light (blue) in the visible area.