28 research outputs found
Exciton dynamics in tetracene single crystals studied using femtosecond laser spectroscopy
Full text linkThesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: See full textAFRIKAANSE OPSOMMING: Sien volteksDoctora
Ultrafast dynamics of excitons in tetracene single crystals
Full text linkPlease cite as follows: Birech, Z., Schwoerer, M., Schmeiler, T., Pflaum, J. & Schwoerer, H. 2014. Ultrafast dynamics of excitons in tetracene single crystals. Journal of Chemical Physics, 140, 114501, doi:10.1063/1.4867696.The original publication is available at http://scitation.aip.org/content/aip/journal/jcpUltrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states S n on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S 1 on a 40 ps timescale. The high energy Davydov component of the S 1 exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale.http://scitation.aip.org/content/aip/journal/jcp/140/11/10.1063/1.4867696Publisher's versio
Estimation of HIV‐1 viral load in plasma of HIV‐1‐infected people based on the associated Raman spectroscopic peaks
No full textApplication of Raman spectroscopy in type 2 diabetes screening in blood using leucine and isoleucine amino-acids as biomarkers and in comparative anti-diabetic drugs efficacy studies
No full text
Application of Raman spectroscopy in type 2 diabetes screening in blood using leucine and isoleucine amino-acids as biomarkers and in comparative anti-diabetic drugs efficacy studies.
No full textDiabetes is an irreversible condition characterized by elevated blood glucose levels. Currently, there are no predictive biomarkers for this disease and the existing ones such as hemoglobin A1c and fasting blood glucose are used only when diabetes symptoms are noticed. The objective of this work was first to explore the potential of leucine and isoleucine amino acids as diabetes type 2 biomarkers using their Raman spectroscopic signatures. Secondly, we wanted to explore whether Raman spectroscopy can be applied in comparative efficacy studies between commercially available anti-diabetic drug pioglitazone and the locally used anti-diabetic herbal extract Momordica spinosa (Gilg.)Chiov. Sprague Dawley (SD) rat's blood was used and were pipetted onto Raman substrates prepared from conductive silver paste smeared glass slides. Prominent Raman bands associated with glucose (926, 1302, 1125 cm-1), leucine (1106, 1248, 1302, 1395 cm-1) and isolecucine (1108, 1248, 1437 and 1585 cm-1) were observed. The Raman bands centered at 1125 cm-1, 1395 cm-1 and 1437 cm-1 associated respectively to glucose, leucine and isoleucine were chosen as biomarker Raman peaks for diabetes type 2. These Raman bands displayed decreased intensities in blood from diabetic SD rats administered antidiabetic drugs pioglitazone and herbal extract Momordica spinosa (Gilg.)Chiov. The intensity decrease indicated reduced concentration levels of the respective biomarker molecules: glucose (1125 cm-1), leucine (1395 cm-1) and isoleucine (1437 cm-1) in blood. The results displayed the power and potential of Raman spectroscopy in rapid (10 seconds) diabetes and pre-diabetes screening in blood (human or rat's) with not only glucose acting as a biomarker but also leucine and isoleucine amino-acids where intensities of respectively assigned bands act as references. It also showed that using Raman spectroscopic signatures of the chosen biomarkers, the method can be an alternative for performing comparative efficacy studies between known and new anti-diabetic drugs. Reports on use of Raman spectroscopy in type 2 diabetes mellitus screening with Raman bands associated with leucine and isoleucine molecules acting as reference is rare in literature. The use of Raman spectroscopy in pre-diabetes screening of blood for changes in levels of leucine and isoleucine amino acids is particularly interesting as once elevated levels are noticed, necessary interventions to prevent diabetes development can be initiated
Conductive silver paste smeared glass substrates for label-free Raman spectroscopic detection of HIV-1 and HIV-1 p24 antigen in blood plasma
No full text
