Time Evolution of the Excimer State of a Conjugated Polymer Laser

An excited dimer is an important complex formed in nano- or pico-second time scales in many photophysics and photochemistry applications. The spectral and temporal profile of the excimer state of a laser from a new conjugated polymer, namely, poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO), under several concentrations in benzene were investigated. These solutions were optically pumped by intense pulsed third-harmonic Nd:YAG laser (355-nm) to obtain the amplified spontaneous emission (ASE) spectra of a monomer and an excimer with bandwidths of 6 and 7 nm, respectively. The monomer and excimer ASEs were dependent on the PFO concentration, pump power, and temperature. Employing a sophisticated picosecond spectrometer, the time evolution of the excimer state of this polymer, which is over 400 ps, can be monitored

Relaxation Oscillation with Picosecond Spikes in a Conjugated Polymer Laser

Optically pumped conjugated polymer lasers are good competitors for dye lasers, often complementing and occasionally replacing them. This new type of laser material has broad bandwidths and high optical gains comparable to conventional laser dyes. Since the Stokes’ shift is unusually large, the conjugated polymer has a potential for high power laser action, facilitated by high concentration. This paper reports the results of a new conjugated polymer, the poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}](PFO-co-MEH-PPV) material, working in the green region. Also discussed are the spectral and temporal features of the amplified spontaneous emissions (ASE) from the conjugated polymer PFO-co-MEH-PPV in a few solvents. When pumped by the third harmonic of the Nd:YAG laser of 10 ns pulse width, the time-resolved spectra of the ASE show relaxation oscillations and spikes of 600 ps pulses. To the best of our knowledge, this is the first report on relaxation oscillations in conjugated-polymer lasers

An Efficient Violet Amplified Spontaneous Emission (ASE) from a Conjugated Polymer (PFO-co-pX) in Solution

The optical of conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(2,5-p-xylene)] also known as [(PFO-co-pX), ADS145UV], dissolved in a few solvents, has been measured. The absorption, emission spectra, and quantum yield have been investigated by using a spectrophotometer and spectrofluorometer, respectively. The properties of Amplified Spontaneous Emission (ASE) of conjugated PFO-co-pX polymer under different conditions such as solvent type, concentration, and pumping energy have been examined by using the tripled frequency of a Nd:YAG laser as a source of pumping. The relation between output energy and pumping energy for the samples with different concentrations in three solvents has been studied. In addition, efficiency and optical gain from the ASE were measured. Additionally, the stability of this polymer as a laser material was investigated. Among the host of conjugated polymer lasers obtained by optical pumping, this conjugated polymer has exhibited only one ASE band under a wide range of concentrations and pump power values. This is most likely due to the steric hindrance by the copolymer segment pX (2,5-p-xylene). This investigation has provided new insights into the excited state dynamics of conjugated polymer materials and has shown that this new conjugated polymer is quite efficient in the violet region

Impact of Diabetes Mellitus on Human Erythrocytes: Atomic Force Microscopy and Spectral Investigations

Diabetes mellitus (DM) is a common metabolic disease indicated by high sugar levels in the blood over a prolonged period. When left untreated, it can lead to long-term complications, such as cardiovascular disease, stroke, and diabetic retinopathy or foot ulcers. Approximately 415 million people (about 8.3% of the world’s population) had diabetes worldwide in 2015, with 90% of the cases classified as Type 2 DM, which is caused by insulin resistance that arises mostly from being overweight and from a lack of exercise. DM affects every part of the body, including the erythrocytes. The aim of the present report is to gain insight into the damage done to the erythrocytes of patients classified with pre-diabetes and diabetes (plenty are found in the Kingdom of Saudi Arabia, a country where young people encompass a large segment of the population). The study presents results on the morphological analysis of erythrocytes by atomic force microscopy (AFM) and molecular investigations by fluorescence spectroscopy (FS). Our results indicate significant differences (in the morphology, size, and hemolytic end products) between the erythrocytes of diabetic patients (HbA1C, glycated hemoglobin, levels of 8–10%) and normal controls. It is well-known that DM and smoking are two major contributory factors for cardiovascular diseases (CVDs), and our observations presented in this study suggest that diabetes plays a relatively less damaging role than smoking for CVD

Using a Spectrofluorometer for Resonance Raman Spectra of Organic Molecules

Scattering (Rayleigh and Raman) and fluorescence are two common light signals that frequently occur together, confusing the researchers and graduate students experimenting in molecular spectroscopy laboratories. This report is a brief study presenting a clear discrimination between the two signals mentioned, employing a common spectrofluorometer such as the PerkinElmer LS 55. Even better, the resonance Raman signal of a molecule (e.g., acetone) can be obtained elegantly using the same instrument