Emission Spectrum In Presence Research Articles

Reduced Auger Coefficient through Efficient Carrier Capture and Improved Radiative Efficiency from the Broadband Optical Cavity: A Mechanism for Potential Droop Mitigation in InGaN/GaN LEDs.

Efficiency droop at high carrier-injection regimes is a matter of concern in InGaN/GaN quantum-confined heterostructure-based light-emitting diodes (LEDs). Processes such as Shockley-Reed-Hall and Auger recombinations, electron-hole wavefunction separation from polarization charges, carrier leakage, and current crowding are identified as the primary contributors to efficiency droop. Auger recombination is a critical contributor owing to its cubic dependence on carrier density, which can not be circumvented using an advanced physical layout. Here, we demonstrate a potential solution through the positive effects from an optical cavity in suppressing the Auger recombination rate. Besides the phenomenon being fundamentally important, the advantages are technologically essential. The observations are manifested by the ultrafast transient absorption pump-probe spectroscopy performed on an InGaN/GaN-based multi-quantum well heterostructure with external DBR mirrors of varying optical confinement. The optical confinement modulates the nonlinear carrier and photon dynamics and alters the rate of dominant recombination mechanisms in the heterostructure. The carrier capture rate is observed to be increasing, and the polarization field is reducing in the presence of optical feedback. Reduced polarization increases the effective bandgap, resulting in the suppression of the Auger coefficient. Superluminescent behavior along with enhanced spectral purity in the emission spectra in presence of optical confinement is also demonstrated. The improvement is beyond the conventional Purcell effect observed for the quantum-confined systems.

Fluorescence Chemosensors for Chemical Warfare Agent Mimic Diethylcyanophosphonate Via Co2+ -Naphthalimide Based Nanoaggregate in Aqueous Medium

Two new Naphthalimide based dipodal receptors K1 and K2 has been synthesized and selectively formed upon complexation with cobalt ion. Further, these cobalt complexes (K1.Co2+ and K2.Co2+) were fabricated to nanoaggregate in aqueous medium. The stability of these nanoaggregates was established with DLS, TEM, AFM and emission spectroscopy. The nanoaggregates N1-N2 were utilized to selectively sensing of diethylcyanophosphonate in aqueous medium. The nanoaggregate N1 and N2 exhibit 2 fold enhancement in the emission spectrum in presence of Diethylcyanophosphonate (DECP) which is due to rigidity induced fluorescent enhancement. The detection limit to be achieved for DECP is 21 nM in aqueous medium. Additionally, the solution coated filter paper strip of nanoaggregate N1 can detect DECP, thus providing very simple and low coast sensing kit for DECP.

Photophysics of Przewalskinone-B and its Binding Behavior with β- Cyclodextrin

The photophysical properties of Przewalskinone-B, a plant extract which is reported widely for its medicinal values were studied in the absence and presence of a drug carrier, β-Cyclodextrin. The steady state absorption, fluorescence excitation and emission spectra of Przewalskinone-B were studied in an aqueous medium. The fluorescence emission of Przewalskinone-B was analysed in presence of varying concentrations of β-Cyclodextrin in an alcohol/water medium. An appreciable quenching was observed in the emission intensity of Przewalskinone-B. There was also a red shift observed in both absorption and emission spectra in presence of β-Cyclodextrin which designated a convinced interaction between the two species.