A Low Cost Synthesis and Characterization of CuO Nanoparticles for Photovoltaic Applications

A simple low cost chemical route has been used to synthesize cupric oxide nanoparticles. The synthesized CuO nanoparticles were characterized using XRD, TEM and UV-absorption. X-ray diffraction analysis showed the synthesized nanoparticles to be a pure cupric oxide. EDAX analysis showed the presence of copper and Oxygen in the as prepared CuO nano particles, with the AAS indicating that Cu2+ represented 53.5% of the sample. The particle size and particle size distribution of the cupric oxide nanoparticles were obtained by transmission electron microscopy (TEM) whereas the crystallite size and crystallite size distribution were obtained by X-ray diffraction. The particle size was found to be between 20 nm and 60 nm. The particle size distribution obtained from cumulative percentage frequency plots features a log-normal function. Absorbance measurements and analysis showed that the material has an absorbance peak at 314 nm and energy bandgap of 1.48 eV, making it a good candidate for photovoltaic applications

Emission spectra and intrinsic optical bistability in a two-level medium

Scattering of resonant radiation in a dense two-level medium is studied theoretically with account for local field effects and renormalization of the resonance frequency. Intrinsic optical bistability is viewed as switching between different spectral patterns of fluorescent light controlled by the incident field strength. Response spectra are calculated analytically for the entire hysteresis loop of atomic excitation. The equations to describe the non-linear interaction of an atomic ensemble with light are derived from the Bogolubov-Born-Green-Kirkwood-Yvon hierarchy for reduced single particle density matrices of atoms and quantized field modes and their correlation operators. The spectral power of scattered light with separated coherent and incoherent constituents is obtained straightforwardly within the hierarchy. The formula obtained for emission spectra can be used to distinguish between possible mechanisms suggested to produce intrinsic bistability.Comment: 18 pages, 5 figure

Instrumental analysis and characterization of mineral ores from Yale, Upper East Region, Ghana

Ore samples from underlying rocks (9 - 30 m beneath surface) of the Yale area (Upper East Region, Ghana) were analysed by instrumental techniques for the mineral contents. The three techniques applied in analysing the ores were Instrumental Neutron Activation Analysis (INAA), Atomic Absorption Spectroscopy (AAS) and Powder X-ray Diffraction (XRD). The presence of Ca, Mn, Cr and Cu was confirmed in all the ore samples. The AAS data showed that Ca, Mn and Mg were the main elemental components of the ore samples. About 90.9 % of the ore samples contained more than 5000 mg/kg of Mn, 45% contained no less than 6000 mg/kg of Ca and same proporti-on contained no less than 2000 mg/kg of Mg. The INAA data also indicated a high concentration of Mn (3323 mg/kg) in the ore samples, as well as significant amount of Cr (average concentration of 291.27 mg/kg), and show-ed that Ti was the dominant elemental component in all the samples (average concentration of 6625.3 mg/kg). XRD analysis revealed the presence of oxides of Ca, Mn and of Cr in the ores, thus confirming the INAA and AAS data. The INAA data also showed that the Au content in all ores was between 0.67 - 2.67 mg/kg, which can be considered to be commercially significant. The findings updated the previous data on the mineral ore contents, and confirmed the mining prospects of the locality.Keywords: Instrumental Techniques, INAA, AAS, XRD, Mineralog

Electron–phonon interactions in CsCdBr3:Yb3+CsCdBr3:Yb3+

Pronounced electron–phonon coupling is observed for the 2F7/2↔2F5/22F7/2↔2F5/2 4f4f transitions of Yb3+Yb3+ doped into CsCdBr3.CsCdBr3. A comparison of the Raman spectrum and the luminescence excitation sideband accompanying the 2F7/2(0)→2F5/2(2′)2F7/2(0)→2F5/2(2′) crystal-field transition reveals vibrational properties of the [YbBr6][YbBr6] coordination unit that differ markedly from those of the CsCdBr3CsCdBr3 host. In particular, the vibronic transition associated with the totally symmetric [YbBr6][YbBr6] stretching mode appears as a very weak feature at 191 cm−1191cm−1 in the Raman spectrum, whereas the totally symmetric [CdBr6][CdBr6] stretching mode of the CsCdBr3CsCdBr3 bulk, which appears as a strong feature at 162.5 cm−1162.5cm−1 in the Raman spectrum, is only weakly discernible in the sideband. This is direct evidence for a large contribution from [YbBr6][YbBr6] local modes and a small contribution from bulk modes to the vibronic intensity. The intensity of the local mode is enhanced by approximately a factor of 2 in the Raman spectrum when the laser is tuned into resonance with the 2F7/2(0)→2F5/2(2′)2F7/2(0)→2F5/2(2′) absorption of Yb3+,Yb3+, providing direct confirmation of its assignment. The observation of the first and second members of a Franck–Condon progression for both the local and the bulk totally symmetric modes indicates that a Δ process, rather than an MM process, induces the vibronic intensity. Huang–Rhys factors of Slocal = 0.010±0.002Slocal=0.010±0.002 and Sbulk = 0.15±0.03Sbulk=0.15±0.03 were determined from the data, and reflect quite different electron–phonon coupling strengths. These results suggest that multiphonon relaxation of excited electronic states proceeds by the excitation of local modes of [YbBr6][YbBr6] followed by energy transfer to bulk modes of the lattice, possibly through a nonlinear coupling mechanism which is discussed briefly. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70302/2/JCPSA6-107-13-4886-1.pd

Discovery of periodic methanol masers associated with G323.46-0.08

The 6.7 GHz methanol masers associated with G323.46−0.08 have undergone significant change since their discovery in 1992. After 2009 April, new features with a peak flux density of ∼500 Jy in the velocity channel v = −68.35 km s−1, in the velocity range from −71 to −68.5 km s−1 were detected. It is suggestive that it experienced an accretion event similar to that reported in S255-NIRS3 and NGC 6334I. Evidence of periodicity is found in all of the associated methanol masers with a period of ∼93.5 d. It is not possible to determine if this source was periodic before 2017. However, all the 6.7 GHz methanol masers are probably amplifying a common background periodic radio source