Ultrafast laser dynamics of metal organic frameworks/TiO_2 nano-arrays hybrid composites for energy conversion applications

Herein,we report the victorious synthesis of metal-organic frameworks(MOFs) on TiO_2 nanotubes(NTs)using a layer-by-layer(LbL) approach.Highly crystalline and homogenous thin films of MOFs were grown and characterized using XRD,SEM,FT-IR and UV/Vis spectroscopy.Moreover,the utilization of the MOF films as sensitizers was probed in bespoke Graetzel type liquid junction solar cells.The constructed cell performance revealed an I_(sc) of 1.16 mA cm^(–2),Vocof 0.63 V,FF of 0.33,and E_(ff) of 0.42%.Further,pumpprobe transient laser spectroscopy was performed to investigate the energy and charge transfer dynamics of the MOFs/TiO_2 NTs interface.The results indicated 86% injection efficiency.The ultrafast pump-probe spectroscopy allows the investigation of this process and the differences between MOFs.It also showed that the relaxation of the MOF chromophores is in competition with electron injection in the Ti O2 motif.Thus this study provides a new insight into electron transfer from photoexcited metal-organic frameworks(MOFs) into titanium dioxide.

Effect of Experimental Parameters on the Fabrication of Gold Nanoparticles via Laser Ablation

In this study we report the effect of laser parameters such as laser energy, laser wavelength as well as focusing condition of laser beam on the size and morphology of the gold nanoparticles (GNPs) prepared in deionised water by pulsed laser ablation. The optimum conditions at which gold nanoparticles obtained with controllable average size have been reported as these parameters affected on the size, distribution and absorbance spectrum. Effect of energy was studied. The laser energy was divided into three regions (low, middle and high). A noteworthy change was observed at each region, as the average size changed from 5.9 nm at low energy to 14.4 nm at high energy and the gold nanoparticles reached a critical size of 8 nm at 100 mJ. The Effect of the wavelength on the particle size was examined at 1064 nm, 532 nm. It was found that, the optimum ablation laser wavelength was 1064 nm. Finally, significant results obtained when the effect of focusing conditions studied.

Study of Bacterial Samples Using Laser Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy （LIBS） technique has been applied to inves- tigate two different types of bacteria, Escherichia coli （B1） and Micrococcus luteus （B2） deposited on glass slides using Spectrolaser 7000. LIBS spectra were analyzed using spectrolaser software. LIBS spectrum of glass substrate was compared with bacteria spectra. Ca, Mg, Na, K, P, S, C1, Fe, A1, Mn, Cu, C, H and CN-band appeared in bacterial samples in air. Two carbon lines at 193.02 nm, 247.88 nm and one hydrogen line at 656.28 nm with intensity ratios of 1.9, 1.83 and 1.53 appeared in bacterial samples B1 and B2 respectively. Carbon and hydrogen are the important components of the bio-samples like bacteria and other cancer cells. Investigation on LIBS spectra of the samples in He and Ar atmospheres is also presented. Ni lines appeared only in B2 sample in Ar atmosphere. From the present experimental results we are able to show that LIBS technique has a potential in the identification and discrimination of different types of bacteria.

Numerical Investigation of the Tri-Atomic Ions Formation during Laser Ionization Based on Resonance Saturation

We present a theoretical investigation of plasma generation in sodium vapor induced by laser radiation tuned to the first resonance line (3S-3P) at λ = 589 ns. A set of rate equations that describe the rate of change of the ground and excited states population as well as the temporal variation of the electron energy distribution function (EEDF), beside the formed atomic ion Na+, molecular ion ?and tri-atomic ions are solved numerically. The calculations are carried out at different laser energy and different sodium atomic vapor densities under the experimental conditions of Tapalian and Smith (1993) to test the existence of the formed tri-atomic ions. The numerical calculations of the electron energy distribution function (EEDF) show that a deviation from the Maxwellian distribution due to the super elastic collisions effect. In addition to the competition between associative ionization (3P-3P), associative ionization (3P-3D) and Molnar-Horn- beck ionization processes for producing , the calculations have also shown that the atomic ions Na+ are formed through the Penning ionization and photoionization processes. These results are found to be consistent with the experimental observations.

Calculation of Atomic Data and Gain Coefficient for XUV &Soft X-Ray Laser Emission from Ge XXIII

Energy levels, transition probabilities, oscillator strengths, and collision strengths have been calculated for transitions in Ne-like Ge. The data refer to a 241 fine-structure levels belonging to the configurations 1s2 2s2 2p5nl, 1s2 2s1 2p6nl (n = 3, 4, 5, 6;l = s, p, d, f, g and h), which have been calculated by the fully relativistic flexible atomic code (FAC). These data are used in the determination of the reduced population for the 241 fine structure levels and gain coefficients over a wide range of electron densities (from 2 × 10+20 to 4 × 10+22 cm-3) and at various electron plasma temperatures (650, 850, 1050, 1250, 1450, 1650, 1850) eV by using the MATLAB R2013a Computer program for solving simultaneous coupled rate equations. The reduced population for the 241 fine structure levels the gain coefficients for those transitions with positive population inversion factor are determined and plotted against the electron density.

Numerical Study of Transient Temperature Distribution in Passively Q-Switched Yb:YAG Solid-State Laser

In this work, the thermal characterization of continuously pumped passively Q-switched laser is quantitatively represented. The system under investigation is end-pumped Yb:YAG passively Q-switched by Cr4+:YAG as saturable absorber. The rate equations describing the dynamics of laser action are numerically solved simultaneously with the temperature conductivity heat equation to depict the transient temperature distribution. The study has been performed in the cylindrical coordinates to characterize the temperature distribution in the axial and radial directions. The thermal transient time in both directions as well as the thermal focal length are calculated. The temporal behavior of the temperature distribution has been illustrated in a 3-dimensional diagram.

Primary Study of the Use of Laser-Induced Plasma Spectroscopy for the Diagnosis of Breast Cancer

Breast cancer, or malignant breast neoplasm, is a type of cancer that originates from breast tissue, most commonly from the inner lining of the milk ducts or the lobules that supply the ducts with milk. It is one of the most widespread diseases, especially in women. Thus far, large efforts have been towards the early diagnosis of cancer in general, and breast cancer specifically. Most of these techniques deal with malignant tissues without inducing or increasing pathological tissue changes or causing major side effects for the patient. This paper proposes a new technique for diagnosing the presence or occurrence of cancer and assessing its grade early, accurately, and safely. The presented technique depends on the interaction between the laser and the soft tissue in order to induce plasma, and allows us to classify the cancer by studying the difference in the intensity ratio of the trace elements in normal and malignant tissues. The results presented here are show that only four patients out of the total sample of 30 have erroneous trace elements and that this does not affect the overall decision. Hence, the performance of LIPS can be measured as 87%, while retaining 100% accuracy. Furthermore, LIPS technique is a simple and promising technique that is capable of diagnosing malignant cells and tissues.

Theoretical Study of Laser Emission for C-Like (Ar XIII), (Ti XVII) and (Fe XXI)

Energy levels, transition probability and oscillator strengths have been calculated for the Ar XIII, Ti XVII and Fe XXI. The configurations included in the calculations are 2s2 2p2, 2s2 2p 3l (l = s, p & d) and 4l (l = s, p, d, & f) of C-like Ar XIII, Ti XVII & Fe XXI which has 69 fine structures by using the fully relativistic flexible atomic code (FAC) program. These data are used in the determination of the reduced population and gain coefficients over a wide range of electron densities from (10+18 to 10+23) and at various plasmas temperatures. The results show that the transitions in Ar18+, Ti22+, and Fe26+ ions are the most promising laser emission lines in the XUV and soft X-ray spectral regions.

Soft X-Ray Laser Gain from Neon like Gallium and Germanium

Gain coefficients are calculated for neon-like gallium and germanium ions. Shorter wavelengths are calculated and predicted to be emitted. The gain coefficients are calculated among 457 energy levels of the neon-like ions. Collisional excitations were calculated through the distorted wave approximations through five electron temperatures Te = 300, 500, 700, 1000 and 1500 eV.

Observed Enhancement in LIBS Signals from Nano vs. Bulk ZnO Targets: Comparative Study of Plasma Parameters

In this article, we will report an experimental evidence of enhanced LIBS emission upon replacing a Bulk-Based ZnO target by the corresponding Nano-Based target. The plasma was initiated via interaction of a Nd:YAG laser at the fundamental wavelength with both targets in open air under the same experimental conditions. The measurements show an enhanced emission from the Zn I-lines at the wavelengths of 328.26, 330.29, 334.55, 468.06, 472.2, 481.01, 636.38 nm. The measurements were repeated at different delay times in the range from 1 to 5 μs at constant irradiation level and fixed gate time of 1 μs. The average enhancement over the different Zn I-lines was found increases exponentially up to 8-fold with delay time. The electron density to each plasma was measured utilizing the Hα-line appeared in the emitted spectra from each plasma and was found to give similar values. The electron temperatures were measured via Boltzmann plot method utilizing the relative intensities of the Zn I-lines and were found to give very close values. Moreover, the relative population density of the ground state of the zinc atoms (relative concentration) was measured spectroscopically utilizing the Boltzmann plot method and was found to increase in a very similar trend to that of enhancement. The results of the spectroscopic analysis conclude that these signal enhancements can be attributed to the higher concentration of neutral atoms in the Nano-Based material plasma with respect to the corresponding Bulk-based ZnO material.

Factors affecting improvement of fluorescence intensity of quartet and doublet state of NO diatomic molecule excited by glow discharge

We report on the observation of new fluorescence emission spectral transitions obtained from NO diatomic molecule in the region from ultraviolet （UV） to near infrared （NIR） in a low power glow discharge system. This glow discharge electronic excitation populates different quartet and doublet states of NO in its proximity such as the A2Z （/9 = 2）, b4∑- （υ= 3）, B2М （1） = 4）, and X2Л （u= 33-32） states. Due to inter-system crossing, emission lines originating from these levels to lower lying states are recorded and spectral line assignments are performed. The observed systems include b4∑- a4∏, B21∏-a4∏, a4∏-X2I∏, A2∑X2∏, X2∏-X2∏ （33-15）, X2∏-X2∏ （33-17）, X2∏-X2∏ （33-20）, and X2∏-X2∏ （33- 18）. This new information will conduce to the better understanding of the interesting features of NO molecule. Such parameters that affect the recording of low density of NO molecules are also discussed In addition to the factors such as the time evolution, argon gas concentration relative to NO mixture, the percentage of NO molecular gas concentration, discharge electric current signals and discharge applied voltage are studied. Those factors would enhance the fluorescence signal intensity of NO molecules. The recent results might be significant as reference data for optimizing the glow discharge spectrometer and diagnostics of NO gas.

Thermal Stability and Hot Carrier Dynamics of Gold Nanoparticles of Different Shapes

Anisotropic shapes of gold nanoparticles are prepared using a modified seed method in the presence of silver ions or clusters in order to study the thermal stability and the dynamics of the hot carriers induced by femtosecond laser pulses. Although gold nanospheres are stable towards thermal treatment, the decomposition of the gold nanorods into spherical nanoparticle aggregates upon thermal treatment is mechanistically different from the case of nanoprisms. Great enhancement of thermal stability is achieved by modifying the surface of the nanoparticles by adding specific amounts of polyvinyl pyrrolidone (PVP) after preparation of gold particles of different shapes capped with cetyltrimethylammonium bromide (CTAB). The surface plasmon resonance spectra of the gold nanostructures are used to monitor their morphological changes. In regards to the hot carrier dynamics, it is found that the phonon-phonon (ph-ph) coupling is much slower in dots than in rods and prisms while electron-phonon (e-ph) coupling is almost the same in these particles.

Determination of the Optical Properties of Basal Cancer Using OCT System

The objective of this work is to determinate the optical properties of basal cancer cells using an optical coherence tomography (OCT). OCT system with He-Ne & diode laser was used to make interference pattern for the basal cancer, then the output was displayed by optical detector, information of an electrical signal passed to the digital oscilloscope to give the object information after Fourier transform processing for that signal, then PC and CCD were used to display FFT signal. Finally many steps were done to determine the optical properties for the basal cancer. The intensity of the signals was plotted against scanning distance;the obtained graphs were used to determine the penetration depth and absorption coefficient.

Optical, Photophysical, Stability and Mirrorless Lasing Properties of Novel Fluorescein Derivative Dye in Solution

Novel laser dye, allyl 2-(6-(allyloxy)-3-oxo-3H-xanthen-9-yl) benzoate [diallyl-fluorescein] has been synthesized. Its chemical structure was confirmed by 1HNMR, IR, MS and elemental analysis. Its optical properties were experimentally investigated. The amplified spontaneous emission (ASE) efficiency was 0.29% in case of new dye while it was 0.23% in case of fluorescein by pumping the dye samples with a 532 nm (7 ns) pulsed Nd:YAG laser. Also, the thermal and photostability techniques confirmed the higher stability of new laser dye.

Impact of Initial Electron Development on Sodium Plasma Generation Using LIBORS Technique: Numerical Modeling

The present work reports an investigation on the role played by Na3+ ions formed through triatomic associative ionization collision of Na(4d) atoms with Na2 ground state molecules during the early phase of sodium plasma generation by laser ionization based on resonance saturation (LIBORS). Such ionization mechanism is observed experimentally for the first time by Tapalian and Smith (1993) [1]. In their experiment, stepwise atomic excitations are created using two CW dye lasers;one laser is tuned to 589 nm to excite the Na(3s) to Na(3p) D2 transition of sodium and the other laser is tuned 569 nm to excite the Na(3p) to Na(4d) transition. The analysis is grounded on a numerical study of the role of seed electron processes on the temporal evolution of sodium plasma formation by laser irradiation. A previously developed numerical model based on LIBORS technique is modified and adopted. In the present study, the sodium atom is treated as an atom comprises 22 levels namely: a ground state, 18 excited states and three ionic states (atomic, molecular and tri-atomic). The model tackled various collisional and radiative processes that act to enhance and deplete the free electrons generated in the interaction region. The contribution of these processes is signified by solving numerically a system of time-dependent rate equations, which couple the generated atomic and ionic species with the laser fields. Meanwhile, it solves the time-dependent Boltzmann equation for the electron energy distribution function (EEDF) of the generated electrons. The computed values of the EEDF, time evolution of both excited states population and the formed ionic species considering the individual effect of associative ionization, Penning, and photo-ionization and triatomic associative ionization justified the important effect of each of these ionizing processes in creating the early stage electrons. These seed electrons are assumed to rapidly gain energy through superelastic collisions leading eventually to plasma development.

Gain Coefficient Calculation for Short Wave Laser Emission from Sodium like Co

Level structure, oscillator strengths, transition probabilities and radiative life times are evaluated for 1s2 2s2 2p63l, 4l, 5l (l = 0, 1, 2, 3, 4) states in sodium like Co16+. The calculations are carried out using COWAN code. The calculations made were compared with other results in literature where a good agreement is found. We also report on some unpublished energy values and oscillator strengths. Our results are used in the calculation of reduced population of 21 fine structure levels over a wide rang of electron density values (1018 to 1020) at various electron plasma temperature. For those transitions with positive population inversion factor, the gain coefficients are evaluated and plotted against the electron density.

Spectroscopy and Optical Properties of Sm³⁺:YAG Nanocrystalline Powder Prepared by Co-Precipitation Method: Effect of Sm³⁺Ions Concentrations

Samarium doped Yttrium aluminum garnet (YAG) nanopowders with different concentration (0.5%, 1%, 2%, 3%, 5% and 8% mol) were prepared by simple and low cost co-precipitation method. We found that the precursor begins converting to pure YAG at relatively low temperature around 900°C, and no intermediate phases were detected. The powders annealed at 900°C and 1000°C in air with average particle size around ≈30 nm were characterized by means of X-ray diffraction (XRD) analysis and infrared (IR) spectroscopy. The photoluminescent measurements showed that the reddish-orange (RO) emission transition 4G5/2:6H7/2 is more prominent. In addition, the optimum concentration of doped Sm ions that lead to maximum intensity was reported. Also, fluorescence efficiencies as pumping power dependence for different Sm3+ ions concentrations were explored.

Power Dependent of Nonlinear Absorption Coefficient of CdSe-Au Hybrid Nanocomposites

Power dependent study of optical nonlinear absorption coefficient of semiconductor-plasmonic hybrid nanocomposites of CdSe:Au was investigated using Z-scan technique, provided with nanosecond pulses of second harmonic Nd:YAG laser. The prepared materials were characterized with linear absorption and High Resolution Transmission Electron Microscope (HRTEM) which confirm the quantum confinement of CdSe as well as the formation of CdSe:Au core shell quantum dots. An analysis of power dependence open aperture Z-scan was discussed. A change from saturable absorption (SA) to reverse saturable absorption (RSA) is observed with increasing the laser power. Also, an enhancement of the nonlinear absorption coefficient of CdSe:Au of larger sizes compared to Au nanoparticles was detected.

Tungsten ion source under double-pulse laser ablation system

New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd：YAG laser beams（266＋1064 nm） are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pulse laser ablation configuration is more potent technique for producing more metal ion source deposition, thin film formation, and activated plasma-facing component material.