This research proposes a highly sensitive and simple surface -enhanced Raman spectroscopy (SERS) assay for the detection of SARS-CoV-2 RNA using suitably designed probes specific for RdRp and N viral genes attached to a Raman marker. The sensitivity of the assay was optimized through precise adjustments to the conditions of immobilization and hybridization processes of the target RNA, including modifications to factors such as time and temperature. The assay achieved a remarkable sensitivity down to 58.39 copies/mL, comparable to or lower than the sensitivities reported for commercial fluorescent polymerase chain reaction (PCR) based methods. It has good selectivity in discriminating SARS-CoV-2 RNA against other respiratory viruses, respiratory syncytial virus (RSV), and influenza A virus. The reliability of the assay was validated by testing 24 clinical samples, including 12 positive samples with varying cycle threshold (Ct) values and 12 negative samples previously tested using real-time PCR. The assay consistently predicted true results that were in line with the PCR results for all samples. Furthermore, the assay demonstrated a notable limit of detection (LOD) of Ct (38 for RdRp gene and 37.5 for Ngene), indicating its capability to detect low concentrations of the target analyte and potentially facilitating early detection of the pathogen.

We have applied time dependent Schrodinger equation on Lie algebra potential surface (LPES) representing the ground electronic potentials of the collinear HN2 reaction. The algebraic method especially Lie algebra used to generate the Surface and the contour plot of the reaction H + HN2 → HN2 potential surface. The Lie surface generated reproduces more fine results for the life time. The structure is found to be metastable. The novel reaction dynamics are examined in femtosecond time scale

It is now recognized that graphene and its derivatives are regarded as appropriate surface-enhanced Raman scattering (SERS) substrates. Nevertheless, the reported results show considerable conflicts, and consequently, the mechanism of the SERS effect for graphene-based materials shows wide debate. In this paper, graphene oxide (GO) and laser-irradiated graphene oxide (LGO) suspensions in pure water have been produced and employed for SERS measurements. The utilization of LGO as SERS substrate has not been reported before. LGO substrates suspensions were produced using a nanosecond pulsed laser (532 nm) with constant fluence similar to 0.35 J/cm(2) at different irradiation times (0 to 180 min). R6G dye molecules were used to study and compare SERS activities of both GO and LGO. Depending on the irradiation period, the observed enhancement factor of LGO substrates is as large as 10(3), which is comparable to that of GO. However, the associated fluorescence background is significantly quenched relative to that of the GO substrate. It is found that such LGO substrates can detect R6G molecules at extremely low concentrations down to similar to 10(-9) M. The impact of the irradiation period on GO was illustrated using various spectroscopic techniques. First and second-order Raman bands of GO were utilized as markers to assess the laser impact on oxygen content as well as the reconstruction of the sp(2) domain in irradiated samples. Accordingly, the mechanisms of SERS for GO and LGO are discussed.

We present a method based on surface enhanced Raman spectroscopy (SERS) to detect DNA KRAS-gene with single-base mutation. The KRAS gene belongs to the oncogenes class of genes. KRAS mutations cause normal cells to become cancerous. The detection utilizes DNA gene probes labeled by CY3 dye (as Raman marker) and plasmonic silver nanoparticles (Ag NPs) deposited on SERS substrates. SERS detect DNA via hybridization to the complementary DNA (target) sequences with single-base mutation. This SERS technique is a powerful tool and has a great potential gives both affectability and selectivity. Also, we utilized the Raman mapping to provide chemical information coupled with spatial information. The mapping image was obtained using scanning with three Raman bands over selected areas of the sample. The limit of detection (LOD) was accomplished down to a concentration 9 nM after the addition of magnesium sulfate (MgSO4) aggregated agent, causing hot spots of the aggregated Ag NPs.

Laser ion-molecule reaction interaction through both polarizability and dipole moment contribution leads to intersection in potential energy surface along the reaction path, polarizability is maximum at (s=4.5 a.u.) and dipole changes at (s=1 a.u.) defining a virtual transition state. We will show here by using gauge representation for wave length λ=20.6μm, Intensity I=5×10 W/cm till I=5×10 W/cm, that the laser induced potential energy surface can decrease in height along the reaction path with possibility of creating bound states in the virtual transition state. We illustrate such effects for the Na H + CH3 +  Na + CH4 reaction which takes the form of inverted Morse (without a barrier) using ab-initio methods for calculating the reaction path, electric properties of the ion-molecule reaction. 188 Hassan Talaat, El-Wallid S. Sedik and M. Tag El-Din Kamal

Triangular silver nanoparticles have special properties which increase their importance in chemistry, biology, physical and medical applications. This work concerns with fabrication of truncated nanotriangles, using a simple chemical method. The seed mediated growth method that is usually used to synthesize nanorods, is modified to create nanotriangles. By using this modified method, we successfully obtained silver truncated nanotriangles by adding low concentration of cetyltrimethylammonium bromide (CTAB) into seed solution. UV-visible spectroscopy (UV-Vis) was used to characterize the surface plasmon resonance of the formed nanoparticles. Also, the geometrical properties of nanoparticles were characterized by transmission electron microscopy (TEM) and scanning tunneling microscopy (STM). The average edge length of truncated nanotriangle is affected by varying the amount of seed added to the growth solution; it varies from 56 nm up to 75 nm according to the amount of seed used. The degree of truncation (T) for the produced nanotriangle edges has been estimated. Furthermore, the effect of CTAB concentration as well as the speed in which NaBH4 is added to the seed solution on the formed nanoparticles was investigated.

The size effect of gold nanospheres (AuNS) used as a contrast agent for the photoacoustic imaging (PAI) of breast cancer cell line MDA-MB-231 have been assessed for three different sizes and at four optical densities (ODs). The decrease in the AuNS size at the same OD results in an improved PA signal. The PA signal generally increases linearly with increasing OD, with almost the same rate of increase for the three used particle sizes. It is shown that PEGylation of gold nanoparticles (AuNP) decreases the uptake of the particles by the cancerous cell therefore diminishes the PA images whereas clear images are obtained in the case of unPEGylated AuNPs.

The effect size of CdS Quantum Dots (QDs) on thermal and photovoltaic parameters is investigated. CdS QDs were adsorbed onto TiO 2 electrodes using successive ionic layer adsorption and reaction (SILAR) to act as sensitizers of quantum dots solar cells (QDSSCs). The CdS QDs sizes are estimated using optical absorption spectra and application of effective mass approximation model (EMA) as well as high resolution transmission microscopes (HRTEM). The ratio of TiO 2 /CdS was confirmed by energy dispersive X-ray spectroscopy (EDX). Thermal parameters (thermal diffusivity α, thermal effusivity e and thermal conductivity k are measured by using Photoacoustic (PA) Technique. The photovoltaic parameters (open circuit voltage V oc , short circuit current density J sc , fill factor FF and efficiency η) of the assembled CdS QDs sensitized solar cells (QDSSCs) were determined under a solar illumination of 100 mW/cm2 (AM 1.5 conditions. Our results show that both the effective thermal conductivity k eff and efficiency η of CdS QDs deposited on TiO 2 increase as the size of CdS QDs is increased.

Nanoparticle production by pulsed laser ablation (PLA) is a process that can generate pure nanoparticles (NPs) straight from a varied range of bulk substances and compounds. Silver nanoparticles (Ag NPs) are probably one of the most attractive noble metal nanostructures because of their unique and interesting physical and chemical properties. In this study, laser ablation of pure silver plate immersed in almond oil was carried out for Ag NPs production. Nd: Yag laser of wavelength 1064 nm, was used for the ablation of the Ag plate at different laser energies and ablation times. The almond oil permitted the formation of Ag NPs with a stable and homogeneity particle diameter in a reasonable time. The size distribution of the NPs was examined by High-Resolution Transmission Electron Microscopy (HRTEM). The particle sizes of the produced Ag NPs at laser energy 200 mJ in the solution at 10,15 and 20-min ablation times were 4.82, 3.11 and 1.82 nm respectively. The particle sizes of Ag NPs produced at different laser energies 150,200 and 250 mJ and at ablation time 10 min inside the solution were 5.39,4.82 and 1.92 nm respectively. The absorption peaks of the produced nanoparticles have been characterized using a UV-Vis spectrophotometer.

We report on a comparative study of laser deoxygenation of graphene oxide (GO) suspensions in pure water (pH∼7) using pulsed (nanosecond with wavelength 532 nm and fluence ∼ 0.15 J/cm2) and continuous-wave (CW) (of wavelength 448 nm and power density ∼ 0.25 MW/cm2) lasers at room temperature. Such comparison was not performed previously for GO suspensions. Concentrated GO colloidal suspensions were prepared by a modified Hummer’s method. The presence of oxide groups in GO was proved using X-ray diffraction and Fourier transform infrared (FTIR). The laser deoxygenation processes were verified by means of UV-visible, FTIR and micro-Raman spectroscopies. The impact of changing the laser irradiation time for both lasers has been investigated using the characteristic Raman bands (D and G) of GO as markers to assess the degree of reduction as well as the structural defects of the resulting laser RGO.

Gold Nanorods (AuNRs) can play a fundamental role in the enhancement of photoacoustic imaging (PAI). This is due to their high and tunable optical absorption cross-section. Normally, the most convenient and highly stable AuNRs are synthesized using Cetyltrimethylammonium bromide (CTAB) as a surfactant. In this work, surface modification with poly ethylene glycol (PEGylation) and Silica coating (SiO2-coating) were applied to help in reducing toxicity of CTAB capped AuNRs. Breast cancer cell line (MDA-MB-231) was used to assess the modified AuNRs as contrast agents. A much brighter PAI of cells loaded with SiO2-coated AuNRs was obtained. Such an enhanced PA image is due to the larger cellular uptake, as observed from bright field microscope images taken for the cells. On the other hand, the corresponding PA image for cells with PEGylated AuNRs is diminished. The increase in cell uptake, in case of SiO2-coated AuNRs, could result due to the adsorption of protein, contained in the cell culture media, on the negatively charged silica surface, which increases intercellular uptake by receptor-mediated endocytosis. Moreover, the increase of the brightness of PAI of SiO2-coated AuNRs may be due to the lowering of the interfacial thermal resistance between gold and the surrounding solvent. This allows the particle to release more heat to its environment which increases the generated acoustic signals from these particles.

The optimum choice of the ligand that stabilizes the colloidal quantum dots and passivate the surface is crucial for tuning the energy level and remain elusive. The atomic ligand passivation with iodide remains superior over other surface treatments. Herein, we applied the iodide ligand to passivate the CdSe nanocrystals with an excitonic absorption at 2.1 eV by a liquid-liquid extraction process. We took the view of the change in the optical and structural properties upon ligand exchange. Finally, we tested the performance of the iodide treated dots by employing it in an inverted structure polymer solar cell based on P3HT: PCBM.

Abstract Dye-sensitized solar cells (DSSCs) which have a polymer electrolyte added to with various function groups were studied to determine the effect of their composition on the efficiency of the solar cell. Four function group polymers got employed, those groups are polymethylmethacrylate (PMMA), polyvinyl acetate (PVA), polyethylene oxide (PEO) and polyacrylonitrile (PAN). The iodine salt cation is caged by the function groups which cause a positive shift in the dye HOMO level and result in a deceleration in the recombination rate more than that of ordinary iodine electrolyte. The polymer electrolyte ionic conductivity improves the rate of the dye regeneration to make it faster than ordinary iodine as well. Adding pyridine to electrolyte solution makes the conduction band of the TiO2 more negative leading to an increase in the open circuit voltage (Voc). The photo generated current (Jsc) is increased by the employed configureuration, subsequently, the solar cell photovoltaic efficiency is enlarged. PVA is with highest efficiency at 8%, unlike the rest of the polymers which show lower efficiencies.

The efficiency of carbon-based dye sensitized solar cells (DSSCs) is improved by mixing titania with graphene (GR) sheets. The composite films of GR sheets and TiO 2 were characterized using field emission scanning electron microscopy (SEM). The grinding of GR with TiO 2 leads to smaller size TiO 2 nanoparticles which increases their surface area. The photovoltaic efficiency varied with the mixing ratio giving the highest efficiency at a ratio of 1 wt. % of GR to TiO 2 . The increase in the photovoltaic efficiency is more than doubled the one without GR under the same conditions. Mesoporous carbon from candle flame and N3 dye were used instead of Pt and N719 dye to reduce the cost.

We have studied the coupling of propagating Surface Plasmon Polaritons (SPP) on silver films and excitons in CdS quantum dots (QDs). We employed the Kretschmann-Raether configuration of the attenuated total reflection (ATR) to propagate the SPP on silver film of thickness 47.5 nm at three different wavelengths. The CdS QD have been chemically synthesized with particular size such that its exciton of energy would resonate with SPP. High resolution transmission electron microscopy (HRTEM) and scan tunneling microscopy (STM) were used to measure the corresponding QDs size and confirm its shape. Further confirmation of the size has been performed by the effective mass approximation (EMA) model utilizing the band gap of the prepared QDs. The band gaps have been measured through UV-vis absorption spectra as well as scan tunneling spectroscopy (STS). The coupling has been observed as two branching dips in the ATR spectra indicating Rabi like splitting. To the best of our knowledge, this is the first time that Rabi interaction is directly observed in an ATR angular spectra. This observation is attributed to the use a high resolution angular scan (+/- 0.005 degrees), in addition to the Doppler width of the laser line as well as the energy distribution of the excitons. The effect of three different linker molecules (TOPO, HDA), (Pyridine) and (Tri-butylamine) as surface ligands, on SPP-Exciton interaction has been examined. (C) 2018 Elsevier B.V. All rights reserved.

A laser ion-molecule reaction interaction through both polarizability and dipole moment contribution leads to variation in the intersection point in potential energy surface crossings along the reaction path; the polarizability is maximum and the dipole changes its sign at s = 4 a.u., defining a virtual transition state. Using the gauge representation (electric field gauge) for a wave length λ = 20.6 μm, intensity I = 5×1012 W/cm2, I = 1×1013 W/cm2, I = 3×1013 W/cm2, we show here that we can create a laser-induced potential energy surface crossing along the reaction path (s = 7-8 a.u.). We illustrate such effects for the Li H + CH 3 + ↔ Li+ + CH4 reaction which takes the form of inverted Morse (without a barrier) using ab initio methods for calculating the reaction path and electric properties of the ion-molecule reaction.

Laser atom-molecule reaction interaction through polarizability and dipole moment contribution leads to potential energy surface barrier reshaping and bound states along the reaction path. The polarizability is maximum in the transition state. We will show here by using gauge representation (electric field gauge) for wave length λ = 20.6 μm, intensity I = 1 × 10 12 W/cm 2 , I = 5 × 10 12 W/cm 2 , I = 1 × 10 13 W/cm 2 , I = 3 × 10 13 W/cm 2 , that we can create laser induced potential energy surface barrier reshaping in the transition state region (–1–0.5 a. u.). We illustrate such effects for the LiH + CH 3 ↔ Li + CH 4 reaction with a barrier using ab-initio methods for calculating the reaction path, polarizability and dipole moment contribution of the atom-molecule reaction.

We study numerically the optical properties of low-buckled silicene and AB-stacked bilayer graphene quantum dots subjected to an external electric field, which is normal to their surface. Within the tight-binding model, the optical absorption is calculated for quantum dots, of triangular and hexagonal shapes, with zigzag and armchair edge terminations. We show that in triangular silicene clusters with zigzag edges a rich and widely tunable infrared absorption peak structure originates from transitions involving zero energy states. The edge of absorption in silicene quantum dots undergoes red shift in the external electric field for triangular clusters, whereas blue shift takes place for hexagonal ones. In small clusters of bilayer graphene with zigzag edges the edge of absorption undergoes blue/red shift for triangular/hexagonal geometry. In armchair clusters of silicene blue shift of the absorption edge takes place for both cluster shapes, while red shift is inherent for both shapes of the bilayer graphene quantum dots.

In this study, the back recombination processes of PbS quantum dots sensitized solar cells (QDSSCs) has been investigated. PbS QDs were adsorbed onto titania electrodes to act the role of sensitizers using successive ionic layer adsorption and reaction (SILAR) technique. The energy band gaps of the synthesized PbS QDs/titania are ranged from 1.64 eV (corresponding to 756 nm) to 3.12 eV (397 nm) matching the whole visible solar spectrum. The hyperbolic band model (HBM) was used to calculate PbS QDs size and it ranges from 1.76 to 3.44 nm. The photovoltaic parameters (open circuit voltage V-oc, short circuit current density J(sc), fill factor FF and efficiency eta) of the assembled PbS QDs sensitized solar cells (QDSSCs) were determined under a solar illumination of 100 mW/cm(2) (AM 1.5 conditions). The open circuit voltage-decay (OCVD) rates of the assembled PbS QDSSCs were measured. The time constant (tau) for PbS QDSSCs (4 SILAR cycles) shows one order of magnitude larger than that of PbS QDSSCs (8 SILAR cycles) as a result of a decreased electron-hole back recombination. (C) 2016 Elsevier Ltd. All rights reserved.

Diffusion intermixing processes in nanostructured Ag/Sn thin-film system at room temperature were investigated by means of secondary neutral mass Spectrometry depth profiling technique. As it was confirmed by X-ray diffraction too, the reaction started already in the as-deposited sample. Since the bulk diffusion was frozen at room temperature, the Ag3Sn phase was formed along the grain boundaries (GBs), gradually consuming the interior of grains, and was grown perpendicular to the GBs. At the same time, formation and growth of a small compact reaction layer near the interface were observed and the shift of the bordering parallel interfaces was controlled by GB diffusion. From the kinetics of the diffusion process in the above two mechanisms, both the interface velocity in the diffusion-induced grain boundary motion regime as well as the coefficient of parabolic growth in the planar growth regime were determined.