Photonic Activities Research Articles

Picosecond pulsed laser illumination: an ultimate solution for photonic versus thermal processes\u2019 contest in SOI photo-activated modulator

The functionality of a nanoscale silicon-based optoelectronic modulator is deeply analyzed while it appears that two competing processes, thermal and photonic, are occurring at the same time, and are preventing the optimization of the electro-optics coupling. While an incident illumination-beam first process is translated into photons, generating pairs of electrons–holes, a second process of thermal generation, creating phonons enables a loss of energy. Complementary studies, combining strong analytical models and numerical simulations, enabled to better understand this competition between photonic and thermal activities, in order to optimize the modulator. Moreover, in order to prevent unnecessary heating effects and to present a proposed solution, a picosecond pulsed laser is suggested and demonstrated as the ultimate solution so no energy will be wasted in heat, and still the photonic energy will be fully used. First ever-analytical solution to the heating produced due to the laser illumination applied on a nano-photonic device, while the illumination is produced in a periodic time changing function, e.g. a pulsed illumination, is presented. The present case study and proposed adapted solution can serve as a basis of generic approach in sensors’ activation towards optimized photonics absorption.

Green Synthesis of Copper Oxide Nanoparticles Using Aerva javanica Leaf Extract and Their Characterization and Investigation of In Vitro Antimicrobial Potential and Cytotoxic Activities.

The development of green technology is creating great interest for researchers towards low-cost and environmentally friendly methods for the synthesis of nanoparticles. Copper oxide nanoparticles (CuO-NPs) attracted many researchers due to their electric, catalytic, optical, textile, photonic, monofluid, and pharmacological activities that depend on the shape and size of the nanoparticles. This investigation aims copper oxide nanoparticles synthesis using Aerva javanica plant leaf extract. Characterization of copper oxide nanoparticles synthesized by green route was performed by three different techniques: X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, and Scanning Electron Microscopy (SEM). X-ray diffraction (XRD) reveals the crystalline morphology of CuO-NPs and the average crystal size obtained is 15 nm. SEM images showed the spherical nature of the particles and size is lying in the 15–23 nm range. FTIR analysis confirms the functional groups of active components present in the extract which are responsible for reducing and capping agents for the synthesis of CuO-NPs. The synthesized CuO-NPs were studied for their antimicrobial potential against different bacterial as well as fungal pathogens. The results indicated that CuO-NPs show maximum antimicrobial activities against all the selected bacterial and fungal pathogens. Antimicrobial activities of copper oxide nanoparticles were compared with standard drugs Norfloxacin and amphotericin B antibiotics. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of copper oxide nanoparticles were 128 μg/mL against all selected bacterial pathogens. MIC of fungus and minimum fungicidal concentration (MFC) of CuO-NPs were 160 μg/mL. Thus, CuO-NPs can be utilized as a broad-spectrum antimicrobial agent. The cytotoxic activity of the synthesized CuO-NPs suggested that toxicity was negligible at concentrations below 60 μg/mL.

Aqueous Carbon Quantum Dot-Embedded PC60-PC61BM Nanospheres for Ecological Fluorescent Printing: Contrasting Fluorescence Resonance Energy-Transfer Signals between Watermelon-like and Random Morphologies.

To go beyond the PC60 surfactant structure, the double-layer micelle morphology in water motivates exploration of altered protocols to produce new morphologies. Furthermore, the low photoluminescence quantum yield of aqueous fullerene-based particles encourages high fluorescence to create a light-emitting display. With this in mind, we established new hybrid n-type nanospheres with carbon quantum dot (CQD)-embedded PC60-PC61BM particles, processed using two different protocols. The homogenizer-assisted PC60-CQD-PC61BM resulted in a watermelon-shaped spherical particle, whereas a circular morphology with randomly embedded CQDs was observed in the microwave-treated hybrids. More surprisingly, the watermelon-shaped colloid induced efficient fluorescence resonance energy transfer (FRET) between the CQD and C60 molecules of PC61BM, and the FRET-mediated emission signature diminished gradually as the stripe patterns collapsed. This phenomenon allowed different fluorescent colors in the colloidal printing film. We thereby provided the new carrier dynamics of the particle photonic activities of the developed aqueous PC60-based colloids with the possibility of ecological utilization.

Advances in Magnetic Noble Metal/Iron-Based Oxide Hybrid Nanoparticles as Biomedical Devices.

The study of the noble metal magnetic hybrid nanoparticles is a really promising topic from both the scientific and the technological points of views, with applications in several fields. Iron oxide materials which are hybridized with noble metal nanoparticles (NPs) have attracted increasing interest among researchers because of their cooperative effects on combined magnetic, electronic, photonic, and catalytic activities. This review article contains a summary of magnetic noble metal/iron oxide nanoparticle systems potentially useful in practical biomedical applications. Among the applications, engineered devices for both medical diagnosis and treatments were considered. The preparation to produce different structures, as blends or core-shell structures, of several nanometric systems was also considered. Several characterization techniques available to describe the structure, morphology and different kinds of properties of hybrid nanoparticles are also included in this review.

Origin of the deep band-gap state in TiO2 (110): ddσ bonds between Ti-Ti pairs

Defects play crucial roles in the photonic and chemical activities of ${\mathrm{TiO}}_{2}$. The origin of the deep band-gap defect state ${S}_{bg}$ in the rutile ${\mathrm{TiO}}_{2}$(110) surface has remained controversial for quite a long time. Using many-body Green's function theory, we believe that ${S}_{bg}$ can be attributed only to $\ensuremath{\sigma}$ bonds formed between $3d$ orbitals at the Ti interstitial, while the nonbonded Ti $3d$ defect states from the oxygen vacancy and polaron, which are held to be responsible for ${S}_{bg}$ by the present prevailing view, are shallow regardless of their spatial distribution. Especially, we discover the defect-induced appreciable downshift of unoccupied Ti $3d$ bands which should be the key for accurately describing the electronic structure of ${\mathrm{TiO}}_{2}$ but was missed in previous studies based on density functional theory. Our model could more consistently and more reasonably account for various experimental phenomena on rutile (110) than the current model based on the oxygen vacancy and polaron.

Polarized Induced Magnetic Broadening of Photonic Activities in Fe3O4-Elastomer Composites

AbstractWe report a systematic study of polarization and magnetic field effects on the optical response of Fe3O4-silicone elastomer composite. The Fe3O4 particles were aligned in a silicone elastomer matrix with an external static magnetic field. Films of composites containing 5wt% of 20nm ≤ d ≤ 30nm Fe3O4 particles aligned in- and out-of-plane in the elastomer host were prepared. The optical spectra of the films were measured with the Perkin-Elmer Lambda 950 UV/vis/NIR spectrometer. We observed a systematic redshift in the optical response of the outof-plane composite films with increasing static magnetic field strength, which saturated near 600 Gauss. We obtained a maximum redshift of ∼46 nm at 600 Gauss. The observed redshift in the optical response of the out-of-plane composite film is attributed to the effect of the magnetic field. This facilitated the formation of the highly aligned particles that induced strong electric dipole in the aligned particles. Interestingly, there were no observable shifts with increasing magnetic field strength in the in-plane films, suggesting that the orientation (polarization) of the magnetic dipole and the induced electric dipole play a crucial role in the optical response.

Photoelectrochemical studies on aqueous suspensions of 3‐dodecyl 2–5 di‐thionyl pyrrole/metal oxide photoactive interfaces

Colloidal ZnO, Fe2O3 and Cu2O solutions were used to explore photonic activities at metal oxides/organic semiconductors interfaces. Fluorescence spectroscopic and dynamic electrochemical techniques were performed on colloidal metal oxides articles modified with 3‐dodecyl 2–5 di‐thionyl pyrrole (3‐DODTh‐Py) to investigate the quantum absorbance efficiency at this inorganic/organic interface (IOI). The IOI assemblies were p‐n junction‐type interfaces, where 3‐DODTh‐Py) functions as electron donor. Results were interpreted using the optical and electrochemical parameters of the organic monomer such as IP (ionization potential), EA (electron affinity), and Eg (Energy band gap), and the barrier height at the IOI interface. One of the driving forces for great absorption at IOI was the great difference in electronegativity between inorganic and organic interface. Copyright © 2011 John Wiley & Sons, Ltd.

Fe-ACF/TiO2복합체의 특성화와 가시광선조건에서 MB 용액의 광촉매활성

본 연구에서 종래의 졸-겔법을 사용하여 Fe-ACF/<TEX>$TiO_2$</TEX> 광촉매 복합체를 제조하였고, 이들 광촉매의 분해능은 메틸렌블루 (MB) 용액의 분해에 의하여 나타내었다. 제조된 이들 복합체에 대한 입자크기, 표면구조, 결정상 및 원소분석을 BET, SEM, XRD 및 EDX에 의하여 각각 특성화 하였다. 가시광선 조건에서 분해된 MB 농도에 대한 스펙트라는 UV/Vis 분광기에 의하여 얻어 졌다. 이와 같이 얻어진 스펙트라는 MB의 제거된 농도로부터 광촉매 활성을 입증하였다. 이들 광촉매 활성은 가시광선 조건에서 복합체 광촉매 내에 존재하는 ACF, <TEX>$TiO_2$</TEX> 및 Fe 사이에 강력한 시너지 반응에 의해 유도된 것으로 여겨진다. In present study, a conventional sol-gel method was used to prepare Fe-ACF/<TEX>$TiO_2$</TEX> composites, a kind of composite photocatalysts, whose capability was evaluated by degrading methylene blue (MB) solution. The particle size, surface structure, crystal phase and elemental identification of the composites prepared were characterized by BET, SEM, XRD and EDX, respectively. The spectra of MB concentration degraded under visible light were obtained by UV/Vis spectrophotometer. These obtained spectra demonstrated the photocaltalytic activity from removal concentrations of MB. It was considered that these photonic activities are induced by a strong synergetic reaction among ACF, <TEX>$TiO_2$</TEX> and Fe in the composite photocatalysts under visible light.

Photoelectrochemical studies on colloidal copper (I) oxide/modified with some organic semiconductors: Incentive for use of nanoparticle systems

Colloidal Cu2O solutions were used to explore photonic activities at the semiconductor/electrolyte interface. Fluorescence spectroscopic studies were performed on Cu2O colloidal particles modified with some conjugated organic monomers such as 2-amino-phenyl pyrrole (2-APPy), tri-phenyl amine (TPA), or 2-thionyl pyrrole (2-Th-Py) to investigate the quantum absorbance efficiency at this inorganic/organic interface (IOI). Our study shows that colloidal p-type Cu2O possesses a bandgap with direct transition of ≈ 2·2 eV and indirect transition of 1·85 eV. The recorded rates of charge injection into colloidal Cu2O, k ct, were 2·31 × 109 s−1, 5·05 × 108 s−1, and 7·22 × 108 s−1 for 2-APPy, TPA and 2-Th-Py, respectively. The studied systems show more stability in colloidal form than in thin solid form. Results were interpreted using the optical and electrical parameters of the organic monomer such as ionization potential (IP), electron affinity (EA) and energy bandgap (Eg), and the barrier height at the IOI interface. Stability of the colloidal system is attributed to the physical dimensions of the photoactive system. The nano-colloidal particle offers a condition where its size is less than √Dt.

Platelet-activating factor and granulocyte-mediated oxidative stress. Strategy for in vivo oxyradical visualization.

Platelet-activating factor (PAF) and leukotriene B4 are potent lipid mediators of endothelium-granulocyte interaction which results in granulocyte-dependent increased microvascular permeability. The specific mechanism by which PAF induces granulocyte-mediated endothelial injury has not been fully investigated. Digital imaging photonic intensified microscopy has revealed that PAF effectively induces granulocyte-mediated oxidative stress on microvascular beds. The method has made it possible to visualize luminol-dependent photonic burst released from PAF-treated microvascular beds in the rat mesentery. The photonic activities clearly corresponded to the localization of sticking granulocytes in post-capillary venules. By contrast, no significant chemilumigenic response could be detected in the leukotriene B4-induced activation of endothelium-granulocyte interaction in vivo. The present findings suggest that oxygen radicals are not prerequisites for granulocyte adhesion in the microcirculation and provide evidence for a dissociation of in vivo granulocyte function between leukotactic and oxidative activation in leukotriene B4-induced microvascular changes.

Luminol-dependent photoemission from single neutrophil stimulated by phorbol ester and calcium ionophore — role of degranulation and myeloperoxidase

Luminol-dependent photonic burst from phorbol ester-treated single neutrophil was visually investigated by using an ultrasensitive photonic image intensifier microscope. Neutrophils stimulated by phorbol myristate acetate (0.1 microgram/ml) alone produced a negligible level of photonic activities in the presence of luminol (10 micrograms/ml). The additional application of 0.1 microM Ca2+ ionophore A23187 induced explosive changes of photonic burst corresponding to the distribution of neutrophils, and these photonic activities were gradually spread to extracellular space. Sodium azide, which prevents myeloperoxidase activity, inhibited Ca2+ ionophore-induced photonic burst from phorbol ester-treated neutrophil. These findings suggest a prerequisite role of degranulation and myeloperoxidase release in luminol-dependent photoemission from stimulated neutrophils.

Real-time visualization of oxyradical burst from single neutrophil by using ultrasensitive video intensifier microscopy.

Dynamics of oxyradical burst from single human neutrophils stimulated by opsonized zymosan was visualized by using an ultrasensitive video intensifier microscopy in the presence of chemiluminescence probe. Luminol-dependent photonic burst activities were clearly corresponding to the distribution of zymosan-treated neutrophils. Heterogeneity of photon-bursting period and the maximum photonic intensity among reactive cells was demonstrated. This may reflect functional heterogeneity of the ability to release oxyradicals among neutrophils.