Strong Photoabsorption Research Articles

Semimetal nanomaterials of antimony as highly efficient agent for photoacoustic imaging and photothermal therapy

In this study we report semimetal nanomaterials of antimony (Sb) as highly efficient agent for photoacoustic imaging (PAI) and photothermal therapy (PTT). The Sb nanorod bundles have been synthesized through a facile route by mixing 1-octadecane (ODE) and oleyl amine (OAm) as the solvent. The aqueous dispersion of PEGylated Sb NPs, due to its broad and strong photoabsorption ranging from ultraviolet (UV) to near-infrared (NIR) wavelengths, is applicable as a photothermal agent driven by 808 nm laser with photothermal conversion efficiency up to 41%, noticeably higher than most of the PTT agents reported before. Our in vitro experiments also showed that cancer cell ablation effect of PEGylated Sb NPs was dependent on laser power. By intratumoral administration of PEGylated Sb NPs, 100% tumor ablation can be realized by using NIR laser irradiation with a lower power of 1 W/cm2 for 5 min (or 0.5 W/cm2 for 10 min) and no obvious toxic side effect is identified after photothermal treatment. Moreover, intense PA signal was also observed after intratumoral injection of PEGylated Sb NPs and NIR laser irradiation due to their strong NIR photoabsorption, suggesting PEGylated Sb NPs as a potential NIR PA agent. Based on the findings of this work, further development of using other semimetal nanocrystals as highly efficient NIR agents can be achieved for vivo tumor imaging and PTT.

Dynamic Analysis of High-Efficiency InP-Based Photodiode for 40 Gbit/s Optical Interconnect Across a Wide Optical Window (0.85 to 1.55 μm)

The detailed dynamic analysis of novel high-speed InP-based photodiodes (PDs) has been performed. Such device can sustain an invariable high external efficiency (∼74%; no antireflection coating) across a wide optical operation window (0.85 to 1.55 μm). Furthermore, compared with the traditional GaAs-based high-speed PD for optical interconnect applications, our proposed device structure can offer an enlarged device active diameter and eliminate the degradation in responsivity performance when the desired speed performance is increased. This is because the strong photoabsorption process and the elimination of slow hole drift in the In0.53Ga0.47As based collector layer at 0.85-μm wavelength operation. By measuring the dynamic performance of PDs with different active diameters across such wide optical window, we can accurately extract the electron drift-velocity under different wavelengths excitations in the In0.53Ga0.47As collector layer. This result indicates that at short-wavelength (0.85 μm) operation, the photogenerated electron in the In0.53Ga0.47As collector suffers from significant intervalley scattering effect due to its high excess energy. By using such device with diameter of optical window as large as 40 μm, 40 Gbit/s error-free transmissions have been successfully demonstrated through 5-km single-mode (SMF-28) and 0.1-km multimode (OM4) fibers at long- and short-wavelengths operations with reasonable sensitivity, respectively.

Yb-doped ZnSe nanoparticles: synthesis, physical properties and photocatalytic activity.

In this study, Yb-doped ZnSe nanoparticles were synthesized by co-reduction method at 150 degrees C and pH = 12 for 24 h. The obtained materials were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Powder XRD patterns indicated that the Yb(x)Zn(1-x)Se crystals (x = 0.00-0.10) are isostructural with ZnSe. SEM and TEM images confirmed doping of Yb3+ into the lattice of ZnSe nanoparticles. The UV-Vis diffuse reflectance characteristics of the Yb-doped ZnSe samples were quite similar to that of the undoped sample and showed a strong photoabsorption at visible light range. The electrical conductivity of Yb-doped ZnSe nanomaterials was higher than pure ZnSe at room temperature, and increased with temperature. The photocatalytic activity of synthesized nanoparticles was investigated by the degradation of Orange II solution under visible light irradiation. It was observed that the color removal efficiency of Yb-doped ZnSe catalyst was much higher than that of pure ZnSe (26.28 and 77.10% after 120 min of treatment for ZnSe and Yb(0.06)Zn(0.94)Se, respectively). The results demonstrated the good photocatalytic ability of synthesized nanoparticles under visible light. Also, it was revealed that the decolorization efficiency of Orange II over Yb-doped ZnSe increased with increasing Yb loading up to 6 mol% and then decreased.

Efficient adsorption and photocatalytic degradation of Rhodamine B under visible light irradiation over BiOBr/montmorillonite composites

BiOBr/Na–montmorillonite composites (BiOBr–Mt) were prepared under laboratory ambient conditions by using the surfactant cetyltrimethylammonium bromide (CTAB) as the Br source and template, and the as-synthesized samples were characterized by XRD, FT-IR, FESEM, TEM equipped with EDS, BET and UV–vis DRS techniques. Interestingly, the particle size of BiOBr can be controlled by CTAB modified Na-montmorillonite. The photocatalytic activity of the as-prepared was further evaluated by decomposition of Rhodamine B (RhB) under visible light irradiation; the obtained results revealed that the BiOBr–Mt sample had strong photoabsorption in the visible light region. It has higher photocatalytic activity than pure BiOBr alone. There exists an efficient adsorption for RhB onto BiOBr–Mt contrast to that onto the pure BiOBr. The adsorption processes can be well described by pseudo-second-order kinetic model; meanwhile, the adsorption behaviors can be described by both Freundlich and Langmuir equations but the former was better. Additionally, the relevant adsorption and degradation mechanisms were explored and the possible mechanisms were presented. The photocatalytic activity has high effect both in acidic and basic conditions on the degradation reaction but in acidic condition is more favorable. After three recycles, BiOBr–Mt did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst was essentially stable.

Enhanced photoabsorption properties of composites of Ti/TiO2 nanotubes decorated by Sb2S3 and improvement of degradation of hair dye

The present work illustrates the great potentiality of Ti/TiO2/Sb2S3 composite electrode prepared by electrochemical anodization of Ti foil in aqueous electrolyte (1 mol L−1 NaH2PO4 + 0.3 wt.% HF followed by chemical bath deposition of Sb2S3) in environmental electrochemistry. The electrodes are characterized by deposits of particles of 500 nm of diameter formed on the top of TiO2 nanotubes of 900 nm of length, 110 nm of diameter and 13 nm of wall thickness. The band gap obtained for Ti/TiO2/Sb2S3 composite electrode was 1.68 eV, contributing to strong photoabsorption properties of the material in the visible light region (λ < 740 nm). The photocurrent on this material is remarkably improved in relation to that obtained on comparable nanotubes TiO2 films. The electrodes promote complete degradation of the investigated hair dyeing commercialized as Arianor Tyrian Purple® after 120 min of photoelectrocatalytic oxidation under potential of 1.2 V and commercial light irradiating under UV/Visible light. Finally, the degradation products generated by photoelectrocatalysis were analyzed by HPLC–MS/MS.

Synthesis and photocatalytic property of BiOBr/palygorskite composites

BiOBr/palygorskite composite photocatalysts were prepared by a hydrothermal method for the first time, which were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), N2-sorption and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared samples was evaluated by decomposition of methyl orange (MO) under visible light irradiation. The results revealed that BiOBr/palygorskite composites had strong photoabsorption in the visible light region. All BiOBr/palygorskite composites possessed higher photocatalytic activity than pure BiOBr. The highest activity was obtained by S5.0 sample. The enhanced photocatalytic performance was attributed to strong photoabsorption, the synchronous role of adsorbability and photocatalytic oxidation on BiOBr/palygorskite composites and the efficient separation of photogenerated electron–hole pairs.

Gold Nanowires: A Time-Dependent Density Functional Assessment of Plasmonic Behavior

The surface plasmon resonance has been theoretically investigated in gold nanowires by means of time-dependent density functional theory. Linear chains of Au atoms and nanowires with the structure of the fcc bulk gold grown along the ⟨110⟩ and ⟨111⟩ directions have been considered. The effects of changing the length and the section on the plasmon have been studied. Strong photoabsorption is found when the length is above 2 nm: in that case the absorption profile is characterized by a sharp peak, and its analysis reveals that many configurations contribute to the transition, confirming its collective nature as an s ← s intraband transition. As expected, the effect of increasing the length is reflected in a red shift of the plasmon.

Simultaneous and Stoichiometric Water Oxidation and Cr(VI) Reduction in Aqueous Suspensions of Functionalized Plasmonic Photocatalyst Au/TiO2–Pt under Irradiation of Green Light

Titanium(IV) oxide (TiO2) having both small platinum (Pt) nanoparticles and large gold (Au) particles without alloying and nanoparticle coagulation was successfully prepared by the combination of traditional photodeposition of Pt and subsequent Au colloid photodeposition onto TiO2–Pt. The Au/TiO2 and Au/TiO2–Pt samples exhibiting strong photoabsorption due to surface plasmon resonance (SPR) of supported Au particles were used for the reduction of hexavalent chromium (Cr6+ in Cr2O72–) in aqueous suspensions under irradiation of visible light from a green light emitting diode (LED). These SPR-type photocatalysts reduced Cr6+ and evolved dioxygen (O2) with O2-reduced Cr6+ ratio of 3:4 until consumption of Cr6+, indicating that these SPR-type photocatalysts had the ability to oxidize water (H2O) utilizing visible light (λ = 540 nm) and that a photocatalytic reaction (2Cr2O72– + 16H+ → 4Cr3+ +3O2 + 8H2O) occurred. The Au/TiO2–Pt sample exhibited a reaction rate about twice larger than that of Pt-free Au/TiO2, ...

Microwave hydrothermal synthesis and optical properties of flower-like Bi2MoO6 crystallites

Abstract Flower-like Bi 2 MoO 6 crystallites were successfully synthesized by the microwave hydrothermal process using Bi(NO 3 ) 3 ·5H 2 O and Na 2 MoO 4 ·2H 2 O as source materials and adding hexamethylene tetramine (HMT) as a template. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were used to characterize the products. Ultraviolet–visible (UV–vis) spectroscopy was employed to study the optical properties of Bi 2 MoO 6 . Results show that the product morphology is flower-like on adding the template. These flower-like Bi 2 MoO 6 crystallites are a self-assembly of many thin nanoplates. HMT plays an important role in the formation of the flower-like morphology. UV–vis absorption spectra of all the Bi 2 MoO 6 samples show strong photoabsorption properties from the ultraviolet region to the visible-light region with wavelength shorter than 500 nm. The band gap of flower-like Bi 2 MoO 6 crystallites displays a slight red-shift compared with the Bi 2 MoO 6 plate-like structures.

Size-controllable hydrothermal synthesis of ZnS nanospheres and the application in photocatalytic degradation of organic dyes

Herein, using histidine as the additive, well-dispersed ZnS nanospheres with the controllable size and large specific surface area were prepared successfully in large scale via a facile one-pot hydrothermal synthesis method. The as-prepared ZnS nanospheres exhibited strong photo absorption in the UV and visible light region. From the results, the as-prepared ZnS nanospheres prepared at 160°C for 6h could photocatalytically degrade the rhodamine B efficiently through the mediation of photo-generated hydroxyl radicals under UV light irradiation. These suggest that the ZnS nanospheres prepared in this study might be used as the potential photocatalysts to treat the organic pollutants efficiently.

Preparation of Au/TiO2 with Metal Cocatalysts Exhibiting Strong Surface Plasmon Resonance Effective for Photoinduced Hydrogen Formation under Irradiation of Visible Light

Titanium(IV) oxide (TiO2) having both small platinum (Pt) nanoparticles and large gold (Au) particles without alloying and nanoparticle coagulation was successfully prepared by the combination of traditional photodeposition of Pt in the presence of a hole scavenger (PH) and subsequent Au colloid photodeposition in the presence of a hole scavenger (CPH) onto TiO2–Pt. Au particles having an average diameter of 13 nm were fixed on both TiO2 and TiO2–Pt samples without change in the original size of Au particles, and the Au/TiO2 and Au/TiO2–Pt samples exhibited strong photoabsorption around 550 nm as a result of surface plasmon resonance (SPR) of Au to which the large size of Au particles was attributed. Bare TiO2, TiO2–Pt, Au/TiO2, and Au/TiO2–Pt samples were used for photoinduced hydrogen (H2) formation from 2-propanol in aqueous solutions under irradiation of visible light. The first two samples yielded no H2 because of no response to visible light, but the latter two formed H2, indicating that SPR photoab...

Gold–Titanium(IV) Oxide Plasmonic Photocatalysts Prepared by a Colloid-Photodeposition Method: Correlation Between Physical Properties and Photocatalytic Activities

Colloidal gold (Au) nanoparticles were prepared and successfully loaded on titanium(IV) oxide (TiO(2)) without change in the original particle size using a method of colloid photodeposition operated in the presence of a hole scavenger (CPH). The prepared Au nanoparticles supported on TiO(2) showed strong photoabsorption at around 550 nm due to surface plasmon resonance (SPR) of Au and exhibited a photocatalytic activity in mineralization of formic acid in aqueous suspensions under irradiation of visible light (>ca. 520 nm). A linear correlation between photocatalytic activity and the amount of Au loaded, that is, the number of Au nanoparticles, was observed, indicating that the activity of Au/TiO(2) plasmonic photocatalysts can be controlled simply by the amount of Au loading using the CPH method and that the external surface area of Au nanoparticles is a decisive factor in mineralization of formic acid under visible light irradiation. Very high reaction rates were obtained in samples with 5 wt % Au or more, although the rate tended to be saturated. The CPH method can be widely applied for loading of Au nanoparticles on various TiO(2) supports without change in the original size independent of the TiO(2) phase. The rate of CO(2) formation also increased linearly with increase in the external surface area of Au. Interestingly, the TiO(2) supports showed different slopes of the plots. The slope is important for selection of TiO(2) as a material supporting colloidal Au nanoparticles.

Preparation of Au/CeO2 Exhibiting Strong Surface Plasmon Resonance Effective for Selective or Chemoselective Oxidation of Alcohols to Aldehydes or Ketones in Aqueous Suspensions under Irradiation by Green Light

Au/CeO(2) samples with various Au contents were prepared by the multistep (MS) photodeposition method. Their properties including Au particle size, particle dispersion, and photoabsorption were investigated and compared with properties of samples prepared by using the single-step (SS) photodeposition method. The MS- and SS-Au/CeO(2) samples were used for selective oxidation of benzyl alcohols to corresponding benzaldehydes in aqueous suspensions under irradiation by visible light from a green LED, and the correlations between reaction rates and physical properties of the MS- and SS-Au/CeO(2) samples were investigated. Difference in the two photodeposition methods was reflected in the average size and number of Au nanoparticles, for example, 92 nm and 1.3 × 10(12) (g-Au/CeO(2))(-1) for MS photodeposition and 59 nm and 4.8 × 10(12) (g-Au/CeO(2))(-1) for SS photodeposition in the case of 1.0 wt % Au samples. Fixation of larger Au particles resulted in strong photoabsorption of the MS-Au/CeO(2) samples at around 550 nm due to the surface plasmon resonance, and the Kubelka-Munk function of the photoabsorption linearly increased with increase in Au content up to 2.0 wt %, in contrast to the photoabsorption of SS-Au/CeO(2) samples, which was weak and was saturated even at around 0.5 wt %. Due to the strong photoabsorption, the MS-Au/CeO(2) samples exhibited reaction rates approximately twice larger than those of SS-Au/CeO(2) samples with the same Au contents, and apparent quantum efficiency of MS-Au/CeO(2) reached 4.9% at 0.4 mW cm(-2). Linear correlations were observed between reaction rates (r) and surface area of Au nanoparticles (S) in both MS- and SS-Au/CeO(2) samples, though the two slopes of r versus S plots were different, suggesting that oxidation of benzyl alcohol occurred on the Au surface and that S was one of the important factors controlling the reaction rate. Photocatalytic oxidation of benzyl alcohol having an amino group revealed that the Au/CeO(2) photocatalyst exhibited high chemoselectivity toward the hydroxyl group of alcohol, i.e, the Au/CeO(2) photocatalyst almost quantitatively converted aminobenzyl alcohol to aminobenzaldehyde with 99% yield.

Efficient Sunlight-Induced Methylene Blue Removal over One-Dimensional Mesoporous Monoclinic BiVO(4) Nanorods.

Sunlight-driven mesoporous BiVO4 nanorods with monoclinic structure have been successfully synthesized via a simple hydrothermal method. The as-prepared one-dimensional BiVO4 nanorods exhibited high specific surface area due to their unique mesoporous structure. The mesoporous BiVO4 nanorods possessed strong photoabsorption properties in the visible light region as well as the ultravisible region, and the band gap was estimated to be ca. 2.18 eV. The photocatalytic activities were evaluated by decolorization of methylene blue under sunlight irradiation. Photocatalytic tests demonstrated that the decolorization rate of as-prepared mesoporous BiVO4 nanorods was even up to 98.8% in 180 min, much better than that prepared by solid-state reaction (23.1%) and the commercial TiO2 (Degussa P25) (14.2%) under the same conditions, due to their higher specific surface area and appropriate band gap. Moreover, the unique BiVO4 nanorods exhibit high stability after five photocatalytic degradation recycles.

N‐2‐Aryl‐1,2,3‐triazoles: A Novel Class of UV/Blue‐Light‐Emitting Fluorophores with Tunable Optical Properties

The N-2-aryl-1,2,3-triazole derivatives (NATs) were developed as a new class of UV/blue-light-emitting fluorophores. Though both N-1-aryl-1,2,3-triazoles and N-2-aryl-1,2,3-triazoles gave strong photo absorption under excitation at 330 nm, only the N-2-analogous showed strong fluorescence emission in the UV/blue range with high efficiency in various solvents (quantum yield Φ around 0.3-0.5). Significant substituted group effects were observed, allowing tunable optical properties with emission (λ(max)) from 350-400 nm and Stokes shift from 38-93 nm. The computational studies along with X-ray crystal structures indicated the significance of the effective conjugation between triazole ring and aryl groups on the N-2 position. The planar intramolecular charge transfer (PICT) mechanism was proposed, which was supported by solvent effect studies. Simple derivatizations gave NAT-modified lysine and strong UV/blue emitting bis-NAT (Φ=0.76, λ(max)=390), which suggested the great potential of this new class of fluorophores in biological and material science research.

Fluoride ion yield and absorption spectral analysis of irradiated imidazolium-based room-temperature ionic liquids

The radiation chemical yields of F ions (G(F−) values) were measured for a group of imidazolium-based room-temperature ionic liquids following 60Co gamma ray irradiation. The G(F−) values of ionic liquids: hexafluorophosphate, bis[(trifluoromethyl)sulfonyl]imide, trifluoromethanesulfonate and tetrafluoroborate anions associated with 1-butyl-3-methylimidazolium cations were determined to be 0.227, 0.136, 0.101 and 0.008μmolJ−1, respectively. The G(F−) value is dependent on the F–X (X=B, P, etc.) bond energy and the anion structure and can be considered as an indicator of the radiation stability of fluorine-containing ionic liquids. In addition, as confirmed by UV–Vis absorption measurement, the radiolytic products with strong photoabsorption and color darkening depend on the structures of both the cation and the anion.

Synthesis and visible light photocatalysis water splitting property of chromium-doped Bi 4Ti 3O 12

Photocatalysts Bi 4Ti 3 − x Cr x O 12( x = 0.00, 0.06, 0.15, 0.30, 0.40, and 0.50) with perovskite structure were synthesized by sol–gel method and their electronic structures and photocatalytic activities were investigated. The Bi 4Ti 2.6Cr 0.4O 12 photocatalyst exhibited the highest performance of H 2 evolution in methanol aqueous solution (58.1 μmol h − 1 g − 1 ) under visible light irradiation ( λ > 400 nm) without a co-catalyst, whereas no H 2 evolution is observed for Bi 4Ti 3O 12 under the same conditions. The UV–vis spectra indicated that the Bi 4Ti 2.6Cr 0.4O 12 had strong photoabsorption in the visible light region. The results of density functional theory (DFT) calculation illuminate that the conduction bands of Bi 4Ti 3O 12 are mainly attributable to the Ti 3 d + Bi 6 p orbitals, and the valence bands are composed of O 2 p + Bi 6 s hybrid orbitals, while the conduction bands of chromium-doped Bi 4Ti 3O 12 are mainly attributable to the Ti 3 d + Bi 2 p + Cr 3 d orbitals, and the O 2 p + Cr 3 d hybrid obitals are the main contribution to the valence band.

Nanoscale substrate recognition by porphyrin dendrimers with patched structures

Dendrimer technology has enabled us to build macromolecules with nanosized defined structures. By introducing unsymmetrical patched structures in dendrimers, sophisticated artificial receptors exhibiting nanoscale substrate recognition can be obtained. In this review article, our recent studies on molecular recognition by porphyrin dendrimers with patched structures are summarized. Three topics are presented: (1) oligopeptide-patched dendrimers as a nanoscale receptor of cytochrome c protein; (2) pocket dendrimers as a nanoscale receptor for bimolecular guest accommodation; and (3) energy transfer in unsymmetrical dendrimers. These dendrimers nicely mimic proteins and enzymes, and also act as photofunctional artificial receptors, in which porphyrin’s strong photoabsorption and intense fluorescence signals can respond sensitively to the substrate binding.

Diagnostics of SS433 with the RXTE

We present our analysis of the extensive monitoring of SS433 by the RXTE observatory collected over the period 1996–2005. The difference between energy spectra taken at different precessional and orbital phases shows the presence of strong photoabsorption ( cm-2) near the optical star, probably due to its powerful, dense wind. Therefore the size of the secondary deduced from analysis of X-ray orbital eclipses might be significantly larger than its Roche lobe size, which must be taken into account when evaluating the mass ratio from analysis of X-ray eclipses. Assuming that a precessing accretion disk is geometrically thick, we recover the temperature profile in the X-ray emitting jet that best fits the observed precessional variations in the X-ray emission temperature. The hottest visible part of the X-ray jet is located at a distance of , or ~ cm from the central compact object, and has a temperature of about keV. We discovered appreciable orbital X-ray eclipses at the “crossover” precessional phases (jets are in the plane of the sky, disk is edge-on), which under model assumptions put a lower limit on the size of the optical component and an upper limit on a mass ratio of binary companions , if the X-ray opaque size of the star is not larger than .

Matrix-assisted laser desorption/ionization (MALDI) mechanism revisited

Although matrix-assisted laser desorption/ionization (MALDI) was developed more than a decade ago and broad applications have been successfully demonstrated, detailed mechanism of MALDI is still not well understood. Two major models; namely photochemical ionization (PI) and cluster ionization (CI) mechanisms have been proposed to explain many of experimental results. With the photochemical ionization model, analyte ions are considered to be produced from a protonation or deprotonation process involving an analyte molecule colliding with a matrix ion in the gas phase. With the cluster ionization model, charged particles are desorbed with a strong photoabsorption by matrix molecules. Analyte ions are subsequently produced by desolvation of matrix from cluster ions. Nevertheless, many observations still cannot be explained by these two models. In this work, we consider a pseudo proton transfer process during crystallization as a primary mechanism for producing analyte ions in MALDI. We propose an energy transfer induced disproportionation (ETID) model to explain the observation of an equal amount of positive and negative ions produced in MALDI for large biomolecules. Some experimental results are used for comparisons of various models.