Twentyfold Enhancement Research Articles

Laser peening induced mitigation of severe pitting corrosion in titanium stabilized 321 steel

Titanium stabilized 321 stainless steel, as a structural component in oil and petrochemical industries, often susceptible to severe pitting corrosion under aggressive corrosion environments (sulfuric acid and chloride ions). This study explores the applicability of laser peening without protective coating (at 6 GW cm−2 intensity and 75 % pulse overlap rate) to enhance the electrochemical stability of 321 steel against such severe pitting corrosion. Laser peening altered surface-mechanical and electrochemical properties were investigated by AFM, SEM and potentiodynamic polarization/impedance spectroscopy techniques. On the account of laser peening induced compressive residual stress (-408 MPa) hardness enhancement, a stable/dense and uniform oxide film was formed on 321 steel, subsequently mitigating the pitting corrosion. By contrast, unpeened surface exhibited more number of wider and deeper merged pits (maximum diameter of ∼ 2197 μm). Laser peening promoted oxidation has been confirmed via elemental composition analysis. A twentyfold enhancement in charge transfer resistance and improved oxide film resistance, attributed from the laser peening increased defect density as demonstrated by the improved hardness, evidenced a highly electrochemical stability on 321 steel.

Effect of Organic Additives on the Intensity of Metal Lines in the Emission Spectrum of a Drop-Spark Discharge upon Sample Introduction into an Electrolyte Anode

The effect of the nature and concentration of organic medium modifiers on the intensity of lines of some heavy metals (Ag, Cd, Hg, Pb, Tl, Zn) in the spectrum of a drop-spark discharge upon sample introduction into an electrolyte anode is studied. It is shown that additives of 0.1–6 wt % of polar organic compounds greatly increase the intensity of Pb, Tl, and Zn lines and reduce the intensity of Ag lines. The greatest effect, a twenty-fold enhancement of zinc lines, is observed upon the introduction of methanol into dilute acids. The cadmium signal is insensitive to organic impurities in dilute acids, but is enhanced in concentrated salt solutions.

Synergistic enhancement of π-electron density in graphitic carbon nitride for significantly improved photocatalytic hydrogen evolution under visible-light irradiation

In this work, a synergistic strategy integrated elemental doping and defect engineering has been developed to modulate the electronic and bandgap structure of g-C3N4 by controlling its conjugated aromatic system. Experimental analysis and theoretical calculations confirm that the generation of imbalanced spatial distributions of charge carriers not only greatly increases the π-electron availability, but also decreases the energy barrier for hydrogen adsorption due to the synergistic effect of the high valence electron of the W dopant and the decreased electronegativity by two-coordinated nitrogen defects, which strengthens the charge transfer efficiency and favors the light capturing capability. The combined benefits of the electronic, optical and textural modification lead to a significant improvement of photocatalytic activity of 3.3 mmol h−1 g−1 for hydrogen evolution under λ ≥ 400 nm light irradiation, about twentyfold enhancement than that of pristine g-C3N4. Such proposed synergistic strategy provides a promising route to promote the performance of g-C3N4 for potential applications in solar energy conversion.

Physicomechanical, rheological and in vitro cytocompatibility properties of the electron beam irradiated blend hydrogels of tyramine conjugated gum tragacanth and poly (vinyl alcohol)

In the present study, preparation of blend hydrogels of tyramine conjugated gum tragacanth and poly (vinyl alcohol) was carried out by electron beam irradiation, and modification of hydrogel properties with poly (vinyl alcohol) was demonstrated. Gel content, swelling behavior, pore size and mechanical and rheological properties of hydrogels prepared at 14, 28 and 56 kilogray (kGy) with different ratios of polymers were investigated. Gel content increased from 67±2% for pure tyramine conjugated gum tragacanth hydrogel to >92% for blend hydrogels. However, the corresponding equilibrium swelling degree decreased from 35.21±1.51 to 9.14±1.66 due to the higher crosslink density of blend hydrogel. The mechanical strength of the hydrogels with interconnected pores increased significantly in the presence of poly (vinyl alcohol) and increasing irradiation dose up to 28kGy with a twenty-fold enhancement of stress fracture and excellent elastic recovery in cyclic compression analysis. The equilibrium swelling degree of blend hydrogel containing 3% w/v tyramine conjugated gum tragacanth and 2% w/v poly (vinyl alcohol) prepared at 28kGy was 16.59±0.81. The biocompatibility of hydrogels was tested in the presence of rabbit bone marrow mesenchymal stem cells. The viability of cells exposed to hydrogel extract was >92% after 7days of culture and indicated hydrogel biocompatibility with potential biomedical applications.

Multi-fold plasmon-enhanced photoluminescence of a-C:H thin films

The regularities study of a-C:H film photoluminescence (PL) enhancement by localized surface plasmon resonance (LSPR) in hybrid structures with nanogranulated Ag film was the main aim of this work. We have compared the PL spectra of two thin-film hybrid structures in which the a-C:H optical gap was 2.7 eV and 0.4 eV. The a-C:H films with the thickness of ~50 nm were deposited on quartz substrates using the chemical vapor deposition of toluene vapor in glow discharge plasma. The nanogranulated silver film by 10 nm thickness was deposited on all a-C:H film by the thermal evaporation method at the same time. The optical density spectra and the surface morphology of Ag nanoparticles (NPs) by AFM as well as the PL spectra of a-C:H in the hybrid structures at the visible range and room temperature were obtained. It has been shown that PL intensity of wide-gap a-C:H in the hybrid structure increased fourfold but the narrow-gap film – sevenfold against the intensity of initial films at excitation wavelength 405 nm. The intensity of dipole and quadrupole mode peaks increased in the optical density spectra after annealing of the hybrid structures at 200 °C. This fact was connected with the form and size changes of Ag NPs. The blue shift of PL maximum to 498 nm and the twentyfold enhancement of PL intensity of the hybrid structure with the narrow-gap a-C:H was observed after annealing. The mechanism of plasmon-enhanced of a-C:H PL in hybrid structures with Ag NPs was discussed. Obtained results can find practice applications in both light-emitting devices and biosensor chip.

Solubilization of Carbamazepine in TPGS Micelles: Effect of Temperature and Electrolyte Addition.

D-α-Tocopheryl polyethylene glycol succinate (TPGS), a polyethylene glycol condensate, is a biologically important nonionic amphiphile. In this study, we report on aqueous solution behavior of TPGS with a focus on its clouding, surface activity, micellar characteristics, and solubilization capacity for a model hydrophobic drug, carbamazepine (CBZ). Micelles were characterized by dynamic light and small-angle neutron scattering studies as a function of temperature, salt addition, and CBZ solubilization. TPGS showed a cloud point of 78°C and possessed good surface activity (as observed from surface tension reduction and adsorption parameters). The critical micelle concentration (CMC), obtained from surface tension and fluorescence studies, was 0.02mM. Scattering studies showed formation of stable micelles (average diameter-12nm), exhibiting no significant changes in size upon salt addition (up to 1M NaCl), CBZ incorporation (up to 5mM), and temperature increase (40°C). Micelles in 5wt% TPGS showed about twentyfold enhancement in CBZ solubility. Considering the remarkable CBZ solubilization and its positioning in the core, we suggest that the formulation can be exploited as a sustained delivery vehicle.

“Water-in-deep eutectic solvent” electrolytes enable zinc metal anodes for rechargeable aqueous batteries

Metallic zinc (Zn) is one of the most promising anodes for aqueous batteries, but so far its applicability for rechargeable systems remains elusive, mainly owing to the free water-induced parasitic reactions. Here, we report a new “water-in-deep eutectic solvent (water-in-DES)” electrolyte (~30 mol.% H2O in a eutectic mixture of urea/LiTFSI/Zn(TFSI)2; TFSI, bis(trifluoromethanesulfonyl)imide), in which all water molecules participate in DES's internal interaction (H-bonding and coordinating) network, leading to a suppressed reactivity with Zn anode from both thermodynamic and electrochemical aspects. Inheriting characteristics from aqueous and DES media, this electrolyte enables stable and reversible Zn plating/stripping with over twentyfold enhancement in cycling life compared to routine aqueous electrolytes, even at low rates. With these merits, a desirable rechargeability (>90% capacity retention after 300 cycles at 0.1 C) is achieved for a 1.92 V (average dicharge voltage) Zn/LiMn2O4 battery, together with a practical energy density of 52 Wh/kg (pouch cell, 2 Ah, ~9.8 × excess Zn on anode).

Twenty-fold Enhancement of Gadolinium-Porphyrin Phosphorescence at Room Temperature by Free Gadolinium Ion in Liquid Phase

The influence of free gadolinium ion (Gd3+) on room-temperature phosphorescence (RTP) of gadolinium labeled hematoporphyrin monomethyl ether (Gd-HMME) was studied. Twenty-fold enhancement of Gd-HMME RTP by the titration of free Gd3+ was achieved. We found that the absorption from the ground (S0) to singlet excited states of Gd-HMME did not change with the addition of Gd3+, which means that the phosphorescence quantum yield has been tuned from 1.4% to 28%. According to the excitation spectra, the transition possibility from S0 to the lowest triplet excited state (T1) is increased by 1.2-fold because of the heavy atom effect of free Gd3+. The phosphorescence lifetime of Gd-HMME with free Gd3+ is 7.0-fold greater than that of Gd-HMME itself, which demonstrates that the nonradiative processes of Gd-HMME is decreased by Gd3+ with the rate constant of nonradiative processes decreasing from 2.2(2) × 105 to 2.8(2) × 104 s–1. This sharp decrease is mainly responsible for the huge enhancement of Gd-HMME RTP. The reason for the decrease of nonradiative processes is due to the formation of a rigid microenvironment, which protects Gd-HMME from being quenched.

Spectral superresolution with ultrashort optical pulses

A superresolution technique for the measurement of transmission, reflection, and absorption spectra is proposed. An ultrashort laser pulse is propagated in a dispersive element and then periodically phase modulated. The temporal modulation is transformed into periodic spectral modulation, for which the number of harmonics, 2M+1, is determined by the modulation index. The modulated pulse is transmitted through (reflected from) the sample to be tested and measured by a spectrometer. By performing 2M+1 measurements for 2M+1 delays between the dispersed pulse and modulation signal, one can restore the spectral response of the sample with superresolution after simple processing. We numerically demonstrate the measurement of the transmission spectrum of an ultranarrow optical filter with a minimum feature of 0.43 pm by an optical spectrum analyzer with a 10 pm resolution. A twentyfold enhancement of the resolution is achieved in the presence of noise with a level of 0.1%. The advantage of the system is its full reconfigurability.

Light-matter interaction in a microcavity-controlled graphene transistor.

Graphene has extraordinary electronic and optical properties and holds great promise for applications in photonics and optoelectronics. Demonstrations including high-speed photodetectors, optical modulators, plasmonic devices, and ultrafast lasers have now been reported. More advanced device concepts would involve photonic elements such as cavities to control light–matter interaction in graphene. Here we report the first monolithic integration of a graphene transistor and a planar, optical microcavity. We find that the microcavity-induced optical confinement controls the efficiency and spectral selection of photocurrent generation in the integrated graphene device. A twenty-fold enhancement of photocurrent is demonstrated. The optical cavity also determines the spectral properties of the electrically excited thermal radiation of graphene. Most interestingly, we find that the cavity confinement modifies the electrical transport characteristics of the integrated graphene transistor. Our experimental approach opens up a route towards cavity-quantum electrodynamics on the nanometre scale with graphene as a current-carrying intra-cavity medium of atomic thickness.

Twenty-Fold Enhancement of Molecular Fluorescence by Coupling to a J-Aggregate Critically Coupled Resonator

We report a 20-fold enhancement in the fluorescence of the organic dye DCM when resonantly coupled to a strongly optically absorbing structure of a thin film of spin-deposited molecular J-aggregates in a critically coupled resonator (JCCR) geometry. A submonolayer equivalent of DCM molecules is shown to absorb and re-emit 2.2% of the incident resonant photons when coupled to the JCCR enhancement structure, compared to 0.1% for the bare film of same thickness on quartz. Such a JCCR structure is a general energy focusing platform that localizes over 90% of incident light energy within a 15 nm thin film layer in the form of excitons that can subsequently be transferred to colocated lumophores. Applications of the exciton-mediated concentration of optical energy are discussed in the context of solid-state lighting, photodetection, and single photon optics.

Photocatalytic Oxidation of Carbon Monoxide over Nanocomposites under UV Irradiation

The NiO/SnO2nanocomposites have been prepared by the simple coprecipitation method and further characterized by the XRD, SEM, TEM, UV-Vis, and BET. X-ray diffraction (XRD) data analyses indicate the exclusive formation of nanosized particles with rutile-type phase (tetragonal SnO2) for Ni contents below 10 mol%. Only above 10 mol% Ni, the formation of a second NiO-related phase has been determined. The particle size is in the range from 12 to 6 nm. It decreases with increasing amounts of doping NiO. The morphology of NiO-doped SnO2nanocrystalline powders is spherical, and the distribution of particle size is uniform, as seen from transmission electron microscopy (TEM). The photocatalytic oxidation of CO over NiO/SnO2photocatalyst has been investigated under UV irradiation. Effects of NiO loading on SnO2, photocatalyst loading, and reaction time on photocatalytic oxidation of CO have been systematically studied. Compared with pure SnO2, the 33.3 mol% NiO/SnO2composite exhibited approximately twentyfold enhancement of photocatalytic oxidation of CO. Our results provide a method for pollutants removal. Due to simple preparation, high photocatalytic oxidation of CO, and low cost, the NiO/SnO2photocatalyst will find wide application in the coming future of photocatalytic oxidation of CO.

Photocatalytic H 2 production from acetic acid solution over CuO/SnO 2 nanocomposites under UV irradiation

The CuO/SnO 2 composites have been prepared by the simple co-precipitation method and further characterized by the XRD, FESEM and Raman spectroscopy. The photocatalytic H 2 production from acetic acid (HAc) solution over CuO/SnO 2 photocatalyst has been investigated at room temperature under UV irradiation. Effects of CuO loading, photocatalyst concentration, acetic acid concentration and pH on H 2 production have been systematically studied. Compared with pure SnO 2, the 33.3 mol%CuO/SnO 2 composite exhibited approximately twentyfold enhancement of H 2 production. The H 2 yield is about 0.66 mol-H 2/mol-HAc obtained under irradiation for prolonged time. The Langmuir-type model is applied to study the dependence of hydrogen production rate on HAc concentration. A possible mechanism for photocatalytic degradation of acetic acid over CuO/SnO 2 photocatalyst is proposed as well. Our results provide a method for pollutants removal with simultaneous hydrogen generation. Due to simple preparation, high H 2 production activity and low cost, the CuO/SnO 2 photocatalyst will find wide application in the coming future of hydrogen economy.

Two polyaminophenolic fluorescent chemosensors for H+and Zn(ii). Spectroscopic behaviour of free ligands and of their dinuclear Zn(ii) complexes

The UV-Vis and fluorescence optical properties of the two polyamino-phenolic ligands 3,3′-bis[N,N-bis(2-aminoethyl)aminomethyl]-2,2′-dihydroxybiphenyl (L1) and 2,6-bis{[bis(2-aminoethyl)amino]methyl}phenol (L2) were investigated in aqueous solution at different pH values as well as in the presence of Zn(II) metal ion. Both ligands show two diethylenetriamine units separated by the 1,1′-bis(2-phenol) (BPH) or the phenol (PH) for L1 and L2, respectively. Both ligands are fluorescence-emitting systems in all fields of pH examined, with L1 showing a higher fluorescence emission than L2. In particular, the emission of fluorescence mainly depends on the protonation state of the phenolic functions and thus on pH. The highest emitting species is H3L3+ for both systems, where the BPH is monodeprotonated (in L1) and the PH is in the phenolate form (in L2). On the contrary, when BPH and PH are in their neutral form both ligands show the lowest fluorescence, since H-bonds occurring between the phenol and the closest tertiary amine functions decrease fluorescence. The Zn(II)-dinuclear species are also fluorescent in the pH range where they exist; the highest emitting species being [Zn2(H−2L1)]2+ and [Zn2(H−1L2)]3+ which are present in a wide range of pH including the physiological one. Fluorescence experiments carried out at physiological pH highlighted that, in the case of L1, the presence of Zn(II) ion in solution produces a simultaneous change in λem with a drop in fluorescence due to the formation of the [Zn2(H−2L1)]2+ species, while, in the case of L2, it gives rise to a strong CHEF effect (a twenty-fold enhancement was observed) due to the formation of the [Zn2(H−1L2)]3+ species. These results, supported by potentiometric, 1H and 13C NMR experiments, are of value for the design of new efficient fluorescent chemosensors for both H+ and Zn(II) ions.

Aromatic interactions in homeodomains contribute to the low quantum yield of a conserved, buried tryptophan.

Trp 48, a conserved, buried residue commonly found in the hydrophobic core of homeodomains, has an unusually low fluorescence quantum yield. Chemical denaturation of Drosophila homeodomains Engrailed and Antennapedia(C39S) result in a four-fold increase in quantum yield, while unfolding of Ultrabithorax causes a twenty-fold enhancement. Global analysis of time-resolved fluorescence decay monitored at multiple emission wavelengths reveals sub-nanosecond lifetime components which dominate the overall intensity. Based on structure and sequence analysis of several homeodomains, we deduce that quenching is due to a transient, excited-state NH ellipsis pi hydrogen bond involving Trp 48 and a conserved aromatic residue at position 8. Additionally, both time-resolved fluorescence of indole-benzene mixtures and an electrostatic model of the proposed tryptophan-aromatic interaction substantiate different aspects of this mechanism. A survey of the Protein Data Bank reveals many proteins with tryptophan-aromatic pairs where the indole nitrogen participates in a NH ellipsis pi hydrogen bond with the ring of another aromatic residue. Chemical denaturation of one protein found in this survey, human fibronectin type III module 10, causes an enhancement of the fluorescence quantum yield. This unique interaction has implications for many other systems and may be useful for studying larger, multi-tryptophan containing proteins.

Far infrared Faraday rotation in a two-dimensional electron gas

The Faraday rotation is a sensitive method for determining the effective mass of the charge carriers in a two-dimensional electron gas. At light frequencies much larger than the cyclotron frequency the Faraday rotation is independent of scattering. Faraday rotation, combined with transport measurements, allows a determination of the populations of the subbands and the subband energy separations in an inversion layer on p-Si (100). A metal-oxide-semiconductor (MOS) system will show an enhancement of the measured Faraday rotation because of multiple internal reflections of the light between the metal and substrate boundaries of the system. Our calculations give a twentyfold enhancement. The resonance Faraday rotation at light frequencies close or equal to the cyclotron frequency permits the determination of scattering parameters.