Spectroelectrochemistry (SEC) enables
in-operando
UV–vis study of electrochemical cells to explore the evolution of different cell components and understand cell mechanisms. Researchers have ...demonstrated various custom UV–vis cell designs to accommodate SEC experiments. However, existing designs do not easily permit temperature ramp techniques to examine the effects of rapidly changing cell temperature or high temperature conditions on cell mechanisms. This communication presents two easy-to-replicate, low-cost cell designs that are incorporable with existing UV–vis systems (transmittance, reflectance) and enable high temperature, rapid heating SEC experiments. Each cell design was tested to evaluate temperature ramp and sealing performance.
UV–Vis can be used as an easy and forthright technique to accurately estimate the band gap energy of organic π-conjugated materials, widely used as thin films/composites in organic and hybrid ...electronic devices such as OLEDs, OPVs and OFETs. The electronic and optical properties, including HOMO–LUMO energy gaps of π-conjugated systems were evaluated by UV–Vis spectroscopy in CHCl3 solution for a large number of relevant π-conjugated systems: tris-8-hydroxyquinolinatos (Alq3, Gaq3, Inq3, Al(qNO2)3, Al(qCl)3, Al(qBr)3, In(qNO2)3, In(qCl)3 and In(qBr)3); triphenylamine derivatives (DDP, p-TTP, TPB, TPD, TDAB, m-MTDAB, NPB, α-NPD); oligoacenes (naphthalene, anthracene, tetracene and rubrene); oligothiophenes (α-2T, β-2T, α-3T, β-3T, α-4T and α-5T). Additionally, some electronic properties were also explored by quantum chemical calculations. The experimental UV–Vis data are in accordance with the DFT predictions and indicate that the band gap energies of the OSCs dissolved in CHCl3 solution are consistent with the values presented for thin films.
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•Solution absorption spectra of low molecular weight conjugated systems typically used in thin films of semiconductors are presented.•UV–Vis can be used as an easy and straightforward technique to accurately estimate the band gap energy of organic π-conjugated semiconductors.•The band gap energies of the OSCs dissolved in CHCl3 solution are consistent with the values presented for thin films.
Abstract
C
60
–bodipy triads and tetrads based on the energy‐funneling effect that show broadband absorption in the visible region have been prepared as novel triplet photosensitizers. The new ...photosensitizers contain two or three different light‐harvesting antennae associated with different absorption wavelengths, resulting in a broad absorption band (450–650 nm). The panchromatic excitation energy harvested by the bodipy moieties is funneled into a spin converter (C
60
), thus ensuring intersystem crossing and population of the triplet state. Nanosecond time‐resolved transient absorption and spin density analysis indicated that the T
1
state is localized on either C
60
or the antennae, depending on the T
1
energy levels of the two entities. The antenna‐localized T
1
state shows a longer lifetime (
τ
T
=132.9 μs) than the C
60
‐localized T
1
state (ca. 27.4 μs). We found that the C
60
triads and tetrads can be used as dual functional photocatalysts, that is, singlet oxygen (
1
O
2
) and superoxide radical anion (O
2
.
−
) photosensitizers. In the photooxidation of naphthol to juglone, the
1
O
2
photosensitizing ability of the C
60
triad is a factor of 8.9 greater than the conventional triplet photosensitizers tetraphenylporphyrin and methylene blue. The C
60
dyads and triads were also used as photocatalysts for O
2
.
−
‐mediated aerobic oxidation of aromatic boronic acids to produce phenols. The reaction times were greatly reduced compared with when Ru(bpy)
3
Cl
2
was used as photocatalyst. Our study of triplet photosensitizers has shown that broadband absorption in the visible spectral region and long‐lived triplet excited states can be useful for the design of new heavy‐atom‐free organic triplet photosensitizers and for the application of these triplet photosensitizers in photo‐organocatalysis.
In this study, graphene oxide (GO) nanosheets were synthesized by the modified Hummers method. GO structure was estimated by XRD, UV–vis-spectrophotometer and SEM imaging. Then homogeneous and stable ...GO/water nanofluid was prepared. The effects of GO concentration and temperature on the thermal conductivity were investigated.
The measurements of thermal conductivity indicate that the nanofluids have substantially higher thermal conductivities than the base fluid.
The thermal conductivity enhancement depends strongly on the concentration of GO and increases with the increasing loading. When the nanosheet loading is 0.25wt.%, the enhancement ratio is 33.9% at 20°C and when the temperature increased to 40°C the enhancement is up to 47.5%. Therefore the level of enhancement is dependent of temperature in the measured temperature range.
Plants extract from Ocimum tenuiflorum, Solanum tricobatum, Syzygium cumini, Centella asiatica and Citrus sinensis was used for the synthesis of silver nanoparticles (Ag NPs) from silver nitrate ...solution. Ag NPs were characterized by UV–vis spectrophotometer, X-ray diffractometer (XRD), atomic force microscope (AFM) and scanning electron microscope (SEM). The formation and stability of the reduced silver nanoparticles in the colloidal solution were monitored by UV–vis spectrophotometer analysis. The mean particle diameter of silver nanoparticles was calculated from the XRD pattern according to the line width of the plane, refraction peak using the Scherrer’s equation. AFM showed the formation of silver nanoparticle with an average size of 28 nm, 26.5 nm, 65 nm, 22.3 nm and 28.4 nm corresponding to O. tenuiflorum, S. cumini, C. sinensis, S. tricobatum and C. asiatica, respectively. SEM determination of the brown color stable samples showed the formation of silver nanoparticles and well dispersed nanoparticles could be seen in the samples treated with silver nitrate. Antimicrobial activity of the silver bio-nanoparticles was performed by well diffusion method against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae. The highest antimicrobial activity of silver nanoparticles synthesized by S. tricobatum, O. tenuiflorum extracts was found against S. aureus (30 mm) and E. coli (30 mm) respectively. The Ag NPs synthesized in this process has the efficient antimicrobial activity against pathogenic bacteria. Of these, silver nanoparticles are playing a major role in the field of nanotechnology and nanomedicine.
In recent years, brown carbon (BrC) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (UV) part of the solar ...spectrum. Emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (PAHs) were determined for combustion of five globally important fuels: Alaskan, Siberian, and Florida swamp peat, cheatgrass (Bromus tectorum), and ponderosa pine (Pinus ponderosa) needles. The emission factors of total analyzed PAHs were between 1.9±0.43.0±0.6 and 9.6±1.2–42.2±5.4mgPAHkg−1fuel for particle- and gas phase, respectively. Spectrophotometric analysis of the identified PAHs showed that perinaphthenone, methylpyrenes, and pyrene contributed the most to the total PAH light absorption with 17.2%, 3.3 to 10.5%, and 7.6% of the total particle-phase PAH absorptivity averaged over analyzed emissions from the fuels. In the gas phase, the top three PAH contributors to BrC were acenaphthylene (32.6%), anthracene (8.2%), and 2,4,5-trimethylnaphthalene (8.0%). Overall, the identified PAHs were responsible for 0.087–0.16% (0.13% on average) and 0.033–0.15% (0.11% on average) of the total light absorption by dichloromethane-acetone extracts of particle and gas emissions, respectively. Toxic equivalency factor (TEF) analysis of 16 PAHs prioritized by the United States Environmental Protection Agency (EPA) showed that benzo(a)pyrene contributed the most to the PAH carcinogenic potency of particle phase emissions (61.8–67.4% to the total carcinogenic potency of Σ16EPA PAHs), while naphthalene played the major role in carcinogenicity of the gas phase PAHs in the biomass-burning emission analyzed here (35.4–46.0% to the total carcinogenic potency of Σ16EPA PAHs). The 16 EPA-prioritized PAHs contributed only 22.1±6.2% to total particle and 23.4±11% to total gas phase PAH mass, thus toxic properties of biomass-burning PAH emissions are most likely underestimated.
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•113 PAHs and PAH derivatives were analyzed in gas and particle phase combustion emissions of five different biomass fuels.•Light absorption properties of individual biomass-burning PAHs were analyzed.•Emission factors of the most effective light absorbing brown carbon PAHs were determined in biomass-emissions.•Benzo(a)pyrene and naphthalene contributed the most to the PAH carcinogenic potency of biomass-burning emissions.
Pulsed laser ablation in a liquid medium is a promising technique as compared to the other synthetic methods to synthesize different materials in nanoscale form. The laser parameters (e.g., ...wavelength, pulse width, fluence, and repetition frequency) and liquid medium (e.g., aqueous/nonaqueous liquid or solution with surfactant) were tightly controlled during and after the ablation process. By optimizing these parameters, the particle size and distribution of materials can be adjusted. The UV–vis absorption spectra and weight changes of targets were used for the characterization and comparison of products.
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•Experimental parameters•Ablated materials and its medium parameters•Monodispersed CdS synthesized by pulsed laser ablation in water
Quantification of Cr(VI) in an aqueous solution is conducted by direct UV–visible spectrophotometry based on the yellow coloring of the chromate ion. Measurements show that absorption follows the ...Beer–Lambert law over a wide range of concentrations. At pH below the pKa of 6.4 (HCrO4−/CrO4−2), the absorption maximum lies at 350 nm wavelength and the linear range spans from 0.5 to 100 mg Cr(VI)/L; above the pKa (pH 6.4), the absorption maximum is 373 nm and linearity occurs in the range of 0.5–25 mg/L. The wide range of validity of the Beer–Lambert law is advantageous for the measurement of concentrated samples. The standard method of analysis of aqueous Cr(VI) is by colorimetry with the 1,5-diphenylcarbazide (DPC)–Cr(VI) complex. This method, although very sensitive, bears a narrow range of linearity from 0 to 0.8 mg Cr(VI)/L. It is shown that when analyzing Cr(VI) solutions with concentrations in the range of 30–500 mg/L, the DPC method gives inaccurate results and relative standard deviations of 20–50%. This is due to high dilution factors. On the contrary, the direct method performs with high accuracy. Relative standard deviation is only 0.5% at 500 mg Cr(VI)/L. The direct method is fast, reliable, and nondestructive for the sample. The direct method is recommended for the quantification of Cr(VI) at concentrations greater than 1 mg/L.
Le dosage du Cr(VI) en solution aqueuse est effectué par spectrométrie UV–visible directe, grâce à la couleur jaune de l'ion chromate. Les mesures montrent que la loi de Beer–Lambert est respectée sur un large intervalle de concentrations. A pH inférieur à 6,4 (pKa HCrO4−/CrO4−2), l'absorption maximale se situe à la longueur d'onde 350 nm et la game linéaire d’étalonnage s’étend de 0,5 à 100 mg Cr(VI)/L; au dessus du pKa, l'absorption maximale se situe à 373 nm, la game de linéarité couvre l'intervalle 0,5–25 mg/L. Au contraire, la méthode standard d'analyse du Cr(VI) en solution, méthode colorimétrique au 1,5 diphénylcarbazide (DPC), présente une fenêtre de mesure très étroite, de 0 à 0,8 mg Cr(VI)/L. On montre que la méthode DPC appliquée à des échantillons de concentrations 30–500 mg/L, donne des résultats avec une incertitude importante et des écarts types de 20–50% autour de la moyenne. Les fortes déviations sont attribuées aux forts facteurs de dilution nécessaires. Pour la même game de concentrations, la méthode directe donne des résultats avec une très faible incertitude. Pour un échantillon de 500 mg Cr(VI)/L, l’écart type est de seulement 0,5%. La méthode directe est rapide, fiable, et elle permet de préserver l’échantillon. La méthode directe est conseillée pour le dosage du Cr(VI) à concentrations supérieures à 1 mg/L.
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Composite films of polyvinyl alcohol (PVA)/Silver nanoparticles (AgNPs) were synthesized via casting method. The presence of AgNPs in PVA was approved by an apparition of Surface Plasmon Resonance ...(SPR) around 427nm of the composite absorption spectra. The nanocomposite films were irradiated at different times (5, 10, and 15min) pulsed Nd:YAG laser. The integral intensity of diffracted X-ray photons from films has been increased noticeably after the doping process denotes increasing in the ordering character of the PVA/Ag nanocomposite irradiated to different time's laser, which can be assigned to the reduction that has been induced by laser. Observations of IR spectra indicated that laser enhances the structural modifications between the chains in PVA and the silver nanoparticles with further increasing laser irradiation time. The observed increase in refractive index (n) and the decreasing in the optical band gap of PVA/Ag nanocomposite films after irradiated to the laser with different times (5, 10, and 15min) comparing with pure PVA suggesting its possibility to using optical device applications. The behavior of ɛ′ and ɛ″ are gradually decreased with the increase of the frequency. The value of ɛ′ and ɛ″ are decreases due to the contribution of interfacial polarization effect in dielectric permittivity. The relation between M’ and M″ depicts the formation of a semicircle arc indicating the presence of broad relaxation processes.
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