Maximum Absorption Wavelength Research Articles

Xác định acetamiprid bằng phương pháp quang học sử dụng dung dịch nano vàng được ổn định bằng Polydiallyldimethylammoni clorua

On this research, the development of a simple, cost-efective and highly sensitive spectrophotometric method for acetamiprid detection based on the localized surface plasmon resonance of polydiallyldimethylammonium chloridestabilized gold nanoparticles. By naked eyes, one can detect acetamiprid by the visual change of gold solution color from red to purple, corresponding to the shift of maximum absorbance wavelength in the UV-Vis spectrum. Quantification of acetamiprid is possible through a linear relationship between the maximum absorbance wavelength and the acetamiprid concentrations in the range of 8×10-8 -2×10-6 M. Under the optimum conditions including pH 5, NaCl concentration of 0.02 M and incubation time 20 min, the present method has high precision (RSD < 5%), very low limit of detection (LOD) of 2.7×10-8 M, limit of quantification (LOQ) of 8.2×10-8 M. This method has been successfully applied to determine acetamiprid in several pesticide samples and vegetable samples. The measurement results of acetamiprid in the pesticide samples of the research method with the HPLC-UV method showed a difference of < 2%, while for the vegetable sample, the difference between the research method and the LC-MS/method method/ MS < 5% shows that the method has high accuracy and reliability.

Absorption by a Layered Microbolometer Pixel’s Active Element

Microbolometer arrays, i.e., arrays of micro-scale pixels sensing temperature via resistance changes, have proven to be an effective basis for real-time imaging instrumentation in infrared as well as terahertz frequencies. In previous work, a design of THz and IR absorbing nano-laminates of dielectric and metal layers was studied. It was shown via numerical modeling that absorption may be maximized by appropriate choices of thickness, permittivity and conductivity. In this work, an analytical approach to the problem is formulated based on the standard recursive multiple reflection formulas for multi-layered planar structures. The results fully confirm and extend previous numerical work. A previous relationship between wavelength and silicon thickness for maximum absorption, derived numerically for specific parameter combinations, is now generalized in a parametric closed form. The method can be extended to include multiple lossy dielectric layers and may serve as a tool for optimizing the absorption characteristics of more complex layered absorbing structures. This could enhance the sensitivity of the detection scheme of interest, providing benefits in terms of cost, efficiency, precision, and adjustability.

Synthesis of Styrylbenzazole Photoswitches and Evaluation of their Photochemical Properties.

Styrylbenzazoles form a promising yet under-represented class of photoswitches that can perform a light-driven E-Z isomerization of the central alkene double bond without undergoing irreversible photocyclization, typical of the parent stilbene. In this work, we report the synthesis and photochemical study of 23 styrylbenzazole photoswitches. Their thermal stabilities, quantum yields, maximum absorption wavelengths and photostationary state (PSS) distributions can be tuned by changing the benzazole heterocycle and the substitution pattern on the aryl ring. In particular, we found that push-pull systems show large redshifts of the maximum absorption wavelengths and the highest quantum yields, whereas ortho-substituted styrylbenzazole photoswitches exhibit the most favorable PSS ratios. Taking advantage of both design principles, we produced 2,6-dimethyl-4-(dimethylamino)-styrylbenzothiazole, a thermally stable and efficient P-type photoswitch which displays negative photochromism upon irradiation with visible light up to 470 nm to obtain a near-quantitative isomerization with a very high quantum yield of 59%. Furthermore, 4-hydroxystyrylbenzothiazole was demonstrated to be a pH-sensitive switch which exhibits a 100 nm redshift upon deprotonation. Ortho-methylation of this switch improved the obtained PSS ratio in its deprotonated state from E:Z=53:47 to E:Z=18:82. We anticipate that this relatively unexplored class of photoswitches will form a valuable expansion of the current family of photoswitches.

Ruthenium complexes bearing nile red chromophore and one of its derivative: Theoretical evaluation of PDT-related properties.

The outcomes of DFT-based calculations are here reported to assess the applicability of two synthesized polypyridyl Ru(II) complexes, bearing ethynyl nile red (NR) on a bpy ligand, and two analogues, bearing modified-NR, in photodynamic therapy. The absorption spectra, together with the non-radiative rate constants for the S1 - Tn intersystem crossing transitions, have been computed for this purpose. Calculations evidence that the structural modification on the chromophore destabilizes the HOMO of the complexes thus reducing the H-L gap and, consequently, red shifting the maximum absorption wavelength within the therapeutic window, up to 620 nm. Moreover, the favored ISC process from the bright state involves the triplet state closest in energy, which is also characterized by the highest SOC value and by the involvement of the whole bpy ligand bearing the chromophore in delocalising the unpaired electrons. These outcomes show that the photophysical behavior of the complexes is dominated by the chromophore.

Doping Engineering To Modulate Surface Plasmon Resonance and Enzyme-like Activities for Enhancing Photoacoustic Imaging-Guided Targeted Cancer Therapy in the Second Near-Infrared Window.

Biological imaging-guided targeted tumor therapy has been a soughtafter goal in the field of cancer diagnosis and treatment. To this end, we proposed a strategy to modulate surface plasmon resonance and endow WO3-x nanoparticles (NPs) with enzyme-like catalytic properties by doping Fe2+ in the structure of the NPs. Doping of the Fe2+ introduced oxygen vacancies into the structure of the NPs, inducing a red shift of the maximum absorption wavelength into the near-infrared II (NIR-II) region and enhancing the photoacoustic (PA) and photothermal properties of the NPs for more effective imaging-guided cancer therapy. Under NIR-II laser irradiation, the Fe-WO3-x NPs produced very strong NIR-II PA and photothermal effects, which significantly enhanced the PA imaging and photothermal treatment effects. On the other hand, Fe2+ in Fe-WO3-x could undergo Fenton reactions with H2O2 in the tumor tissue to generate ·OH for chemodynamic therapy. In addition, Fe-WO3-x can also catalyze the above reactions to produce more reactive oxygen species (ROS) and induce the oxidation of NADH to interfere with intracellular adenosine triphosphate (ATP) synthesis, thereby further improving the efficiency of cancer therapy. Specific imaging of tumor tissue and targeted synergistic therapy was achieved after ligation of a MUC1 aptamer to the surface of the Fe-WO3-x NPs by the complexing of -COOH in MUC1 with tungsten ions on the surface of the NPs. These results demonstrated that Fe-WO3-x NPs could be a promising diagnosis and therapeutic agent for cancer. Such a study opens up new avenues into the rational design of nanodiagnosis and treatment agents for NIR-II PA imaging and cancer therapy.

Development and validation of a UV spectrophotometric method for biowaiver studies in pyrazinamide tablets

Development and validation of a UV spectrophotometric method for biowaiver studies in pyrazinamide tablets

CdS/ZnS quantum dots based on an amphipathic polymer platform for fluorescent probe of dopamine with high sensitivity and selectivity

Due to the widespread presence of dopamine in living organisms and its physiological and pharmacological effects, developing rapid and sensitive methods for detecting dopamine has been of great significance. Fluorescent probes are a commonly used and highly sensitive detection method. In this work, based on a self-developed amphipathic polymer template, CdS/ZnS fluorescent quantum dots (QDs) with a maximum absorption wavelength of 500–550 nm were synthesized and characterized. They exhibited stable fluorescence in the pH range from weak acid to alkaline, and fluorescence quenching occurred at pH = 4.5. The QDs could be applied as fluorescent probes for detecting dopamine, with a limit of detection 0.027 mM and high selectivity, unaffected by common metal ions, amino acids, glucose, etc. Compared to the high activity of dopamine being oxidized easily, this fluorescent QDs and its template polymer PEI played a stabilizing role during the testing process. Therefore, this work provides a promising dopamine fluorescent probe with application prospects.

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study.

We conducted a study on the photophysics of three indoline dyes, D102, D149, and D205, in binary mixtures of ionic liquids (IL) and polar aprotic molecular solvents (MS). Specifically, we examined the behavior of these dyes in IL-MS mixtures containing four different imidazolium-based ILs and three different polar aprotic MSs. Our investigation involved several techniques, including stationary absorption and emission measurements, as well as femtosecond transient absorption (TA) spectroscopy. Through our analysis, we discovered a peculiar behavior of several photophysical properties at low IL mole fractions (0 < XIL < 0.2). Indeed, in this range of mixture composition, the absorption maximum wavelength decreases noticeably, while the emission maximum wavelength and the Stokes shift, expressed in wavenumbers, reach a maximum. while a minimum occurs in the relative quantum yield and the excited state lifetime. These results indicate that the solvation of dye undergoes a large change in this range of mixture composition. We found that, at high ionic liquid content, the excited relaxation times are correlated with the high viscosity, while at low content, it is the polarity of the solvent that influences the behavior of the excited relaxation times. At a mixture composition of around 0.10, the behavior of the photophysical properties of the studied IL-MS mixtures indicates a crossover between situations where the solvation is dominated by that of ions and that dominated by the solvent.

Implementation of bridged copolymerisation to optimise the optical properties of porphyrin: applications in dye-sensitized solar cells

This study explores the concept of all-organic sensitisation of dye-sensitized solar cells (DSSCs) by using a cosensitization approach to model efficient porphyrin-based photosensitizers. The aim is to enhance the absorption defects and light response current of porphyrin dyes, which have been reported in the literature. In this work, eight (8) natural porphyrin derivatives obtained through bridged copolymerisation of free base porphyrin and tetraazaporphyrin have been modelized and analysed. Their geometric parameters, stability energies, chemical stabilities, and photochemical properties were studied using density functional theory (DFT) methods in both gaseous and dichloromethane (DCM) phases. The analysis of photochemical properties, including maximum absorption wavelength ( λ max ), light harvesting efficiency (LHE), electron injection driving force ( Δ G inj ), regeneration driving force ( Δ G reg ), and excited state lifetime ( τ ) of the studied photosensitizers, show significant improvement compared to the parent dye (free base porphyrin) and some recent derivatives SM315 and YD2-o-C8. It is worth noting that the eight ( 8 ) modelled dyes from porphyrin show broader LHE curves not only compared to the parent dye, but also compared to the SM315 dye, which may lead to a higher running photo density. This study highlights the effectiveness of bridged copolymerisation for developing high-performance DSSCS based on porphyrin.

Effect of emulsified lipid and saponified lipid on the enzyme desizing of starch and its mechanism

To enhance the flexibility of starch film adhesion on yarns, sizing lipids (saponified lipid or emulsified lipid) must be added during the sizing process. However, different types of sizing lipids may have diverse combinations with starch to impact enzyme desizing. Therefore, this study investigated the effects of saponified lipid and emulsified lipid commonly used in warp sizing on the hydrolysis of starch. Additionally, the desizing efficiency and chain structure of desizing residues were analyzed. Experimental results demonstrated that the existence of saponified lipid or emulsified lipid led to a reduction in the degree of hydrolysis (1.1 % and 2.6 %, respectively) compared to the original corn starch. Notably, saponified lipid exhibited a relatively strong negative impact. Furthermore, the desizing efficiency decreased after adding emulsified lipid (1.2 %) or saponified lipid (2.9 %). Starch-lipid V-type complexes and physical hindrance could inhibit the enzyme desizing, resulting in a larger wavelength of maximum absorbance for desizing residues, along with higher molecular weight, z-average radius of gyration, and an increased proportion of long chains. The presence of saponified lipid significantly negatively influenced desizing, possibly due to the smaller particle size and propensity for complex formation with starch.

Rational design by DFT calculations of new metal complexes for photodynamic therapy based on an H2O2-Responsive Ir(III) photosensitizer activatable in physiological environment

A series of complexes based on the structure of an H2O2-responsive Ir(III) phenylpyridine(ppy)-containing complex were designed. The effect of changing the conjugation in the ppy ligands as well as of replacing the Ir(III) metal centre with the isoelectronic Os(II) were evaluated by means of DFT and its time-dependent formulation. The computational exploration of the photophysical properties of all the designed complexes suggest that the character of the low-lying singlet state represent the main factor affecting the region of absorption. In particular, for some of the Ir(III)-based complexes the change of the band character from mixed MLCT/LLCT to almost exclusively LLCT is essential for red-shifting the maximum absorption wavelength together with the destabilization of HOMO thus reducing the HOMO-LUMO energy gap; similarly, the replacement of Ir(III) with Os(II) converts the character of the band to mainly MLCT. The computed spin–orbit coupling constants and the triplet states’ energy confirm that all the designed complexes could, in principle, be able to generate the cytotoxic singlet oxygen under one-photon excitation by energy transfer from the triplet state of the photosensitizer to molecular oxygen, while the production of other types of ROS is precluded, similarly to the reference complex.

Highly efficient donor-acceptor configurated Nicotinaldehyde-based small molecules for NLO materials: Base-free deformylation and DFT study

In the current study, 6-methyl nicotinaldehyde derivatives (MNP-BTMP) were synthesized by using the Suzuki- cross-coupling method which involved deformylation approach. The FTIR, UV–Visible, 1HNMR and 13CNMR spectroscopic analyses were performed to validate the structures of newly synthesized derivatives. Additionally, the density functional theory (DFT) approach at M06/6–311G(d,p) level was utilized in order to calculate their optoelectronic and nonlinear optical (NLO) properties. Consequently, their HOMO-LUMO band gaps (Egap) were obtained in the range of 4.77–5.55 eV. A significant charge transfer from HOMO towards LUMO was investigated which was further supported by DOS. Moreover, they exhibited the maximum absorption wavelengths (λmax) in the UV- Vis region as 269.989–303.496 nm. Among the derivatives, BTMP was found with the least energy gap (4.77 eV) and the red-shifted absorption spectra (λmax =303.496 nm) as compared to other derivatives. Owing to these unique properties, BTMP was also found with significant linear polarizability ⟨α⟩ and hyperpolarizability (βtot and γtot) values i.e., 2.816×10−23, 1.855 × 10−30 and 4.553 × 10−35esu., respectively among the titled compounds. These findings indicated the potential use of these organic derivatives in the NLO applications.

Associating protein sequence positions with the modulation of quantitative phenotypes

Although protein sequences encode the information for folding and function, understanding their link is not an easy task. Unluckily, the prediction of how specific amino acids contribute to these features is still considerably impaired. Here, we developed a simple algorithm that finds positions in a protein sequence with potential to modulate the studied quantitative phenotypes. From a few hundred protein sequences, we perform multiple sequence alignments, obtain the per-position pairwise differences for both the sequence and the observed phenotypes, and calculate the correlation between these last two quantities. We tested our methodology with four cases: archaeal Adenylate Kinases and the organisms optimal growth temperatures, microbial rhodopsins and their maximal absorption wavelengths, mammalian myoglobins and their muscular concentration, and inhibition of HIV protease clinical isolates by two different molecules. We found from 3 to 10 positions tightly associated with those phenotypes, depending on the studied case. We showed that these correlations appear using individual positions but an improvement is achieved when the most correlated positions are jointly analyzed. Noteworthy, we performed phenotype predictions using a simple linear model that links per-position divergences and differences in the observed phenotypes. Predictions are comparable to the state-of-art methodologies which, in most of the cases, are far more complex. All of the calculations are obtained at a very low information cost since the only input needed is a multiple sequence alignment of protein sequences with their associated quantitative phenotypes. The diversity of the explored systems makes our work a valuable tool to find sequence determinants of biological activity modulation and to predict various functional features for uncharacterized members of a protein family.

Computational analysis of ligand design for Ru half-sandwich sensitizers in bulk heterojunction (BHJ) solar cells: Exploring the role of –NO2 group position and π-conjugation in optimizing efficiency

Bulk Heterojunction (BHJ) solar cells offer cost-effective photovoltaic solutions, flexible manufacturing, and improved efficiency with reduced environmental impact. Organometallic half-sandwich complexes, specifically a series of monometallic ruthenium complexes (Ru(1)–Ru(6)), have emerged as promising candidates for BHJ solar cells due to their outstanding charge transport properties. This study utilised Density Functional Theory (DFT) calculations with the B3LYP functional and SDD basis set augmented with 6-31 + G(d,p) to assess these Ru complexes with various N,O-chelating ligands, featuring distinct π-conjugated systems and positions of nitro groups, for BHJ solar cell applications. Our investigation focused on elucidating their electronic structures, identifying key electrophilic and nucleophilic sites, and exploring their optical properties. Our findings indicate that these complexes have maximum absorption wavelengths (λmax) ranging from 702 to 1083 nm, highlighting their strong photon absorption capabilities. Specifically, Ru(6), which includes the NO2 group, exhibits the narrowest energy gap but shows relatively lower values for oscillator strengths (f) and light harvesting efficiencies (LHE), indicating efficient light absorption but reduced energy conversion efficiency. In contrast, Ru(3), lacking the NO2 group but featuring enhanced π conjugation through cyclisation, demonstrates the widest energy gap yet boasts the highest values for f and LHE, suggesting superior efficiency in converting absorbed energy into electronic energy. These results emphasise the crucial role of ligand π-conjugation in enhancing energy conversion efficiency, while the strategic positioning of the NO2 group aids effective light absorption. Our study offers valuable insights into the design principles for optimizing organometallic ruthenium complexes in BHJ solar cell applications.

The Impact of Substitution of Diphenyl Dialumene on the Molecular Structure and Energetic Properties

The molecular structure, energetic properties, electronic, and vibrational spectroscopy of meta-substituted phenyl dialumene, DPD (Ar–Al=Al–Ar; Ar of the formula C6H5X2, where X = H, CH3, NH2, OH, F, Cl, Br, NO2, and COOH) are investigated by DFT. The singlet states of unsubstituted and substituted DPD adopt trans-planar geometry, while the triplet states adopt non-planar trans-bent geometry. The Al=Al bond length of unsubstituted DPD-H in a singlet state is calculated to be 2.734 Å, and there is no systematic and significant change upon substitution (2.734–2.744 Å). The substitution affects the absolute energy, ionization potential, electron affinity, and reorganization energy. The wavelength of maximum absorbance of DPD-H is determined to be 443 nm, and the substitute analogues DPD-X (X = OH, F, Cl, Br, NO2, CHO, COOH) show a hypsochromic shift, while DPD-CH3 and DPD-NH2 exhibit a bathochromic effect. The HOMO to LUMO+1 transition is the major transition for the meta-substituted DPD, except for X=NO2, where the transition is to LUMO+2. Considering the reorganization energy values, meta-substituted DPD can be useful as hole transporters. In addition, the theoretical data will aid in predicting the behavior of this class of compounds, facilitating the design and synthesis of similar compounds with desired properties.

Influence of external electric field on properties of Cyclotriparaphenyl[6]carbon

Cyclotriparaphenyl[6]carbon is a hypothetical derivative compound of cyclo[12]carbon, in which three CC triple bonds are replaced by three benzene rings. Comprehensive investigations of influence of external electric field (EEF) on cyclotriparaphenyl[6]carbon have been performed from theoretical aspect in this work. The maximum appropriate applied electric field strength is 0.0265 a.u., electron detachment will occur when EEF exceeds this value. When the EEF is in the range of 0–0.0265 a.u., with the increase of EEF, the shape of cyclotriparaphenyl[6]carbon turns from a circle to oval, the HOMO-LUMO gap gradually decreases from 6.046 eV at 0 a.u. to 2.322 eV at 0.0265 a.u., and its absorption band extends to VL (visible light) region and near-infrared region little by little. When the EEF are 0.025 a.u. and 0.0265 a.u., its maximum absorption wavelengths are 1220.6 nm and 1383.5 nm, respectively. HOMA (Harmonic oscillator measure of aromaticity), AV1245 and electron localization function (ELF) calculation results indicate that cyclotriparaphenyl[6]carbon has no aromaticity in the EEF range of 0–0.0265 a.u.. The compound exhibitspromising potential forapplication inthefield of colordevelopingcompound materials.

Structure–Property Relationships of Solution‐Processable Diarylethene‐Based Main‐Chain Photochromic Polymers

AbstractA series of alternating copolymers of a dithienylethene with di‐n‐alkyl‐fluorene (P1–P3), di‐n‐hexylphenylene (P4), 9‐heptadecanylcarbazole (P5), and 4,8‐bis(3,5‐dioctyl‐2‐thienyl)‐1,5‐dithia‐s‐indacene (P6) are designed, synthesized, and characterized. All of the polymers are soluble in common organic solvents such as chloroform, dichloromethane, toluene, and tetrahydrofuran. The side‐chain length affected the solubility of the polymer, molecular weight, and the glass transition temperature. Solutions of P1–P6 show photochromism with high quantum yields of 6‐π electrocyclization (41–87%) and cycloreversion (0.4–1.1%). These polymers also formed uniform thin films and the rates of solid state photoisomerization are measured relative to P4, which has the highest cyclization and cycloreversion rates. The color of the photochromic polymer is tuned according to the comonomer and the maximum absorption wavelength ranged from 569 to 675 nm in the closed isomeric form. All the polymers are thermally stable and show no signs of photodegradation after being exposed to UV‐light for 120 min in air. Based on these promising results, these polymers may be useful for multifunctional organic electronic devices.

The Influence of Mechanical Strains and Quantum-Size Effects on the Photosensitivity of Ge/Ge(x)Si(1-x) Nanofilm

Calculations of the maximum light wavelength of intrinsic absorption for the unstrained and strained germanium nanofilm were carried out. It was established that the photosensitivity of such nanofilm with the thickness of d 10 nm significantly depends on the effects of dimensional quantization and the magnitude of internal mechanical strains. It is shown that the variation of the thickness of the germanium nanofilm and the component composition of the Ge(x)Si(1–x) substrate allow controlling by its photosensitivity in the range from 0.8 to 4 μm.

Styryl hemicyanine-DNA assembly for selective Hg2+ sensing and molecular computing

A styryl dye with a chromophore based on methyl-benzothiazolium and 1-methyl-4-phenylpiperazine end group was synthesized under new improved reaction conditions. The synthesis was carried out in a way that ensured the direct production of a pure (>98 %) dye. The dye exhibits pronounced vertical and horizontal solvatochromism in both light absorption and fluorescence spectra. In the UV–Vis spectra of the dye, a difference in the longest wavelength absorption maximum from dichloromethane to water of about 100 nm was observed. In buffer (pH = 7.2), the dye absorbs at 445 nm, and in dichloromethane at 547 nm. The interaction of the dye with DNA and with protons and various metal ions was investigated, and the ability of the target fluorochrome to be used as a logic gate in the simultaneous presence of H+ and DNA was demonstrated. The dye is sensitive in the presence of mercury ions as well.

Variability in spectral absorption within cryptophyte phycobiliprotein types.

Cryptophytes are known to vary widely in coloration among species. These differences in color arise primarily from the presence of phycobiliprotein accessory pigments. There are nine defined cryptophyte phycobiliprotein (Cr-PBP) types, named for their wavelength of maximal absorbance. Because Cr-PBP type has traditionally been regarded as a categorical trait, there is a paucity of information about how spectral absorption characteristics of Cr-PBPs vary among species. We investigated variability in primary and secondary peak absorbance wavelengths and full width at half max (FWHM) values of spectra of Cr-PBPs extracted from 75 cryptophyte strains (55 species) grown under full spectrum irradiance. We show that there may be substantial differences in spectral shapes within Cr-PBP types, with Cr-Phycoerythrin (Cr-PE) 545 showing the greatest variability with two, possibly three, subtypes, while Cr-PE 566 spectra were the least variable, with only ±1 nm of variance around the mean absorbance maximum of 565 nm. We provide additional criteria for classification in cases where the wavelength of maximum absorbance alone is not definitive. Variations in spectral characteristics among strains containing the same presumed Cr-PBP type may indicate differing chromophore composition and/or the presence of more than one Cr-PBP in a single cryptophyte species.