Hybrid Sol-Gel Matrices Doped with Colorimetric/Fluorimetric Imidazole Derivatives

Organic-inorganic hybrids (OIH) are materials that can be easily synthesized by the sol-gel method and combine the advantages of organic and inorganic moieties within a single polymeric matrix. Imidazole derivatives are versatile organic compounds that can change their optical properties with the variation of pH due to the protonation or deprotonation of the nitrogen atoms. This work reports the preparation of different OIHs doped with different contents of two imidazole compounds (3a,b). The obtained materials were characterized structurally by FTIR, and the dielectric properties were studied by electrochemical impedance spectroscopy. The optical properties were studied by UV-Vis absorption and fluorescence spectroscopies. The FTIR analysis showed that the presence of the imidazole does not change the structural properties of the matrices. The normalized resistance values obtained for the doped matrices ranged between 8.57 and 9.32 Ω cm2, all being higher than the undoped matrix. The σ ranged between 9.49 and 10.28 S cm−1, being all higher than the pure OIH samples. Compound 3a showed a maximum absorption peak at 390 nm, which is present in the OIH spectra, proving the presence of the compound. In the case of compound 3b, a maximum absorption wavelength at 412 nm was found, and the compound peak was not clear, which may indicate that an interaction between the compound and the matrix occurred. A synergetic effect between the intrinsic emission of the matrix and the fluorescence of 3a is found on the OIH-doped matrices.

Remarkable Size Effect on Photophysical and Nonlinear Optical Properties of All-Carboatomic Rings, Cyclo[18]carbon and Its Analogues

Inspired by recent experimental observation of molecular morphology and theoretical predictions of multiple properties of cyclo[18]carbon, we systematically studied photophysical and nonlinear optical properties of cyclo[2<i>N</i>]carbons (<i>N</i> = 3−15) allotropes through density functional theory. This work unveils the unusual optical properties of the sp-hybridized carbon rings with different sizes. The remarkable size dependence of optical properties of these systems and its underlying natures are profoundly explored, and the relevance between aromaticity and optical properties are highlighted. The extrapolation curves fitted for energy level of frontier molecular orbitals, maximum absorption wavelength, and (hyper)polarizability of considered carbon rings are presented, which can be used to reliably predict corresponding properties for arbitrarily large rings. The findings in this study will facilitate the exploration of potential application of the cyclocarbons in the field of optical material.

Remarkable Size Effect on Photophysical and Nonlinear Optical Properties of All-Carboatomic Rings, Cyclo[18]carbon and Its Analogues

Inspired by recent experimental observation of molecular morphology and theoretical predictions of multiple properties of cyclo[18]carbon, we systematically studied photophysical and nonlinear optical properties of cyclo[2<i>N</i>]carbons (<i>N</i> = 3−15) allotropes through density functional theory. This work unveils the unusual optical properties of the sp-hybridized carbon rings with different sizes. The remarkable size dependence of optical properties of these systems and its underlying natures are profoundly explored, and the relevance between aromaticity and optical properties are highlighted. The extrapolation curves fitted for energy level of frontier molecular orbitals, maximum absorption wavelength, and (hyper)polarizability of considered carbon rings are presented, which can be used to reliably predict corresponding properties for arbitrarily large rings. The findings in this study will facilitate the exploration of potential application of the cyclocarbons in the field of optical material.

Remarkable Size Effect on Photophysical and Nonlinear Optical Properties of All-Carboatomic Rings, Cyclo[18]carbon and Its Analogues

Inspired by recent experimental observation of molecular morphology and theoretical predictions of multiple properties of cyclo[18]carbon, we systematically studied photophysical and nonlinear optical properties of cyclo[2<i>N</i>]carbons (<i>N</i> = 3−15) allotropes through density functional theory. This work unveils the unusual optical properties of the sp-hybridized carbon rings with different sizes. The remarkable size dependence of optical properties of these systems and its underlying natures are profoundly explored, and the relevance between aromaticity and optical properties are highlighted. The extrapolation curves fitted for energy level of frontier molecular orbitals, maximum absorption wavelength, and (hyper)polarizability of considered carbon rings are presented, which can be used to reliably predict corresponding properties for arbitrarily large rings. The findings in this study will facilitate the exploration of potential application of the cyclocarbons in the field of optical material.

Determination of Cysteine by Discoloration Spectrophotometry using Copper(II)-Bis-Cyclohexanone Oxalydihydrazone

In the alkaline medium of pH=9.18, Cu2+ can be reduced to Cu+ by the sulfhydryl (-SH) of cysteine, and it result in the decrease the amount of Cu2+ in the system. The decrement of Cu2+ is directly proportional to the addition of cysteine, then using bis-cyclohexanone oxalyldihydrazone (BCO) as chromogenic reagent for Cu2+ to determinate the content of cysteine indirectly by discoloration spectrophotometry. A new method for the determination of cysteine by discoloration spectrophotometry using Copper(II)-BCO has been established. The influencing factors of the determination of cysteine is investigated. The results show that the maximum absorption wavelength of chromogenic system was 602 nm, in the range of 0.008000~0.06800 mg/mL, the linear relationship between the decrease of absorbance and the mass concentration of methimazol is A=0.2162+2.4824C (mg/mL), and the linear correlation coefficient is r=0.9959. The method has been applied to the determination of cysteine in food, and the results are basically consistent with those determined by pharmacopoeial method.

Determination of Isoniazid by Fe(II)-2,2’-Bipyridine Spectrophotometry

In acidic media, Fe(Ш) could be reduced to Fe(Ⅱ) by isoniazid, Fe(Ⅱ) reacts with 2,2'-bipyridine to form an orange complex with a maximum absorption wavelength of 522 nm. According to this principle, the content of isoniazid can be measured indirectly by measuring the amount of Fe(Ⅱ). A new method for the determination of isoniazid by Fe(Ⅱ)-2,2'-bipyridine spectrophotometry has been established. At the optimum conditions, the linear relationship is good between the mass concentration of isoniazid and absorbance of Fe(Ⅱ)-2,2'-bipyridine complex in the range of 0.0004000-0.002800 mg/mL. The linear regression equation is A=0.0251+138.04C(mg/mL), and the linear correlation coefficient is 0.9995. This method is used to determine the content of isoniazid in isoniazid tablets, and the results are similar to those obtained by pharmacopoeia method.

Development and Validation of Highly Sensitive Spectrophotometric Methods for Cefpirome Determination in Pharmaceutical Dosage Forms

Quantitative spectrophotometric determination of cefpirome in pure and pharmaceutical dosage has been developed. Method I produces a pink-coloured chromogen peak at λmax 510 nm by reacting diazotized cefpirome drugs with diphenylamine (DPA) in a neutral medium. Method II obtained of a coloured Schiff bases when cefpirome reacts with alcoholic p-dimethylaminobenzaldehyde (PDAB) to produce a yellow-coloured chromogen with a maximum absorption wavelength of 415 nm. In both methods I and II, Beer’s law is followed in the concentration ranges of 0.3-3.0 and 0.5-5.0 μg/mL, respectively, with molar absorptivity of 5.13 × 104 and 2.54 × 104 for each form. At three separate concentrations, intra-day and inter-day (RSD) and relative error (RE) are measured. The current methods are simple, reliable, inexpensive, speedy and highly reproducible and have been tested in broad range of pharmaceutical formulations with statistical comparisons to reference methods.

A new ultrafast energy funneling material harvests three times more diffusive solar energy for GaInP photovoltaics

There is no theoretical limit in using molecular networks to harvest diffusive sun photons on large areas and funnel them onto much smaller areas of highly efficient but also precious energy-converting materials. The most effective concept reported so far is based on a pool of randomly oriented, light-harvesting donor molecules that funnel all excitation quanta by ultrafast energy transfer to individual light-redirecting acceptor molecules oriented parallel to the energy converters. However, the best practical light-harvesting system could only be discovered by empirical screening of molecules that either align or not within stretched polymers and the maximum absorption wavelength of the empirical system was far away from the solar maximum. No molecular property was known explaining why certain molecules would align very effectively whereas similar molecules did not. Here, we first explore what molecular properties are responsible for a molecule to be aligned. We found a parameter derived directly from the molecular structure with a high predictive power for the alignability. In addition, we found a set of ultrafast funneling molecules that harvest three times more energy in the solar’s spectrum peak for GaInP photovoltaics. A detailed study on the ultrafast dipole moment reorientation dynamics demonstrates that refocusing of the diffusive light is based on ∼15-ps initial dipole moment depolarization followed by ∼50-ps repolarization into desired directions. This provides a detailed understanding of the molecular depolarization/repolarization processes responsible for refocusing diffusively scattered photons without violating the second law of thermodynamics.

Spectrophotometric Determination of Calcium with Dibromo-p-methylsulfonazo

Calcium is a necessary trace element in the human body, and its low or high content in the human body is not appropriate. It is very meaningful to study the level of calcium in the human body and to determine calcium content in blood. As people take calcium through food, the determination of calcium content in certain tea and calcium supplements is of great significance. In this study, a new method for the determination of calcium was established using dibromo-p-methylsulfonazo as a chromogenic agent. In this article, the optimal conditions for the color reaction of Ca2+ with dibromo-p-methylsulfonazo were established. In a hydrochloric acid medium, Ca2+ and dibromo-p-methylsulfonazo form a blue complex. At 624 nm maximum absorption wavelength, the apparent molar absorptivity for the determination of calcium is 3.32 × 104 L·mol−1·cm−1. Beer’s law is applied for 0–0.60 μg/mL. The method has already been used in the determination of calcium in blood serum, whole blood, tea leaf, and calcium fudge with satisfactory results.

Graphene Oxide Nanoparticles Having Long Wavelength Absorbing Chlorins for Highly-Enhanced Photodynamic Therapy with Reduced Dark Toxicity

The long wavelength absorbing photosensitizer (PS) is important in allowing deeper penetration of near-infrared light into tumor tissue for photodynamic therapy (PDT). A suitable drug delivery vehicle is important to attain a sufficient concentration of PS at the tumor site. Presently, we developed graphene oxide (GO) nanoparticles containing long wavelength absorbing PS in the form of the chlorin derivative purpurin-18-N-ethylamine (maximum absorption wavelength [λmax] 707 nm). The GO–PS complexes comprised a delivery system in which PS was loaded by covalent and noncovalent bonding on the GO nanosheet. The two GO–PS complexes were fully characterized and compared concerning their synthesis, stability, cell viability, and dark toxicity. The GO–PS complexes produced significantly-enhanced PDT activity based on excellent drug delivery effect of GO compared with PS alone. In addition, the noncovalent GO–PS complex displayed higher photoactivity, corresponding with the pH-induced release of noncovalently-bound PS from the GO complex in the acidic environment of the cells. Furthermore, the noncovalently bound GO‒PS complex had no dark toxicity, as their highly organized structure prevented GO toxicity. We describe an excellent GO complex-based delivery system with significantly enhanced PDT with long wavelength absorbing PS, as well as reduced dark toxicity as a promising cancer treatment.