Interplay of surface conditions, particle size, stoichiometry, cell parameters, and magnetism in synthetic hematite-like materials

We have studied several synthetic hematite-like materials, produced via different reactions using various hydrothermal conditions and various temperatures of annealing in air, by bulk elemental analysis, weight loss measurements, scanning electron microscopy, powder X-ray diffraction, Mössbauer spectroscopy, and SQUID magnetometry. We conclude that hematite-like materials cannot be related to pure stoichiometric hematite via a single stoichiometric or physical parameter and that at least two degrees of freedom are required. This is most clearly seen when we introduce a plot of the cell parameter c versus the cell parameter a on which hematite-like materials do not fall on a single line but occupy an entire region that is bounded by hydrohematite-hematite and protohematite-hematite lines. A Morin transition boundary on this c-a plot separates a region where Morin transitions occur from a larger region where Morin transitions do not occur down to 4.2 K. Previous claims that particle size is the dominant factor controlling the Morin transition are understood in terms of correlations between stoichiometry and particle size that are produced at synthesis. Changing contents of incorporated molecular water and structural hydroxyls with associated cation vacancies have different characteristic effects on the crystal structure and move the sample coordinates in different directions on a c-a plot. It is also shown that an accessory sulphate content is adsorbed on the individual hematite crystallites and is not structurally incorporated. Mössbauer spectroscopy is used, as usual, to identify and characterize the spin structure. In addition, hyperfine field distributions from room temperature spectra, extracted by a new method, give a sensitive measure of sample conditions but not a unique one since several factors affect the extracted distributions in similar ways.     

Aluminum(III) selective potentiometric sensor based on morin in poly(vinyl chloride) matrix

Al³⁺ selective sensor has been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier morin as ionophore. Best performance was exhibited by the membrane having composition as morin:PVC:sodium tetraphenyl borate:tri-n-butylphosphate in the ratio 5:150:5:150 (w/w, mg). This membrane worked well over a wide activity range of 5.0 × 10⁻⁷ to 1.0 × 10⁻¹ M of Al³⁺ with a Nernstian slope of 19.7 ± 0.1 mV/decade of Al³⁺ activity and a limit of detection 3.2 × 10⁻⁷ M. The response time of the sensor is ∼5 s and membrane could be used over a period of 2 months with good reproducibility. The proposed sensor works well over a pH range (3.5-5.0) and demonstrates good discriminating power over a number of mono-, di- and trivalent cations. The sensor can also be used in partially non-aqueous media having up to 20% (v/v) methanol, ethanol or acetone content with no significant change in the value of slope or working activity range. The sensor has also been used in the potentiometric titration of Al³⁺ with EDTA and for its determination in zinc plating mud and red mud.     

乳化剂OP存在下桑色素与Al（Ⅲ）Mo（Ⅵ）显色反应的研究及应用

研究了非离子型表面活性剂ＯＰ存在下，桑色素与Ａｌ（Ⅲ）Ｍｏ（Ⅵ）显色反应的适宜条件。在０．１２ｍｏｌ．Ｌ＾－１乙酸介质中，桑色素与Ａｌ（Ⅲ）的配合物最大吸收波长为４２０ｎｍ，表观摩尔吸光系数为１．３７＊１０＾５，Ａｌ（Ⅲ）浓度在０－２．０μｇ／１０ｍｌ范围内呈良好的线性关系。     

油酸包裹对不同尺寸纳米α-Fe_2O_3晶体Morin相变影响的Mssbauer研究

用 Mossbauer方法研究了冻油酸中的 35nm与 6 0 nm均匀α- Fe2 O3 微晶的 Morin相变温度 ,发现它比未包裹样品分别高了 50 K和 2 4 K     

The interaction between morin and CTAB aggregates

Electronic absorption spectra, fluorescence emission spectra, ATR-FTIR spectra, cyclic voltammetric measurements, and ab initio quantum calculation are used to study the properties of morin in CTAB micelles with different microstructures and microenvironments and to gain information about the binding of morin with CTAB micelles. Morin can be located in the CTAB micelle with its phenyl group (deviating with 38.98 degrees from the planarity) only in the form of the monomer, which leads to increase of the planarity and extension of the pi conjugation of the whole molecule. The embedding of two hydroxyl groups on the phenyl into a more hydrophobic microenvironment makes the oxidation peak of morin move to a higher potential with a decreased peak current. The binding of morin with CTAB micelles is a spontaneous (DeltaG<0) and endothermic process (DeltaH>0), and the hydrophobic and electrostatic force is the main driving force for its solubilization.     

Online Monitoring of Aluminium in Drinking Water with Fluorimetric Detection

We report a procedure for the online monitoring of aluminium in drinking water by flow injection analysis. The reaction used is the formation of a complex with morin. Under the working conditions, this can be accomplished in an ethanol-rich hydroalcoholic medium, which modifies the fluorescent characteristics of the complex, allowing the determination of aluminium concentrations higher than 3.1 μgl⁻¹, with a linear application range between 2 and 250 μgl⁻¹, an R.S.D. of 2.3% (n = 10, 120 μgl⁻¹) and a sampling frequency of 90 h⁻¹. The method can thus be considered one of the most sensitive and fastest for the continuous determination of aluminium. In the presence of anionic surfactants, the sensitivity of the determination is increased. In this form, aluminium is detected at concentrations higher than 2.8 μgl⁻¹, with a linear application range of 2–50 μgl⁻¹. The procedure was applied to the analysis of aluminium in drinking, river, and underground water. Under the proposed working conditions, only Fe(III), fluoride and phosphates interfere. The interference of Fe(III) can be avoided with hydroxylamine and that of phosphates and polyphosphates by acid digestion of the samples.     

基于聚乙烯亚胺碳纳米点的桑色素比率型荧光探针

利用水热合成法制备了一种基于聚乙烯亚胺的荧光碳纳米点,用光谱方法研究了其对桑色素的识别作用.结果表明,该碳纳米点对桑色素具有比率型荧光响应,且响应速度快、选择性和灵敏度高、抗干扰能力强.将桑色素加入到碳纳米点溶液中后,碳纳米点自身的荧光(460 nm)立即被猝灭,同时在555 nm处出现新的荧光发射峰并逐渐增强;其新发射峰(555 nm)与原发射峰(460 nm)的强度比值在此过程中呈线性增加.基于此,在1.0×10^-6～4.0×10^-5mol/L浓度范围内,可实现对桑色素的检测,该比率荧光响应非常灵敏,检出限可达3.0×10^-8mol/L.另外,该碳纳米点与常见金属离子、氨基酸及其它具有类似桑色素结构的黄酮醇均不反应,显示出对桑色素的高选择性.该检测方法的荧光强度随桑色素浓度的增加而逐渐增强,并伴随着由蓝色到黄色的荧光颜色变化,可实现对桑色素的可视化检测;同时该碳纳米点还可用于稀释胎牛血清中桑色素的定量检测.     

A comparison of the impacts of different polysaccharides on the sono-physico-chemical consequences of ultrasonic-assisted modifications

This study aimed to examine the sono-physico-chemical effects of ultrasound (UND) and its impact on the conjugate rates of morin (MOI) following the addition of polysaccharides in various conditions. In comparison to the control group, the incorporation of quaternary ammonium chitosan decreased the rate of MOI conjugation by 17.38%, but the addition of locust bean gum enhanced the grafting rate by 29.89%. Notably, the highest degree of myofibrillar protein (MRN) unfolding (fluorescence intensity: 114435.50), the most stable state (−44.98 mV), and the greatest specific surface area (393.06 cm²/cm³) were observed in the UMP/LBG group. The outcomes of atomic force microscopy and scanning electron microscopy revealed that the inclusion of locust bean gum led to a different microscopic morphology than the other two polysaccharides, which may be the primary cause of the strongest sono-physico-chemical effects of the system. This work demonstrated that acoustic settings can be tuned based on the characteristics of polysaccharides to maximize the advantages of sono-physico-chemical impacts in UND-assisted MOI processing.