Assessment of terbium (III) as a luminescent probe for the detection of tuberculosis biomarkers

A detection method for nicotinic acid, a specific metabolite marker of Mycobacterium tuberculosis present in cultures and patients' breath, is studied in complex solutions containing other metabolites and in biological media such as urine, saliva and breath condensate. The method is based on the analysis of the luminescence increase of Tb³⁺ complexes in the presence of nicotinic acid due to the energy transfer from the excited ligand to the lanthanide ion. It is shown that other potential markers found in M. tuberculosis culture supernatant, such as methyl phenylacetate, p-methyl anisate, methyl nicotinate and 2-methoxy biphenyl, can interfere with nicotinic acid via a competitive absorption of the excitation photons. A new strategy to circumvent these interferences is proposed with an upstream trapping of volatile markers preceding the detection of nicotinic acid in the liquid phase via the luminescence of Tb³⁺ complexes. The cost of the method is evaluated and compared with the Xpert MTB/RIF test endorsed by the World Health Organization.     

Capillary electrophoretic studies on quantum dots and histidine appended peptides self‐assembly

Herein, we designed four peptides appended with different numbers of histidine (His_n‐peptide). We launched a systematic investigation on quantum dots (QDs) and His_n‐peptide self‐assembly in solution using fluorescence coupled CE (CE‐FL). The results indicated that CE‐FL was a powerful method to probe how ligands interaction on the surface of nanoparticles. The self‐assembly of QDs and peptide was determined by the numbers of histidine. We also observed that longer polyhistidine tags (n ≤ 6) could improve the self‐assembly efficiency. Furthermore, the formation and separation of QD‐peptide assembly were also studied by CE‐FL inside a capillary. The total time for the mixing, self‐assembly, separation, and detection was less than 10 min. Our method greatly expands the application of CE‐FL in QDs‐based biolabeling and bioanalysis.     

纳米壳聚糖修饰的开管毛细管电色谱柱的制备及对碱性蛋白质的分离

采用离子交联法制得纳米壳聚糖粒子溶液,通过静电吸附作用将其修饰于石英毛细管内表面形成涂层毛细管柱.通过场发射扫描电子显微镜观察到毛细管内壁有小丘状突起,表明纳米壳聚糖粒子已吸附于柱内层.检测了不同p H值下的电渗流变化趋势并与裸柱比较,结果显示修饰后的柱电渗流受到明显抑制,并在p H4.7的环境中能产生反向电渗流,该柱在不同p H值下电渗流的相对标准偏差(RSD)6%,日内、日间和柱间的RSD分别为1.46%,4.64%和14.43%,表明柱稳定性较好.通过分离3种中性物质甲苯、苯酚和硫脲考察了该柱的色谱行为,出峰顺序与其极性大小顺序一致,表明纳米涂层起到极性固定相的作用.用该柱成功分离了3种碱性蛋白质溶菌酶、细胞色素c和核糖核酸酶A,柱效分别为39481,42610和245373Plate/m,重现性良好,表明纳米涂层可有效抑制碱性蛋白质的吸附作用.     

UV Emission of Gd3+ in the Presence of Cu2+: Towards Luminescence Quenching through Quantum Cutting?

The first investigation into the ultraviolet (UV) photoluminescence of gadolinium(III) in the presence of copper(II) is reported. A melt‐quenched barium phosphate glass was used as a model matrix. The optical spectroscopy assessment shows that with increasing CuO concentration the Cu²⁺ absorption band grows steadily, whereas the UV emission from Gd³⁺ ions is progressively quenched. The data, thus, suggests the existence of a Gd³⁺→Cu²⁺ energy‐transfer process ocurring through quantum cutting. A downconversion/cross‐relaxation pathway proceeding through a virtual state in Gd³⁺ is proposed. These findings suggest gadolinium(III) could potentially be used in the optical sensing of copper(II).     

Tuning the Upconversion Luminescence Lifetimes of KYb2F7:Ho3+ Nanocrystals for Optical Multiplexing

Conventional luminescent color coding is limited by spectral overlap and the interference of background fluorescence, thus restricting the number of distinguishable identities that can be used in practice. Here, we demonstrate the possibility of generating diverse time‐domain codes, specially designed for a single emission band, using lanthanide‐doped upconversion nanocrystals. Based on the knowledge of concentration quenching, the upconversion luminescence kinetics of KYb₂F₇: Ho³⁺ nanocrystals can be precisely controlled by modifying the dopant concentration of Ho³⁺ ions, resulting in a tunable emission lifetime from 75.8 to 1944.5 μs, which suggests the practicality of these time‐domain codes for optical multiplexing.     

Carbon Dots: The Newest Member of the Carbon Nanomaterials Family

Carbon nanomaterials have been extensively researched in the past few years owing to their interesting properties. The massive research efforts resulted in the emergence of carbon dots, which belong to the carbon nanomaterials family. Carbon dots (C‐dots) have garnered the attention of researchers mainly due to their convenient availability from organic as well as inorganic materials and also due to the novel properties they exhibit. C‐Dots have been said to overcome the era of quantum dots, referring to their levels of toxicity and biocompatibility. In this review, we focus on the discovery of C‐dots, their structure and composition, surface passivation to enhance their optical properties, the various synthetic methods used, their applications in different areas, and future perspectives. Emphasis has been given to greener approaches for the synthesis of C‐dots in order to make them cost effective as well as to improve their biocompatibility.     

Simple in‐house flow‐injection capillary electrophoresis with capacitively coupled contactless conductivity method for the determination of colistin

An in‐house flow‐injection capillary electrophoresis with capacitively coupled contactless conductivity detection method was developed for the direct measurement of colistin in pharmaceutical samples. The flow injection and capillary electrophoresis systems are connected by an acrylic interface. Capillary electrophoresis separation is achieved within 2 min using a background electrolyte solution of 5 mM 2‐morpholinoethanesulfonic acid and 5 mM histidine (pH 6). The flow‐injection section allows for convenient filling of the capillary and sample introduction without the use of a pressure/vacuum manifold. Capacitively coupled contactless conductivity detection is employed since colistin has no chromophore but is cationic at pH 6. Calibration curve is linear from 20 to 150 mg/L, with a correlation coefficient (r²) of 0.997. The limit of quantitation is 20 mg/L. The developed method provides precision, simplicity, and short analysis time.     

A Nanoscale Multiresponsive Luminescent Sensor Based on a Terbium(III) Metal–Organic Framework

A nanoscale terbium‐containing metal–organic framework ( nTbL ), with a layer‐like structure and [H₂NMe₂]⁺ cations located in the framework channels, was synthesized under hydrothermal conditions. The structure of the as‐prepared sample was systematically confirmed by powder XRD and elemental analysis; the morphology was characterized by field‐emission SEM and TEM. The photoluminescence studies revealed that rod‐like nTbL exhibited bright‐green emission, corresponding to ⁵D₄→⁷F_J (J=6–3) transitions of the Tb³⁺ ion under excitation. Further sensing measurements revealed that as‐prepared nTbL could be utilized as a multiresponsive luminescent sensor, which showed significant and exclusive detection ability for Fe³⁺ ions and phenylmethanol. These results highlight the practical applications of lanthanide‐containing metal–organic frameworks as fluorescent probes.     

A Ratiometric Luminescent Thermometer Co‐doped with Lanthanide and Transition Metals

Herein, we report the fabrication of a sensitive ratiometric and colorimetric luminescent thermometer with a wide operating‐temperature range, from cryogenic temperatures up to high temperatures, through the combination of lanthanide and transition metal complexes. Benefiting from the transition metal complex as a self‐reference, the lanthanide content in the mixed‐coordination complex, Eu_0.05(Mebip‐mim bromine)_0.15Zn_0.95(Mebip‐mim bromine)_1.9, was lowered to 5 %.