Optical sensor arrays: one-pot, multiparallel synthesis and cellulose immobilization of pH and metal ion sensitive azo-dyes

A sixteen component array of acid-base and metal ion sensors was synthesized and covalently immobilized onto a transparent cellulose-based membrane. Dye synthesis and cellulose dyeing were carried out in one-pot, parallel, microscale reactions not requiring any isolation or purification steps. In addition, pH and metal ion optical sensing properties of the sixteen component array have been tested using a high-throughput screening based on digital imaging analysis.     

Spectroscopy of proteins at low temperature. Part I: Experiments with molecular ensembles

We discuss aspects of the physics of proteins at low temperature as they are reflected in highly resolved optical spectra of molecular probes. Typical probe molecules are heme-like dyes, aromatic amino acids, but also extended molecular aggregates in light harvesting complexes. We put emphasis on the interactions of the probe with its protein environment, on the range of these interactions, on their specific behavior in external fields, as well as on the characteristic parameters of the protein which can be determined with optical techniques at low temperatures but are not easily accessible otherwise. However, the focus of the review is on spectral diffusion physics of proteins, i.e. on their motion in conformational phase space, and on how this motion is reflected in the optical spectra. These structure changing-processes reflect the non-ergodic nature of low temperature proteins. They are most clearly detected at low temperature where the resolution of the experiment is close to the ultimate limit as given by the natural linewidth and where the dynamics become slow enough to be conveniently measured. In part I we discuss aspects of ensemble experiments, in part II we focus on experiments with single protein complexes. We offer lines of reasoning which may serve as guidelines for an understanding of the phenomena.     

A new type of boronic acid fluorescent reporter compound for sugar recognition

Fluorescent boronic acids that change fluorescent properties upon carbohydrate binding are very useful for the preparation of fluorescent sensors for sugars. Herein we report 5-quinolineboronic acid (5-QBA) that shows significant fluorescent property changes through a unique pK_a-switching mechanism upon binding a diol in aqueous solution.     

Theoretical analysis of 2D laser angle sensor and several design parameters

Having adopted several sets of new technology and techniques, such as cube-corner prism of higher refractive index, orthogonal holographic grating, non-linear compensation, and fringe fractionization, etc., we have developed a new type of laser angle sensor that can be used to measure two-dimensional angle of moving target. The sensor has high sensitivity, high precision and longer measuring range compared with the original sensor, and its measuring range will achieve ±35°, while its minimum resolution angle is 0.004°. The experimental results show that the measuring error is not greater than ±0.01°. In this paper, several design parameters and measuring results for 2D laser angle sensor are given.     

1,8-Naphthalimide-based colorimetric and fluorescent sensor for recognition of GMP,TMP, and UMP and its application in in vivo imaging

In this study, a series of 1,8-naphthalimide-based analogs were developed for fluorescence imaging of nucleotides in Caenorhabditis elegans. In DMSO, compound 1 proved to be an effective and selective colorimetric and fluorescent sensor for recognition of GMP, TMP, and UMP over other structurally similar nucleotides. Among all the tested nucleotides, only the addition of GMP, TMP, and UMP resulted in a fluorescence color change from blue to brown with a fluorescence enhancement of more than 600-fold, with the colorless solution turning brown. NMR spectroscopic titration, theoretical calculations, and spectral tests performed using various solvent compositions confirmed that compound 1 formed multiple hydrogen bonds with the related base groups in the nucleotide. Compound 1 demonstrated its utility as a fluorescent chemosensor for detecting GMP, TMP, and UMP in in vivo imaging of GMP, TMP, and UMP in C. elegans.     

在色氨酸存在下利用多壁碳纳米管糊电极和萘酚介质构成的伏安传感器测定N-乙酰半胱氨酸(英文)

A multiwall carbon nanotube modified electrode prepared by incorporating multiwall carbon nanotubes in the electrode of a sensor and naphthol green as a homogeneous mediator was used as a voltammetric sensor for the determination of N‐actylcysteine(N‐AC) in the presence of trypto-phan(Trp). The voltammograms of differential pulse voltammetry of N‐AC in a mixture with Trp were separated from each other by a potential difference of 200 mV, which allowed the determina-tion of both N‐AC and Trp simultaneously. Under the optimum conditions, the electrocatalytic cur-rents increased linearly with N‐AC concentration in the range of 0.25–400 μmol/L(two linear seg-ments with different slopes). The detection limit for N‐AC was 0.08 μmol/L. The kinetic parameters of the system were determined using electrochemical methods. The method was applied for the determination of N‐AC in drug and urine samples.     

Amino-functionalized mesoporous silica modified glassy carbon electrode for ultra-trace copper(II) determination

This paper described a facile and direct electrochemical method for the determination of ultra-trace Cu²⁺ by employing amino-functionalized mesoporous silica (NH₂-MCM-41) as enhanced sensing platform. NH₂-MCM-41 was prepared by using a post-grafting process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared (FTIR) spectroscopy. NH₂-MCM-41 modified glassy carbon (GC) electrode showed higher sensitivity for anodic stripping voltammetric (ASV) detection of Cu²⁺ than that of MCM-41 modified one. The high sensitivity was attributed to synergistic effect between MCM-41 and amino-group, in which the high surface area and special mesoporous morphology of MCM-41 can cause strong physical absorption, and amino-groups are able to chelate copper ions. Some important parameters influencing the sensor response were optimized. Under optimum experimental conditions the sensor linearly responded to Cu²⁺ concentration in the range from 5 to 1000 ng L⁻¹ with a detection limit of 0.9 ng L⁻¹ (S/N = 3). Moreover, the sensor possessed good stability and electrode renewability. In the end, the proposed sensor was applied for determining Cu²⁺ in real samples and the accuracy of the results were comparable to those obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) method.     

Ligand displacement-induced fluorescence switch of quantum dots for ultrasensitive detection of cadmium ions

This paper reports the construction of a simple CdTe quantum dots (QDs)-based sensor with 1,10-phenanthroline (Phen) as ligand, and the demonstration of a novel ligand displacement-induced fluorescence switch strategy for sensitive and selective detection of Cd²⁺ in aqueous phase. The complexation of Phen at the surface quenches the green photoluminescence (PL) of QDs dominated by a photoinduced hole transfer (PHT) mechanism. In the presence of Cd²⁺, the Phen ligands are readily detached from the surface of CdTe QDs, forming [Cd(Phen)₂(H₂O)₂]²⁺ in solution, and as a consequence the PL of CdTe QDs switches on. The detection limit for Cd²⁺ is defined as ∼0.01 nM, which is far below the maximum Cd²⁺ residue limit of drinking water allowed by the U.S. Environmental Protection Agency (EPA). Two consecutive linear ranges allow a wide determination of Cd²⁺ from 0.02 nM to 0.6 μM. Importantly, this CdTe QDs-based sensor features to distinctly discriminate between Cd²⁺ and Zn²⁺, and succeeds in real water samples. This extremely simple strategy reported here represents an attempt for the development of fluorescent sensors for ultrasensitive chemo/biodetection.     

One-pot synthesis of a new rhodamine-based dually-responsive pH sensor and its application to bioimaging

A new colorimetric and fluorescent sensor for the highly acidic pH was developed from rhodamine B, 1-(2-aminoethyl)piperazine, and 4-chloro-7-nitro-2,1,3-benzoxadiazole. The sensor could be synthesized in one pot with an 82.5% yield, and for the first time N,N-diisopropylethylamine was found to be crucial for the rhodamine spirolactam formation. The sensor responded to pH rapidly, visibly, reversibly, highly selectively, and sensitively. From pH 7.77 to 2.03, the absorption and fluorescence intensity of the sensor increased by 285 and 50.3 folds, respectively. The pK_a value based on the fluorescence titration was 2.87. Fluorescent imaging of living cells treated with the sensor in different pH media indicated that the sensor could provide intracellular pH information.     

A phenanthrene-based calix[4]arene as a fluorescent sensor for Cu and F

A new phenanthrene-based fluorescent calix[4]arene (4) has been synthesized in cone conformation. This compound was examined for its fluorescent properties towards different metal ions (Na⁺, Li⁺, Mg²⁺, Ni²⁺, Ba²⁺, Ca²⁺, Cu²⁺, Pb²⁺) and anions (F⁻, Cl⁻, Br⁻, H₂₄PO⁻,${{\text{H}}_2{\text{PO}}_4}^{-}\text{,}$₃NO⁻,${{\text{NO}}_3}^{-}\text{,}$₄HSO⁻,${{\text{HSO}}_4}^{-}\text{,}$ CH₃COO⁻) by fluorescence spectroscopy. The properties of the compound were evaluated and show that it is a fluorescence sensor for Cu²⁺ and F⁻. With the addition of Cu²⁺ and F⁻, the fluorescence was severely quenched.