In situ measurements of subsurface contaminants with a multi-channel laser-induced fluorescence system.

A new multi-channel laser-induced fluorescence (LIF) probe with novel optical fiber probe geometry has been designed and integrated into a cone penetrometer testing (CPT) system for in situ contamination detection. The system is capable of collecting excitation and emission matrices (EEMs) of subsurface contaminants as a function of depth in seconds. Compared to our previous multi-channel LIF-CPT system, the new system is faster and more compact, with reduced probe size and sampling area. This article describes the first field demonstration of the system at Hanscom Air Force Base, Massachusetts. One contaminated site within the base was characterized through in situ measurements of 26 LIF-CPT pushes. To validate the LIF results, core samples taken at five locations were analyzed by both on-site LIF measurements and by off-site laboratory analyses with EPA methods. The comparison of the LIF and laboratory results is presented, along with the results of the in situ measurements.     

Synthesis and photophysical properties of novel succinimidyl benzazole derivatives, evaluated by Candida albicans ATCC 10231 fluorescent staining

New fluorescent succinimidyl benzazole derivatives were synthesised and successfully used to stain Candida albicans ATCC 10231 cells. The dyes were characterised by means of infrared, ¹³C and ¹H NMR spectroscopies and elemental analysis. UV-Vis and steady-state fluorescence in solution were also applied to characterise their photophysical behaviour. The novel dyes were fluorescent in the yellow-green region by a phototautomerism in the excited state (ESIPT) with a large Stokes shift (9065-10962 cm⁻¹). Dual fluorescence could also be observed depending on the solvent polarity. The present dyes were used as new probes by means of culture methodology or direct staining to study the micromorphology of Candida albicans.     

Invader probes: harnessing the energy of intercalation to facilitate recognition of chromosomal DNA for diagnostic applications

Development of probes capable of recognizing specific regions of chromosomal DNA has been a long-standing goal for chemical biologists. Current strategies such as PNA, triplex-forming oligonucleotides, and polyamides are subject to target choice limitations and/or necessitate non-physiological conditions, leaving a need for alternative approaches. Toward this end, we have recently introduced double-stranded oligonucleotide probes that are energetically activated for DNA recognition through modification with +1 interstrand zippers of intercalator-functionalized nucleotide monomers. Herein, probes with different chemistries and architectures – varying in the position, number, and distance between the intercalator zippers – are studied with respect to hybridization energetics and DNA-targeting properties. Experiments with model DNA targets demonstrate that optimized probes enable efficient (C ₅₀ < 1 μM), fast (t ₅₀ < 3 h), kinetically stable (>24 h), and single nucleotide specific recognition of DNA targets at physiologically relevant ionic strengths. Optimized probes were used in non-denaturing fluorescence in situ hybridization experiments for detection of gender-specific mixed-sequence chromosomal DNA target regions. These probes present themselves as a promising strategy for recognition of chromosomal DNA, which will enable development of new tools for applications in molecular biology, genomic engineering and nanotechnology.     

Sampling and characterization of nanoaerosols in different environments

Efficient sampling and characterization of nanoparticles have been challenging tasks in environmental research due to the limitations of regular analytical techniques (e.g., dynamic light scattering, and nuclear magnetic resonance and UV-Vis spectroscopies) - especially the difficulties in their application to in situ and real-time monitoring, which are intrinsically related to the nanometer-size range.This critical overview aims at characterizing recent instrumental techniques (e.g., hygroscopic tandem-differential mobility analysis, thermal desorption-gas chromatography-mass spectrometry, and time-of-flight secondary ion mass spectrometry) for sampling and characterization of individual nanoaerosols in terms of their general operation principles, analytical parameters, advantages and limitations. We also discuss classification of this instrumentation based on off-line and/or in situ methods, and on physical and chemical characterization of nanoaerosols. Further, we summarize recent air-quality studies aimed at understanding the physical and chemical behavior of aerosols in different environments.     

In situ determination of organic compounds in liquid samples using a combined UV-Vis/fluorescence submersible sensor

In order to improve the in situ evaluation and quantitative analysis of complex contaminations of liquid media such as ground-, surface, and wastewaters, an integrated submersible sensor probe has been developed. It is especially characterized by the option of simultaneously measuring ultraviolet/visible (UV/Vis) and fluorescence spectra. Owing to the compact construction with light sources, flow cell, detection system, and data acquisition/processing unit in the waterproof case, the data transfer to the surface can be realized electrically, and the operation depth is practically not limited. The variability in the measuring techniques allows a wide variety of chemical compounds to be analysed within a broad concentration range. The performance of the new submersible sensor probe was tested ex situ in laboratory scale, and the performance was comparable with that of stationary measuring instruments. As an example for an in situ application, the sensor probe was successfully used to monitor the migration of chemical substances during a tracer experiment in groundwater. The concentration of the tracer compound uranin (sodium fluorescein) was measured in the range of 5–500 µg L^?1 using fluorescence spectroscopy, while at the same time the contents of toluene were continuously detected in the same groundwater wells using the UV/Vis sensor channel.     

In situ examination of uranium contaminated soil particles by micro-X-ray absorption and micro-fluorescence spectroscopies

Two complimentary spectroscopic techniques, X-ray absorption and fluorescence spectroscopy have been conducted at spatial scales of 1 to 25 μm on uranium contaminated soil sediments collected from two former nuclear materials processing facilities of the DOE: Fernald, OH and Savannah River Site, SC. A method of imbedding particles in a non-reactive Si polymer was developed such that individual particles could be examined before and after extraction with a wide range of chemicals typically used in sequential extraction techniques and others proposed forex situ chemical intervention technologies. Using both the micro-X-ray fluorescence (XRF) and micro-X-ray Absorption Near Edge Structure (XANES) techniques, both elemental and oxidation state distribution maps were generated on individual particles before and following chemical extraction. XANES can determine the relative proportion of U(VI) and U(IV) in phases comprising individual particles before and after extraction and showed that greater than 85% of the uranium existed as hexavalent U(VI). Fluorescence spectra of contaminated particles containing mainly U(VI) revealed populations of uranyl hydroxide phases and demonstrated the relative efficacy and specificity of each extraction method. Correlation of XAS and fluorescence data at micron scales provides information of U oxidation state as well as chemical form in heterogeneous samples.     

Redox-responsive polymer prodrug/AgNPs hybrid nanoparticles for drug delivery

The redox-responsive hybrid nanoparticles of P(MACPTS-co-MAGP)@AgNPs is developed for drug delivery and fluorescence monitoring of the drug release by applying the NSET-based strategy.     

Photoabsorption spectra of Cs n O and Cs n clusters

Photoabsorption spectra of several Cs _N+2O and Cs _N clusters were obtained by means of laser-induced beam-depletion techniques. The strong absorption of clusters withN≥3 in the near infrared indicates that collective motion might play an important role. Dipole transitions between molecular orbitals, enhanced by plasmon oscillations, generate remarkably distinct spectra for(a) closed-shell clusters atN=8 and(b) geometrically symmetric clusters like Cs₆O and Cs₁₄O.     

A concise chemical synthesis of a fluorescent βGal-(1,4)-S-βGlc-Cer derivative and its enzymatic elongation by glycosyltransferases

A straightforward chemical synthesis of lyso-lactosylceramide with the terminal galactose linked to glucose through a β-S-glycosidic bond is reported. The product is labeled on the amino-group with tetramethylrhodamine enabling its ultrasensitive detection in capillary electrophoresis using laser-induced fluorescence. The fluorescent product disaccharide is resistant to hydrolysis by glycosidases but is shown to remain as an acceptor substrate for glycosyltransferases for the conversion into the trisaccharides GM3 and Gb3.     

Characterization of polycyclic aromatic hydrocarbons in environmental samples by selective fluorescence quenching

Selective fluorescence quenching is used to profile polycyclic aromatic hydrocarbons (PAHs) in samples of environmental origin. After separation by high-efficiency capillary liquid chromatography, the PAHs are detected by laser-induced fluorescence spectroscopy. Nitromethane is added to selectively quench the fluorescence of alternant PAHs, whereas diisopropylamine is added to quench nonalternant PAHs. The chromatograms in the absence and presence of fluorescence quenching are evaluated by means of the product moment correlation method to quantify the statistical similarities and differences. This method is demonstrated by application to three samples: a standard mixture of 16 priority pollutants, a coal-derived fluid, and a contaminated soil. The correlation coefficients (r) are typically 0.99 or higher for samples that are identical in origin, 0.90-0.50 for closely related samples, and less than 0.50 for samples that are distinctly unrelated. This method can be used to confirm with high statistical confidence the cause or source of an event with environmental impact, such as an oil leak or spill, contamination or waste by-products from petroleum fuel production and processing, etc.     

A general strategy to quantify analytes through fluorescence chromaticity and luminosity

To realize a fast, easy-operation and precise way using fluorescence probes to quantify analytes is a goal to facilitate detection, especially in situ. Herein, we are reporting an approach which can be generally employed for the differentiation and quantitation of analytes through fluorescence chromaticity and luminosity. Seven representative fluorescent probes, targeting pH, cysteine, hydrogen sulfide, hydrogen peroxide, palladium and hydrazine, were synthesized and tested. Without utilizing costly instrumentations, portable devices were employed to collect data of photographs from the fluorescence samples in responses to different analytes. Subsequently, the photographic images were digitally processed to generate calibration curves between chromaticity/luminosity verse concentrations after mapping to the CIE 1931 xyY standard color space. Good linear calibration curves and quantitative analysis of unknown samples with low errors through the spectral technology demonstrated the reliability of this method. Thus, we showed the analytical method with a simple and on-site constructible/portable device which is promising for applications in more fluorescence probes     

A general strategy for in situ assembly of light-up fluorophores via bioorthogonal Suzuki-Miyaura cross-coupling

Herein we presented a general strategy for in situ assembly of intramolecular charge-transfer (ICT)-based light-up fluorophores via bioorthogonal Suzuki-Miyaura cross-coupling reaction. By introducing iodo group at the appropriate position, five fluorophores with different scaffolds including naphthalimide, coumarin, naphthalene sulfonate, nitrobenzoxadiazole, and acetonaphthone, were designed as bioorthogonal multicolor fluorogenic probes, which could produce significant fluorescence enhancement and high fluorescence quantum yield after Suzuki-Miyaura reaction with aryl boronic acid or boronate. Manipulating the substituents and π scaffold in the fluorophores allows fine-tuning of their photophysical properties. With this strategy, we succeeded in peptide conjugation, no-wash fluorogenic protein labeling, and mitochondria-selective bioorthogonal imaging in live cells.     

Photoinduced transformation of camptothecin in the presence of iron(III) ions

To obtain the information on the photoactivated action of camptothecin (CPT) promoted by transition metals, CPT was UVA irradiated (λ = 365 nm) in dimethylsulfoxide (DMSO) solutions. Fe(III) ions present were efficiently reduced to Fe(II) under argon and also in the presence of oxygen. The photoinduced electron transfer under argon resulted into the generation of carbon-centered radicals identified by EPR spin trapping evidencing the cleavage of CPT skeleton. Whereas the absorption UV/vis experiments with equimolar ratio Fe(III):CPT excluded the formation of charge-transfer complexes, the fluorescence spectra of CPT in the presence of Fe(III) revealed a significant fluorescence quenching indicating the probability of physical association between Fe(III) and CPT species in DMSO solutions confirming Fe(III) involvement in the photoinduced transformation.     

Two highly selective fluorescence probes for imaging Pd2+ in cells and mice

Two rhodamine-based probes were designed and prepared, which exhibited highly sensitive and selective fluorescence enhancement upon binding to Pd²⁺ by UV–vis and fluorescence spectroscopies. Meanwhile the distinct color changes and rapid switch-on fluorescence also provided “naked-eyes” detection for Pd²⁺ over a broad pH range. The recognition mechanism was explored through Job’s plot, MS data, IR spectra and related theoretical calculations. Furthermore, the probes were applied for biological imaging to confirm that they can be used for monitoring Pd²⁺ in living cells (L929 and A549 cells) and living mice with satisfying results, which further demonstrated their value of practical applications in environmental and biological systems.     

Determination of226Ra in environmental samples using high-resolution inductively coupled plasma mass spectrometry

A time-saving and accurate technique for determining²²⁶Ra in groundwater and soil was examined, using high-resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). The technique was applied to the determination of²²⁶Ra in groundwater and soil samples and compared with the conventional liquid scintillation counting method. This technique was capable of completing²²⁶Ra counting within 3 minutes, without the in-growth period to allow radon and its progeny to achieve secular equilibrium with the parent²²⁶Ra. The detection limits of HR-ICP-MS for²²⁶Ra in groundwater and soil were 0.19 mBq·1⁻¹ and 0.75 Bq·kg⁻¹, respectively, which were about 10 times lower than that of the liquid scintillation counter. The results obtained from HR-ICP-MS in groundwater and soil were in accordance with those of LSC within a relative error of about 13%.     

Experimental Conditions Optimization and Sample Contamination Avoidance for the Fluorescence Measurement of Subsurface Soil or Rock Extracts

A great effort has been made to reveal the correlation between the traces of hydrocarbons present in subsurface soil and the underground petroleum gas field. In recent years, fluorescence spectrophotometry has gained applications in chemical prospecting analysis.     

Visualisation of electrochemical processes by coupled electrochemistry and fluorescence microscopy

The in situ coupling between electrochemistry and fluorescence microscopy is gaining popularity in the electrochemical community as a tool to image electrode processes in real time, providing useful spatial information which is not accessible by purely electrochemical methods. In recent years, new applications of electrochemical-fluorescence microscopy coupling have emerged, together with methodological developments that have expanded the possibilities of this technique. These recent trends are discussed in the present contribution, with an emphasis on the fluorogenic probes being employed.     

激光诱导纳秒时间分辨荧光法原位测定吸附于红树叶片表面的菲

实现吸附于植物叶片表面多环芳烃(Polycyclic aromatic hydrocarbons,PAHs)的现场原位测定,是该研究领域的发展方向之一。本实验利用激光诱导纳秒时间分辨荧光(Laser-induced nanosecond time-resolved fluorescence,LITRF)系统,建立了原位测定吸附于秋茄(Kandelia obovata,Ko)、木榄(Bruguiera gymnorhiza,Bg)和桐花树(Aegiceras corniculatum,Ac)3种红树叶片表面菲(Phenanthrene,Phe)的新方法。本方法测定吸附于Ko、Bg和Ac叶片表面Phe的线性范围分别为2~1400 ng/spot,1~1000 ng/spot和4~2000 ng/spot,检测限分别为0.20,0.14和0.42 ng/spot,加标回收率为89.6%~108.1%,78.2%~92.4%和93.2%~112.9%,且方法的相对标准偏差小于6.0%(n=9)。将方法用于实验室暴露样品的原位测定,并与光纤荧光法对比,其灵敏度、线性范围改善显著,更有利于实现植物叶片上PAHs的现场原位测定。     

Microwave-assisted <Emphasis Type="Italic">in situ</Emphasis> synthesis of fluorescent gold nanoclusters with BSA/montmorillonite and application on latent fingermark imaging

A method for in situ preparation of fluorescent gold nanoclusters (AuNCs) with bovine serum albumin/montmorillonite composite powder (AuNC-BSA/MMT) was developed, and the products were used to detect latent fingermarks. In this work, AuNCs were “grown” both inside and on the surface of BSA/MMT clay using one-step reduction of HAuCl4 by BSA. The as-prepared AuNC-BSA/MMT nanocomposites emit intensive red fluorescence under the excitation of UV-visible light and show stable chemical features and low toxicity. The obtained fluorescent powders were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction to depict their sizes, structural information and optical features. Given their environmentally friendly preparation, simple operation, low cost, efficient UVvisible radiation-dependent photoluminescence and good affinity with finger residues, the in situ synthesized AuNC-BSA/MMT nanocomposite powders were used as an alternative fluorescent developing reagent for developing latent fingermarks deposited on various object surfaces (such as glass, aluminum foil, painted metal, plastic products and weighing papers) for individual identification. As results, the developed fingermarks with clear patterns and satisfactory level-2 (minutiae points) and level-3 (sweat pores) ridge details were obtained. Notably, treated prints could be excited by red light and emitted near infrared fluorescence, which was beneficial to avoid background interference and reduce the damage caused by UV light. With the advantages of the simple preparation process and good enhancement performance for latent fingermarks, the proposed method might be used in the preparation of various fluorescent probes for detecting trace evidence in forensic sciences.     

Preparation of the crosslinked polyethersulfone films by high-temperature electron-beam irradiation

The radiation-crosslinked polyethersulfone (RX-PES) films were prepared by means of electron-beam irradiation under nitrogen atmosphere at 230 °C, where the temperature is around the glass transition temperature of PES (222 °C). The gel formation of RX-PES films was observed when the absorbed doses exceeded 300 kGy, which indicated the crosslinking structure formation. The G(S) of 0.10 and G(X) of 0.23 were calculated according to the Y-crosslinking mechanism. The irradiation was also performed at ambient temperature for comparison. There was no gel formation of the irradiated films even for the absorbed doses as high as 2250 kGy. The thermal properties of the original and irradiated PES films were measured by means of DSC and TGA analyses. The chemical structure of the original and the irradiated films was analyzed by means of FT-IR ATR and UV-vis spectroscopies.