Time-Resolved Spectroscopy of Fluorescence Quenching in Optical Fibre-Based pH Sensors

Numerous optodes, with fluorophores as the chemical sensing element and optical fibres for light delivery and collection, have been fabricated for minimally invasive endoscopic measurements of key physiological parameters such as pH. These flexible miniaturised optodes have typically attempted to maximize signal-to-noise through the application of high concentrations of fluorophores. We show that high-density attachment of carboxyfluorescein onto silica microspheres, the sensing elements, results in fluorescence energy transfer, manifesting as reduced fluorescence intensity and lifetime in addition to spectral changes. We demonstrate that the change in fluorescence intensity of carboxyfluorescein with pH in this “high-density” regime is opposite to that normally observed, with complex variations in fluorescent lifetime across the emission spectra of coupled fluorophores. Improved understanding of such highly loaded sensor beads is important because it leads to large increases in photostability and will aid the development of compact fibre probes, suitable for clinical applications. The time-resolved spectral measurement techniques presented here can be further applied to similar studies of other optodes.

Download Full-text

Proton Triggered Colorimetric and Fluorescence Response of a Novel Quinoxaline Compromising a Donor-Acceptor System

Sensors ◽

10.3390/s18103433 ◽

2018 ◽

Vol 18 (10) ◽

pp. 3433 ◽

Cited By ~ 2

Author(s):

Yogesh More ◽

Sachin Padghan ◽

Rajesh Bhosale ◽

Rajendra Pawar ◽

Avinash Puyad ◽

...

Keyword(s):

Density Functional ◽

Fluorescence Emission ◽

Emission Spectra ◽

Paper Strip ◽

Time Resolved ◽

Fluorescence Studies ◽

Color Changes ◽

Spectral Changes ◽

Donor Acceptor ◽

Strip Test

Quinoxaline-based novel acid-responsive probe Q1 was designed on the basis of a conjugated donor-acceptor (D-A) subunit. Q1 shows colorimetric and fluorometric changes through protonation and deprotonation in dichloromethane. With the addition of the trifluoroacetic acid (TFA), UV-vis absorption spectral changes in peak intensity of Q1 was observed. Moreover, the appearance of a new peaks at 284 nm 434 nm in absorption spectra with the addition of TFA indicating protonation of quinoxaline nitrogen and form Q1.H+ and Q1.2H+. The emission spectra display appearance of new emission peak at 515 nm. The optical property variations were supported by time resolved fluorescence studies. The energy band gap was calculated by employing cyclic voltammetry and density functional calculations. Upon addition of triethylamine (TEA) the fluorescence emission spectral changes of Q1 are found to be reversible. Q1 shows color changes from blue to green in basic and acidic medium, respectively. The paper strip test was developed for making Q1 a colorimetric and fluorometric indicator.

Download Full-text

Space- and time-resolved study of impurities by visible spectroscopy in the high-density regime of JIPP T-II tokamak plasma

Nuclear Fusion ◽

10.1088/0029-5515/20/2/010 ◽

1980 ◽

Vol 20 (2) ◽

pp. 209-212 ◽

Cited By ~ 88

Author(s):

K. Kadota ◽

M. Otsuka ◽

J. Fujita

Keyword(s):

High Density ◽

Tokamak Plasma ◽

Visible Spectroscopy ◽

Time Resolved ◽

Space And Time ◽

Density Regime

Download Full-text

Protein crystallography in a vapour stream: data collection, reaction initiation and intermediate trapping in naked hydrated protein crystals

Journal of Applied Crystallography ◽

10.1107/s0021889801020702 ◽

2002 ◽

Vol 35 (1) ◽

pp. 113-116 ◽

Cited By ~ 21

Author(s):

Tove Sjögren ◽

Gunilla Carlsson ◽

Gisela Larsson ◽

Andras Hajdu ◽

Christer Andersson ◽

...

Keyword(s):

Data Collection ◽

Gas Phase ◽

Protein Crystals ◽

Stream Data ◽

Time Resolved ◽

Spectral Changes ◽

Wet Gas ◽

Hydrated Protein ◽

High Concentrations ◽

Reaction Initiation

A procedure is presented for experiments on naked unfrozen protein crystals with the crystal mounted in a conventional cryo-loop and surrounded by a stream of a wet gas. The composition and temperature of the vapour stream can be adjusted to keep the crystal without deterioration for many hours. The arrangement allows (i) for rapidly testing crystals for diffraction before freezing, (ii) for data collection between 268–303 K with greatly reduced background, (iii) for the controlled drying or wetting of crystals, (iv) for the anaerobic manipulation of protein crystals, and (v) for the introduction of gaseous or volatile ingredients and reactants into the crystal. The technique offers new experimental possibilities,e.g.in time-resolved structural studies. Reaction initiation in many protein crystals can be achieved by changing the composition of the vapour stream to create a new chemical environment around the crystal and to introduce substrates/reactants either in the gas phase or as microdroplets. Spectral changes during such reactions can be monitored by single-crystal microspectrophotometry, and, once an intermediate has been detected at high concentrations, the crystal can be frozen,e.g.by rapidly switching the warm vapour stream to a cryogenically cooled helium or nitrogen jet. Representative examples are presented in this paper.

Download Full-text

Six-year source apportionment of submicron organic aerosols from near-continuous measurements at SIRTA (Paris area, France)

10.5194/acp-2019-515 ◽

2019 ◽

Author(s):

Yunjiang Zhang ◽

Olivier Favez ◽

Jean-Eudes Petit ◽

Francesco Canonaco ◽

Francois Truong ◽

...

Keyword(s):

Source Apportionment ◽

Biomass Burning ◽

Ambient Air ◽

Carbonaceous Aerosols ◽

Time Resolved ◽

Pronounced Increase ◽

Paris Area ◽

Multi Wavelength ◽

High Concentrations

Abstract. Organic aerosol (OA) particles are recognized as key factors influencing air quality and climate change. However, highly-time resolved year-round characterizations of their composition and sources in ambient air are still very limited due to challenging continuous observations. Here, we present an analysis of long-term variability of submicron OA using the combination of Aerosol Chemical Speciation Monitor (ACSM) and multi-wavelength aethalometer from November 2011 to March 2018 at a background site of the Paris region (France). Source apportionment of OA was achieved via partially constrained positive matrix factorization (PMF) using the multilinear engine (ME-2). Two primary OA (POA) and two oxygenated OA (OOA) factors were identified and quantified over the entire studied period. POA factors were designated as hydrocarbon-like OA (HOA) and biomass burning OA (BBOA). The latter factor presented a significant seasonality with higher concentrations in winter with significant monthly contributions to OA (18–33 %) due to enhanced residential wood burning emissions. HOA mainly originated from traffic emissions but was also influenced by biomass burning in cold periods. OOA factors were distinguished between their less- and more-oxidized fractions (LO-OOA and MO-OOA, respectively). These factors presented distinct seasonal patterns, associated with different atmospheric formation pathways. A pronounced increase of LO-OOA concentrations and contributions (50–66 %) was observed in summer, which may be mainly explained by secondary OA (SOA) formation processes involving biogenic gaseous precursors. Conversely high concentrations and OA contributions (32–62 %) of MO-OOA during winter and spring seasons were partly associated with anthropogenic emissions and/or long-range transport from northeastern Europe. The contribution of the different OA factors as a function of OA mass loading highlighted the dominant roles of POA during pollution episodes in fall and winter, and of SOA for highest springtime and summertime OA concentrations. Finally, long-term trend analyses indicated a decreasing feature (of about 200 ng m−3 yr−1) for MO-OOA, very limited or insignificant decreasing trends for primary anthropogenic carbonaceous aerosols (BBOA and HOA, along with the fossil fuel and biomass burning black carbon components), and no trend for LO-OOA over the 6+-year investigated period.

Download Full-text

Optical, electrochemical and third-order nonlinear optical studies of triphenylamine substituted zinc phthalocyanine

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424616500838 ◽

2016 ◽

Vol 20 (08n11) ◽

pp. 1173-1181 ◽

Cited By ~ 5

Author(s):

Narra Vamsi Krishna ◽

Puliparambil Thilakan Anusha ◽

S. Venugopal Rao ◽

L. Giribabu

Keyword(s):

Nonlinear Optical ◽

Emission Spectra ◽

Optical Emission ◽

Soret Band ◽

Laser Pulses ◽

Zinc Phthalocyanine ◽

Third Order ◽

Time Resolved ◽

Nlo Properties ◽

Scan Data

Zinc phthalocyanine possessing triphenylamine at its peripheral position has been synthesized and its optical, emission, electrochemical and third-order nonlinear optical (NLO) properties were investigated. Soret band was broadened due to the presence of triphenylamine moiety. Electrochemical properties indicated that both oxidation and reduction processes were ring centered. Emission spectra were recorded in different solvents and the fluorescence yields obtained were in the range of 0.02–0.17 while the time-resolved fluorescence data revealed radiative lifetimes of typically few ns. Third-order NLO properties of this molecule have been examined using the Z-scan technique with picosecond (ps) and femtoseocnd (fs) pulses. Closed and open aperture Z-scan data were recorded with 2 ps/1 50 fs laser pulses at a wavelength of 800 nm and NLO coefficients were extracted from both the data. Our data clearly suggests the potential of this molecule for photonics applications.

Download Full-text

Light and electron microscopical observations of the effects of high-density lipoprotein on growth of Plasmodium falciparum in vitro

Parasitology ◽

10.1017/s0031182004005025 ◽

2004 ◽

Vol 128 (6) ◽

pp. 577-584 ◽

Cited By ~ 5

Author(s):

H. IMRIE ◽

D. J. P. FERGUSON ◽

M. CARTER ◽

J. DRAIN ◽

A. SCHIFLETT ◽

...

Keyword(s):

Plasmodium Falciparum ◽

High Density Lipoprotein ◽

Light And Electron Microscopy ◽

Density Lipoprotein ◽

Acid Synthesis ◽

High Density ◽

High Concentrations ◽

Electron Microscopical ◽

Necessary And Sufficient

Human serum high-density lipoprotein (HDL) is necessary and sufficient for the short-term maintenance of Plasmodium falciparum in in vitro culture. However, at high concentrations it is toxic to the parasite. A heat-labile component is apparently responsible for the stage-specific toxicity to parasites within infected erythrocytes 12–42 h after invasion, i.e. during trophozoite maturation. The effects of HDL on parasite metabolism (as determined by nucleic acid synthesis) are evident at about 30 h after invasion. Parasites treated with HDL show gross abnormalities by light and electron microscopy.

Download Full-text

Time-resolved and temperature tuneable measurements of fluorescent intensity using a smartphone fluorimeter

The Analyst ◽

10.1039/c7an00535k ◽

2017 ◽

Vol 142 (11) ◽

pp. 1953-1961 ◽

Cited By ~ 13

Author(s):

Md Arafat Hossain ◽

John Canning ◽

Zhikang Yu ◽

Sandra Ast ◽

Peter J. Rutledge ◽

...

Keyword(s):

Steady State ◽

Fluorescence Intensity ◽

Time Resolved Fluorescence ◽

Time Resolved ◽

Fluorescent Intensity ◽

Intensity Measurements

A smartphone fluorimeter is demonstrated for steady-state and time-resolved fluorescence intensity measurements at tunable temperatures.

Download Full-text

Ion Mobility Spectrometry-Mass Spectrometry (IMS-MS) for on- and off-line analysis of atmospheric gas and aerosol species

10.5194/amt-2016-132 ◽

2016 ◽

Cited By ~ 1

Author(s):

Jordan E. Krechmer ◽

Michael Groessl ◽

Xuan Zhang ◽

Heikki Junninen ◽

Paola Massoli ◽

...

Keyword(s):

Mass Spectrometry ◽

Ion Mobility Spectrometry ◽

Ion Mobility ◽

Measurement Techniques ◽

Molecular Ions ◽

Molecular Structures ◽

Water Soluble ◽

Oxidation Products ◽

Time Resolved ◽

Organic Species

Abstract. Measurement techniques that provide molecular-level information are needed to elucidate the multi-phase processes that produce secondary organic aerosol (SOA) species in the atmosphere. Here we demonstrate the application of ion mobility spectrometry-mass spectrometry (IMS-MS) to the simultaneous characterization of the elemental composition and molecular structures of organic species in the gas and particulate phases. Molecular ions of gas-phase organic species are measured online with IMS-MS after ionization with a custom build nitrate chemical ionization (CI) source. This CI-IMS-MS technique is used to obtain time-resolved measurements (5 min) of highly oxidized organic molecules during the 2013 Southern Oxidant and Aerosol Study (SOAS) ambient field campaign in the forested SE US. The ambient IMS-MS signals are consistent with laboratory IMS-MS spectra obtained from single-component carboxylic acids and multicomponent mixtures of isoprene and monoterpene oxidation products. Mass-mobility correlations in the 2-dimensional IMS-MS space provide a means of identifying ions with similar molecular structures within complex mass spectra and are used to separate and identify monoterpene oxidation products in the ambient data that are produced from different chemical pathways. Water-soluble organic carbon (WSOC) constituents of fine aerosol particles that are not resolvable with standard analytical separation methods, such as liquid chromatography (LC), are shown to be separable with IMS-MS coupled to an electrospray ionization (ESI) source. The capability to use ion mobility to differentiate between isomers is demonstrated for organosulfates derived from the reactive uptake of isomers of isoprene epoxydiols (IEPOX) onto wet acidic sulfate aerosol. Controlled fragmentation of precursor ions by collisional dissociation (CID) in the transfer region between the IMS and the MS is used to validate MS peak assignments, elucidate structures of oligomers, and confirm the presence of the organosulfate functional group.

Download Full-text