Miniaturization of fluorescence sensing in optofluidic devices

International audienceSuccessful development of a micro-total-analysis system (μTAS, lab-on-a-chip) is strictly related to the degree of miniaturization, integration, autonomy, sensitivity, selectivity, and repeatability of its detector. Fluorescence sensing is an optical detection method used for a large variety of biological and chemical assays, and its full integration within lab-on-a-chip devices remains a challenge. Important achievements were reported during the last few years, including improvements of previously reported methodologies, as well as new integration strategies. However, a universal paradigm remains elusive. This review considers achievements in the field of fluorescence sensing miniaturization, starting from off-chip approaches, representing miniaturized versions of their lab counter-parts, continuing gradually with strategies that aim to fully integrate fluorescence detection on-chip, and reporting the results around integration strategies based on optical-fiber-based designs,optical layer integrated designs, CMOS-based fluorescence sensing, and organic electronics. Further successful development in this field would enable the implementation of sensing networks in specific environments that, when coupled to Internet of-Things (IoT) and artificial intelligence (AI), could provide real-time data collection and, therefore, revolutionize fields like health, environmental, and industrial sensing

Optofluidic Formaldehyde Sensing: Towards On-Chip Integration

International audienceFormaldehyde (HCHO), a chemical compound used in the fabrication process of a broad range of household products, is present indoors as an airborne pollutant due to its high volatility caused by its low boiling point ( T=−19 °C). Miniaturization of analytical systems towards palm-held devices has the potential to provide more efficient and more sensitive tools for real-time monitoring of this hazardous air pollutant. This work presents the initial steps and results of the prototyping process towards on-chip integration of HCHO sensing, based on the Hantzsch reaction coupled to the fluorescence optical sensing methodology. This challenge was divided into two individually addressed problems: (1) efficient airborne HCHO trapping into a microfluidic context and (2) 3,5–diacetyl-1,4-dihydrolutidine (DDL) molecular sensing in low interrogation volumes. Part (2) was addressed in this paper by proposing, fabricating, and testing a fluorescence detection system based on an ultra-low light Complementary metal-oxide-semiconductor (CMOS) image sensor. Two three-layer fluidic cell configurations (quartz–SU-8–quartz and silicon–SU-8–quartz) were tested, with both possessing a 3.5 µL interrogation volume. Finally, the CMOS-based fluorescence system proved the capability to detect an initial 10 µg/L formaldehyde concentration fully derivatized into DDL for both the quartz and silicon fluidic cells, but with a higher signal-to-noise ratio (SNR) for the silicon fluidic cell ( SNRsilicon=6.1 ) when compared to the quartz fluidic cell ( SNRquartz=4.9 ). The signal intensity enhancement in the silicon fluidic cell was mainly due to the silicon absorption coefficient at the excitation wavelength, a(λabs=420 nm)=5×104 cm−1 , which is approximately five times higher than the absorption coefficient at the fluorescence emission wavelength, a(λem=515 nm)=9.25×103 cm−

Synchrotron radiation study of the RgCI*, Rg

In a Cl2 + Rg doped neon matrix, the RgCl* and Rg2Cl* excimers are not formed from a primary excitation of the free or complexed molecular chlorine. They are only observed when Cl atoms or RgCl van der Waals complexes preexist in the Ne matrix after photolysis of Cl2. The XeCl* B1/2 and C3/2 states are shown to be nearly isoenergetic. The vibrational structure of the D1/2 state is resolved for the first time

Effets d'additifs sur la postluminescence de He2 dans l'hélium excité par une impulsion intense d'électrons

The excitation of helium at pressures between 50 and 1 500 torrs by a short electron pulse, leads to afterglow emissions due to transitions between electronically excited states of the He2 molecule. The oscillograms obtained for the emission He 2 (d3 Σ+u → b3 Π g) at 6 400 Å at different helium pressures are discussed. The late afterglow seems controlled by the neutralisation kinetics of He+ 2 ions. Measured rate constants for the He+2 reactions with O2, H2, N2, CO, CO2, N 2O, H2O, NH3, CH4, Ne, Ar, Kr, Xe are reported.En excitant par une brève impulsion d'électrons de l'hélium entre 50 et 1 500 torrs, on observe en postluminescence des émissions correspondant aux transitions entre états excités électroniques de la molécule He2. Les oscillogrammes donnant l'évolution de l'émission He2 (d 3 Σ+u → b3 Πg ) à 6 400 Å en fonction de la pression d'hélium sont discutés. La fin de la postluminescence paraît contrôlée par la cinétique de neutralisation des ions He+ 2. Par addition à une pression fixée d'hélium de faibles quantités d'un autre gaz M, on détermine les constantes de vitesse de la réaction de l'ion He+2 avec M pour M = O2, H2, N2, CO, CO2, N2O, H2O, NH 3, CH4, Ne, Ar, Kr, Xe

Vacuum ultraviolet spectroscopy of the Cl2\mathrm{Cl^2} molecule trapped in pure neon, pure argon, or mixed neon–argon matrices

Synchrotron radiation excitation and emission spectra with lifetime measurements are reported for the first time in the VUV region for systems consisting of Cl$^2$ molecules trapped in a neon matrix, an argon matrix, and mixed Ar/Ne matrices. In pure neon, the emission spectrum of the D’→A’ ‘‘laser’’ transition at 4.7 eV of the Cl$^2$ molecule is vibrationally well resolved and constitutes an interesting example of UV spectroscopy of a matrix ‘‘isolated’’ molecule. In pure argon or mixed Ar/Ne matrices, new broad emissions at 4.1, 3.8, and 3.5 eV are clearly identified, which result from the specific interaction between Cl*2 and Ar and are attributed to different charge–transfer states of the ArCl$^+$Cl$^−$ entity. The Ar concentration dependence and the time‐gated spectra are shown to be especially useful in interpreting the large differences observed between the pure neon and the pure argon matrix case

Site effects in the VUV-spectroscopy of chlorine atoms in neon matrices

Excitation and emission spectra of chlorine atoms isolated in neon matrices were studied in the VUV spectral range using synchrotron radiation. Spectra of the electronic transitions between the $^2$P ground state and the first $^2$P and $^2$D excited states clearly show the existence of three different possible sites for the chlorine atom in a neon surrounding. by annealing, a rearrangement takes place so that only one site is left. The fine structure of the excitation and emission peaks shows the spin-orbit splittings of the electronic states with values very close to the gas phase.Are you connected with an institution? Enjoy full time acces

Molecular solvation in van-der-Waals heteroclusters: the benzene-argon system revisited

New spectroscopic and dynamical results obtained on the benzene-argonn clusters allow us to assign the spectroscopic features of these clusters to cocoon-like wetting forms alone, in contrast to the previous Interpretations reported in the literature, like the simultaneous existence of two phases (liquid vs. solid) or of several types of isomers (wetting vs. non-wetting). In particular, from data provided by three different solvation indicators (electronic shifts, ionization potentials and microsecond time scale dynamics in the ion), a clear evidence is given for the closure of the first solvent shell at n ~ 20. The misinterpretations given in the former studies are shown to be due to a systematic underestimation of the effects of evaporation in the ion, which are found to be particularly present In one-color ionization experiments and as soon as the cocoon-like cluster ions possess a few weakly-bound solvent atoms in a second layer

Mesure des durées de vie radiatives de CO+2(A 2IIu), CO+2(B2Σ +u), CH.(A2Δ) et CO(C 1Σ+) par radiolyse pulsée

Gas phase pulsed radiolysis of CO2, CH4, CO using a 600 keV, 30 ns, 10 joules pulsed electron source, enabled measurement of the radiative lifetime of excited states. The results obtained are : CO+2(A 2Πu) = 147 ± 10 ns ; CO+2(B 2Σ+u) = 135 ± 10 ns CH.(A 2 Δ) = 800 ± 100 ns ; CO(C1Σ+) = 50 ± 10 ns.Le bombardement de gaz, CO2, CH4, CO à l'aide d'une source pulsée d'électrons de 600 keV fournissant 10 joules en 30 nanosecondes, a permis la mesure des durées de vie radiatives suivantes : CO+(A 2Πu) = 147 ± 10 ns ; CO+2(B 2Σ+u) = 135 ± 10 ns CH.(A 2Δ) = 800 ± 100 ns ; CO(C1Σ+) = 50 ± 10 ns

Microfluidic photoionization detector: channel geomtery and signal evalutation, (oral presentation & poster & proceedings with peer review)

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