Abstract:Nanocrystalline diamond (NCD) films were grown on gold/Al 2 O 3 substrate using microwave plasma-enhanced chemical vapor deposition (PECVD) process. The NCD morphology was controlled by the deposition time and it was investigated by scanning electron microscopy (SEM). Gas sensing properties of NCD surface conductivity to humid air, CO 2 , NH 3 , and COCl 2 gases were measured by impedance measurements at room and at high temperature (140 • C). The H-terminated NCD surface shows a significant response to oxidiz… Show more
“…In our experiment, the LOD of I 2 was ~3 µg/l, which was much lower than the results of UV–Vis spectrometry, starch colorization and FRET as their LODs were at milligrams per liter level. This method affords a great potential to achieve more sensitivity.…”
Phosgene and its analogs are greatly harmful to the public health, environmental safety and homeland security as widely used industrial substances with extremely high toxicity. In order to rapidly evaluate the emergency risk caused by these chemicals, a new highly sensitive method based on surface-enhanced Raman spectroscopy (SERS) technique for measurement of phosgene agents was developed for the first time. Coupled with a chemical transformation approach, the highly toxic phosgene was conveniently converted to a SERS-sensitive probe, i.e. iodine (I 2 ), with low toxicity or non-toxicity. The characteristic SERS peak in 459 cm À1 was used for quantitation and was presumed as a formation of triiodide anion (I 3 À ), which was induced in an iodide (I À )-aggregation Au NPs system. The total measurement can be completed in~20 min with the limits of detection of~60 μg/l (phosgene) and~30 μg/l (diphosgene), respectively, on a portable Raman spectrometer. This work is the first report of SERS measurement on phosgene and diphosgene in a quantitative level. This method is expected to meet the requirements of on-site detection of phosgene agents, promote emergency responses and raise more opportunities for the portable SERS applications.
“…In our experiment, the LOD of I 2 was ~3 µg/l, which was much lower than the results of UV–Vis spectrometry, starch colorization and FRET as their LODs were at milligrams per liter level. This method affords a great potential to achieve more sensitivity.…”
Phosgene and its analogs are greatly harmful to the public health, environmental safety and homeland security as widely used industrial substances with extremely high toxicity. In order to rapidly evaluate the emergency risk caused by these chemicals, a new highly sensitive method based on surface-enhanced Raman spectroscopy (SERS) technique for measurement of phosgene agents was developed for the first time. Coupled with a chemical transformation approach, the highly toxic phosgene was conveniently converted to a SERS-sensitive probe, i.e. iodine (I 2 ), with low toxicity or non-toxicity. The characteristic SERS peak in 459 cm À1 was used for quantitation and was presumed as a formation of triiodide anion (I 3 À ), which was induced in an iodide (I À )-aggregation Au NPs system. The total measurement can be completed in~20 min with the limits of detection of~60 μg/l (phosgene) and~30 μg/l (diphosgene), respectively, on a portable Raman spectrometer. This work is the first report of SERS measurement on phosgene and diphosgene in a quantitative level. This method is expected to meet the requirements of on-site detection of phosgene agents, promote emergency responses and raise more opportunities for the portable SERS applications.
“…Unlike the standard transmission mode that requires up to 24 h KBr annealing to get a water-free spectrum, ATR spectrum is recorded in several minutes. NCD coated ATR prism offers several other advantages: mechanical robustness, the stable hydrophobicity/hydrophilicity that can be tuned for studies of proteins and other biomolecules [21], inertness of the material to heat or gas treatments [22], as well as the biocompatibility of diamond [23]. The diamond ATR coating may also provide new insights on the diamond chemistry due possible in situ monitoring of any kind of reactions performed on surface-adsorbed nanoparticles or directly on diamond thin films.…”
Linear antenna microwave chemical vapor deposition process was used to homogeneously coat a 7 cm long silicon prism by 85 nm thin nanocrystalline diamond (NCD) layer. To show the advantages of the NCD-coated prism for attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) of nanoparticles, we apply diamond nanoparticles (DNPs) of 5 nm nominal size with various surface modifications by a drop-casting of their methanol dispersions. ATR-FTIR spectra of as-received, air-annealed, plasma-oxidized, and plasma-hydrogenated DNPs were measured in the 4000-1500 cm −1 spectral range. The spectra show high spectral resolution, high sensitivity to specific DNP surface moieties, and repeatability. The NCD coating provides mechanical protection against scratching and chemical stability of the surface. Moreover, unlike on bare Si surface, NCD hydrophilic properties enable optically homogeneous coverage by DNPs with some aggregation on submicron scale as evidenced by scanning electron microscopy and atomic force microscopy. Compared to transmission FTIR regime with KBr pellets, direct and uniform deposition of DNPs on NCD-ATR prism significantly simplifies and speeds up the analysis (from days to minutes). We discuss prospects for in situ monitoring of surface modifications and molecular grafting.
“…However, the detection of phosgene in the gas phase for most of these procedures is only shown as a proof of concept even for those papers where this point is treated explicitly. For instance, we can find the works of Davydova et al , or Vijri et al based on conductometric measurements, that employed nanocrystalline diamond layers and modified polyaniline nanofibers, respectively. Alternatively, classical dry colorimetric approaches based on specific chemicals like Harrison’s reagent (an equimolar mixture of diphenylamine and 4-(dimethylamino)benzaldehyde) infiltrated in paper strips or glass tubes represent a simple method whose efficiency has not been sufficiently exploited …”
We present here a cheap, fast, and highly selective dosimeter for the colorimetric detection of gaseous phosgene with an ultralow detection limit. The disposable device is based on Harrison's reagent supported into a porous nanocrystalline TiO matrix film. We exposed the films to phosgene streams while the absorbance was monitored by an optic fiber in a gas chamber. The pronounced spectral changes were unaffected by humidity and oxygen and permitted us to use the response rate at 464 nm as a very stable calibration signal for quantitative analysis purposes. The use of a specific sensing reaction guaranteed a very high selectivity of the device even against saturated vapors of primary interferences like halide gases and other oxidizing and volatile agents. With this simple method, whose response is compatible with affordable and efficient miniature LED-photodiode devices, we reach an ultralow limit of detection well below the ppm level.
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