1,721,173 research outputs found
Structural features of triethylammonium acetate through molecular dynamics
Full text linkI have explored the structural features and the dynamics of triethylammonium acetate by means of semi-empirical (density functional tight binding, DFTB) molecular dynamics. I find that the results from the present simulations agree with recent experimental determinations with only few minor differences in the structural interpretation. A mixture of triethylamine and acetic acid does not form an ionic liquid, but gives rise to a very complex system where ionization is only a partial process affecting only few molecules (1 over 4 experimentally). I have also found that the few ionic couples are stable and remain mainly embedded inside the AcOH neutral moiety
Theoretical insights into the structure of the aminotris(methylenephosphonic acid) (ATMP) anion: A possible partner for conducting ionic media
No full textWe present a computational characterisation of Aminotris(methylenephosphonic acid) (ATMP) and its potential use as an anionic partner for conductive ionic liquids (ILs). We argue that for an IL to be a good candidate for a conducting medium, two conditions must be fulfilled: (i) the charge must be transported by light carriers; and (ii) the system must maintain a high degree of ionisation. The result trends presented herein show that there are molecular ion combinations that do comply with these two criteria, regardless of the specific system used. ATMP is a symmetric molecule with a total of six protons. In the bulk phase, breaking the symmetry of the fully protonated state and creating singly and doubly charged anions induces proton transfer mechanisms. To demonstrate this, we used molecular dynamics (MD) simulations employing a variable topology approach based on the reasonably reliable semiempirical density functional tight binding (DFTB) evaluation of the atomic forces. We show that, by choosing common and economical starting compounds, we can devise a viable prototype for a highly conductive medium where charge transfer is achieved by proton motion
Quality Control of Ethanol-Based Hand Sanitizer Gels in Micro-Opto-Fluidic Devices
No full textWe present a smart micro-opto-fluidic platform for quality control of ethanol-based hand sanitizer gels. Analyses rely on the study of the near infrared absorption features of fluids flowing in rectangular glass micro-capillaries with integrated reflectors
Near Infrared Absorption Spectroscopy in Microfluidic Devices with Selectable Pathlength
No full textIn this work we present a smart micro-opto-fluidic platform based on rectangular-section glass micro-capillaries with integrated reflectors. The micro-opto-fluidic setup was exploited for absorption spectroscopy measurements in the near infrared range from 1.0 μm to 1.7 μm. The external flat sides of the micro-capillaries are coated with thin Aluminum layers to create multipath micro-devices in which light can bounce multiple times. Broadband light provided by a Tungsten lamp is coupled into a multimode optical fiber and shone onto the flat surface of the micro-capillary. After travelling inside the micro-channel filled with the sample, radiation is directed towards an optical spectrum analyzer. The line-shape of the output light spectrum depends on the absorption features of the sample and, in particular, on the concentration of water in alcoholic solutions. Experimental results are in good agreement with the prediction given by the developed theoretical model that describes light transmission through the fluidic micro-channel. Moreover, a responsivity parameter, defined as the output power ratio at two wavelengths, is retrieved: water sensitivity is greatly enhanced by the multipath effect since it is proved to be directly proportional to the light bounces in the micro-channel
Assessing the structure of protic ionic liquids based on triethylammonium and organic acid anions
Full text linkWe present a computational analysis of the short-range structure of three protic ionic liquids based on strong organic acids: trifluoracetate, methanesulfonate, and triflate of triethylammonium. Accurate ab initio computations carried out on the gas-phase dimers show that the protonation of triethylamine is spontaneous. We have identified the anion-cation binding motif that is due to the presence of a strong hydrogen bond and to electrostatic interactions. The strength of the hydrogen bond and the magnitude of the binding energy decrease in the order trifluoroacetate ≳ methanesulfonate > triflate. The corresponding simulations of the bulk phases, obtained using a semiempirical evaluation of the interatomic forces, reveal that on short timescales, the state of the three liquids remains highly ionized and that the gas-phase cation-/anion-binding motif is preserved while no other peculiar structural features seem to emerge
Micro-opto-fluidic platform for spectroscopic identification of water-based fluids
No full textIn this work, we present two micro-opto-fluidic platforms for smart recognition of water-based fluids exploiting absorption spectroscopy. The identification of the samples is based on their absorption properties in the near infrared region from 1165 nm to 1650 nm and, in particular, on the analysis of the absorption band of water located around 1450 nm. In the instrumental setup, the fiber-coupled light emitted by a Tungsten lamp is shone onto the micro-devices and the output radiation is directed to an optical spectrum analyzer. The first platform works in reflection by means of a rectangular glass micro-capillary with integrated reflectors. Thanks to the presence of the double metallization, light can cross the capillary channel multiple times in order to enhance measurement sensitivity. The second platform works in transmission and exploits a commercial device with a micro-fluidic polymeric channel. The performances of the sensing platforms were initially theoretically studied by implementing a MATLAB® model based on geometrical optics and Lambert-Beer formula for absorption. Then, experiments were carried out by testing water-alcohol dilutions, proving results in a good level of agreement with the theoretical predictions. We also successfully employed our platforms for specific measurement of the water content in Scottish whisky and Venezuelan white rum liquor. The proposed readout technique is remote, contactless, non-invasive, and thus totally safe. Moreover, borosilicate glass micro-capillary and polymeric channel are both sterile, biocompatible and low-cost devices. These features make our opto-fluidic-platforms highly suitable also for many other applications, ranging from biology to food analysis
Optical Readout Techniques for Smart Detection of Fluids in the Near Infrared Wavelength Region by Means of Rectangular Glass Micro-capillaries
No full textThree different approaches for the analytical detection of fluids by means of rectangular glass micro-capillaries working in the near infrared wavelength region are presented. At first, a non-specific refractometric measurement for the detection of glucose concentration in solutions is reported, exploiting the micro-capillaries as optical resonators: by monitoring the spectral shift of the ratio between the transmitted and reflected optical spectra (T/R) from the capillary, it is possible to extract the wavelength positions of the cavity resonances (maxima of T/R) for fluids with different refractive index. When the refractive index of the sample fluid filling the channel increases, a shift towards longer wavelengths is observed. Then, a spectral phase shift interferometric technique for the detection of the wavelength position of the resonances is proposed. When the capillary is inserted in an interferometric setup, it is possible to distinguish fluids by knowing the dependence of the wavelength positions of the steep jumps in the cosine signal on the refractive index of the filling fluid. Finally, the potentiality of micro-capillaries is investigated for specific sensing, exploiting absorption spectroscopy. All the proposed optical readout approaches are remote, contactless and non-invasive. In addition, the glass-micro-capillaries are very suitable for analytical detection of fluids: they are low-cost devices, available in several formats. Thanks to their micrometric size, they can be incorporated in micro-fluidic circuits. Borosilicate glass is a bio-compatible material, allowing the use of the micro-fluidic platforms in a wide range of applications for label-free optical sensing
Spectral Fingerprint Investigation in the near Infra-Red to Distinguish Harmful Ethylene Glycol from Isopropanol in a Microchannel†
No full textEthylene glycol (EG) and isopropanol (ISO) are among the major toxic alcohols that pose a risk to human health. However, it is important to distinguish them, since EG is more prone to cause renal failure, and can thus be more dangerous when ingested than ISO. Analysis of alcohols such as isopropanol and ethylene glycol generally can be performed with a complex chromatographic method. Here, we present an optical method based on absorption spectroscopy, performed remotely on EG-ISO mixtures filling a microchannel. Mixtures of ethylene glycol in isopropanol at different volume concentrations were analyzed in a contactless manner in a rectangular-section glass micro-capillary provided with integrated reflectors. Fiber-coupled broadband light in the wavelength range 1.3–1.7 μm crossed the microchannel multiple times before being directed towards an optical spectrum analyzer. The induced zig-zag path increased the fluid–light interaction length and enhanced the effect of optical absorption. A sophisticated theoretical model was developed and the results of our simulations were in very good agreement with the results of the experimental spectral measurements. Moreover, from the acquired data, we retrieved a responsivity parameter, defined as power ratio at two wavelengths, that is linearly related to the EG concentration in the alcoholic mixtures
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