Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- Non‐Newtonian Thermosensitive Nanofluid Based on Carbon Dots Functionalized with Ionic LiquidsPublication . Gonçalves, Helena M R; Pereira, Rui F. P.; Lepleux, Emmanuel; Pacheco, Louis; Valente, Artur J. M.; Duarte, Abel J.; Zea Bermudez, VerónicaNon-Newtonian nanofluids present outstanding features in terms of energy transfer and conductivity with high application in numerous areas. In this work, non-Newtonian nanofluids based on carbon dots (Cdots) functionalized with ionic liquids (ILs) are developed. The nanofluids are produced using a simple, single-step method where the raw materials for the Cdots synthesis are glucose and waste biomass (chitin from crab shells). The use of ILs as both reaction media and functionalization molecules allows for the development of a new class of nanofluids, where the ILs on the Cdots surface represent the base-fluid. Here, the well-known benign IL 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and a novel home-made IL (1-tosylate-3-methyl-imidazolium triflate) [Tmi][Trif] are used. The nanofluids obtained from both substrates show, apart from high conductivity and viscosity, light absorption, and good wettability, an appealing thermal sensitivity behavior. This thermal sensitivity is preserved even when applied as thin films on glass slides and can be boosted using the surface plasmon resonance effect. The results reported demonstrate that the new Cdots/IL-based nanofluids constitute a versatile and cost-effective route for achieving high-performance thermosensitive non-Newtonian sustainable nanofluids with tremendous potential for the energy coatings sector and heat transfer film systems.
- Proton conducting electrolytes composed of chondroitin sulfate polysaccharide and citric acidPublication . Santos, Filipe M.; Barbosa, Paula C.; Pereira, Rui F.P.; Silva, M. Manuela; Gonçalves, Helena M R; Nunes, Sílvia C.; Figueiredo, Filipe L.; Valente, Artur J.M.; Zea Bermudez, Verónica deNovel electrolytes composed of chondroitin sulfate A (CSA) and citric acid (CA) have been prepared using a clean, safe, and fast route. These electrolytes exhibit different physical-chemical properties, depending on the amount of CA. For X > 82.3%, where X is the mass ratio, in %, of CA/(CA + CSA), whitish polycrystalline powders result. Lower amounts of CA leads to the production of translucent, amorphous films, sticky for X = 75.6 and 82.0, brittle for X < 43.6 and crack-free, self-standing for 43.6 < X < 75.6%. The results obtained provide evidence that, at low pH, strong hydrogen bonding interactions take place between the anionic sulfonic and carboxylic groups of CSA and CA. CA exerts a key role, acting as a cross-linker and proton source, while simultaneously influencing sample morphology. At room temperature the highest ionic conductivity is achieved at X = 60.8%. A significant enhancement of the ionic conductivity of this sample occurs with the increase of relative humidity (RH) (from 3.1 × 10−7 to 3.7 × 10−2 S cm−1 30% for RH = 30 and ~100%, respectively).
- Electrochromic Device Composed of a Di-Urethanesil Electrolyte Incorporating Lithium Triflate and 1-Butyl-3-Methylimidazolium ChloridePublication . Gonçalves, Maria Cristina; Pereira, Rui F. P.; Alves, Raquel; Nunes, Sílvia C.; Fernandes, Mariana; Gonçalves, Helena M R; Pereira, Sónia; Silva, M. Manuela; Fortunato, Elvira; Rego, Rosa; Zea Bermudez, Verónica deA di-urethane cross-linked poly(oxyethylene)/silica hybrid matrix [di-urethanesil, d-Ut(600)], synthesized by the sol-gel process, was doped with lithium triflate (LiCF3SO3) and the 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) ionic liquid. The as-produced xerogel film is amorphous, transparent, flexible, homogeneous, hydrophilic, and has low nanoscale surface roughness. It exhibits an ionic conductivity of 3.64 × 10–6 and 5.00 × 10–4 S cm–1 at 21 and 100°C, respectively. This material was successfully tested as electrolyte in an electrochromic device (ECD) with the glass/ITO/a-WO3/d-Ut(600)10LiCF3SO3[Bmim]Cl/c-NiO/ITO/glass configuration, where a-WO3 and c-NiO stand for amorphous tungsten oxide and crystalline nickel oxide, respectively. The device demonstrated attractive electro-optical performance: fast response times (1–2 s for coloring and 50 s for bleaching), good optical memory [loss of transmittance (T) of only 41% after 3 months, at 555 nm], four mode modulation [bright mode (+3.0 V, T = 77% at 555 nm), semi-bright mode (−1.0 V, T = 60% at 555 nm), dark mode (−1.5 V, T = 38 % at 555 nm), and very dark mode (−2.0 V, T = 11% and −2.5 V, T = 7% at 555 nm)], excellent cycling stability denoting improvement with time, and high coloration efficiency [CEin = −6727 cm2 C–1 (32th cycle) and CEout = +2794 cm2 C–1 (480th cycle), at 555 nm].
- Highly Conducting Bombyx mori Silk Fibroin-Based Electrolytes Incorporating Glycerol, Dimethyl Sulfoxide and [Bmim]PF6Publication . Fernandes, Tânia C. D.; Gonçalves, Helena M R; Paz, Filipe A. A.; Sousa, Joana F. M.; Valente, Artur J. M.; Silva, Maria M.; Zea Bermudez, Verónica de; Pereira, Rui F. P.Green, transparent and flexible electrolyte films composed of a Bombyx mori silk fibroin (SF) host biopolymer doped with glycerol (G), dimethyl sulfoxide (DMSO, D) and 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) ionic liquid (IL), were synthesized. The materials were represented by the notation SF@GD@ILx (x = 15, 20 and 30 is the mass ratio of SF/[Bmim]PF6 in %). SF@, SF@G, SF@D and SF@GD samples were also prepared. DMSO was found to play a dual-role, acting as solvent of [Bmim]PF6, and enhancing ionic conductivity. DMSO, alone or combined with [Bmim]PF6, led to the increase of the mean roughness and induced the formation of more ordered Silk II conformations (β-sheets). No structural modifications were detected in the SF@GD@ILx samples upon increasing the temperature up to 100 °C. The highest ionic conductivity was exhibited by the IL-rich sample SF@GD@IL30 (1.07 and 4.61 mS cm−1, at 22 and 100 °C, respectively). In the [Bmim]PF6-doped electrolytes "free" and coordinated PF6− ions coexist. The weight losses occurring below 200 °C involved essentially the release of adsorbed water and DMSO. The suitable mechanical properties, high ionic conductivity and good electrochemical stability suggest that these electrolytes are attractive candidates for application in electrochemical devices.
- Fluorescence-based biosensor for SARS-CoV-2 detection and quantificationPublication . Duarte, Abel José Assunção; Gonçalves, Helena Maria Rodrigues; Lopes, Paula Filomena MartinsThe present disclosure relates to a method for detection of biomolecules comprising the steps of collecting a biological sample comprising an analyte at a concentration of at least 0.01 pM; exposing the collected sample to a temperature ranging from 70-100 °C; incubating the sample with Cdots previously incubated with the probe, therefore obtaining a solution; carefully homogenising the resulting solution; subjecting the solution to an excitation source for acquisition of fluorescence; determining the fluorescence shift between a negative control and the sample; wherein the Cdots are in a suspension state and the proportion of Cdots for analyte in the sample are in a ratio of at least 1:0.5; and wherein a shift of fluorescence from the negative control to the sample indicates the presence of the biomolecule. The present disclosure also relates to an apparatus for carrying out the process according to the present invention comprising a sensing unit (A), connected by an optical fiber (B) to a sample holder (C), and a LED (D) and a kit for detection of biomolecules, in particular for diagnosis of SARS-CoV-2.