| 1. |
- Labrador-Páez, Lucia, et al.
(author)
-
pH dependence of water anomaly temperature investigated by Eu(III) cryptate luminescence
- 2020
-
In: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 412:1, s. 73-80
-
Journal article (peer-reviewed)abstract
- Although water has been extensively studied, not all of its unique properties have been fully understood. There is still controversy about the temperature at which hydrogen bonds are broken or weakened, producing the anomalous temperature dependence of many water properties. Different temperatures between 23 and 48 °C have been reported, but no study has scrutinized the reasons for this discrepancy. We suggest the determining role of pH in the alteration of the water anomaly temperature. We employed a luminescent europium trisbipyridine cryptate, which is highly sensitive to changes in the arrangement of water molecules and whose luminescence intensity and lifetime are not significantly influenced by variations over a broad pH range. Our results revealed an increase of the crossover temperature from circa 35 °C at pH 3.5 to circa 45 °C at pH 7 to 9, which explains the discrepancies of previous studies. The pH dependence of water anomaly temperature is an important property for a better understanding of water and water-based systems and applications.
|
|
| 2. |
- Labrador Paez, Lucia, et al.
(author)
-
Eu 3+luminescent ions detect water density anomaly
- 2020
-
In: Journal of Luminescence. - : Elsevier. - 0022-2313 .- 1872-7883. ; 223
-
Journal article (peer-reviewed)abstract
- It is well known that water density varies anomalously with temperature. However, nowadays there is still a lack of agreement on the causes of this phenomenon. In this work, we use Eu3+ luminescent ion as a probe to investigate the changes in the arrangement of water molecules around the temperature of maximum density. The slight changes in the arrangement of water molecules in the first coordination sphere of Eu3+ ions due to the water density anomaly affect the variation with temperature of Eu3+ ions emission spectra and intensity decay time. This is the first time, to the best of our knowledge, that the effect of the anomaly in the density of water is detected by a luminescent material. From these experimental results we can infer that possibly the anomaly could be caused by variation in the length of hydrogen bonds between molecules with temperature for both water and heavy water.
|
|
| 3. |
- Lu, Dasheng, et al.
(author)
-
Exploring Single-Nanoparticle Dynamics at High Temperature by Optical Tweezers
- 2020
-
In: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 20:11, s. 8024-8031
-
Journal article (peer-reviewed)abstract
- The experimental determination of the velocity of a colloidal nanoparticle (v(Np)) has recently became a hot topic. The thermal dependence of v(Np) is still left to be explored although it is a valuable source of information allowing, for instance, the discernment between ballistic and diffusive regimes. Optical tweezers (OTs) constitute a tool especially useful for the experimental determination of v m , although they have only been capable of determining it at room temperature. In this work, we demonstrate that it is possible to determine the temperature dependence of the diffusive velocity of a single colloidal nanoparticle by analyzing the temperature dependence of optical forces. The comparison between experimental results and theoretical predictions allowed us to discover the impact that the anomalous temperature dependence of water properties has on the dynamics of colloidal nanoparticles in this temperature range.
|
|
