In Situ Growth Intercalation Structure MXene@Anatase/Rutile TiO2 Ternary Heterojunction with Excellent Phosphoprotein Detection in Sweat

Abnormal protein phosphorylation may relate to diseases such as Alzheimer's, schizophrenia, and Parkinson's. Therefore, the real-time detection of phosphoproteins in sweat was of great significance for the early knowledge, detection, and treatment of neurological diseases. In this work, anatase/rutile TiO₂ was in situ grown on the MXene surface to constructing the intercalation structure MXene@anatase/rutile TiO₂ ternary heterostructure as a sensing platform for detecting phosphoprotein in sweat. Here, the intercalation structure of MXene acted as electron and diffusion channels for phosphoproteins. The in situ grown anatase/rutile TiO₂ with n-n-type heterostructure provided specific adsorption sites for the phosphoproteins. The determination of phosphoprotein covered concentrations in sweat, with linear range from 0.01 to 1 mg/mL, along with a low LOD of 1.52 μM. It is worth noting that, since the macromolecular phosphoprotein was adsorbed on the surface of the material, the electrochemical signal gradually decreased with the increase of phosphoprotein concentration. In addition, the active sites in the MXene@anatase/rutile TiO₂ ternary heterojunction and synergistic effect of the heterojunction were verified by first-principle calculations to further realize the response to phosphoproteins. Additionally, the effective diffusion capacity and mobility of phosphoprotein molecules in the ternary heterojunction structure were studied by molecular dynamics simulation. Furthermore, the constructed sensing platform showed high selectivity, repeatability, reproducibility, and stability, and this newly developed sensor can detect for phosphoprotein in actual sweat samples. This satisfactory sensing strategy could be promoted to realize the noninvasive and continuous detection of sweat.

Theoretical and Experimental Studies of KLi6TaO6 as a Li-Ion Solid Electrolyte

We study a hexagonal oxide KLi₆TaO₆ (KLTO), proposed as a Li-ion solid electrolyte, by using a recently developed screening method. First-principles calculations predict that KLTO presents a good Li-ion conductivity (σ_Li) and a low activation energy (E_a). Li migration is enhanced by the presence of excess Li ions in the interstitial region via a kick-out mechanism. Our experimental results demonstrate that Sn-doped KLTO presents a conductivity of 1 × 10^-5 S cm^-1, a σ_Li of 6 × 10^-6 S cm^-1, and a relatively low E_a of 36 kJ mol^-1, which confirm the validity of the proposed screening method. Conversely, detailed analyses of the microstructure and X-ray diffraction patterns of KLTO samples indicate that a stable Li-excess condition is not achieved, therefore leaving potential improvement of the performance of KLTO as a Li-ion solid electrolyte by optimizing extrinsic doping and fabrication processes.

First-principles prediction of high oxygen-ion conductivity in trilanthanide gallates Ln3GaO6

We systematically investigated trilanthanide gallates (Ln3GaO6) with the space group Cmc21 as oxygen-ion conductors using first-principles calculations. Six Ln3GaO6 (Ln = Nd, Gd, Tb, Ho, Dy, or Er) are both energetically and dynamically stable among 15 Ln3GaO6 compounds, which is consistent with previous experimental studies reporting successful syntheses of single phases. La3GaO6 and Lu3GaO6 may be metastable despite a slightly higher energy than those of competing reference states, as phonon calculations predict them to be dynamically stable. The formation and the migration barrier energies of an oxygen vacancy (V O) suggest that eight Ln3GaO6 (Ln = La, Nd, Gd, Tb, Ho, Dy, Er, or Lu) can act as oxygen-ion conductors based on V O. Ga plays a role of decreasing the distances between the oxygen sites of Ln3GaO6 compared with those of Ln2O3 so that a V O migrates easier with a reduced migration barrier energy. Larger oxygen-ion diffusivities and lower migration barrier energies of V O for the eight Ln3GaO6 are obtained for smaller atomic numbers of Ln having larger radii of Ln3+. Their oxygen-ion conductivities at 1000 K are predicted to have a similar order of magnitude to that of yttria-stabilized zirconia.

Discovery of zirconium dioxides for the design of better oxygen-ion conductors using efficient algorithms beyond data mining

It is important to find crystal structures with low formation (E_v) and migration-barrier (E_m) energies for oxygen vacancies for the development of fast oxygen-ion conductors. To identify crystal structures with lower E_v and E_m than those of ground-state ZrO₂, we first reoptimize the crystal structures of various oxides reported in the database, and then directly construct them using an evolutionary algorithm. For efficient searching, we employ the linearized ridge regression model for E_v using descriptors obtained from density functional theory calculations of the unit cells and apply the predicted E_v as a fitness value in the evolutionary algorithm. We also find a correlation between the E_v and E_m for the crystal structures of ZrO₂. On the basis of this correlation, we confirm that the newly constructed crystal structures, as well as certain reoptimized structures from the database, that possess low E_v also have E_m lower than that of ground-state ZrO₂. Our successful strategy consisting of a combination of the evolutionary algorithm, first-principles calculations, and machine-learning techniques may be applicable to other oxide systems in finding crystal structures with low E_v and E_m.

Search for crystal structures of ZrO₂ with higher oxygen-ion conductivity by evolutionary algorithms, first-principles calculations, and regression analysis.