Osmotic swelling and exfoliation behaviors in a lepidocrocite-type titanate H 1.07 Ti 1.73 O 4 •H 2 O were investigated upon reactions with tetramethylammonium (TMA + ) and tetrabutylammonium (TBA + ) cations. The reaction products in various physical states (suspension, wet aggregate, and deposited nanosheets) were characterized by several techniques, including X-ray diffraction under controlled humidity, small-angle X-ray scattering, particle size analysis, and atomic force microscopy. As the ratio of tetraalkylammonium ion in a solution to exchangeable proton in a solid decreased, the predominant product changed from the osmotically swollen phase, having an interlayer spacing d of several tens of nanometers, to the exfoliated nanosheets. The different behaviors of two cations in the osmotic swelling were evident from the slope and the transition point in the d versus C −1/2 plot, where C is the concentration of the cations. At a short reaction time, crystallites of a few stacks were obtained as a major product in the reaction with TMA + . On the other hand, a mixture of those crystallites and a significant portion of unilamellar nanosheets were obtained in the reaction with TBA + . In both cases, those stacks were ultimately thinned down at long reaction time to unilamellar nanosheets. The lateral size of the nanosheets could be controlled, depending on the type of the cations, the tetraalkylammonium-to-proton ratios, and the mode of the reaction (manual versus mechanical shaking). The nanosheets produced by TMA + had large lateral sizes up to tens of micrometers, and the suspension showed a distinctive silky appearance based on liquid crystallinity. Our work provides insights into the fundamentals of osmotic swelling and exfoliation, allowing a better understanding of the preparation of nanosheets, which are one of the most important building blocks in nanoarchitectonics.

In order to commercialize the rapidly developing technology of energy harvesters, the following devices need to be developed further for enhancing output performance, flexibility, scalability, facile fabrication, and cheaper price. The composite-based triboelectric nanogenerator (CTENG), which contains the above properties, is a promising technology that has attracted special interest for a decade. Focus has been placed on the hybrid concept between the composite-based piezoelectric nanogenerator (CPENG) and CTENG in order to enhance CTENG efficiency. This study presented a high-performance hybridized CPENG and CTENG device, which operated from the composite film of Ti0.8O2 nanosheets (Ti NSs)/silver nanoparticles (Ag NPs) co-doped BaTiO3 nanopowders (BT NPOs) inside the polydimethyl­siloxane (PDMS) host. The 0.3 vol % of Ti NSs and 1.5 vol % of Ag NPs exhibited the optimum harvesting performance in all compositions, with an output voltage and current density reaching approximately 150 V and 0.32 μA/cm2, respectively. Their harvesting performance was approximately 60 and 32 times higher than that of the CPENG constructed from pure PDMS. In addition, practical demonstration of the proposed device was investigated. The hybridized CPENG and CTENG device could operate in a long-term cyclic operation, charge the capacitor for storing energy, and also drive LEDs to brighten. This work suggested facile device fabrication and made a guideline to develop high-performance nanogenerators, which is crucial for device development and practical usage in the future.

While the soft chemistry of layered alkali metal oxides is adequately understood, the effect of the post-synthesis thermal treatment on their structure, composition, and properties has been underexplored. In this article, we thoroughly investigated the bulk and surface modifications of KMTiO (M = Ni, Cu, Zn) lepidocrocite titanate thermally treated within 200 °C above its synthetic temperature under air. This practice was typically employed in e.g., specimen fabrication for physical property measurements. We observed the expansion of the interlayer distance (b/2) accompanied by a reduction in layer charge density. These findings can be explained by the deintercalation of interlayer K ions and the loss of intralayer Ti, M, and O species. Meanwhile, the enrichment of potassium and carbonate on the surfaces was evident. The slight differences in dielectric properties of the pellets thermally treated at different temperatures were attributed to the combination of bulk and surface modifications. At 10 Hz and RT-250 °C, the maximum dielectric constants ε' of ∼10 with the dielectric loss (tan δ) ∼0.9-1.5 were obtained for KZnTiO.

A series of ternary graphite intercalation compounds (GICs) of alkali metal cations (M = Li, Na, K) and diamines [EN (ethylenediamine), 12DAP (1,2-diaminopropane), and DMEDA (N,N-dimethylethylenediamine)] are reported. These include stage 1 and 2 M-EN-GIC (M = Li, d(i) = 0.68-0.84 nm; M = Na, d(i) = 0.68 nm), stage 2 Li-12DAP-GIC (d(i) = 0.83 nm), and stage 1 and 2 Li-DMEDA-GIC (d(i) = 0.91 nm), where d(i) is the gallery height. For M = Li, a perpendicular-to-parallel transition of EN is observed upon evacuation, whereas for M = Na, the EN remains in parallel orientation. Li-12DAP-GIC and Li-DMEDA-GIC contain chelated Li(+) and do not show the perpendicular-to-parallel transition. We also report the quaternary compounds of mixed cations (Li,Na)-12DAP-GIC and mixed amines Na-(EN,12DAP)-GIC, with d(i) values in both cases between those of the ternary end members. (Li,Na)-12DAP-GIC is a solid solution with lattice dimensions dependent on composition, whereas for Na-(EN,12DAP)-GIC, the lattice dimension does not vary with amine content.

The lepidocrocite-type layered alkali titanate A x M y Ti 2−y O 4 has diverse chemical compositions with variation in charge per formula unit x, the interlayer cation A + , and the intralayer metal M. Despite this multivariable nature, the composition dependence of physical properties is not well explored. We report herein the AC conductivity and the complementary dielectric properties of Cs 0.7 M 0.35 Ti 1.65 O 4 , K 0.8 M 0.4 Ti 1.6 O 4 (M = Zn, Ni), and the mixed-interlayer ion Cs 0.6 K 0.1 Zn 0.35 Ti 1.65 O 4 . For Cs 0.7 Zn 0.35 Ti 1.65 -O 4 , the total AC conductivity is ∼7 × 10 −8 to 2 × 10 −6 S•cm −1 at 200−350 °C, associating with an activation energy E a ∼ 865 meV. Meanwhile, the conductivity of K 0.8 Zn 0.4 Ti 1.6 O 4 is higher by 1 order of magnitude at much lower temperature (25−150 °C) and a smaller E a ∼ 250 meV. This difference originates from the compositional robustness of the cesium-containing samples, contrasting with the sintering-induced changes in the potassium analogues. For the latter, the loss of the interlayer K + ion results in (i) generation of carriers due to charge compensation, (ii) reduction of sheet charge density and weakening of electrostatic attraction, and (iii) widening of the interlayer distance, all contributing to a lower E a in K 0.8 M 0.4 Ti 1.6 O 4 . The angular frequency dependence of conductivity, dielectric permittivity (up to a colossal value of 10 9 ), and dielectric loss follows the universal power law. Our work demonstrates the potential of simple compositional variation for electrical properties tuning, prompting a more in-depth investigation covering a wider range of possible candidates of x, A + , and M in lepidocrocite titanate.

New ternary graphite intercalation compounds (GICs) containing Na+ and linear alkylamines (Na-Cx-GIC) are reported. The following new GICs with indicated stages and intercalate arrangements are obtained: stage 1, monolayer (C3, C4); stage 1, bilayer (C6, C8); and stage 2 bilayer (C12, C14). Two features new to donor-type GICs found are (i) an intercalate bilayer arrangement with guest alkyl chains parallel to encasing graphene layers, and (ii) the transition from an intercalate bilayer to monolayer arrangement upon evacuation for C6. Although there are many reports on the intercalation of short, medium, and long-chain alkylamines in layered hosts, this is the first example of a homologous compound series for GICs. The products obtained are characterized using powder X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry.

There is a need to develop inexpensive, lightweight, and flexible high‐performance triboelectric nanogenerators (TENGs) from renewable resources. Here, a multifunctional cellulose filter paper (CFP)‐based TENG consisting of dielectric Ti0.8O2 nanosheets (Ti0.8O2 NSs) and conducting Ag nanoparticles (Ag NPs) is prepared by a simple dip coating method. The incorporation of dielectric Ti0.8O2 NSs onto the CFP significantly improves charge generation, while the inclusion of Ag NPs provides an electrically conductive path for charge transportation. The presence of these fillers can be deduced from XRD, SEM, EDS, X‐ray photoelectron spectroscopy, and Raman spectroscopy. Their distribution is visualized in 3D by synchrotron radiation X‐ray tomography. The present CFP‐based TENG provides an output voltage and current density of ≈42 V and ≈1 µA cm−2, respectively with the power density of ≈25 µW cm−2. It is capable of lighting up 40 light‐emitting diode bulbs and charging a 0.22 µF capacitor to 8 V in only 5 s. The developed TENG is also capable of detecting simple human motions, i.e., finger tapping, finger rubbing, and foot trampling. This work offers a facile design of low cost yet efficient paper‐based TENG by dual modification with multifunctional nanomaterials, and also demonstrates its use as a feasible power source that not only drives small electronics, but also scavenges energy from human actions.

No abstract