By seamlessly integrating the wearing comfortability of textiles with the biomechanical energy harvesting function of a triboelectric nanogenerator (TENG), an emerging and advanced intelligent textile, i.e., smart textile TENG, is developed with remarkable abilities of autonomous power supply and self-powered sensing, which has great development prospects in the next-generation human-oriented wearable electronics. However, due to inadequate interface contact, insufficient electrification of materials, unavoidable air breakdown effect, output capacitance feature, and special textile structure, there are still several bottlenecks in the road towards the practical application of textile TENGs, including low output, high impedance, low integration, poor working durability, and so on. In this review, on the basis of mastering the existing theory of electricity generation mechanism of TENGs, some prospective strategies for improving the mechanical-to-electrical conversion performance of textile TENGs are systematically summarized and comprehensively discussed, including surface/interface physical treatments, atomic-scale chemical modification, structural optimization design, work environmental control, and integrated energy management. The advantages and disadvantages of each approach in output enhancement are further compared at the end of this review. It is hoped that this review can not only provide useful guidance for the research of textile TENGs to select optimization methods but also accelerate their large-scale practical process.

https://www.mdpi.com/2673-706X/2/1/6/pdf?version=1646647807

Smart Textile Triboelectric Nanogenerators: Prospective Strategies for Improving Electricity Output Performance

Pure organic room temperature phosphorescence (RTP) materials become increasingly important in advanced optoelectronic and bioelectronic applications. Current phosphors based on small aromatic molecules show emission characteristics generally limited to short wavelengths. It remains an enormous challenge to achieve red and near-infrared (NIR) RTP, particularly for those from nonaromatics. Here we demonstrate that succinimide derived cyclic imides can emit RTP in the red (665, 690 nm) and NIR (745 nm) spectral range with high efficiencies of up to 9.2%. Despite their rather limited molecular conjugations, their unique emission stems from the presence of the imide unit and heavy atoms, effective molecular clustering, and the electron delocalization of halogens. We further demonstrate that the presence of heavy atoms like halogen or chalcogen atoms in these systems is important to facilitate intersystem crossing as well as to extend through-space conjugation and to enable rigidified conformations. This universal strategy paves the way to the design of nonconventional luminophores with long wavelength emission and for emerging applications. 

/pdf/clustering-and-halogen-effects-enabled-red-near-infrared-2h30ng38.pdf

Clustering and halogen effects enabled red/near-infrared room temperature phosphorescence from aliphatic cyclic imides

The ongoing effort toward stabilizing hybrid perovskite solar cells and enhancing their performance has stimulated the community to pursue a number of strategies. Over the recent years, these efforts have focused on perovskite materials design, which increasingly relies on molecular modulators that engage in halogen bonding, a uniquely directional noncovalent (supramolecular) interaction. Halogen bonding in hybrid perovskites is reported to drive perovskite assembly, increase its stability against moisture and ion migration, passivate defects, and tune interfacial energetics. The resulting perovskites are shown to exhibit superior mechanical properties, and devices incorporating these materials have seen drastic improvements in their performance, all of which have been ascribed to halogen bonding. While most of these developments have so far relied on the incorporation of off-the-shelf molecular modulators that interact with the perovskite surface to effect interfacial properties, further advancements will require careful consideration of the nature of halogen bonding and rigorous structural assessments in order to aid development of next-generation materials. Here, we provide a critical overview of the recent developments in the use of halogen bonding agents in hybrid perovskite photovoltaics with a perspective on their utility in the future. 

The Emerging Role of Halogen Bonding in Hybrid Perovskite Photovoltaics

The nitrogen bond in chemical systems occurs when there is evidence of a net attractive interaction between the electrophilic region associated with a covalently or coordinately bound nitrogen atom in a molecular entity and a nucleophile in another, or the same molecular entity. It is the first member of the family of pnictogen bonds formed by the first atom of the pnictogen family, Group 15, of the periodic table, and is an inter- or intra-molecular non-covalent interaction. In this featured review, we present several illustrative crystal structures deposited in the Cambridge Structure Database (CSD) and the Inorganic Crystal Structure Databases (ICSD) to demonstrate that imide nitrogen is not the only instance where nitrogen can act as an electrophilic agent. Analysis of a set of carefully chosen illustrative crystal systems shows that a covalently bound nitrogen atom in a variety of molecular entities features a σ-hole or even a π-hole, and these have the ability to sustain attractive engagements with negative sites to form inter- and/or intramolecular interactions that drive, or assist, the formation of a crystalline phase.

/pdf/the-nitrogen-bond-or-the-nitrogen-centered-pnictogen-bond-5jsfvjkc.pdf

The Nitrogen Bond, or the Nitrogen-Centered Pnictogen Bond: The Covalently Bound Nitrogen Atom in Molecular Entities and Crystals as a Pnictogen Bond Donor

The effects on the CI··N halogen bond between iodobenzene and NH3 of placing various substituents on the phenyl ring are monitored by quantum calculations. Substituents R = N(CH3)2, NH2, CH3, OCH3, COCH3, Cl, F, COH, CN, and NO2 were each placed ortho, meta, and para to the I. The depth of the σ-hole on I is deepened as R became more electron-withdrawing which is reflected in a strengthening of the halogen bond, which varied between 3.3 and 5.5 kcal/mol. In most cases, the ortho placement yields the largest perturbation, followed by meta and then para, but this trend is not universal. Parallel to these substituent effects is a progressive lengthening of the covalent C-I bond. Formation of the halogen bond reduces the NMR chemical shielding of all three nuclei directly involved in the C-I··N interaction. The deshielding of the electron donor N is most closely correlated with the strength of the bond, as is the coupling constant between I and N, so both have potential use as spectroscopic measures of halogen bond strength.

Influence of Substituents in the Benzene Ring on the Halogen Bond of Iodobenzene with Ammonia.

An anisotropic charge distribution on individual atoms, such as σ-holes, may strongly affect the material and structural properties of systems. However, the spatial resolution of such anisotropic c...

Real-space imaging of anisotropic charge of σ-hole by means of Kelvin probe force microscopy.

An anisotropic charge distribution on individual atoms, such as e.g. {\sigma}-hole, may strongly affect material and structural properties of systems. Nevertheless, subatomic resolution of such anisotropic charge distributions represents a long-standing experimental challenge. In particular, the existence of the {\sigma}-hole on halogen atoms has been demonstrated only indirectly through determination of crystal structures of organic molecules containing halogens or via theoretical calculations. Nevertheless, its direct experimental visualization has not been reported yet. Here we demonstrate that Kelvin probe force microscopy, with a properly functionalized probe, can reach subatomic resolution imaging the {\sigma}-hole or a quadrupolar charge of carbon monoxide molecule. This achievement opens new way to characterize biological and chemical systems where anisotropic atomic charges play decisive role.

V. Špirko

Papers

Real-space imaging of anisotropic charge of σ-hole by means of Kelvin probe force microscopy.

Real-space imaging of {\sigma}-hole by means of Kelvin probe force microscopy with subatomic resolution