Formation of persistent free radicals from epigallocatechin Gallate in tea processing and their implications on DNA damage and cell cytotoxicity.

Tea is widely consumed in both beverages and food. Epigallocatechin gallate (EGCG) is the most crucial active ingredient in tea. Currently, knowledges on transformation processes of EGCG during tea processing are lacking. Understanding the chemical reactions of EGCG and its products during tea processing is important for assessing the safety of tea-containing food. Here, we revealed the formation of persistent free radicals (PFRs) from EGCG under the influence of heating and light irradiation, which was substantiated with evidence. These PFRs exhibited stability for >30 min in simulated gastric fluid. Furthermore, we observed potential effects of these PFRs on DNA damage and cell cytotoxicity in vitro. By combining electron paramagnetic resonance spectrometer with Fourier transform ion cyclotron resonance mass spectrometry, we elucidated the pathways involved in free radical formation. These findings are expected to contribute to a comprehensive understanding of free radical chemistry in tea-containing food.

Confined Space Dual-Type Quantum Dots for High-Rate Electrochemical Energy Storage.

Owing to the quantum size effect and high redox activity, quantum dots (QDs) play very essential roles toward electrochemical energy storage. However, it is very difficult to obtain different types and uniformly dispersed high-active QDs in a stable conductive microenvironment, because QDs prepared by traditional methods are mostly dissolved in solution or loaded on the surface of other semiconductors. Herein, dual-type semiconductor QDs (Co9S8 and CdS) are skillfully constructed within the interlayer of ultrathin-layered double hydroxides. In particular, the expandable interlayer provides a very suitable confined space for the growth and uniform dispersion of QDs, where Co9S8 originates from in situ transformation of cobalt atoms in laminate and CdS is generated from interlayer pre-embedding Cd2+. Meanwhile, XAFS and GGA+U calculations are employed to explore and prove the mechanism of QDs formation and energy storage characteristics as compared to surface loading QDs. Significantly, the hybrid supercapacitors achieve a high energy density of 329.2 µWh cm-2, capacitance retention of 99.1%, and coulomb efficiency of 96.9% after 22 000 cycles, which is superior to the reported QDs-based supercapacitors. These findings provide unique insights for designing and developing stable, ordered, and highly active QDs.

Asymmetric XMoGeY2 (X = S, Se, Te; Y = N, P, As) monolayers as potential flexible materials for nano piezoelectric devices and nanomedical sensors.

Highly efficient nano piezoelectric devices and nanomedical sensors are in great demand for high-performance piezoelectric materials. In this work, we propose new asymmetric XMoGeY2 (X = S, Se, Te; Y = N, P, As) monolayers with excellent piezoelectric properties, dynamic stability and flexible elastic properties. The piezoelectric coefficients (d11) of XMoGeY2 monolayers range from 2.92 to 8.19 pm V-1. Among them, TeMoGeAs2 exhibits the highest piezoelectric coefficient (d11 = 8.19 pm V-1), which is 2.2 times higher than that of common 2D piezoelectric materials such as 2H-MoS2 (d11 = 3.73 pm V-1). Furthermore, all XMoGeY2 monolayers demonstrate flexible elastic properties ranging from 96.23 to 253.70 N m-1. Notably, TeMoGeAs2 has a Young's modulus of 96.23 N m-1, which is only one-third of that of graphene (336 N m-1). The significant piezoelectric coefficients of XMoGeY2 monolayers can be attributed to their asymmetric structures and flexible elastic properties. This study provides valuable insights into the potential applications of XMoGeY2 monolayers in nano piezoelectric devices and nanomedical sensors.

Unexpected hydroxyl radical production in brewed tea under sunlight.

Tea is one of the world's most popular and widely consumed beverages. It is a common pastime to enjoy a cup of tea in the sunshine. However, little attention has been given to understanding the possible photochemical reactions occurring beneath the calm surface of brewed tea. Epigallocatechin gallate (EGCG), which is widely used in food and beverages, is the most significant active ingredient found in tea. In this study, we investigated the presence of free radicals in both an aqueous EGCG solution and brewed tea under simulated sunlight conditions. To our surprise, we unexpectedly observed the production of hydroxyl radicals (•OH) in brewed tea. It was found that sunlight irradiation played a critical role in the formation of •OH, independent of the presence of metal ions. Furthermore, we demonstrated that the •OH generated from the EGCG aqueous solution induced cell cytotoxicity and DNA damage in vitro. Considering the crucial role of •OH in various fields, including human health and the environment, it is important to further explore the practical implications of •OH production in brewed tea under sunlight. In summary, our study unveils the unexpected formation of •OH in brewed tea and emphasizes the significance of sunlight-induced reactions. The observed cytotoxic and DNA-damaging effects of •OH emphasize the importance of understanding the potential health consequences associated with tea consumption. Further research in this area will contribute to a better understanding of the broader implications of •OH production in brewed tea under sunlight.

Interfacial Roughness Enhanced Gel/Elastomer Interfacial Bonding Enables Robust and Stretchable Triboelectric Nanogenerator for Reliable Energy Harvesting.

Gel-based triboelectric nanogenerator (TENG) has demonstrated promising potentials in stretchable electronics owing to gel electrodes' intrinsic softness, stretchability, and conductivity. However, delamination between gel and elastomer layers in deformations remains a considerable challenge for gel-based TENG, which most often induces structure failure. Herein, gels are regarded as adhesives and further effectively enhances interfacial bonding strength by a rough interface in adhesives' view, which exploits gels' liquid-to-solid transformation. This method just needs surface roughness of elastomer, which avoids chemical modification. Moreover, this method is effective to both organogel with good stickiness and hydrogel with weak stickiness, demonstrating wide applicability to different gels. Owing to the tough gel/elastomer interfacial bonding, TENG-Rough largely solves delamination problem under various deformations and the corresponding output performances of TENG-Rough are also maintained, implying a robust stretchable TENG device for reliable energy harvesting. This work demonstrates a general and facile method to enhance interfacial bonding in an adhesives' way, which provides a view for addressing delamination problem in gel-based TENGs and other kinds of gel-based devices.

Comprehensive Evaluation of Dietary Exposure and Health Risk of Polychlorinated Naphthalenes.

Intake from food is considered an important route of human exposure to polychlorinated naphthalenes. To our knowledge, several studies have quantified dietary exposure but only in European countries and measuring only a few of the 75 congeners. In addition, the influence of source diversity on human exposure has seldom been assessed. We analyzed 192 composite food samples composed of 17,280 subsamples from 24 provinces in China to measure the concentrations of polychlorinated naphthalenes and estimate their daily intake and potential health risks on a national scale. The estimated cancer risk was in the range of 6.8 × 10-8 to 4.6 × 10-7. We compared our findings for 75 congeners with reports in the literature that quantified only 12 congeners. We estimate that these 12 congeners contribute only approximately 4% to the total mass daily intake of polychlorinated naphthalenes and 70% to the total toxic equivalent quantity, indicating underestimation of dietary exposure. The contributions of combustion-associated congeners to the total concentrations of polychlorinated naphthalenes were in the range of 31-52%, suggesting that the ongoing unintentional release of these compounds from industrial thermal processes is an important factor in polychlorinated naphthalene contamination and human exposure in China.

Identification of emerging organic pollutants from solid waste incinerations by FT-ICR-MS and GC/Q-TOF-MS and their potential toxicities.

Emissions from the incineration of solid waste are a global public health concern, but little attention has been paid to previously unrecognized chemical compounds that are generated by waste incineration and released into the atmosphere. We conducted nontarget analysis of organic chemicals formed during waste incineration by Fourier-transform ion cyclotron resonance mass spectrometry and gas chromatography-quadrupole time-of-flight mass spectrometry. Using toxicity data in the ToxCast library and predicted toxicity data for traditional priority polycyclic aromatic hydrocarbons and 2,3,7,8-tetrachlorodibenzo-p-dioxin, we prioritized 13 compounds including hexachloro-1,3-butadiene, 9 of which are reported here for the first time as constituents of emissions from the incineration of solid waste and hexachloro-1,3-butadiene was included in the Stockholm Convention in 2017. The predicted activity of these pollutants to androgen receptors and to the aryl hydrocarbon receptor were comparable to, or higher than, the 2,3,7,8-tetrachlorodibenzo-p-dioxin and benzo[a]pyrene. In addition, some alkylated polycyclic aromatic hydrocarbons and heteroatom polycyclic aromatic hydrocarbons were also identified in solid waste incineration processes, peak areas of which were 1-2 orders of magnitude higher than dioxins and 1-3 orders of magnitude lower than their parent polycyclic aromatic hydrocarbons. Our study can provide information for better recognizing and regulating the emissions of organic pollutants formed by the incineration of solid waste.

Raman Anisotropy and Polarization-Sensitive Photodetection in 2D Bi2O2Se-WSe2 Heterostructure.

Two-dimensional (2D) bismuth oxyselenide (Bi2O2Se) has attracted increasing attention due to its high mobility, tunable band gap, and air stability. The surface reconstruction of cleaved Bi2O2Se due to the electrostatic interlayer interactions can lead to the in-plane anisotropic structure and physics. In this work, we first discovered the strong anisotropy in phonon modes through the angle-resolved polarized Raman (ARPR) spectra. Benefiting from the anisotropic feature, a high-performance polarization-sensitive photodetector has been achieved by constructing a heterostructure composed of the multilayer Bi2O2Se as polarized-light sensitizers and 2D WSe2 as a photocarrier transport channel. The detectors exhibit broadband response spectra from 405 to 1064 nm along with high responsivity, fast speed, and high sensitivity owing to the photogating effect in this device architecture. More importantly, the photocurrent shows strong light polarization dependence with the maximum dichroism ratio of 4.9, and a reversal is observed for the angle-dependent photocurrent excited by polarized 405 and 635 nm light. This work provides new insight in terms of optical and photocurrent anisotropy of exfoliated Bi2O2Se and expands its applications in angle-resolved electronics and optoelectronics.

Conductive Composite Fiber with Customizable Functionalities for Energy Harvesting and Electronic Textiles.

A fiber-based triboelectric nanogenerator (F-TENG) is an important technology for smart wearables, where conductive materials and triboelectric materials are two essential components for the F-TENG. However, the different physicochemical properties between conductive metal materials and organic triboelectric materials often lead to interfacial failure problems, which is a great challenge for fabricating high-performance and stable F-TENGs. Herein, we designed a new conductive composite fiber (CCF) with customizable functionalities based on a core-spun yarn coating approach, which was applicable for a fiber-based TENG (CCF-TENG). By combing a core-spun method and a coating approach, triboelectric materials could be better incorporated on the surface of conductive fibers with the staple fibers to form a new composite structure with enhanced interfacial properties. The applicability of the method has been studied using different conductive and staple fibers and coating materials as well as different CCF diameters. As a demonstration, the open-circuit voltage and power density of the CCF-TENG reached 117 V and 213 mW/m2, respectively. Moreover, a 2D fabric TENG was woven and used as a wearable sensor for motion detection. This work provided a new method for 1D composite fibers with customizable functionalities for the applications in smart wearables.

High hole mobility in physical vapour deposition-grown tellurium-based transistors.

Carrier mobility is one of most important figures of merit for materials that can determine to a large extent the corresponding device performances. So far, extensive efforts have been devoted to the mobility improvement of two-dimensional (2D) materials regarded as promising candidates to complement the conventional semiconductors. Graphene has amazing mobility but suffers from zero bandgap. Subsequently, 2D transition-metal dichalcogenides benefit from their sizable bandgap while the mobility is limited. Recently, the 2D elemental materials such as the representative black phosphorus can combine the high mobility with moderate bandgap; however the air-stability is a challenge. Here, we report air-stable tellurium flakes and wires using the facile and scalable physical vapour deposition (PVD) method. The prototype field-effect transistors were fabricated to exhibit high hole mobility up to 1485 cm2 V-1 s-1 at room temperature and 3500 cm2 V-1 s-1 at low temperature (2 K). This work can attract numerous attentions on this new emerging 2D tellurium and open up a new way for exploring high-performance optoelectronics based on the PVD-grown p-type tellurium.

An Adhesive Surface Enables High-Performance Mechanical Energy Harvesting with Unique Frequency-Insensitive and Pressure-Enhanced Output Characteristics.

Viscoelastic polymer adhesives (VPAs) are common materials broadly used in adhesive tapes for bonding objects tightly in daily life. This work presents a conceptually new strategy of using contact electrification (rather than strong adhesion) of VPAs to directly convert mechanical energy to electric energy, generally showing 202-419% of the electric energy generated by conventional mechanical energy harvesters under the same triggering conditions. More notably, the VPA-based generators (VPAGs) possess unique frequency-insensitive and pressure-enhanced output characteristics. The output power of a VPAG not only does not show regular degradation of performance with the decrease of triggering frequency, but also can be further enhanced by simple introduction of a second VPA layer with a smaller area to increase the applied pressure without the requirement of rising applied force. The average output power density of a VPAG with a second layer of 0.5 cm × 0.5 cm can reach 216.7 µW cm-2 , which is ≈150% larger than that of a VPAG without a second VPA layer. This research is of significance to harvesting the random, irregular, and low-frequency (bio-)mechanical energy that widely exists but is wasted in the environment for both stable electric energy generation and electronic device operation.

High carrier mobility in monolayer CVD-grown MoS2 through phonon suppression.

Mobility engineering is one of the most important challenges that determine the optoelectronic performance of two-dimensional (2D) materials. So far, charged-impurity scattering and electrical-contact barriers have been suppressed through high-κ dielectrics and seamless contact engineering, giving rise to carrier-mobility improvement in exfoliated 2D semiconducting MoS2. Here we demonstrate a facile and scalable technique to effectively suppress both Coulomb scattering and electron-phonon scattering via the HfO2 overlayer, resulting in a large mobility improvement in CVD-grown monolayer MoS2, in excess of 60 cm2 V-1 s-1. Surface passivation and suppression of Coulomb scattering can partially contribute to the mobility increase. Interestingly, we correlate the mobility increase with phonon quenching through Raman and temperature-dependent mobility measurements. The experimental method is facile, industrially scalable, and renders phonon engineering an additional leverage towards further improvements in 2D semiconductor mobility and device performance.