Creating Anti-Chiral Exceptional Points in Non-Hermitian Metasurfaces for Efficient Terahertz Switching.

Non-Hermitian degeneracies, also known as exceptional points (EPs), have presented remarkable singular characteristics such as the degeneracy of eigenvalues and eigenstates and enable limitless opportunities for achieving fascinating phenomena in EP photonic systems. Here, the general theoretical framework and experimental verification of a non-Hermitian metasurface that holds a pair of anti-chiral EPs are proposed as a novel approach for efficient terahertz (THz) switching. First, based on the Pancharatnam-Berry (PB) phase and unitary transformation, it is discovered that the coupling variation of ±1 spin eigenstates will lead to asymmetric modulation in two orthogonal linear polarizations (LP). Through loss-induced merging of a pair of anti-chiral EPs, the decoupling of ±1 spin eigenstates are then successfully realized in a non-Hermitian metasurface. Final, the efficient THz modulation is experimentally demonstrated, which exhibits modulation depth exceeding 70% and Off-On-Off switching cycle less than 9 ps in one LP while remains unaffected in another one. Compared with conventional THz modulation devices, the metadevice shows several figures of merits, such as a single frequency operation, high modulation depth, and ultrafast switching speed. The proposed theory and loss-induced non-Hermitian device are general and can be extended to numerous photonic systems varying from microwave, THz, infrared, to visible light.

Left ventricular reverse remodelling as a promising strategy for resolving left ventricular thrombus.

AIMS: Recent years, several studies have suggested that abnormal baseline left ventricular (LV) function and structure are associated with left ventricular thrombus (LVT) formation. Despite this, most studies have given less attention to the potential role of left ventricular reverse remodelling (LVRR), that is, the improvement of LV function and structure, in resolving LVT. In this study, we aim to investigate the clinical characteristics, prognosis, and LVT resolution in patients with LVRR. METHODS AND RESULTS: This is a retrospective study conducted at The First Affiliated Hospital of Dalian Medical University. Our cohort consists of patients diagnosed with LVT between 1 November 2015 and 31 May 2020. Enrolled patients were categorized into two groups: LVRR and Failure of LVRR. The primary endpoints included LVT resolution and embolic events. A total of 84 patients were included in the study, with 59 patients in the LVRR group and 25 patients in the Failure of LVRR group. In our study, patients in the LVRR group experienced higher incidence of LVT resolution and a lower risk of embolic events. Multivariate logistic analysis revealed that Failure of LVRR was the only independent negative predictor for LVT resolution and positive predictor for embolic events. CONCLUSIONS: Patients with LVRR experience higher incidence of LVT resolution and have lower risk of embolic events, highlighting the significance of identifying and mitigating risk factors that contribute to abnormal LV function and structure in management of patients with LVT.

JD-02, a novel Hsp90 inhibitor, induces ROS/SRC axis-dependent cytoprotective autophagy in colorectal cancer cells.

Heat shock protein 90 (Hsp90) is a tumor marker that accelerates cancer growth by disrupting protein homeostasis. However, concerns such as low clinical efficacy and drug resistance continue to be obstacles to the successful marketing of Hsp90 inhibitors. The cytoprotective function of autophagy has been identified as one of the mechanisms by which tumor cells gain resistance to chemotherapy. JD-02 was identified as a new Hsp90 inhibitor that suppressed colorectal cancer (CRC) growth by lowering client protein levels in vivo and in vitro. We found that JD-02 increased cellular autophagy, which inhibited apoptosis. JD-02 enhanced cytoprotective autophagy and regulated apoptotic suppression by increasing intracellular reactive oxygen species and inhibiting SRC protein levels, as demonstrated by quantitative proteomics, bioinformatic analysis, western blotting, and flow cytometry. This effect was reversed by autophagy inhibition. Therefore, due to the synergistic effects of Hsp90 and autophagy inhibitors in efficiently activating apoptotic pathways, they could potentially serve as promising therapeutic options for CRC.

Predictors and prognostic implications of left ventricular ejection fraction trajectory improvement in the spectrum of heart failure with reduced and mildly reduced ejection fraction.

BACKGROUND: The latest guidelines emphasize the significance of evaluating the left ventricular ejection fraction (LVEF) trajectory in patients with heart failure (HF). Because patients with HF with reduced ejection fraction (HFrEF) and HF with mildly reduced ejection fraction (HFmrEF) have reduction in systolic function, they might be in a trajectory of LVEF improvement after medical and device-based therapies. While previous studies have primarily focused on LVEF improvement in HFrEF, there is limited research on LVEF trajectory improvement across the spectrum of HFrEF and HFmrEF. This study aimed to assess the determinants and prognostic implications of LVEF trajectory improvement in HFrEF and HFmrEF patients. METHODS: The cohort was classified into the improved group (HFrEF-to-HF with improved ejection fraction (HFimpEF) and HFmrEF-to-HF with preserved ejection fraction (HFpEF)) and the unimproved group (lack of improved group criteria). The primary endpoints were the composite of all-cause mortality or HF hospitalization, all-cause mortality, and HF hospitalization. Predictors of LVEF trajectory improvement were also evaluated. RESULTS: A total 1303 patients were included in the study (improved/unimproved group: n = 497/806). Cox regression analysis showed that the improved group experienced lower risks of prespecified end points than the unimproved group. Multivariate logistic regression analysis showed that atrial flutter, use of spironolactone, and treatment with catheter ablation were associated with LVEF trajectory improvement, while myocardial infarction, prior percutaneous catheter intervention or coronary artery bypass graft, E/e', and left ventricular end-diastolic diameter were identified as negative predictors of LVEF trajectory improvement. In the improved subgroup, the prognosis for the HFrEF-to-HFimpEF and HFmrEF-to-HFpEF was comparable. CONCLUSIONS: LVEF trajectory improvement patients had improved clinical outcomes and it was associated with important clinical, baseline cardiac structure and function, and treatment factors. Outcomes were similar in both HFrEF-to-HFimpEF and HFmrEF-to-HFpEF subgroups. These results suggest that emphasis should be placed on LVEF trajectory improvement to improve the outcomes of this population.

Transient Loss-Induced Non-Hermitian Degeneracies for Ultrafast Terahertz Metadevices.

Non-Hermitian degeneracies, also known as exceptional points (EPs), have attracted considerable attention due to their unique physical properties. In particular, metasurfaces related to EPs can open the way to unprecedented devices with functionalities such as unidirectional transmission and ultra-sensitive sensing. Herein, an active non-Hermitian metasurface with a loss-induced parity-time symmetry phase transition for ultrafast terahertz metadevices is demonstrated. Specifically, the eigenvalues of the non-Hermitian transmission matrix undergo a phase transition under optical excitation and are degenerate at EPs in parameter space, which is accompanied by the collapse of chiral transmission. Ultrafast EP modulation on a picosecond time scale can be realized through variations in the transient loss at a non-Hermitian metasurface pumped by pulsed excitation. Furthermore, by exploiting the physical characteristics of chiral transmission EPs, a switchable quarter-wave plate based on the photoactive metasurface is designed and experimentally verified and realized the corresponding function of polarization manipulation. This work opens promising possibilities for designing functional terahertz metadevices and fuses EP physics with active metasurfaces.

Prognostic implications of left ventricular ejection fraction trajectory changes in heart failure.

Aims: The latest guidelines recommended to assess the trajectory of left ventricular ejection fraction (LVEF) in patients with heart failure (HF). However, there is limited data on the trajectory of LVEF in real-world settings. In this study, we investigated the frequency and prognostic implications of changes in LVEF trajectory. Methods: Patients were divided into intensified LVEF, static LVEF, and worsening LVEF groups based on the transitions of HF types from baseline to follow-up. The intensified and worsening LVEF groups were further subdivided into mild (≤10% absolute changes of LVEF) and significant (>10% absolute changes of LVEF) increase or decrease groups according to the magnitude of change. The incidences and associations of changes in LVEF with patient outcomes were analyzed. Results: Among the 2,429 patients in the study cohort, 38.3% of HF with reduced ejection fraction (HFrEF) and 37.6% of HF with mildly reduced ejection fraction (HFmrEF) showed an improvement in their LVEF. In contrast, a decline in LVEF was observed in 19.3% of HF patients with preserved ejection fraction (HFpEF) and 34.9% of those with HFmrEF. Cox regression analysis showed that the intensified LVEF group was associated with a lower risk of composite endpoints, while the worsening LVEF group yielded opposite findings. Subgroup analysis revealed that compared to those with mild changes in LVEF, baseline HFrEF patients with significant increase showed a lower risk of composite outcome, while baseline HFpEF patients were the opposite. Conclusions: The trajectories of LVEF changes are strongly correlated with outcomes in patients with HF who had prior history of HF admission. The most significant prognostic implications observed in patients with significant LVEF changes. Trajectory LVEF and type of HF changes are useful tools recommended for prognostication.

Antiviral activities of Artemisia vulgaris L. extract against herpes simplex virus.

BACKGROUND: Artemisia vulgaris L. is often used as a traditional Chinese medicine with the same origin of medicine and food. Its active ingredient in leaves have multiple biological functions such as anti-inflammatory, antibacterial and insecticidal, anti-tumor, antioxidant and immune regulation, etc. It is confirmed that folium Artemisiae argyi has obvious anti-HBV activity, however, its antiviral activity and mechanism against herpesvirus or other viruses are not clear. Hence, we aimed to screen the crude extracts (Fr.8.3) isolated and extracted from folium A. argyi to explore the anti-herpesvirus activity and mechanism. METHODS: The antiherpes virus activity of Fr.8.3 was mainly characterized by cytopathic effects, real-time PCR detection of viral gene replication and expression levels, western blotting, viral titer determination and plaque reduction experiments. The main components of Fr.8.3 were identified by using LC-MS, and selected protein targets of these components were investigated through molecular docking. RESULTS: We collected and isolated a variety of A. vulgaris L. samples from Tangyin County, Henan Province and then screened the A. vulgaris L. leaf extracts for anti-HSV-1 activity. The results of the plaque reduction test showed that the crude extract of A. vulgaris L.-Fr.8.3 had anti-HSV-1 activity, and we further verified the anti-HSV-1 activity of Fr.8.3 at the DNA, RNA and protein levels. Moreover, we found that Fr.8.3 also had a broad spectrum of antiviral activity. Finally, we explored its anti-HSV-1 mechanism, and the results showed that Fr.8.3 exerted an anti-HSV-1 effect by acting directly on the virus itself. Then, the extracts were screened on HSV-1 surface glycoproteins and host cell surface receptors for potential binding ability by molecular docking, which further verified the phenotypic results. LC-MS analysis showed that 1 and 2 were the two main components of the extracts. Docking analysis suggested that compounds from extract 1 might similarly cover the binding domain between the virus and the host cells, thus interfering with virus adhesion to cell receptors, which provides new ideas and insights for clinical drug development for herpes simplex virus type 1. CONCLUSION: We found that Fr.8.3 has anti-herpesvirus and anti-rotavirus effects. The main 12 components in Fr.8.3 were analyzed by LC-MS, and the protein targets were finally predicted through molecular docking, which showed that alkaloids may play a major role in antiviral activity.

Ethanol extract from Artemisia argyi leaves inhibits HSV-1 infection by destroying the viral envelope.

Herpes simplex virus type 1 (HSV-1) is a widely disseminated virus that establishes latency in the brain and causes occasional but fatal herpes simplex encephalitis. Currently, acyclovir (ACV) is the main clinical drug used in the treatment of HSV-1 infection, and the failure of therapy in immunocompromised patients caused by ACV-resistant HSV-1 strains necessitates the requirement to develop novel anti-HSV-1 drugs. Artemisia argyi, a Traditional Chinese Medicine, has been historically used to treat inflammation, bacterial infection, and cancer. In this study, we demonstrated the antiviral effect and mechanism of ethanol extract of A. argyi leaves (hereafter referred to as 'AEE'). We showed that AEE at 10 µg/ml exhibits potent antiviral effects on both normal and ACV-resistant HSV-1 strains. AEE also inhibited the infection of HSV-2, rotavirus, and influenza virus. Transmission electron microscopy revealed that AEE destroys the membrane integrity of HSV-1 viral particles, resulting in impaired viral attachment and penetration. Furthermore, mass spectrometry assay identified 12 major components of AEE, among which two new flavones, deoxysappanone B 7,3'-dimethyl ether, and 3,7-dihydroxy-3',4'-dimethoxyflavone, exhibited the highest binding affinity to HSV-1 glycoprotein gB at the surface site critical for gB-gH-gL interaction and gB-mediated membrane fusion, suggesting their involvement in inactivating virions. Therefore, A. argyi is an important source of antiviral drugs, and the AEE may be a potential novel antiviral agent against HSV-1 infection.

Reassessing Fano Resonance for Broadband, High-Efficiency, and Ultrafast Terahertz Wave Switching.

Miniaturized ultrafast switchable optical components with high efficiency and broadband response are in high demand to the development of optical imaging, sensing, and high-speed communication. Sharp Fano-type resonance switched by active materials is one of the key concepts that underpins the control of light in metaoptics with high sensitivity. However, actuating such metasurfaces exhibits a long-standing trade-off between modulation depth and operational bandwidth. Here, the limitations are circumvented by theoretical analysis, numerical simulation, and experimental realization of an achromatic Fano metasurface so that a high contrast of tunability with ultrafast switching rate over a broad range of frequency is achieved. By developing the physics of inter-mode coupling, the Fano metasurface is designed according to a complete phase diagram derived from coupled mode theory. Unlike conventional Fano metasurfaces, the cross-polarized inter-metaatoms coupling is discovered as a superior ability of high-efficiency broadband achromatic polarization conversion. To prove the ultrasensitive nature, a metadevice is constructed by incorporating a thin amorphous Ge layer with a weak photoconductivity perturbation. Transmission modulation over broadband frequency range from 0.6 to 1.1 THz is thus successfully realized, featuring its merits of modulation depth over 90% and On-Off-On switching cycle less than 10 ps.

ß-Caryophyllene Acts as a Ferroptosis Inhibitor to Ameliorate Experimental Colitis.

Macrophage infiltration is one of the main pathological features of ulcerative colitis (UC) and ferroptosis is a type of nonapoptotic cell death, connecting oxidative stress and inflammation. However, whether ferroptosis occurs in the colon macrophages of UC mice and whether targeting macrophage ferroptosis is an effective approach for UC treatment remain unclear. The present study revealed that macrophage lipid peroxidation was observed in the colon of UC mice. Subsequently, we screened several main components of essential oil from Artemisia argyi and found that ß-caryophyllene (BCP) had a good inhibitory effect on macrophage lipid peroxidation. Additionally, ferroptotic macrophages were found to increase the mRNA expression of tumor necrosis factor alpha (Tnf-α) and prostaglandin-endoperoxide synthase 2 (Ptgs2), while BCP can reverse the effects of inflammation activated by ferroptosis. Further molecular mechanism studies revealed that BCP activated the type 2 cannabinoid receptor (CB2R) to inhibit macrophage ferroptosis and its induced inflammatory response both in vivo and in vitro. Taken together, BCP potentially ameliorated experimental colitis inflammation by inhibiting macrophage ferroptosis. These results revealed that macrophage ferroptosis is a potential therapeutic target for UC and identified a novel mechanism of BCP in ameliorating experimental colitis.

Sesquiterpenoids and triterpenoids with anti-inflammatory effects from Artemisia vulgaris L.

In this study, eight undescribed sesquiterpenoids (artemvulactone A-G and artemvulemdiol A), and two undescribed triterpenoids, (3S)-dammar-20,25-diene-3-hydroxy-24-one and (3S,23E)-dammar-20,23-diene-25- methoxy-3-ol were isolated from the leaves of Artemisia vulgaris L., together with ten known sesquiterpenoids and three known triterpenoids. The structures of these undescribed terpenoids were determined by extensive spectroscopy methods, including 1D and 2D-NMR, HRESIMS, IR, UV, X-ray diffraction, and ECD. The absolute configurations of artemvulactone A, artemvulactone D, and artemvulactone E were determined by X-ray diffraction (Cu Kα). All isolates were evaluated for their anti-inflammatory efficacy by detecting the expression of inflammatory mediator NO in LPS-induced RAW264.7 cells, and the results indicated that artemvulactone E exhibited significant anti-inflammatory effect with an IC50 value of 0.9 ± 0.2 µM. Furthermore, artemvulactone E could reduce LPS-induced COX-2 protein expression dose-dependently by western blotting experiments.

Sesquiterpene lactones from Artemisia vulgaris L. as potential NO inhibitors in LPS-induced RAW264.7 macrophage cells.

Twelve new guaianolide sesquiterpene lactones (1-12), along with ten known analogs (13-22) were isolated from an EtOH extract of the dried aerial parts of Artemisia vulgaris L. The new structures were elucidated via abundant spectroscopic data analyses (HRESIMS, IR, 1D, and 2D NMR), and the absolute configurations of these compounds were determined by X-ray crystallography and ECD calculations. The compounds (1-22) were identified as guaiane-type sesquiterpenes with characteristic α-methylene-γ-lactone and α,ß-unsaturated carbonyl moieties. All compounds were tested for their inhibitory activity against NO production in lipopolysaccharide-stimulated RAW264.7 macrophages. The isolated sesquiterpenoids dose-dependently exhibited an NO production inhibitory activity by inhibiting the expression of inducible NO oxidase (iNOS) and cyclooxygenase-2 (COX-2) with IC50 values ranging from 1.0 to 3.6 µM. The inhibitory effect on the NO production of the compounds (1-4 and 6-22) is better than that of the positive control (dexamethasone). The different substitutions of compounds on C-8 influence anti-inflammatory effects, as evidenced by the in silico analysis of related binding interactions of new compounds (1-12) with iNOS.

Polydatin, A Glycoside of Resveratrol, Is Better Than Resveratrol in Alleviating Non-alcoholic Fatty Liver Disease in Mice Fed a High-Fructose Diet.

Resveratrol (RES) is considered to be an activator of AMP-activated protein kinase (AMPK) with many reported health benefits. Polydatin (POD) is a natural precursor and glycosylated form of RES. The glycoside structure of POD alters the bioactivity. Overnutrition-stimulated reactive oxygen species (ROS) promote the AMPK suppression and metabolic dysregulation. The present work compared the effects of POD and RES in ameliorating energy homeostasis imbalance in mice fed a high-fructose diet and elucidated the underlying mechanisms of action. Our results showed that POD elevated the fecal levels of valeric acid and caproic acid via modification of gut microbiota, while RES did not significantly influence the levels of fecal short-chain fatty acids (SCFAs). Both POD and RES markedly decreased the oxidative stress and activated the AMPK signaling pathways in the liver. POD and RES exerted a similar effect in alleviating glucose dysmetabolism, but POD was more effective in ameliorating lipid dysmetabolism than RES. Furthermore, valeric acid and caproic acid alone can activate the AMPK and ameliorate hypercholesterolemia, and enhance the effects of POD on improving lipid metabolism in mice. Overall, for the first time, we demonstrated that POD administration elevated the fecal levels of valeric acid and caproic acid by modifying gut microbiota, thus promoting AMPK activation may be the underlying mechanism that POD is superior to RES in alleviating the lipid dysmetabolism. Our results suggest that POD may be an alternative for RES as an AMPK activator.

Light-Driven Spintronic Heterostructures for Coded Terahertz Emission.

The extraordinary proliferation of digital coding metasurfaces turns the real-time manipulation of electromagnetic (EM) waves into reality and promotes the programmable operation of multifunctional equipment. However, current studies are mainly involved in the modulation of the transmission process, and little attention has been given to the control of EM wave generation, especially in the terahertz (THz) band. Here, we conceptually propose and experimentally demonstrate coded terahertz emission, which integrates the efficient generation and control of THz waves across a wide frequency band. For validation, two types of stripe-patterned ferromagnetic heterostructures with opposite spin Hall angles were utilized as coding units. The two distinct states in each coding unit (with two polarization or phase states of 0° and 180°) can be characterized as "0" and "1" digits, which can be switched by manipulating the optical field distribution of the pump beam. Such an ability to realize simultaneous terahertz coding and terahertz emission is essential for meeting the increasingly demanding requirements of integration and miniaturization. Our work endows ferromagnetic heterostructures with controllable spatial characteristics and benefits their applications in wireless communications and holographic imaging.

Ultraefficient Terahertz Emission Mediated by Shift-Current Photovoltaic Effect in Layered Gallium Telluride.

Generating terahertz waves using thin-layered materials holds great potential for the realization of integrated terahertz devices. However, previous studies have been limited by restricted radiation intensity and finite efficiency. Exploiting materials with higher efficiency for terahertz emission has attracted increasing interest worldwide. Herein, with visible-light excitation, a thin-layered GaTe film is demonstrated to be a promising emitter of terahertz radiation induced by the shift-current photovoltaic effect. Through theoretical calculations, a transient charge-transfer process resulting from the asymmetric structure of GaTe is shown to be the origin of an ultrafast shift current. Furthermore, it was found that the amplitude of the resulting terahertz signals can be manipulated by both the fluence of the pump laser and the orientation of the sample. Such high emission efficiency from the shift current indicates that the layered material (GaTe) is an excellent candidate for photovoltaics and terahertz emitters.

Bifunctional Spatiotemporal Metasurfaces for Incident Angle-Tunable and Ultrafast Optically Switchable Electromagnetically Induced Transparency.

Advances in tunable metamaterials/metasurfaces facilitates their utilization in novel optical components, and lead to many breakthroughs in light tailoring by giving birth to diverse spatiotemporal dynamics. In the ascendant field of terahertz (THz) photonics, the ultrafast modulation is the fundamental process of technological advancements in high-speed wireless communications, sensing, and imaging. However, the current research efforts have been mainly devoted to studies of single functionality under the control of one stimulus, which has plateaued in terms of innovative new features. Here, building on the incident angle-induced C2 symmetry breaking of split ring pairs, we experimentally demonstrate extremely versatile, ultrafast THz switching behaviors at continuously alterable resonant states. The direction-controlled resonance hybridization provides another excellent degree of routing freedom, owing to its robustness, simplicity, and wide tunability. By leveraging such virtues, single LC mode and EIT-like resonance under normal and oblique incidence conditions are both effectively switched-off by means of photon injection. Considering the ultrashort lifetime of free carriers in MoSe2 crystal, the corresponding transient dynamics show an ultrafast recovery time within 700 ps. The strategy proposed here is a viable pathway for multidimensional THz wave manipulation, which gears up a crucial step for diversified functionalities in deployable metaphotonic devices.

Enhanced Terahertz Radiation by Efficient Spin-to-Charge Conversion in Rashba-Mediated Dirac Surface States.

The enhancement of terahertz (THz) radiation is of extreme significance for the realization of the THz probe and imaging. However, present THz technologies are far from being enough to realize high-performance and room-temperature THz sources. Fortunately, topological insulators (TIs), with spin-momentum-locked Dirac surface states, are expected to exhibit a high terahertz emission efficiency. In this work, the novel concept of a Rashba-state-enhanced spintronic THz emitter is demonstrated on the basis of ferromagnet/heavy metal/topological insulator (FM/HM/TI) heterostructure. We find that the THz emission intensity changes as a function of HM interlayer thickness, and a 1.98 times higher intensity compared to that of FM/TI can be achieved when a meticulously designed thickness of the HM layer is inserted. The improvement of terahertz radiation is ascribed to the additive effect of Rashba splitting and topological surface states at the HM/TI interface. These results offer new possibilities for realizing spintronic THz emitters in TI-based magnetic heterostructures.

Pump-Color Selective Control of Ultrafast All-Optical Switching Dynamics in Metaphotonic Devices.

Incorporating active materials into metamaterials is expected to yield exciting advancements in the unprecedented versatility of dynamically controlling optical properties, which sheds new light on the future optoelectronics. The exploration of emerging semiconductors into terahertz (THz) meta-atoms potentially allows achieving ultrafast nanodevices driven by various applications, such as biomedical sensing/imaging, ultrawide-band communications and security scanners. However, ultrafast optical switching of THz radiation is currently limited to a single level of tuning speed, which is a main hurdle to achieve multifunctionalities. Here, a hybrid metadevice which can realize the pump-wavelength controlled ultrafast switching response by the functionalization of double photoactive layers is demonstrated experimentally. A whole cycle of electromagnetically induced transparency switching with a half-recovery state changes from 0.78 ns to 8.8 ps as pump wavelength varies from near infrared to near ultraviolet regions. The observed pump-color selective switching speed changing from nanosecond scale to picosecond scale is ascribed to the wavelength-dependent penetration length of Ge and the contrasting defect states between noncrystalline Ge and epitaxial Si layers. It is believed that the schemes regarding pump-color controllable ultrafast switching behavior introduced here can inspire more innovations across the field of ultrafast photonics and can boost the reconfigurable metamaterial applications.

Near-Infrared Photoelectric Properties of Multilayer Bi2O2Se Nanofilms.

The near-infrared (NIR) photoelectric properties of multilayer Bi2O2Se nanofilms were systematically studied in this paper. Multilayer Bi2O2Se nanofilms demonstrate a sensitive photo response to NIR, including a high photoresponsivity (~ 101 A/W), a quick response time (~ 30 ms), a high external quantum efficiency (~ 20,300%), and a high detection rate (1.9 × 1010 Jones). These results show that the device based on multilayer Bi2O2Se nanofilms might have great potentials for future applications in ultrafast, highly sensitive NIR optoelectronic devices.

Bolometric Effect in Bi2 O2 Se Photodetectors.

Bi2 O2 Se is emerging as a photosensitive functional material for optoelectronics, and its photodetection mechanism is mostly considered to be a photoconductive regime in previous reports. Here, the bolometric effect is discovered in Bi2 O2 Se photodetectors. The coexistence of photoconductive effect and bolometric effect is generally observed in multiwavelength photoresponse measurements and then confirmed with microscale local heating experiments. The unique photoresponse of Bi2 O2 Se photodetectors may arise from a change of hot electrons during temperature rises instead of photoexcited holes and electrons. Direct proof of the bolometric effect is achieved by real-time temperature tracking of Bi2 O2 Se photodetectors under time evolution after light excitation. Moreover, the Bi2 O2 Se bolometer shows a high temperature coefficient of resistance (-1.6% K-1 ), high bolometric coefficient (-31 nA K-1 ), and high bolometric responsivity (>320 A W-1 ). These findings offer a new approach to develop bolometric photodetectors based on Bi2 O2 Se layered materials.