Transition Metal Functionalized C30N12S6 as High-Performance Trifunctional Catalysts with Integrated Descriptors toward Hydrogen Evolution, Oxygen Evolution, and Oxygen Reduction Reactions: A Case of High-Throughput First-Principles Screening within the Framework of TM-N2@C30N10S6.

In energy conversion and storage technologies, the design of highly efficient trifunctional electrocatalysts integrating with the high hydrogen evolution reaction (HER) and oxygen evolution/reduction reaction (OER/ORR) activities is highly desirable. Herein, utilizing first-principles computations, a novel periodically ordered macropore C30N12S6 monolayer was proposed, and the stability analysis attests to its good stability. Single transition metal (TM) atom anchored onto this newly proposed C30N12S6 monolayer to form single-atom catalysts, as achieved by TM-N2@C30N10S6, among which the Co-N2@C30N10S6 is the most promising multifunctional catalyst toward HER/OER/ORR with low overpotential of 0.01/0.59/0.3 V; meanwhile, the Rh-N2@C30N10S6 can be used as a bifunctional OER/ORR catalyst with low overpotential of 0.37/0.44 V, overmatching the landmark Pt (111) and IrO2/RuO2 catalysts. Particularly, the TM-d orbital in TM@CNS is remarkably hybridized with the O-p orbital of oxygenated intermediates, so that the lone electrons initially located at the antibonding orbital pair up and fill the downward bonding orbital, allowing OH* to be suitably adsorbed on TM@CNS, enhancing the catalytic performance. The relevant attributes, such as good stabilities and metallic features, ensured their applications in ambient conditions. Moreover, multilevel descriptors were constructed to clarify the origin of activity on TM@CNS, such as ΔGOH* (Gibbs free energy of OH*), εd (d-band center), COHP (crystal orbital Hamilton population), Nd/Nd + s (number of d/d + s electrons) and φ (descriptor), among which the filling of outer d-electrons of TM atom significantly affects the value of ΔGOH* that can determine the overpotential and, thus, become a key descriptor.

Surface-enhanced Raman spectroscopy long-range detection investigation based on the alternating coupling of a surface plasmonic array and dielectric waveguide.

Surface-enhanced Raman spectroscopy (SERS) is widely used to detect low-concentration samples in biology, medicine, etc. We design and theoretically investigate a SERS sensor with a surface plasmonic array coupled alternately with a dielectric waveguide. The effect of the incident angle on the coupling efficiency of an evanescent field is systematically studied. The results show that the maximum evanescent field coupling efficiency can be obtained at an incident angle of 66°. The proposed SERS sensor has a transmission length of 1.027 cm and a high enhancement performance with an enhancement factor of 1.574×104 at a wavelength of 633 nm. The integration of this SERS sensor with a metal array and a dielectric waveguide prevents the direct illumination of the sample molecules by the excited light. Furthermore, the long-range nondestructive detection of the SERS signals of the low-concentration sample molecules can be achieved.

Urbanization shifts long-term phenology and severity of phytoplankton blooms in an urban lake through different pathways.

Climate change can induce phytoplankton blooms (PBs) in eutrophic lakes worldwide, and these blooms severely threaten lake ecosystems and human health. However, it is unclear how urbanization and its interaction with climate impact PBs, which has implications for the management of lakes. Here, we used multi-source remote sensing data and integrated the Virtual-Baseline Floating macroAlgae Height (VB-FAH) index and OTSU threshold automatic segmentation algorithm to extract the area of PBs in Lake Dianchi, China, which has been subjected to frequent PBs and rapid urbanization in its vicinity. We further explored long-term (2000-2021) trends in the phenological and severity metrics of PBs and quantified the contributions from urbanization, climate change, and also nutrient levels to these trends. When comparing data from 2011-2021 to 2000-2010, we found significantly advanced initiation of PBs (28.6 days) and noticeably longer duration (51.9 days) but an insignificant trend in time of disappearance. The enhancement of algal nutrient use efficiency, likely induced by increased water temperature and reduced nutrient concentrations, presumably contributed to an earlier initiation and longer duration of PBs, while there was a negative correlation between spring wind speed and the initiation of PBs. Fortunately, we found that both the area of the PBs and the frequency of severe blooms (covering more than 19.8 km2 ) demonstrated downward trends, which could be attributed to increased wind speed and/or reduced nutrient levels. Moreover, the enhanced land surface temperature caused by urbanization altered the thermodynamic characteristics between the land and the lake, which, in turn, possibly caused an increase in local wind speed and water temperature, suggesting that urbanization can differently regulate the phenology and severity of PBs. Our findings have significant implications for the understanding of the impacts of urbanization on PB dynamics and for improving lake management practices to promote sustainable urban development under global change.

Concentrations of dissolved organic matter and methane in lakes in Southwest China: Different roles of external factors and in-lake biota.

Many factors have been reported to affect material cycling in lakes, but the combined and cascading impacts of external environmental factors and in-lake biota on lake carbon cycling are poorly understood. We elucidated the influencing pathways of geoclimatic factors, lake morphometry, land-use type, chemical and physical factors, and biological taxa (phytoplankton and macroinvertebrates) on the concentrations of two important components of carbon cycling, i.e., dissolved organic matter (DOM) and methane (CH4) based on datasets from 64 plateau lakes in Southwest China. Partial least squares path modelling (PLS-PM) indicated that (1) geoclimatic factors influenced DOM and CH4 by affecting land use and lake physical factors (e.g., water temperature), (2) lake morphometry (water depth and lake area) had a direct and great negative effect on the CH4 concentration related to the production and oxidation of CH4 and affected phytoplankton and macroinvertebrates by influencing chemical and physical factors, (3) land-use type affected DOM and CH4 concentrations in both direct and indirect ways, (4) terrestrial humic-like DOM was mainly discharged from forestland and also affected by macroinvertebrates, while the impacts of agricultural and construction land on autochthonous DOM and CH4 concentrations mainly occurred by changing nutrients and then the aquatic biota. Moreover, changes in aquatic biota, primarily affected by water quality, influenced DOM spectral properties, and the two biotas affected DOM and CH4 concentrations differently. Phytoplankton, especially cyanobacteria contributed to (protein-like and humic-like) DOM in both direct and indirect ways related to eutrophication, whereas macroinvertebrates influenced DOM possibly by utilization, bioturbation, and microbial decomposition of feces according to their different relationships with DOM spectral indices. Additionally, CH4 production can be enhanced by DOM accumulation, and the significant positive correlations of CH4 concentrations with protein-like DOM and biological index indicate that autochthonous DOM may play an important role for the CH4 production. Our findings contribute to the understanding of lake carbon cycling under natural conditions and anthropogenic disturbances.

Patterns of thermocline structure and the deep chlorophyll maximum feature in multiple stratified lakes related to environmental drivers.

Thermal stratification and the deep chlorophyll maximum (DCM), two commonly related phenomena in stratified lakes, play fundamental roles in eco-environmental processes. However, the progressive linkages among multi-dimensional environmental factors, thermal stratification and DCM were poorly explored, which greatly constrains our understanding of cross-level governance in deep lakes. In this study, the thermocline structure (i.e., thermocline depth, thickness and strength) and DCM feature (depth and thickness) and their driving factors were investigated at regional scale using data from 18 stratified lakes differing in limnological characteristics, Southwest China. Our study showed that (1) DCM occurred close to the thermocline in most lakes (represented by their depth and thickness), (2) the depths of the thermocline and DCM were both shallower than the euphotic depth, and (3) spatial heterogeneity occurred the thermocline structure and the DCM feature, reflecting different environmental factors. Specifically, water depth and light penetration depths were both positively correlated with thermocline depth and thickness and the DCM feature, and ultraviolet radiation (UVR) was more important than photosynthetically active radiation (PAR) for thermocline depth, but PAR was more important for thermocline thickness; moreover, PAR played a more prominent role than UVR for the DCM feature. As there were interactions between some environmental factors, we built a cascading path using a partial least squares path modelling for the DCM feature: lake morphometry directly impacted the thermocline structure and surface water quality; the water quality further affected light penetration depths as well as the thermocline structure; light penetration depth and thermocline structure combined directly determined the DCM feature, where the importance of light was larger. Our findings provide information on the cascading drivers of the thermocline structure and DCM feature in deep lakes and also constitute a valuable reference for deep lake management under the dual pressure of climate change and eutrophication.

Cooccurrence of Antibiotic Resistance and Hypervirulence in High-Risk Carbapenem-Resistant K14.K64 and Wzi209 Klebsiella pneumoniae Strains Driven by Plasmids and Their Derivatives.

Emerging hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) is a severe public health problem worldwide. To assess the cooccurrence of CRKP and hv-CRKP, a total of 1,181 CRKP isolates were collected from 2009 to 2018, covering their initial occurrence to outbreaks. Overall, two major capsular serotypes, namely, wzi209-CRKP and K14.K64-CRKP, were identified as being prevalent in pediatric and adult patients, respectively. Most isolates carried blaKPC, and the blaKPC-carrying hybrid plasmid IncFII-IncR, which was stable and transferable, was identified. The conjugation region (traN/traC) of IncFII-IncR was found to be variable, and the genes were used as markers to identify the transmission of strains among patient groups in this study. Notably, hv-CRKP was characterized by screening for four virulence genes (rmpA, iroN, terW, and rmpA2) in all 977 blaKPC-carrying K14.K64-CRKP and wzi209-CRKP strains. Two virulence types, namely, rmpA/iroN/terW/rmpA2 positive and terW/rmpA2 positive, were found. The corresponding virulence plasmids Vir1, i.e., nonconjugative IncFIB(k)-IncHI1B, and Vir2, i.e., conjugative antibiotic-resistant IncFIB-IncHI1B, were further characterized. Both Vir1 and Vir2 were stable, and the transferability of Vir2 was significantly higher than that of IncFII-IncR. However, none of the Vir1- or Vir2-carrying strains exhibited the hypervirulent phenotype. Meanwhile, hv-CRKP (terW/rmpA2 positive) was found in late 2018 among wzi209-CRKP strains. The corresponding Vir2-related fragment was characterized as chromosomally integrated, which dramatically enhanced the virulence of wzi209-CRKP. Transmission of hv-CRKP among patient groups was also confirmed according to virulence elements. Taken together, CRKP and hv-CRKP occurred on a large scale. Plasmids and their derivatives played an important role on this process. Surveillance and intervention of hv-CRKP are urgently needed. IMPORTANCE Currently, an increasing number of hv-CRKP strains have been reported and pose a substantial threat to public health worldwide, because these strains are considered to be simultaneously hypervirulent, carbapenem resistant, and transmissible. In this study, we provided a complete transition process of CRKP and hv-CRKP from their early emergence to outbreak in 10 years. We identified two epidemic groups, K14.K64 (wzi64)-CRKP and wzi209-CRKP, in adult and pediatric patients, respectively. K14.K64 (wzi64)-CRKP was widely present, while wzi209-CRKP was rarely reported as an epidemic type. We discovered a large scale of hv-CRKP transmission from CRKP and determined the importance of antibiotic resistance and virulence plasmids and their derivatives for the transition of CRKP and hv-CRKP. Two virulence plasmids coexist in out hospital, but neither of them enhanced virulence. Notably, we found a newly emerged type of CRKP, hypervirulent wzi209-CRKP, which had dramatically enhanced virulence, making it a great threat to human health.

[Expression of Runt-related Transcription Factor 3 in Human Colon Cancer Cell Line HCT-116 Resistant to 5-Fluorouracil and the Mechanism of Drug Resistance].

Objective To establish a human colon cancer cell line HCT-116/5-FU resistant to 5-fluorouracil(5-FU)and explore the relationship between runt-related transcription factor 3(RUNX3)and drug resistance of colorectal cancer.Methods The human colon cancer cell line HCT-116/5-FU with resistance to 5-FU was established by low concentration gradient increment combined with high-dose intermittent shock.CCK-8 method was used to determine the half maximal inhibitory concentration(IC50)of 5-FU on the parent line HCT-116 and drug-resistant line HCT-116/5-FU.The cell growth curve was established for the calculation of population doubling time(TD).The mRNA levels and protein levels of RUNX3,P-glycoprotein(P-gp),multidrug resistance-associated protein 1(MRP1),and lung resistance-related protein(LRP)in HCT-116 and HCT-116/5-FU cells were determined by qRT-PCR and Western blotting,respectively.The RUNX3 expression in HCT-116 cells was knocked down by siRNA technique,and the cells were divided into RUNX3 knockdown groups(si-RUNX3-1 group and si-RUNX3-2 group)and negative control group(si-NC group).The knockdown efficiency was verified by qRT-PCR at the mRNA level and Western blotting at the protein level.The IC50 in si-RUNX3 groups and si-NC group was determined with CCK-8 method,and the expression of P-gp,MRP1,and LRP in the two groups was detected by Western blotting.Results A stable human colon cancer drug-resistant cell line HCT-116/5-FU was successfully constructed.HCT-116/5-FU showed the TD 1.38 times as long as that of HCT-116(P=0.002)and changed morphology.The mRNA level of RUNX3 in HCT-116/5-FU cells was significantly lower than that in HCT-116 cells(P=0.048),and those of P-gp(P=0.008),MRP1(P=0.001),and LRP(P=0.001)showed the opposite trend.The protein level of RUNX3 in HCT-116/5-FU cells was significantly lower than that in HCT-116(P<0.001),and those of P-gp,MRP1,and LRP presented the opposite trend(all P<0.001).The HCT-116 cell model with low expression of RUNX3 was successfully established.The mRNA level of RUNX3 had no significant difference between si-RUNX3-1 group and si-NC group(P=0.064),while the level in si-RUNX3-2 group was significantly lower than that in si-NC group(P=0.034).The protein levels of RUNX3 in si-RUNX3-1 group and si-RUNX3-2 group were lower than that in si-NC group(both P<0.001).The results demonstrated higher knocking efficiency in si-RUNX3-2 group,which was thus selected to complete the follow-up test.The IC50 of si-RUNX3 group was significantly higher than that of si-NC group(P<0.001),which indicated that the down-regulated expression of RUNX3 could reduce the sensitivity of HCT-116 cells to 5-FU.The relative protein levels of P-gp,MRP1,and LRP in si-RUNX3 group were significantly higher than those in si-NC group(all P<0.001).Conclusion The down-regulation of RUNX3 expression can reduce the sensitivity of HCT-116 cells to 5-FU,which is considered to be related to the up-regulated expression of P-gp,MRP1,and LRP.

Endolysin, a Promising Solution against Antimicrobial Resistance.

Antimicrobial resistance (AMR) is a global crisis for human public health which threatens the effective prevention and control of ever-increasing infectious diseases. The advent of pandrug-resistant bacteria makes most, if not all, available antibiotics invalid. Meanwhile, the pipeline of novel antibiotics development stagnates, which prompts scientists and pharmacists to develop unconventional antimicrobials. Bacteriophage-derived endolysins are cell wall hydrolases which could hydrolyze the peptidoglycan layer from within and outside of bacterial pathogens. With high specificity, rapid action, high efficiency, and low risk of resistance development, endolysins are believed to be among the best alternative therapeutic agents to treat multidrug resistant (MDR) bacteria. As of now, endolysins have been applied to diverse aspects. In this review, we comprehensively introduce the structures and activities of endolysins and summarize the latest application progress of recombinant endolysins in the fields of medical treatment, pathogen diagnosis, food safety, and agriculture.

Expression, clinical significance and correlation of RUNX3 and HER2 in colorectal cancer.

BACKGROUND: The incidence of colorectal cancer is high and on the rise. The genetic and protein expressions of RUNT-associated transcription factor 3 (RUNX3) and human epidermal growth factor receptor 2 (HER2) in colorectal cancer (CRC) and adjacent normal tissues were detected to preliminarily explore their correlation and clinical significance. METHODS: CRC specimens excised during general surgery were selected for localization and quantitative analysis of protein and gene expression by SP (Streptavidin-peroxidase conjugated method) immunohistochemical staining, reverse transcription-polymerase chain reaction (RT-qPCR) and western blot. Combined with the patients' data, the relationship between the expression of the two genes and tumor characteristics was analyzed. Log-rank test was used to analyze the correlation between the two proteins and survival prognosis of CRC patients. The expression of RUNX3 in RKO and HCT-116 was knocked down, and the relative expression of HER2 in the two cell lines was detected. RESULTS: Immunohistochemical, RT-qPCR and Western blot results showed that the positive expression rate of RUNX3 in CRC was lower than in the normal group, and HER2 in CRC was higher than in the normal group. The positive expression of the two proteins correlated with the pT and pN stages of CRC. A significant negative correlation between the expression of the two genes in CRC. Follow-up results showed that the number of Runx3-positive patients was higher than negative ones, while HER2 positive were fewer than negative ones. In vitro experiments showed that RUNX3 protein and gene expression decreased, HER2 protein and gene expression increased in RUNX3 knockdown RKO and HCT-116 cells, respectively (P<0.05). CONCLUSIONS: The expression of RUNX3 and HER2 in CRC is related to the occurrence and development of CRC, and the two genes have a negative regulating effect.

Environmental factors associated with cyanobacterial assemblages in a mesotrophic subtropical plateau lake: A focus on bloom toxicity.

Harmful algal blooms caused by cyanobacteria have been increasing in frequency worldwide. However, the main environmental drivers of this change are often difficult to identify because of the effects of the interaction between eutrophication and climate change. Recently, filamentous N2-fixing cyanobacteria and non-diazotrophic Microcystis have been observed to be co-existing and undergoing succession in some eutrophic lakes. However, the succession patterns of dominant cyanobacteria and the factors driving this in mesotrophic lakes are not well understood. We hypothesized that the changes in cyanobacterial assemblages in mesotrophic lakes could result in a relatively high risks of toxic blooms, and that these changes are associated with the global climatic changes. We tested these hypotheses using data from the subtropical mesotrophic Lake Erhai. We found that the high spatiotemporal variability in the cyanobacterial community, and the increase in biomass were driven primarily by the growth of bloom-forming cyanobacterial taxa. Species-specific biomasses were related to a different environmental stressor; increases in dissolved organic carbon (DOC) concentrations were statistically associated with an increase of Microcystis biomass, whereas increases in surface water temperature favored higher biomass of Pseudanabaena at low transparency and high concentration of phosphorus. In addition, low nitrogen- to- phosphorus ratios were identified as potential determinants of the abundance of N2-fixing Dolichospermum. Furthermore, changes in the concentration of DOC, total nitrogen, pH and water transparency levels were found to affect the composition of Microcystis morphotypes and genotypes mostly. This study highlights that the toxic to non-toxic Microcystis ratio might increase with the water darkening and browning (which occurs in many subtropical plateau lakes). Lake management strategies, therefore, need to consider the toxicity of cyanobacterial assemblages in mesotrophic lakes over the intensity of the cyanobacterial blooms.

A memristor-based hybrid analog-digital computing platform for mobile robotics.

Algorithms for mobile robotic systems are generally implemented on purely digital computing platforms. Developing alternative computational platforms may lead to more energy-efficient and responsive mobile robotics. Here, we report a hybrid analog-digital computing platform enabled by memristors on a mobile inverted pendulum robot. Our mobile robotic system can tune the conductance states of memristors adaptively using a model-free optimization method to achieve optimal control performance. We implement sensor fusion and the motion control algorithms on our hybrid analog-digital computing platform and demonstrate more than one order of magnitude enhancement of speed and energy efficiency over traditional digital platforms.

Tellurene Photodetector with High Gain and Wide Bandwidth.

Two-dimensional (2D) semiconductors have been extensively explored as a new class of materials with great potential. In particular, black phosphorus (BP) has been considered to be a strong candidate for applications such as high-performance infrared photodetectors. However, the scalability of BP thin film is still a challenge, and its poor stability in the air has hampered the progress of the commercialization of BP devices. Herein, we report the use of hydrothermal-synthesized and air-stable 2D tellurene nanoflakes for broadband and ultrasensitive photodetection. The tellurene nanoflakes show high hole mobilities up to 458 cm2/V·s at ambient conditions, and the tellurene photodetector presents peak extrinsic responsivity of 383 A/W, 19.2 mA/W, and 18.9 mA/W at 520 nm, 1.55 µm, and 3.39 µm light wavelength, respectively. Because of the photogating effect, high gains up to 1.9 × 103 and 3.15 × 104 are obtained at 520 nm and 3.39 µm wavelength, respectively. At the communication wavelength of 1.55 µm, the tellurene photodetector exhibits an exceptionally high anisotropic behavior, and a large bandwidth of 37 MHz is obtained. The photodetection performance at different wavelength is further supported by the corresponding quantum molecular dynamics (QMD) simulations. Our approach has demonstrated the air-stable tellurene photodetectors that fully cover the short-wave infrared band with ultrafast photoresponse.

Rapid detection of carbapenemase activity of Enterobacteriaceae isolated from positive blood cultures by MALDI-TOF MS.

BACKGROUND: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been proved to be a useful tool for identification of pathogens directly isolated from blood cultures in clinical microbiology laboratories. ß-Lactam antibiotics are commonly used for treatment of bloodstream infections caused by Enterobacteriaceae strains, and carbapenem is the superlative class of ß-lactam antibiotics. Since the carbapenem resistance rate of Enterobacteriaceae strains raised year by year, efficient detection of carbapenemase activity and timely delivery of carbapenem susceptibility reports of Enterobacteriaceae strains isolated from blood cultures is important for clinicians. METHODS: We used 64 simulated blood cultures to establish the method of MALDI-TOF MS based ertapenem hydrolysis assay. The cutoff value of logRQ calculated from the peaks intensity of ertapenem and its hydrolysate was first set to identify the strains with carbapenemase activity. Then, we detected and calculated the logRQ values of 385 Enterobacteriaceae strains from positive clinical blood cultures to distinguish the carbapenemase producers and noncarbapenemase producers. RESULTS: The mean logRQ value of 32 noncarbapenemase producers was - 0.85 ± 0.14 in simulated blood cultures, while the logRQ value of 32 carbapenemase producers was 0.87 ± 0.55. Thus, the cutoff value of logRQ was set at - 0.45 with sensitivity of 100% and specificity of 100%. In 385 clinical positive blood cultures, the logRQ values of all carbapenem-susceptible Enterobacteriaceae strains (81.3%, 313/385) were < - 0.45. Comparing with the detection of carbapenemase genes, carbapenem-resistant Enterobacteriaceae strains (18.7%, 72/385) were well distinguished by MALDI-TOF MS based ertapenem hydrolysis assay with a sensitivity of 92.5% and specificity of 100%. CONCLUSIONS: Our data show that MALDI-TOF MS based ertapenem hydrolysis assay is a rapid and accurate method to detect carbapenemase activity of Enterobacteriaceae strains from positive blood cultures, and can be routinely performed in clinical microbiology laboratories.

Probing Gap Plasmons Down to Subnanometer Scales Using Collapsible Nanofingers.

Gap plasmonic nanostructures are of great interest due to their ability to concentrate light into small volumes. Theoretical studies, considering quantum mechanical effects, have predicted the optimal spatial gap between adjacent nanoparticles to be in the subnanometer regime in order to achieve the strongest possible field enhancement. Here, we present a technology to fabricate gap plasmonic structures with subnanometer resolution, high reliability, and high throughput using collapsible nanofingers. This approach enables us to systematically investigate the effects of gap size and tunneling barrier height. The experimental results are consistent with previous findings as well as with a straightforward theoretical model that is presented here.

Photoinitiated Dynamics in Amorphous Solid Water via Nanoimprint Lithography.

Laser pulses that act on fragile samples often alter them irreversibly, motivating single-pulse data collection. Amorphous solid water (ASW) is a good example. In addition, neither well-defined paths for molecules to travel through ASW nor sufficiently small samples to enable molecular dynamics modeling have been achieved. Combining nanoimprint lithography and photoinitiation overcomes these obstacles. An array of gold nanoparticles absorbs pulsed (10 ns) 532 nm radiation and converts it to heat, and doped ASW films grown at about 100 K are ejected from atop the irradiated nanoparticles into vacuum. The nanoparticles are spaced from one another by sufficient distance that each acts independently. Thus, a temporal profile of ejected material is the sum of about 106 "nanoexperiments," yielding high single-pulse signal-to-noise ratios. The size of a single nanoparticle and its immediate surroundings is sufficiently small to enable modeling and simulation at the atomistic (molecular) level, which has not been feasible previously. An application to a chemical system is presented in which H/D scrambling is used to infer the presence of protons in films composed of D2O and H2O (each containing a small amount of HDO contaminant) upon which a small amount of NO2 has been deposited. The pulsed laser heating of the nanoparticles promotes NO2/N2O4 hydrolysis to nitric acid, whose protons enhance H/D scrambling dramatically.

Nanoimprint-defined, large-area meta-surfaces for unidirectional optical transmission with superior extinction in the visible-to-infrared range.

Optical devices with asymmetric transmission have important applications in optical systems, but optical isolators with the modal asymmetry can only be built using magneto-optical or nonlinear materials, as dictated by the Lorentz reciprocity theorem. However, optical devices with the power asymmetry can be achieved by linear materials such as metals and dielectrics. In this paper, we report a large-area, nanoimprint-defined meta-surface (stacked subwavelength gratings) with high-contrast asymmetric transmittance in the visible-to-infrared wavelength range for TM-polarized light. The physical origin of asymmetric transmission through the meta-surface is studied by analyzing the scattering matrix.