Daily Archives: 13 Mar 2021

PHYSICS

Physicists Observed Cherenkov Radiation In Beryllium For The First Time (Physics)

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Uglov and Vukolov presented the new experimental results on the observation of X-ray Cherenkov radiation generated by 5.7 MeV electrons in the thin Beryllium (Be) and silicon (Si) foils. They observed Cherenkov effect from Beryllium for the first time. They also compared the experimental results with the calculations performed according to the theoretical model of transition radiation taking into account the oxide layer on the target output surface.

Figure 1. a) Scheme for XCR investigation using a multilayer mirror; b) top view of the vacuum chamber – Ch; T is a target, D is a channel-electron multiplier (CEM), M is a multilayer mirror, G is a goniometer, FC is a Faraday cup. © Uglov et al.

Currently, most of the Cherenkov phenomenon researches for the X-ray region are theoretical studies; there are only a few experiments in this area. These experiments presented convincing experimental evidence for the observation of the Cherenkov effect in the X-ray range. At the same time, not all experimental results show complete agreement with the theory.

Thus, after the first experimental observation of the Cherenkov effect in the ultra-soft X-ray range near the K-edge of carbon absorption, Dutch researchers obtained in their study an experimental confirmation of the Cherenkov effect existing near the absorption edges of elements such as titanium, vanadium, and silicon; at the same time, they failed to detect the Cherenkov effect for Ni and to confirm the Cherenkov effect in carbon. The carbon-related researches were carried out using various modifications of carbon such as diamond, amorphous carbon, graphite and carbon in organic compounds using a lower electron energy than Bazylev and colleagues considered in their study, but sufficient for the appearance of Cherenkov radiation according to the theory.

There are also disagreements between the calculations of the X-ray Cherenkov radiation (XCR) angular density and the experimental observation of the one during the sliding interaction of 75 MeV electron beam with targets. For example, the experimental Cherenkov angles for carbon and Si turned out to be the same, which does not agree with the theory.

Intensity of radiation reflected by a multilayer mirror [Mo/B4C]100 depending on 𝜃0 : a) for Be
and b) for Si targets. © Uglov et al.

But, Uglov and Vukolov’s calculations includes the effect of the oxide layer and pinholes which demonstrated an improvement in the agreement between the calculations and the experiment.

The fact of observing the Cherenkov radiation in Be may promote the development of a high-intensity, high-monochrome radiation source with the energy of emitted photons E∼ 111 eV. According to authors, the spectral-angular radiation density of such a source can be increased several times by using the sliding interaction of the electron beam with the target. Besides, the threshold nature of the XCR can be used for the development of threshold counters for the separation of the charged particles.

“These detectors are more promising for use with multiply charged ions since the XCR yield is proportional to the square of the particle charge.“

— told Uglov, lead author of the study.

Reference: S. R. Uglov, A.V.Vukolov, “Observation of soft X-ray Cherenkov radiation in Be and Si foils”, ArXiv, pp. 1-13, 28 Feb 2021. https://arxiv.org/abs/2103.00579

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Medicine

Researchers Reveal Mechanism of Hepatitis B-induced Venous Metastasis & Immune Escape of Hepatocellular Carcinoma (Medicine)

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In China, about 70 million people are infected with hepatitis B virus (HBV), and more than 80% of liver cancer is caused by HBV.

HBV-associated hepatocellular carcinoma (HCC) is often accompanied by severe vascular invasion and portal vein tumor thrombus leading to a poor prognosis. However, the underlying mechanism of this disease remains obscure.

In a study published in Cancer Research, Prof. YANG Pengyuan and Prof. WANG Fan at the Institute of Biophysics (IBP) of the Chinese Academy of Sciences (CAS) revealed how HBV infection induced HCC venous metastasis and immune escape through a chemokine-based network.

The researchers firstly established a cytokines/chemokines array and screened the proinflammatory cytokine IL-8 as a potential target responsively to HBV infection. Multiple models and mechanistic study identified that HBV-induced IL-8 expression can be activated by HBx-mediated MEK-ERK signaling pathway, which enhanced permeability of the endothelium via endothelial CXCR1, the receptor of IL-8.

Based on the identification of IL-8-CXCR1 axis promoting tumor vascular metastasis in vivo, they then constructed a transgenic mouse that selectively express human CXCR1 in endothelial cells.

Interestingly, the IL-8-CXCR1 axis on vascular endothelium dramatically increased liver tumorigenesis and metastasis, and the increase in lung metastasis was observed through overexpression of IL-8, but exogenous CXCR1 overexpression did not further enhance lung metastasis. Mechanistically, the IL-8-CXCR1 axis selectively induced GARP-latent-TGF-β in liver sinusoidal endothelial cells (LSECs) and subsequently provoked preferential regulatory T cell polarization to suppress antitumor immunity.

This study identifies a hepatitis B-induced IL-8/CXCR1/TGF-β signaling cascade that suppresses anti-tumor immunity and enhances metastasis in hepatocellular carcinoma, providing new potential targets for therapeutic intervention.

Featured image: Working model of IL-8-CXCR1 axis promoted venous metastasis and intrahepatic Treg accumulation in HBV-associated HCC (Image by Dr. YANG Pengyuan’s group)

Reference: Changlu Zhang, Yanan Gao, Chengzhi Du, Geoffrey J. Markowitz, Jing Fu, Zhenxing Zhang, Chunliang Liu, Wenhao Qin, Hongyang Wang, Fan Wang and Pengyuan Yang, “Hepatitis B-induced IL-8 Promotes Hepatocellular Carcinoma Venous Metastasis and Intrahepatic Treg Accumulation”, Cancer Res March 2 2021 DOI: 10.1158/0008-5472.CAN-20-3453

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Biology

First Chinese Record of Web-loving Bug Family Plokiophilidae Reported from Xishuangbanna (Zoology / Biology)

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A new species of the web-loving bug family Plokiophilidae has been reported from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences (CAS). The family Plokiophilidae is a new record for the fauna of China and the first record of the genus Plokiophiloides beyond the Afrotropical Region. 

The family Plokiophilidae China is a small group of true bugs, currently containing nine genera. It contains two subfamilies, Embiophilinae and Plokiophilinae: the former possessed heavy forefemoral spines and lived in the webs of Embiidina, and the latter lacked forefemoral spines and lived in the webs of spiders. 

During their field work, researchers from Sun Yat-sen University and XTBG collected some unknown bug specimens from the webs of wolf spiders Hippasa sp in low herbaceous plants in XTBG. After careful morphological studies and literature review, the researchers confirmed that the species is new to science and named it as Plokiophiloides bannaensis to refer its type locality of Xishuangbanna. The new species was published in ZooKeys.

Habitus images of live individuals for Plokiophiloides bannaensis sp. nov. and spider host Hippasa sp. A. an adult of Plokiophiloides bannaensis sp. nov. on web; B. an individual of Hippasa sp. in funnel of the web; C. an adult and a nymph of Plokiophiloides bannaensis sp. nov. near funnel of the web. (Image by LUO Jiuyang)

Plokiophiloides bannaensis can be distinguished from the congeners by the combined characteristics: body with red pigment; exocorium with about 65 corial glands; whitish precuneal spot on forewing conspicuous and hypocostal lamina extending caudally as a short, pale whitish-yellow projection. 

According to the researchers, the new species of Plokiophilidae and its host spider Hippasa sp. are currently only found in tropical China. “More investigation is needed to clarify the species diversity and thus the distribution pattern of Plokiophilidae in pantropical regions,” said Dr. PENG Yanqiong from XTBG. 

Featured image: Habitus of Plokiophiloides bannaensis sp. nov. A. male holotype in dorsal view; B. male holotype in ventral view; C. female paratype in dorsal view; D. female paratype in ventral view. (Image by LUO Jiuyang)

Reference: Luo J, Peng Y, Xie Q (2021) First record of the cimicomorphan family Plokiophilidae (Hemiptera, Heteroptera) from China, with description of a new species of Plokiophiloides. ZooKeys 1021: 145-157. https://doi.org/10.3897/zookeys.1021.56599

Provided by Chinese Academy of Sciences

Medicine

New Study Shows 24-72 Hours of Poor Oral Hygiene Impacts Oral Health (Medicine)

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Poor oral hygiene produces gum-disease bacteria and accelerates oral microbiome aging faster than previously thought. 

A new study shows that within 24-72 hours of the interruption of oral hygiene, there was a steep decrease in the presence of ‘good oral bacteria’ and the beneficial anti-inflammatory chemicals they are associated with. An increase of ‘bad bacteria’ typically present in the mouths of patients with periodontitis, a severe gum disease which can lead to tooth damage or loss, was also discovered. 

The research team, led by scientists from Single-Cell Center, Qingdao Institute of BioEnergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) and Procter & Gamble Company (P&G), published their findings in the journal mBio on Mar. 9, 2021. 

The researchers asked 40 study participants with different levels of naturally occurring gingivitis to perform optimal oral hygiene for three weeks. This led to reduced gingivitis and a healthy baseline for the study. Gingivitis was then induced when their oral hygiene routine was interrupted over the course of four weeks. Restart of oral hygiene leads to recovery due to the reversible nature of gingivitis.

The researchers performed genetic analyses on the population of bacteria in the participants’ gum as it changed. Chemical analyses of the molecules produced by the bacteria were performed and immune responses of the study participants were recorded. 

Within just 24-72 hours of the cessation of oral hygiene, the researchers found there was a steep decrease in the presence of multiple Rothia species as well as the chemical betaine, which was reported to play an anti-inflammatory role in several inflammatory diseases.

In addition, there was a swift, full activation of multiple salivary cytokines – proteins and other molecules produced by immune system cells associated with inflammation. And just as the presence of the ‘good bacteria’ had declined, there was a sharp increase in the presence of the types of bacteria typically present in the mouths of patients with periodontitis even though there weren’t any symptoms of the illness yet.  

Taken together, the positive association with betaine and the negative association with gingivitis suggest that Rothia may be ‘good bacteria’ beneficial to gum health, contributing to the production of betaine in some way. 

“We also found a sudden ‘aging’ of the bacteria in the mouth,” said XU Jian, Director of Single-Cell Center at QIBEBT and senior author of the study. “Their oral microbiome had aged the equivalent of about a year in less than a month.” 

Previous studies have demonstrated that the composition of the population of oral bacteria (the oral microbiome) is a good predictor of the age of a patient. As one ages, one sees less of some species of bacteria and more of others. Older people, for example, tend to have far fewer Rothia species of bacteria.

“After only 28 days of gingivitis, we found the study participants had the ‘oral microbial age’ of those a year older,” said HUANG Shi, one investigator leading this study. 

The researchers now want to continue to study the link between Rothia, betaine and inflammation to see if they can come up with better early-stage responses to gingivitis.  

Featured image: Longitudinal multi-omics and microbiome meta-analysis identify an asymptomatic gingival state that links gingivitis, periodontitis and aging. (Image by LIU Yang)

Reference: Huang S, He T, Yue F, Xu X, Wang L, Zhu P, Teng F, Sun Z, Liu X, Jing G, Su X, Jin L, Liu J, Xu J. 2021. Longitudinal multi-omics and microbiome meta-analysis identify an asymptomatic gingival state that links gingivitis, periodontitis, and aging. mBio 12:e03281-20. https://doi.org/10.1128/mBio.03281-20.

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Physiology

Exercise Linked With Better Health in Patients With Kidney Disease (Physiology)

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The first study to report the optimal amount of physical activity in patients with kidney disease is published on World Kidney Day in the European Journal of Preventive Cardiology, a journal of the European Society of Cardiology (ESC).1 Kidney disease was less likely to progress in active individuals, who also had less heart problems and improved survival.

The World Health Organization (WHO) recommends at least 150 minutes of moderate-intensity (e.g. walking) or at least 75 minutes of vigorous-intensity (e.g. jogging) weekly physical activity, or an equivalent combination, for health benefits in adults.2 This study found that patients with kidney disease whose activity level ranged from the WHO minimum up to twice that amount had the best health over a follow-up of nearly two years. Remaining active was crucial to sustaining the benefits.

Study author Professor Der-Cherng Tarng of Taipei Veterans General Hospital and National Yang-Ming University, Taiwan said: “Our results suggest that physical activity should be integrated into the clinical care of patients with kidney disease.”

Chronic kidney disease affects around 700 million people worldwide.3 Muscle wasting results in physical inactivity which increases the risk of cardiovascular disease – the main cause of death in these patients. Once chronic kidney disease progresses to end-stage renal disease, the risk of cardiovascular death is 10–20 times higher compared with the general population. This means that slowing progression is important for heart health and longevity.

This was the first large-scale study to investigate the association between physical activity and progression of kidney disease. Specifically, the study examined the links between exercise and all-cause mortality, end-stage renal disease, and cardiovascular events in kidney disease patients.

The study included 4,508 patients with chronic kidney disease between 2004 and 2017. Patients were not on dialysis. Patients were divided into three groups according to weekly physical activity assessed with the National Health and Nutrition Examination Survey (NHANES) questionnaire: highly active (WHO minimum or more), low-active (less than the WHO minimum), or inactive (no activity).

A total of 1,915 patients were classified as highly active, 879 were low-active, and 1,714 were inactive. During a median follow-up of 686 days, 739 patients died, 1,059 developed end-stage renal disease, and 521 had a major adverse cardiovascular event (heart attack, stroke, hospitalisation for heart failure, or death from cardiovascular disease). The highly active group had the lowest chance of all these adverse outcomes, followed by the low-active and inactive groups.

The researchers analysed the association between physical activity and adverse outcomes after adjusting for other factors that could influence the relationships including age, sex, smoking, body mass index, blood pressure, medications, and other conditions such as diabetes, coronary artery disease, and cancer. Compared to the inactive group, the highly active group had a 38% lower risk of death, 17% lower risk of end-stage renal disease, and 37% lower risk of major adverse cardiovascular events. The health benefits in the low-active group did not reach statistical significance.

Study author Dr. Wei-Cheng Tseng of Taipei Veterans General Hospital and National Yang-Ming University noted that the likelihood of cardiovascular events did not further decrease once activity surpassed double the WHO minimum. He said: “Extreme amounts of exercise can induce heart rhythm disorders (arrhythmias) in those with kidney disease. It therefore seems sensible to avoid very high levels to maximize the benefits and minimise the risks.”

To examine the impact of changing usual exercise habits, activity was reassessed six months after the first measurement. Highly active patients who became more sedentary had two-fold increased risks of death and cardiovascular events compared to those who stayed highly active. Dr. Tseng said: “This highlights the importance of maintaining physical activity among patients with kidney disease.”

References

1Kuo CP, Tsai MT, Lee KH, et al. Dose-response effects of physical activity on all-cause mortality and major cardiorenal outcomes in chronic kidney disease. Eur J Prev Cardiol. 2021. doi:10.1093/eurjpc/zwaa162. https://academic.oup.com/eurjpc/article-lookup/doi/10.1093/eurjpc/zwaa162

2World Health Organization Global Recommendations on Physical Activity for Health: https://www.who.int/dietphysicalactivity/publications/9789241599979/en/

3GBD Chronic Kidney Disease Collaboration. Global, regional, and national burden of chronic kidney disease, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. Lancet. 2020;395:709–733.

Provided by European Society of Cardiology

Medicine

Exhaustion Linked With Increased Risk of Heart Attack in Men (Medicine)

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Men experiencing vital exhaustion are more likely to have a heart attack, according to research presented today at ESC Acute CardioVascular Care 2021, an online scientific congress of the European Society of Cardiology (ESC).1 The risk of a myocardial infarction linked with exhaustion was particularly pronounced in never married, divorced and widowed men.

“Vital exhaustion refers to excessive fatigue, feelings of demoralisation and increased irritability,” said study author Dr. Dmitriy Panov of the Institute of Cytology and Genetics, Novosibirsk, Russian Federation. “It is thought to be a response to intractable problems in people’s lives, particularly when they are unable to adapt to prolonged exposure to psychological stressors.”

This study examined the relationship between vital exhaustion and the risk of myocardial infarction in men with no history of cardiovascular disease. The study used data from the World Health Organization (WHO) MONICA Project.2 A representative sample of 657 men aged 25 to 64 years in Novosibirsk was enrolled in 1994.

Symptoms of vital exhaustion were assessed at baseline using the Maastricht Vital Exhaustion Questionnaire adopted by the MONICA protocol. Participants were classified according to their level of vital exhaustion: none, moderate, or high. Participants were followed-up for 14 years for the incidence of heart attack.

Overall, two-thirds (67%) of the men had vital exhaustion (15% had a high level and 52% had a moderate level) while 33% were unaffected. Nearly three-quarters (74%) of men with high blood pressure had vital exhaustion –  high in 58% and moderate in 16%.

In the overall group of men, the researchers analysed the association between vital exhaustion at baseline and the risk of having a heart attack. Compared to those without vital exhaustion, men with moderate or high levels had a 2.7-fold greater risk of a heart attack within five years, a 2.25 higher risk within 10 years, and a 2.1 raised risk within 14 years (p for all <0.05).

When the analysis was controlled for social factors (education, occupation, and marital status) and age, the influence of vital exhaustion on heart attack risk decreased but remained statistically significant. For example, compared to those without vital exhaustion, men with moderate or high levels were 16% more likely to have a myocardial infarction over 14 years of follow-up compared to those without after adjusting for social factors and age (p <0.05).

In the adjusted analysis, the risk of a heart attack linked with exhaustion was higher in never married, divorced, and widowed men compared to married men – with hazard ratios of 3.7, 4.7, 7.0, respectively. The risk of a heart attack related to exhaustion was 2.2-fold higher in those with an elementary school education compared to men with a university degree. Middle-aged men were more affected than younger men: compared to 24-34-year-olds, the risk of a heart attack connected with exhaustion was 3.8-fold higher in 45-54-year-olds and 5.9-fold higher in 55-64-year-olds.

Regarding the influence of marital status on the relationship between exhaustion and heart attack, Dr. Panov said: “Living alone indicates less social support, which we know from our prior studies is an independent risk factor for myocardial infarction and stroke.”

He noted that the findings indicate a pattern whereby social disadvantage relates to vital exhaustion, which is associated with a greater risk of heart disease. “The relationship of exhaustion with threatening cardiovascular events should be taken into account when assessing risk,” he said.

Dr. Panov concluded: “Efforts to improve well-being and reduce stress at home and at work can help reduce vital exhaustion. Involvement in community groups is one way to increase social support and become less vulnerable to stress. Together with a healthy lifestyle, these measures should be beneficial for heart health.”

Funding: This survey was performed within the framework of the budgetary theme NIITPM – branch of the ICG SB RAS Reg. № AAAA-A17-117112850280-2, Gov.Task № 0324-2018-0001.

Disclosures: The authors declare no conflict of interest.

References and notes

1Reference: Gafarov VV, Gromova EA, Gagulin IV, Gafarova AV. [Study of the influence of vital exhaustion on myocardial infarction risk in a male population aged 25 to 64 years]. Klin Med (Mosk). 2005;83(5):23-6. Russian. PMID: 15984577. https://pubmed.ncbi.nlm.nih.gov/15984577/

2The analysis was part of the WHO MONICA Optional Psychosocial Substudy (MOPSY).

Provided by European Society of Cardiology

Botany

Most Fern Species in Xishuangbanna are Rare, Research (Botany)

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A researcher from the Xishuangbanna Tropical Botanical Garden (XTBG) said in a floristic study that the majority of fern species in the forest habitat of Xishuangbanna of Yunnan province are locally rare. Two-thirds of terrestrial fern species and nearly all epiphytes are rare. 

Using a transect-based method, the researcher conducted a floristic study at 75 sites to investigate the richness and cover of terrestrial and epiphytic fern species in Xishuangbanna.  

It was found a total of 130 fern species, including 99 terrestrial (i.e. self and non-self-supporting, as climbers and as individuals with rhizomes in the soil) species and 31 epiphytes (i.e. growing on a trunk or tree crown). 66% of the terrestrial and 99% of the epiphytes are rare in Xishuangbanna. 

He evaluated whether the richness of the common and rare species was different between the drier and humid site, and tried to find whether elevation played a major role for the cover values of rare and common fern species. 

He found that the rare species are more frequent at higher elevations with the driest sites being slightly richer in terms of the epiphytes and the total number of species. However, the richness and cover of the terrestrial species was higher at lowland sites. 

According to the investigation, most of the fern species have a narrow and or wide distribution but low cover values, showing that the fern species in Xishuangbanna tend to have a population size characterized by low cover and few individuals.  

“Since there are so many rare fern species with low occurrence, it is urgent to conserve biodiversity in the fragmented tropical landscape of southern Yunnan,” said Daniele Cicuzza, author of the study.

Reference: Daniele Cicuzza, Rare Pteridophytes are disproportionately frequent in the tropical forest of Xishuangbanna, Yunnan, China, Acta Oecologica, Volume 110, 2021, 103717, ISSN 1146-609X, https://doi.org/10.1016/j.actao.2021.103717. (https://www.sciencedirect.com/science/article/pii/S1146609X21000163)

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Chemistry

Meeting Turing Structures in Manmade Interface (Chemistry)

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In 1952, Alan Turing, the father of computer science and artificial intelligence, proposed that certain repetitive natural patterns may be produced by the interaction of two specific substances through the “reaction-diffusion” process. In this system, activator promotes the reaction and inhibitor inhibits the reaction. When the two meet, the reaction diffuses. When the difference in diffusion coefficient between the two reaches a certain level, the high diffusion ratio between them will cause the system imbalance and induce the formation of periodic complex patterns.”Turing structure” exists widely in nature, such as the body patterns of zebras, the phyllotaxis of sunflowers, the follicle spacing of mouse hairs. However, it is difficult to construct a Turing structure in a manmade chemical system since the difference in diffusion coefficients of substances is small.

Recently, Prof. GAO Minrui’s group from the University of Science and Technology of China of the Chinese Academy of Sciences created the Turing structure on inorganic transition metal chalcogenides with the “reaction-diffusion” process for the first time. The results were published in German Applied Chemistry and the study was selected as Back Cover. 

A cation exchange method was used by the researchers to produce Turing-type Ag2Se on CoSe2 nanobelts based on diffusion-driven instability.  

In the binary solution of diethylenetriamine (DETA) and water, the inhibitor, Ag+ reacts with DETA to form Ag(DETA)+. At the same time, the activator, Co2+ overflows from the surface of the cobalt diselenide (CoSe2) nanobelt. When the rapidly diffused Ag(DETA)+ reaches the Nernst layer on the CoSe2 surface, it interacts with the activator Co2+ diffused on the CoSe2 surface, and finally forms a complex and beautiful Ag2Se Turing pattern on the CoSe2 surface. 

This resultant Turing-type Ag2Se-CoSe2 material was an efficient oxygen evolution (OER) electrocatalyst. The intrinsic OER activity was linearly related to the length of Ag2Se-CoSe2 interfaces, indicating that this Turing-type interfaces are more active sites for OER. 

The study uses the “reaction-diffusion” theory to construct complex Turing structures on inorganic nanostructured materials for the first time, and provides new ideas for the design of cheap catalysts with higher performance.

Reference: X.-L. Zhang, P.-P. Yang, Y.-R. Zheng, Y. Duan, S.-J. Hu, T. Ma, F.-Y. Gao, Z.-Z. Niu, Z.-Z. Wu, S. Qin, L.-P. Chi, X. Yu, R. Wu, C. Gu, C.-M. Wang, X.-S. Zheng, X. Zheng, J.-F. Zhu, M.-R. Gao, “An Efficient Turing‐Type Ag2Se‐CoSe2 Multi‐Interfacial Oxygen‐Evolving Electrocatalyst”, Angew. Chem. Int. Ed. 2021, 60, 6553. https://onlinelibrary.wiley.com/doi/10.1002/anie.202017016

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Chemistry

Porous Single-crystalline Monoliths Developed with High-density Lewis Acid Sites to Enhance Propane Dehydrogenation at Reduced Temperature (Chemistry)

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Surface/interface structure and catalytic mechanism are of great significance in many practical catalytic reactions.

Porous single crystals which combine an ordered lattice structure and disordered inter-connected pore provide an alternative to create twisted surfaces with clear and high-density active sites in porous microstructures. They present the advantages of clear lattice structure, precise chemical composition and clear termination surface, which demonstrates a huge potential to build continuously twisted and high density active surface structure. 

In a study published in Angew. Chem. Int. Ed., the research group led by Prof. XIE Kui from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences grew porous single-crystalline Mo2N and MoN monoliths at 2 cm scale to enhance non-oxidative propane dehydrogenation to propylene.  

The creation of high-density Lewis acid sites at the electron-deficient surface effectively improves the catalytic activity at reduced temperatures through control of the unsaturated Mo-N1/6 and Mo-N1/3 coordination structures. 

The researchers firstly grew the parent single crystals of MoO3, then removed the periodic target atomic layer O in ammonia atmosphere at 650-700 °C, and simultaneously nitrified and reconstructed the framework structure of metastable Mo-O single crystal into the mesoporous Mo2N single crystal.  

In the same way, they grew porous MoN single crystals by controlling the temperature, flow rate and pressure of ammonia gas.  

Moreover, the researchers visualized the fine structure of the twisted surfaces and the metal nitrogen unsaturated coordination active structure of the porous single crystal.  

They found that the top-layer Mo ion with unsaturated Mo-N1/6 and Mo-N1/3 coordination structures create high-density Lewis acid sites at surface, leading to effective activation of C-H bond without over cracking of C-C bond during non-oxidative propane dehydrogenation. 

~11% of propane conversion and ~95% of propylene selectivity were demonstrated with porous single-crystalline Mo2N and MoN monoliths at 500 °C without degradation being observed even after the operation of 20 hours. 

This study provides important reference for the research on the surface structure and catalytic mechanism in actual catalytic reactions. 

Featured image: Centimeter scale mesoporous single crystals monoliths with high-density Lewis acid sites at twisted surface and clearly active sites deliver enhanced propane dehydrogenation at reduced temperature (Image by Prof. XIE’s group) 

Reference: Lin, G., Su, Y., Duan, X. and Xie, K. (2021), High‐Density Lewis Acid Sites in Porous Single‐Crystalline Monoliths to Enhance Propane Dehydrogenation at Reduced Temperatures. Angew. Chem. Int. Ed.. https://doi.org/10.1002/anie.202100244

Provided by Chinese Academy of Sciences