Nature-Inspired Photocatalytic Azo Bond Cleavage with Red Light.

The emerging field of photoredox catalysis in mammalian cells enables spatiotemporal regulation of a wealth of biological processes. However, the selective cleavage of stable covalent bonds driven by low-energy visible light remains a great challenge. Herein, we report that red light excitation of a commercially available dye, abbreviated NMB+, leads to catalytic cleavage of stable azo bonds in both aqueous solutions and hypoxic cells and hence a means to photodeliver drugs or functional molecules. Detailed mechanistic studies reveal that azo bond cleavage is triggered by a previously unknown consecutive two-photon process. The first photon generates a triplet excited state, 3NMB+*, that is reductively quenched by an electron donor to generate a protonated NMBH•+. The NMBH•+ undergoes a disproportionation reaction that yields the initial NMB+ and two-electron-reduced NMBH (i.e., leuco-NMB, abbreviated as LNMB). Interestingly, LNMB forms a charge transfer complex with all four azo substrates that possess an intense absorption band in the red region. A second red photon induces electron transfer from LNMB to the azo substrate, resulting in azo bond cleavage. The charge transfer complex mediated two-photon catalytic mechanism reported herein is reminiscent of the flavin-dependent natural photoenzyme that catalyzes bond cleavage reactions with high-energy photons. The red-light-driven photocatalytic strategy offers a new approach to bioorthogonal azo bond cleavage for photodelivery of drugs or functional molecules.

Sub-10 nm Corrugated TiO2 Nanowire Arrays by Monomicelle-Directed Assembly for Efficient Hole Extraction.

Precise synthesis of well-ordered ultrathin nanowire arrays with tunable active surface, though attractive in optoelectronics, remains challenging to date. Herein, well-aligned sub-10 nm TiO2 nanowire arrays with controllable corrugated structure have been synthesized by a unique monomicelle-directed assembly method. The nanowires with an exceptionally small diameter of ∼8 nm abreast grow with an identical adjacent distance of ∼10 nm, forming vertically aligned arrays (∼800 nm thickness) with a large surface area of ∼102 m2 g-1. The corrugated structure consists of bowl-like concave structures (∼5 nm diameter) that are closely arranged along the axis of the ultrathin nanowires. And the diameter of the concave structures can be finely manipulated from ∼2 to 5 nm by simply varying the reaction time. The arrays exhibit excellent charge dynamic properties, leading to a high applied bias photon-to-current efficiency up to 1.4% even at a very low potential of 0.41 VRHE and a superior photocurrent of 1.96 mA cm-2 at 1.23 VRHE. Notably, an underlying mechanism of the hole extraction effect for concave walls is first clarified, demonstrating the exact role of concave walls as the hole collection centers for efficient water splitting.

Smallest Stable Si/SiO_{2} Interface that Suppresses Quantum Tunneling from Machine-Learning-Based Global Search.

While the downscaling of size for field effect transistors is highly desirable for computation efficiency, quantum tunneling at the Si/SiO_{2} interface becomes the leading concern when approaching the nanometer scale. By developing a machine-learning-based global search method, we now reveal all the likely Si/SiO_{2} interface structures from thousands of candidates. Two high Miller index Si(210) and (211) interfaces, being only ∼1 nm in periodicity, are found to possess good carrier mobility, low carrier trapping, and low interfacial energy. The results provide the basis for fabricating stepped Si surfaces for next-generation transistors.

Values of Radial Artery Provocation Tests at Different Doses of Ergonovine in the Diagnosis of Coronary Artery Spasm.

The intracoronary drug provocation test has been the gold standard for diagnosis of coronary artery spasm (CAS); however, it has been identified with severe complications. In this study, we investigated the sensitivity, specificity, and safety of radial artery provocation test at different doses of ergonovine in the diagnosis of CAS. This study enrolled 57 patients, which were then divided into CAS group (n = 24) and control group (n = 33) after intracoronary ergonovine provocation test. All patients underwent radial artery provocation test at different doses of ergonovine. The predictive values of radial artery provocation test for the diagnosis of CAS were analyzed using receiver operator characteristic curve. In the radial artery provocation test at different doses of ergonovine, radial artery stenosis degree was all found to be significantly higher in the CAS group than in the control group (all P < 0.001). In the control group, significant differences were noted in the radial artery stenosis degree between different doses of ergonovine (all P < 0.05). In the CAS group, the radial artery stenosis degree was significantly higher in 160 µg and 100 µg of ergonovine than in 60 µg of ergonovine (all P < 0.001). The radial artery provocation test at 60 µg and 100 µg of ergonovine did not cause CAS, chest pain, and ECG ischemic changes. In the radial artery provocation test at 160 µg of ergonovine, some patients had CAS, chest pain, and ECG ischemic changes. The specificity and sensitivity of radial artery provocation test were 90.91% and 50.00% at 60 µg of ergonovine, 96.97% and 66.67% at 100 µg of ergonovine, and 90.91% and 95.83% at 160 µg of ergonovine for the diagnosis of CAS. As per our findings, we can conclude that the basic tension of radial artery increases in the CAS group. With the increase of ergonovine doses, its sensitivity and specificity improve, but its safety decreases. We will explore the most optimal dose of ergonovine in future studies.

Active Site Revealed for Water Oxidation on Electrochemically Induced δ-MnO2: Role of Spinel-to-Layer Phase Transition.

Seeking for active MnOx material as artificial water splitting catalyst has been a long history since the discovery of PSII system in nature. To date, the highest activity MnOx catalyst reported for oxygen evolution reaction (OER) does however not belong to common MnO2 polymorphs (α-, ß-, δ-MnO2), but rather to nascent δ-MnO2 layer produced in situ from spinel under electrochemical conditions with unknown active site structure. Here with the stochastic surface walking (SSW) pathway sampling method, we for the first time resolve the atomic-level mechanism of spinel-to-layer Mn3O4 solid phase transition in aqueous electrolyte. We show that a transient H0.5MnO2 phase is the precursor of transition that forms at high voltage (>1 V), and it undergoes the solid-to-solid phase transition to produce a δ-MnO2 layer, which is accompanied by Mn dissolution, dislocation, layer-breaking, and insertion of water/cations between layers. This leads to the generation of a variety of possible defective structures. We demonstrate using first-principles calculations that a special edge site with neighboring Mn vacancy provides the best OER activity with an overpotential of 0.59 V, 0.19 V lower than that of pristine MnO2. The high activity of such Mn sites are attributed to its special local structure: pseudocubane with one corner missing. The presence of the Mn vacancy near the active site enhances the adsorption of OH intermediate in OER. This defective cubane structure shares the common geometrical and electronic features found in the PSII system.

Reaction Network of Layer-to-Tunnel Transition of MnO2.

As a model system of 2-D oxide material, layered δ-MnO2 has important applications in Li ion battery systems. δ-MnO2 is also widely utilized as a precursor to synthesize other stable structure variants in the MnO2 family, such as α-, ß-, R-, and γ-phases, which are 3-D interlinked structures with different tunnels. By utilizing the stochastic surface walking (SSW) pathway sampling method, we here for the first time resolve the atomistic mechanism and the kinetics of the layer-to-tunnel transition of MnO2, that is, from δ-MnO2 to the α-, ß-, and R-phases. The SSW sampling determines the lowest-energy pathway from thousands of likely pathways that connects different phases. The reaction barriers of layer-to-tunnel phase transitions are found to be low, being 0.2-0.3 eV per formula unit, which suggests a complex competing reaction network toward different tunnel phases. All the transitions initiate via a common shearing and buckling movement of the MnO2 layer that leads to the breaking of the Mn-O framework and the formation of Mn(3+) at the transition state. Important hints are thus gleaned from these lowest-energy pathways: (i) the large pore size product is unfavorable for the entropic reason; (ii) cations are effective dopants to control the kinetics and selectivity in layer-to-tunnel transitions, which in general lowers the phase transition barrier and facilitates the creation of larger tunnel size; (iii) the phase transition not only changes the electronic structure but also induces the macroscopic morphology changes due to the interfacial strain.

Adsorption and reactions of O2 on anatase TiO2.

CONSPECTUS: The interaction of molecular oxygen with titanium dioxide (TiO2) surfaces plays a key role in many technologically important processes such as catalytic oxidation reactions, chemical sensing, and photocatalysis. While O2 interacts weakly with fully oxidized TiO2, excess electrons are often present in TiO2 samples. These excess electrons originate from intrinsic reducing defects (oxygen vacancies and titanium interstitials), doping, or photoexcitation and form polaronic Ti(3+) states in the band gap near the bottom of the conduction band. Oxygen adsorption involves the transfer of one or more of these excess electrons to an O2 molecule at the TiO2 surface. This results in an adsorbed superoxo (O2(-)) or peroxo (O2(2-)) species or in molecular dissociation and formation of two oxygen adatoms (2 × O(2-)). Oxygen adsorption is also the first step toward oxygen incorporation, a fundamental reaction that strongly affects the chemical properties and charge-carrier densities; for instance, it can transform the material from an n-type semiconductor to a poor electronic conductor. In this Account, we present an overview of recent theoretical work on O2 adsorption and reactions on the reduced anatase (101) surface. Anatase is the TiO2 polymorph that is generally considered most active in photocatalysis. Experiments on anatase powders have shown that the properties of photoexcited electrons are similar to those of excess electrons from reducing defects, and therefore, oxygen on reduced anatase is also a model system for studying the role of O2 in photocatalysis. Experimentally, the characteristic Ti(3+) defect states disappear after adsorption of molecular oxygen, which indicates that the excess electrons are indeed trapped by O2. Moreover, superoxide surface species associated with two different cation surface sites, possibly a regular cation site and a cation close to an anion vacancy, were identified by electron paramagnetic resonance spectroscopy. On the theoretical side, however, density functional theory studies have consistently found that it is energetically more favorable for O2 to adsorb in the peroxo form rather than the superoxo form. As a result, obtaining a detailed understanding of the nature of the observed superoxide species has proven difficult for many years. On reduced anatase (101), both oxygen vacancies and Ti interstitials have been shown to reside exclusively in the susbsurface. We discuss how reaction of O2 with a subsurface O vacancy heals the vacancy while leading to the formation of a surface bridging dimer defect. Similarly, the interaction of O2 with a Ti interstitial causes migration of this defect to the surface and the formation of a surface TiO2 cluster. Finally, we analyze the peroxo and superoxo states of the adsorbed molecule. On the basis of periodic hybrid functional calculations of interfacial electron transfer between reduced anatase and O2, we show that the peroxide form, while energetically more stable, is kinetically less favorable than the superoxide form. The existence of a kinetic barrier between the superoxo and peroxo states is essential for explaining a variety of experimental observations.

[Research progress of synaptic vesicle recycling].

Neurotransmission begins with neurotransmitter being released from synaptic vesicles. To achieve this function, synaptic vesicles endure the dynamic "release-recycle" process to maintain the function and structure of presynaptic terminal. Synaptic transmission starts with a single action potential that depolarizes axonal bouton, followed by an increase in the cytosolic calcium concentration that triggers the synaptic vesicle membrane fusion with presynaptic membrane to release neurotransmitter; then the vesicle membrane can be endocytosed for reusing afterwards. This process requires delicate regulation, intermediate steps and dynamic balances. Accumulating evidence showed that the release ability and mobility of synapses varies under different stimulations. Synaptic vesicle heterogeneity has been studied at molecular and cellular levels, hopefully leading to the identification of the relationships between structure and function and understanding how vesicle regulation affects synaptic transmission and plasticity. People are beginning to realize that different types of synapses show diverse presynaptic activities. The steady advances of technology studying synaptic vesicle recycling promote people's understanding of this field. In this review, we discuss the following three aspects of the research progresses on synaptic vesicle recycling: 1) presynaptic vesicle pools and recycling; 2) research progresses on the differences of glutamatergic and GABAergic presynaptic vesicle recycling mechanism and 3) comparison of the technologies used in studying presyanptic vesicle recycling and the latest progress in the technology development in this field.

Identification of adsorbed molecules via STM tip manipulation: CO, H2O, and O2 on TiO2 anatase (101).

While Scanning Tunneling Microscopy (STM) has evolved as an ideal tool to study surface chemistry at the atomic scale, the identification of adsorbed species is often not straightforward. This paper describes a way to reliably identify H2O, CO and O2 on the TiO2 anatase (101) surface with STM. These molecules are of a key importance in the surface chemistry of this and many other (photo-) catalytic materials. They exhibit a wide variety of contrasts in STM images, depending on the tip condition. With clean, metallic tips the molecules appear very similar, i.e., as bright, dimer-like features located in the proximity of surface Ti5c atoms. However, each species exhibits a specific response to the electric field applied by the STM tip. It is shown that this tip-adsorbate interaction can be used to reliably ascertain the identity of such species. The tip-adsorbate interactions, together with comparison of experimental and calculated STM images, are used to analyse and revisit the assignments of molecular adsorbed species reported in recent studies.

Theoretical study of interfacial electron transfer from reduced anatase TiO2(101) to adsorbed O2.

We study the electron transfer from a reduced TiO2 surface to an approaching O2 molecule using periodic hybrid density functional calculations. We find that the formation of an adsorbed superoxo species, *O2(-), via the reaction O2(gas) + e(-) → *O2(-), is barrierless, whereas the transfer of another electron to transform the superoxo into an adsorbed peroxide, i.e. *O2(-) + e(-) → *O2(2-), is nonadiabatic and has a barrier of 0.3 eV. The origin of this nonadiabaticity is attributed to the instability of an intermediate where the second electron is localized at the superoxo adsorption site. These results can explain the experimental finding that O2 is not an efficient electron scavenger in photocatalysis.

Chemical dynamics of the first proton-coupled electron transfer of water oxidation on TiO2 anatase.

Titanium dioxide (TiO2) is a prototype, water-splitting (photo)catalyst, but its performance is limited by the large overpotential for the oxygen evolution reaction (OER). We report here a first-principles density functional theory study of the chemical dynamics of the first proton-coupled electron transfer (PCET), which is considered responsible for the large OER overpotential on TiO2. We use a periodic model of the TiO2/water interface that includes a slab of anatase TiO2 and explicit water molecules, sample the solvent configurations by first principles molecular dynamics, and determine the energy profiles of the two electronic states involved in the electron transfer (ET) by hybrid functional calculations. Our results suggest that the first PCET is sequential, with the ET following the proton transfer. The ET occurs via an inner sphere process, which is facilitated by a state in which one electronic hole is shared by the two oxygen ions involved in the transfer.

Dual reaction channels for photocatalytic oxidation of phenylmethanol on anatase.

This work explores thoroughly the reaction network of the partial oxidation of phenylmethanol at the TiO(2)-solvent interface under photocatalytic conditions by using a first-principles continuum solvation method. We demonstrate that the photocatalytic oxidation of phenylmethanol has a complex reaction network with dual pathways. The dimer pathway dominates the mechanism under aerobic conditions and a [C(6)H(5)CH(OH)O](2) peroxo dimer is the key intermediate, the decomposition of which leads to an unusual O exchange phenomenon.

In Situ Structure of a Mo-Doped Pt-Ni Catalyst during Electrochemical Oxygen Reduction Resolved from Machine Learning-Based Grand Canonical Global Optimization.

Pt-Ni alloy is by far the most active cathode material for oxygen reduction reaction (ORR) in the proton-exchange membrane fuel cell, and the addition of a tiny amount of a third-metal Mo can significantly improve the catalyst durability and activity. Here, by developing machine learning-based grand canonical global optimization, we are able to resolve the in situ structures of this important three-element alloy system under ORR conditions and identify their correlations with the enhanced ORR performance. We disclose the bulk phase diagram of Pt-Ni-Mo alloys and determine the surface structures under the ORR reaction conditions by exploring millions of likely structure candidates. The pristine Pt-Ni-Mo alloy surfaces are shown to undergo significant structure reconstruction under ORR reaction conditions, where a surface-adsorbed MoO4 monomer or Mo2O x dimers cover the Pt-skin surface above 0.9 V vs RHE and protect the surface from Ni leaching. The physical origins are revealed by analyzing the electronic structure of O atoms in MoO4 and on the Pt surface. In viewing the role of high-valence transition metal oxide clusters, we propose a set of quantitative measures for designing better catalysts and predict that six elements in the periodic table, namely, Mo, Tc, Os, Ta, Re, and W, can be good candidates for alloying with PtNi to improve the ORR catalytic performance. We demonstrate that machine learning-based grand canonical global optimization is a powerful and generic tool to reveal the catalyst dynamics behavior in contact with a complex reaction environment.

Intra-brachial ergonovine, not acetylcholine, is associated with radial artery vasospasm in patients with coronary vasospasm.

BACKGROUND: The intracoronary provocation test is expensive and may cause complications. Therefore, we investigated the sensitivity, specificity and safety of different drug- and dose-peripheral artery provocation tests in the diagnosis of coronary artery spasm (CAS). METHODS: The patients who had repeated chest pain as well as both coronary and radial stenoses <50% were selected. These patients were divided into CAS group (n = 24) and control group (n = 33) after the intracoronary ergonovine provocation test. All patients underwent radial artery provocation tests at different dose-acetylcholine (200 µg, 400 µg and 800 µg) and ergonovine (60 µg, 100 µg and 160 µg). The predictive values of radial provocation tests for CAS diagnosis were analysed using receiver operator characteristic (ROC) curves. RESULTS: In radial acetylcholine provocation tests, 200 µg of acetylcholine failed to induce radial artery spasm, and the radial artery stenosis degree was not significantly different between the CAS group and control group at 400 µg and 800 µg of acetylcholine (all p > 0.05). In the radial artery ergonovine provocation tests, the radial artery stenosis degree was all significantly higher in the CAS group than in the control group at the three different doses (all p < 0.05). The specificity and sensitivity of radial ergonovine provocation tests were 90.91% and 50.00% at 60 µg, 96.97% and 66.67% at 100 µg, and 90.91% and 95.83% at 160 µg. Only the radial 160 µg-ergonovine provocation test caused CAS in one case. CONCLUSION: The radial acetylcholine provocation test has no diagnostic value for CAS. The radial 160 µg-ergonovine provocation test has higher sensitivity and specificity for CAS diagnosis, but its safety should be paid attention to.

The Identity of Nickel Peroxide as a Nickel Superoxyhydroxide for Enhanced Electrocatalysis.

Nickel peroxides are a class of stoichiometric oxidants that can selectively oxidize various organic compounds, but their molecular level structure remained elusive until now. Herein, we utilized structural prediction using the Stochastic Surface Walking method based on a neural network potential energy surface and advanced characterization using the as-synthesized nickel peroxide to unravel its chemical identity as the bridging superoxide containing nickel hydroxide, or nickel superoxyhydroxide. Superoxide incorporation tunes the local chemical environment of nickel and oxygen beyond the conventional Bode plot, offering a 6.4-fold increase in the electrocatalytic activity of urea oxidation. A volcanic dependence of the activity on the oxygen equivalents leads to the proposed active site of the Ni(OO)(OH)Ni five-membered ring. This work not only unveils the possible structures of nickel peroxides but also emphasizes the significance of tailoring the oxygen environment for advanced catalysis.

Particle size, shape and activity for photocatalysis on titania anatase nanoparticles in aqueous surroundings.

TiO(2) nanoparticles have been widely utilized in photocatalysis, but the atomic level understanding on their working mechanism falls much short of expectations. In particular, the correlation between the particle structure and the photocatalytic activity is not established yet, although it was observed that the activity is sensitive to the particle size and shape. This work, by investigating a series of TiO(2) anatase nanoparticles with different size and shape as the photocatalyst for water oxidation, correlates quantitatively the particle size and shape with the photocatalytic activity of the oxygen evolution reaction (OER). Extensive density functional theory (DFT) calculations combined with the periodic continuum solvation model have been utilized to compute the electronic structure of nanoparticles in aqueous solution and provide the reaction energetics for the key elementary reaction. We demonstrate that the equilibrium shape of nanoparticle is sensitive to its size from 1 to 30 nm, and the sharp crystals possess much higher activity than the flat crystals in OER, which in combination lead to the morphology dependence of photocatalytic activity. The conventionally regarded quantum size effect is excluded as the major cause. The physical origin for the shape-activity relationship is identified to be the unique spatial separation/localization of the frontier orbitals in the sharp nanoparticles, which benefits the adsorption of the key reaction intermediate (i.e., OH) in OER on the exposed five-coordinated Ti of {101} facet. The theoretical results here provide a firm basis for maximizing photocatalytic activity via nanostructure engineering and are also of significance for understanding photocatalysis on nanomaterials in general.

Diagnosis of coronary artery spasm by ergonovine provocation test of radial artery.

We investigated the sensitivity, specificity and safety of ergonovine provocation test of radial artery in the diagnosis of coronary artery spasm (CAS). The patients who came to our hospital for chest pain from January to June 2020 as well as had coronary stenosis < 50% and no radial artery stenosis, were enrolled in this study. These patients were divided into CAS group and control group after intracoronary ergonovine provocation test. All patients underwent ergonovine provocation test of radial artery, the inner diameter (D0 and D1) and the peak systolic velocities (PSV0 and PSV1) of the radial artery were measured by ultrasound before and after ergonovine provocation. The predictive value of ergonovine provocation test of radial artery for the diagnosis of CAS was analyzed using receiver operator characteristic (ROC) curve. There were 19 patients in the CAS group and 28 patients in the control group. Low density lipoprotein cholesterol and smoking rate were significantly higher in the CAS group than in the control group (all P < 0.05), but there were no significant differences in other items (P > 0.05) between the two groups. In the ergonovine provocation test of radial artery, degree of radial artery stenosis was significantly higher in the CAS group [41.50% (35.60%, 50.00%)] than in the control group [11.25% (5.15%, 23.00%)] (P = 0.000), but there were no siginificant differences in D0, PSV0 and PSV1 between the two groups (P > 0.05). The area under ROC curve of ergonovine (120 µg) provocation test of radial artery for the diagnosis of CAS was 0.912 with 95%CI: 0.792-0.975, P = 0.001, cut-off of 31%, specificity of 92.86% and sensitivity of 84.21%. The ergonovine (120 µg) provocation test of radial artery did not cause any adverse reactions. We concluded that the ergonovine provocation test of radial artery has high sensitivity, specificity and safety in the diagnosis of CAS.

Mechanism and activity of photocatalytic oxygen evolution on titania anatase in aqueous surroundings.

Due to its high overpotential and low efficiency, the conversion of water to O(2) using solar energy remains a bottleneck for photocatalytic water splitting. Here the microscopic mechanisms of the oxygen evolution reaction (OER) on differently structured anatase surfaces in aqueous surroundings, namely, (101), (001), and (102), are determined and compared systematically by combining first-principles density functional theory calculations and a parallel periodic continuum solvation model. We show that OER involves the sequential removal of protons from surface oxidative species, forming surface peroxo and superoxo intermediates. The initiating step, the first proton removal, dictates the high overpotential. Only at an overpotential of 0.7 V (1.93 V vs SHE) does this rate-controlling step become surmountable at room temperature: the free energy change of the step is 0.69, 0.63, and 0.61 eV for (101), (102), and (001) surfaces, respectively. We therefore conclude that (i) OER is not sensitive to the local surface structure of anatase and (ii) visible light (<∼590 nm) is, in principle, capable of driving the photocatatlytic OER on anatase kinetically. By co-doping high-valent elements into the anatase subsurface, we demonstrate that the high overpotential of the OER can be significantly reduced, with extra occupied levels above the valence band.

A high-performance trace level acetone sensor using an indispensable V4C3T x MXene.

The development of a stringent sensor to detect low levels of acetone, yielding the potential for the point-of-care clinical diagnosis of diabetes, is still a great challenge but is urgently required. Most studies have focused on Ti3C2T x , yet other types of MXenes with good performance are rare. Herein, an emerging kind of MXene, V4C3T x , has been prepared from V4AlC3 via the selective etching of the Al layer using aqueous HF at room temperature (RT), and its performance as an acetone sensor is presented. A V4C3T x based acetone sensor delivers good performance, as demonstrated by its low working temperature of 25 °C, low detection limit of 1 ppm (lower than the 1.8 ppm diabetes diagnosis threshold), and high selectivity towards acetone in a mixed gas of acetone and water vapor, hopefully showing promise for application in the much faster and earlier diagnosis of diabetes. V4C3T x MXene is used for the first time in the field of acetone detection in this work, hopefully opening up a path for the investigation of applications of MXene in gas sensors, and such exciting findings distinguish V4C3T x as a comparable material to the well-known Ti3C2T x . In addition, we used DFT calculations to explore the mechanisms that result in the superior selectivity for acetone with respect to water vapor. Hopefully, the proposed mechanisms combining experimental results and theoretical study will shed light on the design and production of new high-performance acetone sensors.

The computational design of junctions between carbon nanotubes and graphene nanoribbons.

Using first-principles density functional theory calculations, various junction models constructed from different carbon nanotube and graphene nanoribbon units via covalent linkage have been envisioned. These models consist of linear, T- and H-shaped junctions within the connection modes between carbon nanotube and graphene nanoribbon units. The electronic transport properties of different junctions have been systematically investigated by using the non-equilibrium Green's function. The simulation results suggested that the proposed models are promising for future applications in novel nanoelectronics.