First-principles predictions of potential hydrogen storage materials: Novel sandwich-type ethylene dimetallocene complexes

The hydrogen storage capacities of a sandwich-type ethylene dimetallocene complex (Cp₂Ti₂C₂H₄) are studied using first-principles calculations. It is found that the TiC₂H₄Ti molecule can intercalate into the two cyclopentadienyl (Cp) rings and form a stable sandwich-type complex. Each Ti atom can adsorb a maximum of three H₂ molecules, which corresponds to a gravimetric storage capacity of 4.73 wt%. This hydrogen storage capacity is close to the 2015 target of 5.5% set by the US Department of Energy (DOE) in 2009. Furthermore, the Cp₂Ti₂C₂H₄ molecule proposed in this paper is favorable for both adsorption and desorption of hydrogen molecules at room temperature and ambient pressure because its average binding energy of 0.34 eV/H₂.     

Ethylthio-substituted sandwich phthalocyaninato europium (III) semiconductors for sensing NO2 and NH3: Effect of the extended π-conjugate systems on tuning the conductivity and sensing behavior

By using the π-conjugated phthalocyanine macrocycle as the versatile building block, a series of five sandwich-type ethylthio substituted phthalocyaninato europium complexes, namely double-decker Eu[Pc(SC₂H₅)₈]₂ (Pc-1), triple-decker Eu₂[Pc(SC₂H₅)₈]₃ (Pc-2), and their corresponding dimers, [Pc(SC₂H₅)₈]₂Eu₂[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-1), [Pc(SC₂H₅)₈]₃Eu₃[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-2) and [Pc(SC₂H₅)₈]₄Eu₄[BiPc(SC₂H₅)₁₂] (Pc-2@Pc-2), are synthesized and prepared into the solution-processed films by a simple quasi-Langmuir-Shäfer (QLS) method. Combination between the extending π-conjugated system in the longitudinal and transverse directions of Pc macrocycles and/or radical nature of Pc-1 unit among different semiconducting molecules result in unusually small energy gaps (0.345–0.91 eV). Consequently, all of the semiconductors exhibit excellent conductivities. Among these materials, the conductivity for the radical species Pc-1@Pc-1, Pc-1@Pc-2 and Pc-1 is about 3–4 times larger than that for the non-radical compounds Pc-2@Pc-2 and Pc-2. Moreover, the QLS films of five semiconductors take excellent linear responses for both oxidizing NO₂ (100–300 ppb) and reducing NH₃ (4–8.6 ppm). Respectively, the sensitivity (in % ppm⁻¹) gets increased in the order of Pc-1 < Pc-2 < Pc-1@Pc-1 < Pc-1@Pc-2 < Pc-2@Pc-2 for NO₂, and Pc-1@Pc-2 < Pc-1 < Pc-1@Pc-1 < Pc-2@Pc-2 < Pc-2 for NH₃. Depending on the highly extended π-conjugated systems, Pc-2@Pc-2 and Pc-2 films achieve the highest sensitivity of 208.2% ppm⁻¹ and 0.97% ppm⁻¹ to NO₂ and NH₃, respectively. In addition, with a less than 2 min response time within a limit of detection at 10 ppb for NO₂ and 0.48 ppm for NH₃, good reproducibility and selectivity have been revealed for the Pc-2@Pc-2 and Pc-2 films among the best gas sensors obtained so far for all the solution-processed films based on organic semiconductors in dry air at room temperature. More importantly, it is firstly demonstrated that the high NO₂ sensing is resulted from low Oxd₁, and high NH₃ sensing is resulted from high Red₁ among the sandwich Pc-based semiconductors.     

Development of a chemiluminometric immunosensor array for on-site monitoring of genetically modified organisms

Genetically modified organisms (GMOs) have been mainly developed for mass production of agricultural plants; however, there are concerns that transgenic crops might cause side effects on ecosystems and human beings. Therefore, to quantitatively trace the genetically modified products, we constructed a chemiluminometric immunosensor array for the detection of recombinant marker proteins expressed in GMOs, i.e., 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), neomycin phosphotransferase II (NPT II), and phophinothricin acethyltransferase (PAT). Monoclonal and polyclonal antibodies specific to each marker were raised, and the specificities and immunoreactivities to the respective markers were characterized. The capture antibodies were immobilized on predetermined regions of a glass slide where the sandwich-type immunoassays were carried out. Photodiodes were located on the bottom of the slide in an aligned arrangement to the immobilized antibody sites such that the light signals resulting from the immunoassays could be detected in situ. Under optimal conditions, the immunosensors were able to detect 1% GMO marked with EPSPS, which was the minimum content over the total content, and 3% GMOs labeled with NPT II or PAT. The sensor array developed in this study would be useful for measuring a particular GMO in a specimen containing unidentified species.     

Sandwich-type composite multilayer films of strontium titanate and barium strontium titanate and their controllable dielectric properties

It is a challenge to reduce the dielectric loss and increase the tunability of pure barium strontium titanate(BST)films for microwave tunable application because these two properties change simultaneously.Herein,a novel composite of strontium titanate(ST)and potassium-doped BST(KBST)has been designed as ST/KBST/ST sandwich-type film with various ST and KBST layers.X-ray diffraction patterns show that the film exhibits cubic perovskite polycrystalline structure composed of BST and ST phase,mainly grow along(110)crystal plane with average grain size of less than 20 nm and decreasing BST phase/ST phase ratio with increasing film thickness.Scanning electron microscope shows that no interfacial layer can be observed,indicating that ST and KBST are fully compounded.Low dielectric loss and high tunability at-10-10V and stable and excellent dielectric properties at 1 GHz are achieved,meeting the needs of microwave tunable application at high frequency.The surface structures are also studied by other analysis methods,and ST/MgBST/ST sandwich-type film is compared.     

A sandwich-type ELISA for the detection of Listeria monocytogenes using the well-oriented single chain Fv antibody fragment

Listeria monocytogenes (LM) poses a serious threat to public health. The present study details the development of a sandwich-type enzyme-linked immunosorbent assay (S-ELISA) for the detection of LM using well-oriented single chain Fv antibody fragment (scFv) and a polyclonal antibody. The anti-LM scFv, used as capture antibody, was gene-optimized and expressed with a C-terminal PS-tag in Escherichia coli BL21(DE3) for oriented-immobilization on hydrophilic polystyrene microtiter plates. The anti-LM rabbit polyclonal antibody, used as the detection antibody, was prepared using heat-killed LM cells as an immunogen. The developed S-ELISA showed great specificity to LM and had a detection limit of lg 6.5 CFU/mL, which was better than the control S-ELISA using non-oriented scFv as the capture antibody. When the S-ELISA was applied to pork and pasteurized milk samples spiked with LM, strong responses were observed. In conclusion, the developed S-ELISA shows great potential for the rapid detection of LM.     

Enhancement of an immunoassay using platinum nanoparticles and an optical detection

This study proposes a potentially rapid and effective immunoassay using antibody-platinum nanoparticles (Ab-PtNPs) conjugates as a message molecule and a flatbed scanner for the optical scanning and measuring of the immuno-reaction signal. The proposed immunoassay is a sandwich-type immunoassay (three-layer format) along with a silver enhancement reaction, and a signal amplification method was introduced to magnify the detected signal. The signal was the grayscale corresponded to the immuno-reaction, which determined the detection limit and reaction time. Results showed that the rapid silver precipitation phenomenon was catalyzed by Ab-PtNPs conjugates. The color change during the reaction was readily observed by the naked eye and analyzed by an optical flatbed scanner. The relationship between sample concentration and grayscale of signal is discussed. The detection limit (sandwich format assay) for the sample antigen was 0.1 ng/mL which is superior to the detection limit achieved via Au and Ag nanoparticles (AuNPs and AgNPs). Using an optical flatbed scanner, Ab-PtNPs conjugates and a silver enhancement reaction, a novel immunoassay has been constructed.     

Deep oxidative desulfurization of gas oil based on sandwich-type polysilicotungstate supported β-cyclodextrin composite as an efficient heterogeneous catalyst

In this work, in order to obtain deep clean gas oil, a novel organic-inorganic hybrid (n-C₄H₉)₄N)₇H₅Si₂W₁₈Cd₄O₆₈@β-cyclodextrin (abbreviated as TBA-SiWCd@β-CD) composite was synthesized by supporting quaternary ammonium salt of sandwich-type polysilicotungstate on β-cyclodextrin (TBA-SiWCd@β-CD) as an efficient catalyst for oxidative desulfurization (ODS) of gas oil. The successful composition of the materials explained by the formation of host-guest inclusion complex, which confirmed through FTIR, UV-vis, XRD, SEM, and EDX characterization analyses. Experimental results revealed that the levels of sulfur content and mercaptan compounds of gas oil lowered with 97% removal efficiency. Compared with the ODS treatment of gas oil, the TBA-SiWCd@β-CD composite showed an outstanding catalytic performance for the oxidation of dibenzothiophene (DBT) in the prepared model fuel. The main factors that influence the desulfurization efficiency and the kinetic study of the ODS process were investigated. The prepared heterogeneous catalyst was found to give remarkable reusability for five runs without a discernible decrease in its activity. This study suggested the potential application of the TBA-SiWCd@β-CD catalyst for removal of hazardous sulfur compounds from gas oil fuel.     

A zirconium-containing sandwich-type dimer based on trivacant α- and β-[GeW9O34] units, [Zr3O(OH)2(α-GeW9O34)(β-GeW9O34)]

A new zirconium-containing sandwich-type dimer based on trivacant α- and β-[GeW₉O₃₄]¹⁰⁻ units, [Zr₃O(OH)₂(α-GeW₉O₃₄)(β-GeW₉O₃₄)]¹²⁻, was synthesized and characterized by IR spectroscopy, UV electronic spectroscopy and single crystal X-ray diffraction. The central bent of the polyanion contains three oxygen atoms alternating with the three zirconium atoms. The polyanion represents a rare example of the sandwich POMs containing two different isomer subunits.     

Advances in gas sensors of tetrapyrrolato-rare earth sandwich-type complexes——Commemorating the 100th anniversary of the birth of Academician Guangxian Xu

In recent years,sandwich-type rare earth tetrapyrrole derivatives,have attracted more and more attention as material for conductimetric sensors.They have not only great chemical stability and processability,but also flexible molecular structure,which is a key to adjustable semiconductor properties.In this mini review,we focus mainly on the development of tetrapyrrolato-rare earth sandwich-type complexes as the semiconducting active layer in the gas sensors published in the last ten years(2010-2020).The main part includes two sections.In the single component gas sensing of sandwich rare earth tetrapyrrole complexes,we describe the influence factors of the single-component semiconducting active layer on the sensing performance of tetrapyrrolato-rare earth sandwich-type complexes,including substituents,central metals and π-conjugate systems.In the multi-component gas sensors,the synergistic effect between tetrapyrrolato-rare earth sandwich-type complex and other materials on improving sensitivity and conductivity has been discussed briefly.