Light-intensity switch enabled nonsynchronous growth of fluorinated raspberry-like nanoparticles

Raspberry-like (RB) nanoparticles hold potential for diverse applications due to their hierarchical morphology. Here we developed a novel tandem synthetic approach of nonsynchronous growth based on photo-mediated reversible-deactivation radical polymerization, enabling simple, efficient and bottom-up synthesis of RB nanoparticles of uniform sizes at quantitative conversions of fluorinated monomers. Chain transfer agents of different chain lengths, concentrations and chemical compositions were varied to tune the diameter of RB particles. Importantly, fluorinated RB nanoparticles obtained with this method allow facile post modifications via both covalent bond formation and intermolecular physical interactions without disrupting the RB morphology. The facile nature of this method and versatility of the obtained fluorinated RB materials open new opportunities for the development of functional materials using nanoparticles.

Nonsynchronous growth of raspberry-like (RB) nanoparticles in a one-pot and bottom-up fashion, enabling simple post-modification of RB colloids through both covalent bond formation and supramolecular interaction.     

Heteroborospherene nanoclusters as high-performance nonlinear optical materials

Today, the design of new compounds with giant nonlinear optical responses is attracted to many researchers. Inspired by an interesting finding of a new class of heteroborospherenes which were formed by doping four carbon atoms in the B364- nanocluster (C4B32), we suggest the alkali metal-doped C4B32 (M@C4B32, M=Li, Na, and K) nanoclusters as high-performance nonlinear optical materials. Our results show that the alkali metal atoms have a considerable effect on the structural and electronic properties of the C4B32 nanocluster. We found that the doping alkali metal can remarkably decrease the HOMO-LUMO gap and significantly increases the first hyperpolarizability of the C4B32 nanocluster. Also, our results reveal that the first hyperpolarizability of the M@C4B32 nanoclusters can be progressively enhanced by increasing the atomic number of alkali metals. The effect of external electric fields on the nonlinear optical responses of the M@C4B32 has been systematically explored. We found that the first hyperpolarizability of the M@C4B32 compounds can be gradually increased by increasing the imposed external electric field from zero to the critical external electric field along the charge transfer direction (M→C4B32). Accordingly, this work presents an efficient strategy to improve the nonlinear optical responses of the heteroborospherenes.     

Glassy carbon electrode modified with gold nanoparticles and hemoglobin in a chitosan matrix for improved pH-switchable sensing of hydrogen peroxide

Hemoglobin (Hb) has been demonstrated to endow electrochemical sensors with pH-switchable response because of the presence of carboxyl and amino groups. Hb was deposited in a chitosan matrix on a glassy carbon electrode (GCE) that was previously coated with clustered gold nanoparticles (Au-NPs) by electrodeposition. The switching behavior is active (“on”) to the negatively charged probe [Fe(CN)₆ ³⁻] at pH 4.0, but inactive (“off”) to the probe at pH 8.0. This switch is fully reversible by simply changing the pH value of the solution and can be applied for pH-controlled reversible electrochemical reduction of H₂O₂ catalyzed by Hb. The modified electrode was tested for its response to the different electroactive probes. The response to these species strongly depends on pH which was cycled between 4 and 8. The effect is also attributed to the presence of pH dependent charges on the surface of the electrode which resulted in either electrostatic attraction or repulsion of the electroactive probes. The presence of Hb, in turn, enhances the pH-controllable response, and the electrodeposited Au-NPs improve the capability of switching. This study reveals the potential of protein based pH-switchable materials and also provides a simple and effective strategy for fabrication of switchable chemical sensors as exemplified in a pH-controllable electrode for hydrogen peroxide.

A pH “on-off” switchable nanobiosensor was fabricated by casting a chitosan-hemoglobin biocomposite onto nano-gold electrode. This composite film exhibits not only excellent pH-responsive on (pH 4.0)-off (pH 8.0) behavior but also excellent pH-tunable on-off bioelectrocatalysis of H₂O₂.

     

Experimental Study on Purification of Diesel Particulate Matter by Non-thermal Plasma Technology

In order to investigate the effects of non-thermal plasma (NTP) on diesel particulate matter (PM), an engine test bench was built up. An engine exhaust particle sizer (EEPS) was introduced to analyze the emission concentration and size distribution of PM and a thermo-gravimetric analyzer was used to analyze the effects of NTP on the composition of the particulate matter in the exhaust gas. The results show that the size distribution interval of the particle mass concentration falls behind that of the quantity concentration under various loads. When the diesel engine operating speed is 2400 rpm and the load is 25%, after NTP, the proportions of the nucleation mode particles and the accumulative mode particles exhibit a small fluctuation while the proportion of ultrafine particles decreases by 10% due to their large quantity concentration. Under the dual effect of DPF and NTP, the particle quantity concentration decreases by 98%. In order to investigate the effect of NTP on the composition of the PM, a thermo-gravimetric analysis of the particles obtained before and after NTP was carried out. The results show that the proportion of volatile matter falls by 16.05% and solid carbon accounts for an increase of 7.29%. NTP has the ability to improve reduction activity of particles and make particles easier to be oxidized at a lower temperature.     

The effects of counter anions on the dynamic mechanical response in polymer networks crosslinked by metal–ligand coordination

Metal–ligand coordination has been proven to be an attractive strategy to tune a polymer network's dynamic mechanical properties, such as self-healing ability. Nonetheless, the role of counter anions is often overlooked. To address this, a series of polydimethylsiloxane (PDMS) films crosslinked through lanthanide metal cations (Eu³⁺, Tb³⁺)–bipyridine interactions have been prepared and studied. Neutral 2,2'-bipyridine ligands were embedded into the linear polydimethylsiloxane (PDMS) chain through polycondensation. With nitrate ( ) as the coordinating anions, metal salts Eu(NO₃)₃ and Tb(NO₃)₃ were found to be ineffective crosslinkers. With noncoordinating anions, such as triflate (OTf^-: CF₃ ), metal salts Eu(OTf)₃ and Tb(OTf)₃ showed improved interaction strength with bipyridine ligands. Surprisingly, the addition of Eu(OTf)₃ and Tb(OTf)₃ salts also increased the d-spacing distances of the phase-segregated domains between metal–ligand complexes and the PDMS polymer backbone. For the Eu(OTf)₃-, Tb(OTf)₃-PDMS films, the much-improved self-healing abilities are attributed to the crosslinker dynamics and the enhanced chain mobility. This work underlines the importance of counter anions on the mechanical properties, and provides further guidance on the future design of self-healing metal−ligand crosslinked polymers.) © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3110–3116     

Design and synthesis of a Cu(II)-complex-based carbazole-hemicyanine hybrid for fluorescent sensing of H2S in SDS micellar solution

A novel fluorescent chemosensor HACBA with carbazole-hemicyanine fluorophore as signal reporter and N,N,N'-tri(2-pyridylmethyl)ethylenediamine (TPEA) as binding sites was designed and synthesized. Its assemblies with anionic surfactant sodium dodecyl sulfate (SDS) show improved fluorescence emission stability and enhanced fluorescence intensity. HACBA/SDS system can selectively recognize Cu²⁺, which led to a dramatic fluorescence quenching. The in situ resultant HACBA-Cu(II)/SDS ensemble functioned as a highly selective and sensitive sensor for H₂S with a turn-on fluorescent response. Our results show that the “on-off-on” molecular switch occured through the reversible formation-dissociation reaction between HACBA-Cu(II) complex and HACBA/CuS in the SDS micellar solution, and at least 3 cycles of on-off-on switches were observed.     

Ultrasensitive amperometric determination of PSA based on a signal amplification strategy using nanoflowers composed of single-strand DNA modified fullerene and Methylene Blue,and an improved surface-initiated enzymatic polymerization

The authors describe a signal amplification strategy for highly sensitive detection of the prostate-specific antigen (PSA). This is accomplished by a combination of two methods, viz. (a) improved surface-initiated enzymatic polymerization (SIEP), and (b) the use of nanoflowers prepared from C₆₀ fullerene and Methylene Blue (C₆₀/MB) modified with a long single-strand DNA. C₆₀/MB acts as a novel electrochemical indicator. The C₆₀/MB nanoflowers improve the load of MB and promote the electron transfer. The integration of the SIEP technique and the C₆₀/MB nanomaterial also results in improved loading of MB on the nucleic acid. Ultimately, dual cascade signal amplification is accomplished. The biosensor was constructed as follows: (a) Gold nanospheres were modified with antibody 2 (Ab₂) and a thiolated oligonucleotide (referred to as S₀). (2) S₀ is then extended by the SIEP reaction. (3) The redox indicator C₆₀/MB is then connected to the extended guanine-rich ssDNA which then yields the amperometric signal. (4) A sandwich immunoassay is performed by capturing the nanoprobe oy type Ab₂-Au-S₀ on the gold electrode modified with multi-walled carbon nanotubes (MWCNTs) and protein A. Current is measured by using differential pulse voltammetry (DPV). The synergic effect of the biofunctional nanomaterial and the signal amplification strategy greatly improves the performance of this immunoassay. Under optimized conditions and at a working voltage of typically ?0.18 V (vs Ag/AgCl), the assay has a linear range that extends from 15 pg·mL^?1 to 8 ng·mL^?1 of PSA. The detection limit is as low as 1.7 pg·mL^?1 (at an S/N ratio of 3). In our perception, this dual amplification scheme has a wide scope in that it may become applicable to numerous other immunoassays.

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Graphical abstract C₆₀/Methylene blue nanoflowers, a novel electrochemical indicator, connect with the long single-stranded DNA (ssDNA) extended by the improved surface-initiated enzymatic polymerization method. This amplification strategy is utilized to construct a sandwich prostate-specific antigen (PSA) immunosensor.

     

In situ synthesis of CdS/ZnS composite nanoparticles from ZIF-8 for visible light disposal of Cr(VI)

Journal of Sol-Gel Science and Technology - Zeolitic Imidazolate Framework (ZIF-8) micropolyhedra were employed as a raw material for the synthesis of fine cadmium sulfide/zinc sulfide (CdS/ZnS)...     

SYNTHESES,CRYSTAL STRUCTURES,AND ANTIMICROBIAL ACTIVITIES OF ZINC COMPLEXES DERIVED FROM 2-AMINO-N′- (PYRIDIN-2-YLMETHYLENE)BENZOHYDRAZIDE

Journal of Structural Chemistry - New zinc complexes, [ZnBr2(HL)] (1), [ZnBr(HL)(NCS)]·0.5H2O (2), [Zn(HL)I2] (3), and [ZnL2] (4), where L is the monoanionic form of...     

The cantilever strip plate under torision, bending or flexure at infinity

A homogeneous, isotropic plate occupies the region 0x ₁, |x ₂|a, |x ₃|h, where the ratio h/a is sufficiently small so that the classical theory of thin plate bending applies. The short end of the plate at x ₁=0 is clamped while the long sides are free. This cantilever plate is now loaded at x ₁=+ by an applied twisting moment, by a bending moment or by flexure. Despite the fundamental nature of these problems, and the long history of thin plate theory, no solutions are to be found in the existing literature that will determine (for instance) the important unknown resultants V ₁, M ₁₁ at the clamped end x ₁=0. The main reason for this is that this combination of boundary conditions leads to severe oscillating singularities of the field in the corners (0, ±a). The fact that such singularities must exist is widely known, but we present here for the first time a method of solution that takes these singularities fully into account.Our numerical results show that the values of M ₁₁, V ₁ on x ₁=0 bear little resemblance to those of the corresponding Saint-Venant solutions, which do not fully satisfy the boundary conditions at the clamped end. Indeed, significantly large values of these resultants were found at points far enough from the corners so as to be relevant in actual engineering applications. Also of interest are certain weighted integrals of M ₁₁, V ₁ which we calculate. These constants determine the effect of the clamping at large distances (greater than 4a, say) from the cla,ped end. At such distances, the effect of the clamping is merely to impose an additional rigid body deflection on the plate.Finally, we consider the plate of finite length. Provided that the aspect ratio is 2 or more, we give accurate approximate solutions for the torsion, bending or flexure of a finite plate clamped at both ends.