Search

Studying the effect of morphology on the circularly polarized luminescence (CPL) of chiral molecular materials is important for the development of CPL-active materials for applications. Herein, we report that the morphology of Gd(NO3)3/R-,S-AnempH2 [AnempH2 = (1-anthrylethylamino)methylphosphonic acid] assemblies can be controlled by solvent modulation to form spiral bundles Gd(R-,S-AnempH)3·2H2O (R-,S-1), crystals Gd(R-,S-AnempH)3·2H2O (R-,S-2) and spindle-shaped particles Gd(R-,S-AnempH)3·3H2O·0.5DMF (R-,S-3) with similar chain structures. Interestingly, R-,S-1 are CPL active and show the highest value of dissymmetric factor among the three pairs of enantiomers (‖glum‖ = 2.1 × 10–3), which is 2.8 times larger than that of R-,S-2 , while R-,S-3 are CPL inactive with ‖glum‖ ≈ 0. This work provides a new route to control the morphology of chiral coordination polymers and improve their CPL performance. [ABSTRACT FROM AUTHOR]

Two double-stranded metallo-triangles, Dy9 and Dy24, with hexaple-C10H7PO32− bridges were constructed, and their magnetic properties were explored. Compared with the field-induced relaxation phenomenon of Dy9 templated with a chloride anion, Dy24 templated with a sodium cation exhibited zero-field single-molecule-magnet behavior. [ABSTRACT FROM AUTHOR]

The coexistence of spin–orbit coupling and piezoelectricity in a single material may have potential application in multifunctional devices, including spintronics, nanorobotics and piezotronics. Spin–orbit coupling provides a new means to manipulate electron's spin without an additional external magnetic field, while piezoelectricity refers to the interplay between mechanical stresses and electric polarization. Using first-principles calculations, the structural, electronic, optical, spin, and piezoelectric properties of the Janus Ge2XY (X ≠ Y = P, As, Sb, and Bi) monolayers were systematically investigated. All the Ge2XY are energetically and dynamically stable in the α phase. At the GW level, Ge2AsSb, Ge2AsBi, and Ge2SbBi have direct fundamental band gaps of 0.65, 0.64, and 0.91 eV. At the GW + BSE level, their optical gaps are 0.42, 0.45, and 0.63 eV, and the optical absorption coefficients can reach about 10−5 cm−1 in the infrared light region, which reveals that they have potential for application in infrared photodetectors. For Ge2PBi, Ge2AsBi, and Ge2SbBi containing the heavy Bi element, the lowermost conduction band and uppermost valence band have large spin splitting along the M–K and K–Γ lines, and the bands near the Fermi level possess Rashba spin splitting at the Γ point. Ge2PBi and Ge2SbBi have both large in-plane piezoelectric coefficients d11 (−0.75 and −3.18 pm V−1) and out-of-plane piezoelectric coefficients d31 (0.37 and 0.30 pm V−1). Our findings are helpful to understand the mechanism of the spin–orbit physics and piezoelectricity of Janus Ge2XY monolayers and guide experiments in exploring novel multifunctional materials. [ABSTRACT FROM AUTHOR]

Laser-induced Fe3O4 nanoparticle-modified three-dimensional macroporous graphene is fabricated as a near-infrared light responsive nanozyme via a facile and in situ laser-scanning method under ambient conditions for the first time, showing an excellent catalytic–photothermal synergetic bactericidal ability under a low dose of H2O2 (0.1 mM) and short irradiation time (5.0 min). [ABSTRACT FROM AUTHOR]

The elaborate collocation of a layered structure employing sodium dysprosium 1-naphthylphosphonate and a flexible monopyrazinyl hydrazone molecular tool reacting with (E)-N′-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide results in the formation of a cut heterometallic hendecanuclear cluster {Na5Dy6(O3PC10H7)5(μ3-opch)6(H2O)4}·2.0CH3OH·0.5H2O (1) and a recombined two-dimensional Archimedean topology {Na4Dy8(O3PC15H11)8(μ4-opch)2(μ3-opch)2(μ3-O)2(μ2-O)2(AcO)2(H2O)3(CH3OH)2}∞·1.5CH3OH·5.5H2O (2). This all-encompassing synthetic approach is the first report of a recombinant layer sodium dysprosium phosphonate through the triple N-bridges of pyrazinyl groups. Both exhibit slow relaxation phenomena at low temperatures. [ABSTRACT FROM AUTHOR]

Constructing chiral luminescent systems with both large luminescence dissymmetry factor (glum) and high luminous efficiency has been considered a great challenge. We herein describe a highly efficient approach to sterically stabilize the helical configurations of carbo[5]helicenes for improved CPL properties in a series of π-donor and π-acceptor substituted [5]helicenes (1, 2, 3, 4 and 5). Enabled by the ortho-installation of methyl groups as well as the steric effects of triarylamine (Ar3N) and triarylborane (Ar3B) handles in meta-substituted [5]helicenes, their optical resolution into enantiomers has been accomplished using preparative chiral HPLC. The molecular chirality of [5]helicenes can be transferred to Ar3B and Ar3N as light emitters, which allowed further investigations of their chiroptics, including optical rotation, circular dichroism (CD) and circularly polarized luminescence (CPL). Remarkably, 4 has been demonstrated to display dramatically enhanced CPL performance with a much larger glum (>1.2 × 10−2) and an increased emission quantum efficiency (ΦS = 0.75) compared with the other analogues, as a result of the isomeric tuning of substitutions with differential steric and electronic effects. These experimentally observed CPL activities were rationalized by TD-DFT computations for the angle (μ,m) between electric and magnetic transition dipole moments in the excited states. In addition, the conspicuous intramolecular donor–acceptor charge transfer led to thermal responses in the emissions of 2 and 4 over a broad temperature range. [ABSTRACT FROM AUTHOR]

Vertically stacking two-dimensional materials into van der Waals (vdW) heterostructures (HS) is deemed to be an effective strategy to tailor their physical properties and enrich their applications in modern nanoelectronics. Here, we study the geometry, electronic, and optical properties of Janus Ga2SeTe/In2SSe heterostructures by using first-principles calculations. We consider four models of Ga2SeTe/In2SSe heterostructures with an alternative chalcogen atom layer sequence and five potential stacking configurations, and find that the most energy favorable stacking pattern is AB stacking for each model. The heterostructures form type II alignment with a direct band gap. Moreover, the band gap values are highly dependent on the magnitude of the electric dipole, which is related to the sublayer intrinsic dipole direction and interface charge transfer. Additionally, the optical absorption of the heterostructures is intensified in the visible and ultraviolet regime. Furthermore, we predict two heterostructures with the band edge straddling the water redox potential level. These findings can help in understanding the tailored properties of the heterostructures based on Janus two-dimensional materials, and guide experiments in designing novel optoelectronic devices. [ABSTRACT FROM AUTHOR]

This paper reports a quasilinear hydrazone-based mononuclear dysprosium(III) compound, namely, {Dy(Hppyh)2(SCN)3}·2MeOH (I), where Hppyh is pyrazine-2-carboxylic acid pyridin-2-ylmethylene-hydrazide. Compound I behaves as a single-ion magnet (SIM) based on the optimal dc field application of 0.7 kOe, showing a complex magnetic relaxation phenomenon with a tunneling relaxation time of 6.1 ± 0.3 × 10−3 s and an effective spin reversal barrier of 22.6 ± 1.1 K for the low- and high-frequency regions, respectively. More importantly, detailed comparative experimental and theoretical investigations reveal that the complex magnetic relaxation was most likely associated with the single DyIII ion behavior as well as the short-range intermolecular magnetic dipolar interactions. [ABSTRACT FROM AUTHOR]

This paper reports two closely related heteropentanuclear manganese complexes, namely, {Na2Mn3(opch)3(μ4-O)(μ2-N3) (μ2-AcO)(μ2-MeO)}·6CH3OH·0.5H2O (1) and {Na2Mn3(opch)3(μ4-O)(μ2-N3)2(μ2-AcO)}·2.5CH3OH·2H2O (2), where H2opch is (E)-N′-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide. Single-crystal X-ray diffraction analysis reveals that the trigonal bipyramidal skeletons in both complexes are comparable, where a perfect triangular Mn3 motif occupies the equatorial plane. Magnetic investigations suggest that overall antiferromagnetic coupling is present within the triangles of 1 and 2. However, their dynamic magnetic properties are drastically distinct. Indeed, complexes 1 and 2 show two kinds of dual slow magnetic relaxation processes that correspond to anisotropy barriers (Δ) of 9.2 cm−1 (11.4 cm−1 for 2) and 12.8 cm−1 (30.0 cm−1 for 2) for the low- and high-frequency domains, respectively. More importantly, a further comparative study of the structure and magnetism indicates that the coordination sphere of these two model complexes with the homologous hydrazone-based coordination sites undergoes an alteration from methoxide-O to azide-N upon a subtle change of the auxiliary anion accompanied by modulating octahedron geometries, leading to a further influence on different relaxation dynamics. [ABSTRACT FROM AUTHOR]

Three Mn-MOFs {[Mn3(μ4-L)2(H2O)7]·4H2O}n (1), {[Mn3(μ5-L)2(H2O)6]·4H2O}n (2) and {[Mn3(μ7-L)2(H2O)2]}n (3) (H3L = 5-(6-carboxypyridin-3-yl)isophthalic acid) were obtained under different reaction times and temperatures. Interestingly, induced by reaction time, compound 1 can lose one water molecule and SC–SC transform into compound 2. Similarly, compound 2 can also SC–SC transform into 3. Studies on two SC–SC transformation processes were carried out and the transformation mechanisms were deduced, which were verified by TG analyses. Different numbers of water molecules in the three compounds resulted in different coordination environments of the metal cation, coordination modes of the L3− ligand, continuities of hydrogen bonds, dimensions of framework and porosities. The AC impendence spectra studies revealed that compounds 1–3 can enhance the proton conductivities of the Nafion composite membrane to about 47.77%, 36.88% and 21.28%, respectively. It is speculated that the highest proton conductivity of compound 1 may be due to its continuous hydrogen bond chain and highest water uptake, which were mainly decided by the number of water molecules. [ABSTRACT FROM AUTHOR]

Four low dimensional MOFs, {[Mn3(L)2(bipy)2]}n (1), {[Mn3(L)2(phen)2]}n (2), {[Co3(L)2(phen)(H2O)8]·4H2O}n (3) and {[Ni3(L)2(H2O)12]·4H2O}n (4) (H3L = 5-(3′,5′-dicarboxyphenyl) nicotinic acid; bipy = 2,2′-bipyridine; phen = phenanthroline) have been synthesized and characterized. For compounds 1 and 2, Mn(II) cations were connected by L3− ligands to form 2D layered structures. Their crystal structures contained a high proportion of bipy or phen chelated ligands and no water molecules or hydrogen bonds. For compound 3, metal cations were connected to form a 1D coordination chain, the proportion of phen was reduced and some water molecules as terminal ligands occupied partly the coordination sites of metal cations. Hydrogen bonds, existing among water molecules and carboxyl groups, were discontinuous in compound 3. In the structure of compound 4, Ni(II) cations were linked to form a 2D layered structure. There was no phen ligand, more water molecules acted as the terminal ligands and were involved in the formation of continuous hydrogen bonds. The studies of proton conductivity showed that compounds 1 and 2 had little contribution to the proton conductivities of the composite membranes; while compounds 3 and 4 can enhance the proton conductivities of composite membranes by about 29.70% and 50.00% higher than that of pure Nafion. The highest proton conductivity of 4/Nafion may be caused by its highest water uptake and continuous hydrogen bonds, which were affected by the amount of water molecules. Analysis of the structure–property relationship revealed that the smaller the proportion of the chelated ligand, the more water molecules in the compound, which increased the chance of forming continuous hydrogen bonds, enhanced the water absorption ability, and improved the proton conductivity of the compound. [ABSTRACT FROM AUTHOR]

{Dy16(μ6-C10H7PO3)2(μ5-C10H7PO3)8(spch)8(μ3-OH)2(μ2-OH)2(μ2-AcO)6(μ3-COO)2(DMF)2(H2O)6}·0.5CH3OH·4.5H2O (1) and {Dy16(μ5-C10H7PO3)4(μ3-C10H7PO3)12(μ2-C10H7PO3H)8(opch)4(DMF)8(MeOH)4}·2.5CH3OH·3H2O (2), where H2spch is ((E)-N′-(2-hydroxybenzylidene)pyrazine-2-carbohydrazide, C10H7PO3H2 is 1-naphthylphosphonic acid and H2opch is (E)-N′-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide, were successfully synthesized by varying the hydrazone ligands in the Dy-phosphonate system. It is important that the ellipsoidal core experiences a ring forming structural transformation to the supramolecular square motif upon the incorporation of an ortho-methoxy substituent into the hydrazone. Alternating-current (ac) magnetic susceptibility studies of 1 and 2 suggest that similar single molecule magnet behaviors occur for these two complexes. The result represents an effective molecular assembly tactic to develop highly complicated lanthanide coordination clusters through the multicomponent self-assembly of the coalescence of phosphonate- and hydrazone-based ligands and metal salts. [ABSTRACT FROM AUTHOR]

Five isostructural metal–organic frameworks, [M1.5(L)(bpy)(DMF)]·H2O (M = Mn(1), Co(2), Ni(3), Zn(4), Cd(5); L = 3-(3,5-dicarboxylpheny)-5-(3-carboxylphenyl)-1H-1,2,4-triazole, bpy = 2,2′-bipyridine) have been synthesized and characterized. The same structure and similar proton transfer pathway of these compounds offer the chance to explore the relationship between the structure and the proton conductivity deeply and precisely. It is found that the conductivities of compounds 1–5 are very different and adopt the order 1 (Mn2+) > 4 (Zn2+) > 5 (Cd2+) > 2 (Co2+) > 3 (Ni2+). In order to explore the main reason for this difference, the influencing factors on proton conduction, such as morphology, water absorption, proton density, mobility of proton carrier, and acidity of all compounds have been studied via SEM, water uptake tests, and theory calculations, respectively. The results suggest that all compounds display a similar morphology, water absorption, proton density, and mobility of the proton carrier. The Gaussian calculations reveal that the acidities of these compounds are very different. This may be caused by the different coordination ability between the metal cations and the L3− ligand. The order of acidities of the compounds is very consistent with that of the proton conductivity, which suggests that the acidity is the deciding factors of the proton conduction of this series MOFs. [ABSTRACT FROM AUTHOR]

We report a label-free and "signal-on" homogeneous photoelectrochemical cytosensing system for ultrasensitive detection of cancer cells, which is a truly homogeneous PEC cytosensing system without the photoactive material immobilization and target recognition probe modification, providing a new avenue in early and accurate cancer diagnosis and clinical analysis. [ABSTRACT FROM AUTHOR]

We developed a label-free homogeneous photoelectrochemical biosensing strategy based on the synergy of G-quadruplex/hemin catalysed electron donor consumption and the inner filter effect for highly selective and sensitive microRNA assay. [ABSTRACT FROM AUTHOR]

We developed an aptamer recognition-trigged label-free homogeneous electrochemical biosensing method for highly selective and ultrasensitive detection of cancer-derived exosomes. [ABSTRACT FROM AUTHOR]

In typical photoelectrochemical (PEC) biosensing assays, electrodes are generally modified with photoactive probes and/or target recognition probes, which makes the processes complicated, time-consuming, and difficult to achieve excellent reproducibility. Hence, to overcome such shortcomings, we propose here an immobilization-free and label-free PEC aptasensor using solution-phase methylene blue (MB) as the PEC signal probe. Based on the unique T–Hg2+–T base pairs, and the diffusivity difference between free MB molecules and the MB/G-quadruplex composite towards the ITO electrode surface with negative charge, the “signal-off” approach for Hg2+ detection is developed. In the presence of target Hg2+, via the T–Hg2+–T bond formation, the two sticky ends of the hairpin DNA probe form a rigid duplex stem, which triggers the exonuclease III-facilitated target cycling amplification, and the formation of multiple G-quadruplexes. Upon the intercalation of MB in G-quadruplexes, significantly decreased photocurrent is obtained owing to the increased electrostatic repulsion between the MB/G-quadruplex composite and the ITO electrode. Therefore, highly sensitive and ultrasensitive Hg2+ determination is achieved, with a low detection limit of 1.2 pM, well below the maximum allowable Hg2+ level in drinking water defined by the WHO, China's Ministry of Health, and the US EPA. Due to the avoidance of sophisticated electrode modification and recognition probe immobilization processes, as well as an expensive labeling procedure, the PEC aptasensor proposed here demonstrates the advantages of simplicity, good reproducibility, rapidness and low cost. [ABSTRACT FROM AUTHOR]

Herein, a light-driven, membrane-less and mediator-less self-powered cytosensing platform via integration of biofuel cells (BFCs) and a photoelectrochemical strategy was developed for ultrasensitive detection of circulating tumor cells (CTCs). To construct cytosensors, an elaborately designed SH-Sgc8c aptamer/AuNP/g-C3N4 photoelectrode was used as an alternative anode for glucose oxidation, avoiding the introduction of anodic enzymes. Initially, glucose could favorably reach the photoanode surface and be easily oxidized by the photogenerated holes, while the photogenerated electrons would transfer to the biocathode and achieve biocatalytic reduction of O2, leading to a high EOCV. However, in the presence of CTCs, they could preferentially interact with the Sgc8c aptamer via specific recognition, and then complexes with large steric hindrance were immobilized on the photoanode surface, which could greatly affect the electron transfer between glucose and the photoanode surface. In this case, the EOCV decreased sharply. Encouragingly, this self-powered cytosensor exhibited an ultrasensitive response to the target CTCs in a wide concentration range from 20 to 2 × 105 cells mL−1 with a low detection limit of 10 cells mL−1 (S/N = 3), being superior to those of the reported methods. Moreover, this as-proposed self-powered cytosensor integrated with a photoelectrochemical strategy possessed unique advantages of not requiring an external power source, being anodic enzyme-free, having a simple construction process, facile miniaturization, and high selectivity and sensitivity, providing a promising and powerful tool for fundamental biochemical research and clinical diagnosis. [ABSTRACT FROM AUTHOR]

The double chloride-bridged dimer of a dinuclear dysprosium(iii) single-molecule magnet (SMM) was successfully isolated by assembling centrosymmetric dinuclear Dy2 SMMs. Such structural transformation involves the generation and cleavage of chloride bridges and leads to consecutive transformations of one- and two-step slow relaxation of magnetization. [ABSTRACT FROM AUTHOR]

In molecular logic gates, the occurrence of erroneous procedures is a frequently encountered and critical problem in data transmission, and thus it is highly desirable to develop novel logic systems with self-correction abilities. Herein, based on the horseradish peroxidase (HRP)-like activity of the novel metal coordination polymer nanoparticles formed between Cu2+ and guanosine monophosphate (GMP), denoted as Cu–GMP CPNs, a label-free visual platform was constructed and successfully utilized for both self-correcting logic gate construction and sensitive biosensing. The HRP-mimicking ability of Cu–GMP CPNs was verified and utilized for the sensitive detection of both H2O2 and glucose. More importantly, a set of logic gates (AND, OR, NOR, INHIBIT, and XNOR) were fabricated, in which two intermediate outputs, i.e., color change and precipitate formation, were combined in an “AND” mode to produce the final output, and thus the as-proposed logic system exhibited the self-correction ability to automatically correct the erroneous intermediate outputs induced by interfering substances such as HRP. Moreover, in addition to the unique feature of self-correction, the as-proposed logic system also exhibited the advantages of simple operation, rapid response and easy detection of the visual outputs by the naked eye, thus expanding its practical applications to a variety of fields. Therefore, the label-free visual platform we have proposed here offers a promising strategy for logic gate fabrication and may pave the way for the development of novel molecular computing with self-correction abilities. [ABSTRACT FROM AUTHOR]

Novel nanocomposites fabricated by incorporating different types of nanomaterials, especially inorganic and organic nanomaterials, have attracted much attention, and shown promising prospects in the applications in biological research fields. Herein, we propose a facile method to synthesize a novel three-layered SiO2@Au nanoparticle@polyaniline nanocomposite, which exhibited excellent electrical conductivity and good dispersibility in water. The as-proposed nanocomposite has been adopted to construct the modified electrode SiO2@AuNP@PANI/CS/GCE, which was characterized by electrochemical impedance spectroscopy and cyclic voltammetry, and demonstrated excellent electrochemical behaviors in neutral and even alkaline media, making it suitable for sensing species in biological fluids under physiological conditions. Moreover, the SiO2@AuNP@PANI/CS/GCE exhibited excellent catalytic activity towards the electro-oxidation of uric acid (UA) and ascorbic acid (AA), and a difference of 384 mV between the oxidation potentials for UA and AA was obtained, which is large enough for the selective and simultaneous determination of UA and AA in a binary mixture. Thus, the modified electrode has been successfully adopted for the simultaneous electrochemical detection of UA and AA, and the detection limits of 2 μM and 6 μM were obtained, respectively. [ABSTRACT FROM AUTHOR]

A novel enzyme inhibition-based homogeneous electrochemical biosensing strategy was designed for an organophosphorus pesticide assay based on exploiting the resistance of a mercury ion-mediated helper probe (HP) toward nuclease-catalyzed digestion and the remarkable diffusivity difference between HPs and the mononucleotides toward a negatively charged indium tin oxide (ITO) electrode. In particular, the mercury ion-mediated T–Hg2+–T base pairs facilitate the HP labeled with methylene blue (MB) to fold into a hairpin structure, preventing its digestion by exonuclease I, and thus resulting in a low electrochemical response because of the large electrostatic repulsion between the negatively charged ITO electrode and the HPs. The competitive binding by a thiol group (–SH), produced in the hydrolysis reaction of acetylthiocholine (ACh) chloride with acetylcholinesterase (AChE), removes mercury ions from the base pairs, causing a nuclease-catalyzed digestion, and the subsequent electrochemical response increase due to the weak electrostatic repulsion between the product-mononucleotides and the ITO electrode. Mercury ion-mediated HPs were first designed for pesticide detection and diazinon was chosen as the model target. Under the optimal experimental conditions, the approach exhibited high sensitivity for diazinon detection with a detection limit of 0.25 μg L−1. The satisfactory results in the determination of diazinon in real samples demonstrate that the method possesses great potential for detecting organophosphorus pesticides. This new approach is expected to promote the exploitation of mercury-mediated base pair-based homogenous electrochemical biosensors in biochemical studies and in the food safety field. [ABSTRACT FROM AUTHOR]

A novel aggregation induced emission amphiphile is constructed, containing a tetraphenylethene hydrophobic moiety connected to a hydrophilic quarternary ammonium salt. Owing to an ultra low critical micelle concentration in water, the amphiphile tends to self assemble into well-defined organic nanoaggregates that exhibit intense fluorescence, stable dispersibility in dilute solutions, and excellent biocompatibility for cell imaging. [ABSTRACT FROM AUTHOR]

Herein, a highly sensitive and versatile homogeneous electrochemical biosensing strategy is proposed, based on the split aptamer-incorporated DNA three-way junction and the exonuclease (Exo) III-assisted target recycling. The aptamer of adenosine triphosphate (ATP, chosen as the model analyte) is split into two fragments and embedded in single-stranded DNA1 and DNA2, respectively. ATP specifically binds with the split aptamers, bringing DNA1 and DNA2 close to each other, thus inducing the DNA three-way junction formation through the partial hybridization among DNA1, DNA2 and the methylene blue-labelled MB-DNA. Subsequently, MB-DNA is specifically digested by Exo III, releasing a MB-labelled mononucleotide, as well as a DNA1–ATP–DNA2 complex, which acts as the recycled target and hybridizes with another intact MB-DNA to initiate the subsequent cycling cleavage process. As a result, large amounts of MB-labelled mononucleotides are released, generating a significantly amplified electrochemical signal toward the ATP assay. To the best of our knowledge, it is the first example to successfully incorporate split aptamers into DNA three-way junctions and to be adopted in a homogeneous electrochemical assay. In addition to high sensitivity, this strategy also exhibits the advantages of simplicity and convenience, because it is carried out in a homogeneous solution, and sophisticated electrode modification processes are avoided. By simply changing the sequences of the split aptamer fragments, this versatile strategy can be easily adopted to assay a large spectrum of targets. Due to its advantages of high sensitivity, excellent selectivity, versatility and simple operation, the as-proposed approach has great potential to be applied in biochemical research and clinical practices. [ABSTRACT FROM AUTHOR]

Alkaline phosphatase (ALP), a class of enzymes that catalyzes the dephosphorylation of a variety of substrates, is one of the most commonly assayed enzymes in routine clinical practice, and an important biomarker related to many human diseases. Herein, a facile and highly sensitive homogeneous electrochemical biosensing strategy was proposed for the ALP activity detection based on single molecular beacon-initiated T7 exonuclease-assisted signal amplification. One 3′-phosphorylated and 5′-methylene blue (MB) labeled hairpin probe (HP) is ingeniously designed. In the presence of ALP, the dephosphorylation of HP, the subsequent Klenow fragment (KF) polymerase-catalyzed elongation and T7 exonuclease-catalyzed digestion of the duplex stem of HP take place, releasing MB-labeled mononucleotides and the trigger DNA (tDNA). tDNA then hybridizes with another HP and initiates the subsequent cycling cleavage process. As a result, a large amount of MB-labeled mononucleotides are released, generating a significantly amplified electrochemical signal toward the ALP activity assay. A directly measured detection limit as low as 0.1 U L−1 is obtained, which is comparable to that of the fluorescence method and up to three orders of magnitude lower than that of the immobilization-based electrochemical strategy previously reported. In addition to high sensitivity and good selectivity, the as-proposed strategy also exhibits the advantages of simplicity and convenience, because the assay is carried out in the homogeneous solution phase and sophisticated electrode modification processes are avoided. Therefore, the homogeneous electrochemical method we proposed here is an ideal candidate for ALP activity detection in biochemical research and clinical practices. [ABSTRACT FROM AUTHOR]

In the present study, a versatile “signal-on” electrochemical aptasensor based on a triple-helix molecular switch has been developed. An aptamer probe is designed to hybridize with the methylene blue (MB)-modified DNA capture probe immobilized on the gold electrode to form rigid triple-helix DNA, impeding the efficient electron transfer of MB to the electrode and resulting in the decreased oxidation peak current of MB. However, upon introduction of the perfectly matched target, for example, human α-thrombin (Tmb), the interaction between Tmb and the aptamer probe leads to the dissociation of the triple-helix DNA structure and thereby liberates the MB-modified end of the capture probe, allowing the MB to collide with the electrode surface and resulting in an increase of the oxidation peak currents of MB. Therefore, the sensitive signal-on detection of Tmb is realized, and the detection limit of Tmb is 0.12 nM. The proposed approach also demonstrates excellent regenerability, reproducibility and stability. Additionally, it also has the advantages of simplicity in design and easy operation. The success in the present biosensor provides a promising alternative to the electrochemical detection of a variety of analytes and may have potential applications in point-of-care testing and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Two Mn(II) complexes with azide and a new zwitterionic tetracarboxylate ligand 1,2,4,5-tetrakis(4-carboxylatopyridinium-1-methylene)benzene (L¹), {[Mn5(L¹)2(N3)8(OH)2]·12H2O}n (1) and {[Mn5(L¹)2(N3)8(H2O)2]- (ClO4)2·6H2O}n (2), have been synthesized and characterized crystallographically and magnetically. 1 and 2 contain similar alternating chains constructed by azide and carboxylate bridges. The independent sets of bridges alternate in an ABCCB sequence between adjacent Mn(II) ions: (EO-N3)2 double bridges (EO = end-on) (denoted as A), [(EO-N3)(OCO)2] triple bridges (denoted as B) and [(EO-N3)(OCO)] double bridges (denoted as C). The alternating chains are interlinked into 2D coordination networks by the tetrapyridinium spacers. Magnetic studies demonstrate that the magnetic coupling through the double EO azide bridges is ferromagnetic and that through mixed azide/carboxylate bridges is antiferromagnetic. The unprecedented F/AF/AF′/AF′/AF coupling sequence along the chain dictates an uncompensated ground spin state (S = 5/2 per Mn5 unit) and leads to one-dimensional topological ferrimagnetism, which features a minimum in the χT versus T plot. [ABSTRACT FROM AUTHOR]

In this article, a series of isoindoline–benzazole-based boron difluoride complexes (7–12) were synthesized and characterized. Analysis of the X-ray crystal structures of compounds 7, 8 and 10–12 indicates the existence of π–π stacking and H-bond (F–H–C, O–H–N, N–H–C) interactions. These novel boron complexes exhibit large Stokes shifts (3300–8400 cm−1) and moderate quantum yields (0.15–0.64). Time-dependent DFT (TD-DFT) calculations reveal that the maximum absorption bands for 7–12 are attributed to the HOMO → LUMO transitions, and that the calculated absorption wavelengths agree well with the experimental trends. [ABSTRACT FROM AUTHOR]

A simple, label-free and colorimetric method for coralyne detection was successfully established based on the coralyne-induced formation of split G-quadruplex–hemin DNAzyme. It can achieve a detection limit of 31 nM toward coralyne with excellent selectivity. [ABSTRACT FROM AUTHOR]

The coexistence of spin-orbit coupling and piezoelectricity in a single material may have potential application in multifunctional devices, including spintronics, nanorobotics and piezotronics. Spin-orbit coupling provides a new means to manipulate electron's spin without an additional external magnetic field, while piezoelectricity refers to the interplay between mechanical stresses and electric polarization. Using first-principles calculations, the structural, electronic, optical, spin, and piezoelectric properties of the Janus Ge 2 XY (X ≠ Y = P, As, Sb, and Bi) monolayers were systematically investigated. All the Ge 2 XY are energetically and dynamically stable in the α phase. At the GW level, Ge 2 AsSb, Ge 2 AsBi, and Ge 2 SbBi have direct fundamental band gaps of 0.65, 0.64, and 0.91 eV. At the GW + BSE level, their optical gaps are 0.42, 0.45, and 0.63 eV, and the optical absorption coefficients can reach about 10 -5 cm -1 in the infrared light region, which reveals that they have potential for application in infrared photodetectors. For Ge 2 PBi, Ge 2 AsBi, and Ge 2 SbBi containing the heavy Bi element, the lowermost conduction band and uppermost valence band have large spin splitting along the M - K and K - Γ lines, and the bands near the Fermi level possess Rashba spin splitting at the Γ point. Ge 2 PBi and Ge 2 SbBi have both large in-plane piezoelectric coefficients d 11 (-0.75 and -3.18 pm V -1 ) and out-of-plane piezoelectric coefficients d 31 (0.37 and 0.30 pm V -1 ). Our findings are helpful to understand the mechanism of the spin-orbit physics and piezoelectricity of Janus Ge 2 XY monolayers and guide experiments in exploring novel multifunctional materials.

Laser-induced Fe 3 O 4 nanoparticle-modified three-dimensional macroporous graphene is fabricated as a near-infrared light responsive nanozyme via a facile and in situ laser-scanning method under ambient conditions for the first time, showing an excellent catalytic-photothermal synergetic bactericidal ability under a low dose of H 2 O 2 (0.1 mM) and short irradiation time (5.0 min).

Constructing chiral luminescent systems with both large luminescence dissymmetry factor ( g lum ) and high luminous efficiency has been considered a great challenge. We herein describe a highly efficient approach to sterically stabilize the helical configurations of carbo[5]helicenes for improved CPL properties in a series of π-donor and π-acceptor substituted [5]helicenes (1, 2, 3, 4 and 5). Enabled by the ortho -installation of methyl groups as well as the steric effects of triarylamine (Ar 3 N) and triarylborane (Ar 3 B) handles in meta -substituted [5]helicenes, their optical resolution into enantiomers has been accomplished using preparative chiral HPLC. The molecular chirality of [5]helicenes can be transferred to Ar 3 B and Ar 3 N as light emitters, which allowed further investigations of their chiroptics, including optical rotation, circular dichroism (CD) and circularly polarized luminescence (CPL). Remarkably, 4 has been demonstrated to display dramatically enhanced CPL performance with a much larger g lum (>1.2 × 10 -2 ) and an increased emission quantum efficiency ( Φ S = 0.75) compared with the other analogues, as a result of the isomeric tuning of substitutions with differential steric and electronic effects. These experimentally observed CPL activities were rationalized by TD-DFT computations for the angle ( θ μ,m ) between electric and magnetic transition dipole moments in the excited states. In addition, the conspicuous intramolecular donor-acceptor charge transfer led to thermal responses in the emissions of 2 and 4 over a broad temperature range.

Vertically stacking two-dimensional materials into van der Waals (vdW) heterostructures (HS) is deemed to be an effective strategy to tailor their physical properties and enrich their applications in modern nanoelectronics. Here, we study the geometry, electronic, and optical properties of Janus Ga 2 SeTe/In 2 SSe heterostructures by using first-principles calculations. We consider four models of Ga 2 SeTe/In 2 SSe heterostructures with an alternative chalcogen atom layer sequence and five potential stacking configurations, and find that the most energy favorable stacking pattern is AB stacking for each model. The heterostructures form type II alignment with a direct band gap. Moreover, the band gap values are highly dependent on the magnitude of the electric dipole, which is related to the sublayer intrinsic dipole direction and interface charge transfer. Additionally, the optical absorption of the heterostructures is intensified in the visible and ultraviolet regime. Furthermore, we predict two heterostructures with the band edge straddling the water redox potential level. These findings can help in understanding the tailored properties of the heterostructures based on Janus two-dimensional materials, and guide experiments in designing novel optoelectronic devices.

This paper reports two closely related heteropentanuclear manganese complexes, namely, {Na 2 Mn 3 (opch) 3 (μ 4 -O)(μ 2 -N 3 ) (μ 2 -AcO)(μ 2 -MeO)}·6CH 3 OH·0.5H 2 O (1) and {Na 2 Mn 3 (opch) 3 (μ 4 -O)(μ 2 -N 3 ) 2 (μ 2 -AcO)}·2.5CH 3 OH·2H 2 O (2), where H 2 opch is ( E )- N '-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide. Single-crystal X-ray diffraction analysis reveals that the trigonal bipyramidal skeletons in both complexes are comparable, where a perfect triangular Mn 3 motif occupies the equatorial plane. Magnetic investigations suggest that overall antiferromagnetic coupling is present within the triangles of 1 and 2. However, their dynamic magnetic properties are drastically distinct. Indeed, complexes 1 and 2 show two kinds of dual slow magnetic relaxation processes that correspond to anisotropy barriers ( Δ ) of 9.2 cm -1 (11.4 cm -1 for 2) and 12.8 cm -1 (30.0 cm -1 for 2) for the low- and high-frequency domains, respectively. More importantly, a further comparative study of the structure and magnetism indicates that the coordination sphere of these two model complexes with the homologous hydrazone-based coordination sites undergoes an alteration from methoxide-O to azide-N upon a subtle change of the auxiliary anion accompanied by modulating octahedron geometries, leading to a further influence on different relaxation dynamics.

{Dy16(μ6-C10H7PO3)2(μ5-C10H7PO3)8(spch)8(μ3-OH)2(μ2-OH)2(μ2-AcO)6(μ3-COO)2(DMF)2(H2O)6}·0.5CH3OH·4.5H2O (1) and {Dy16(μ5-C10H7PO3)4(μ3-C10H7PO3)12(μ2-C10H7PO3H)8(opch)4(DMF)8(MeOH)4}·2.5CH3OH·3H2O (2), where H2spch is ((E)-N'-(2-hydroxybenzylidene)pyrazine-2-carbohydrazide, C10H7PO3H2 is 1-naphthylphosphonic acid and H2opch is (E)-N'-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide, were successfully synthesized by varying the hydrazone ligands in the Dy-phosphonate system. It is important that the ellipsoidal core experiences a ring forming structural transformation to the supramolecular square motif upon the incorporation of an ortho-methoxy substituent into the hydrazone. Alternating-current (ac) magnetic susceptibility studies of 1 and 2 suggest that similar single molecule magnet behaviors occur for these two complexes. The result represents an effective molecular assembly tactic to develop highly complicated lanthanide coordination clusters through the multicomponent self-assembly of the coalescence of phosphonate- and hydrazone-based ligands and metal salts.

Novel nanocomposites fabricated by incorporating different types of nanomaterials, especially inorganic and organic nanomaterials, have attracted much attention, and shown promising prospects in the applications in biological research fields. Herein, we propose a facile method to synthesize a novel three-layered SiO 2 @Au nanoparticle@polyaniline nanocomposite, which exhibited excellent electrical conductivity and good dispersibility in water. The as-proposed nanocomposite has been adopted to construct the modified electrode SiO 2 @AuNP@PANI/CS/GCE, which was characterized by electrochemical impedance spectroscopy and cyclic voltammetry, and demonstrated excellent electrochemical behaviors in neutral and even alkaline media, making it suitable for sensing species in biological fluids under physiological conditions. Moreover, the SiO 2 @AuNP@PANI/CS/GCE exhibited excellent catalytic activity towards the electro-oxidation of uric acid (UA) and ascorbic acid (AA), and a difference of 384 mV between the oxidation potentials for UA and AA was obtained, which is large enough for the selective and simultaneous determination of UA and AA in a binary mixture. Thus, the modified electrode has been successfully adopted for the simultaneous electrochemical detection of UA and AA, and the detection limits of 2 μM and 6 μM were obtained, respectively.

Two Mn(ii) complexes with azide and a new zwitterionic tetracarboxylate ligand 1,2,4,5-tetrakis(4-carboxylatopyridinium-1-methylene)benzene (L(1)), {[Mn5(L(1))2(N3)8(OH)2]·12H2O}n () and {[Mn5(L(1))2(N3)8(H2O)2](ClO4)2·6H2O}n (), have been synthesized and characterized crystallographically and magnetically. and contain similar alternating chains constructed by azide and carboxylate bridges. The independent sets of bridges alternate in an ABCCB sequence between adjacent Mn(ii) ions: (EO-N3)2 double bridges (EO = end-on) (denoted as A), [(EO-N3)(OCO)2] triple bridges (denoted as B) and [(EO-N3)(OCO)] double bridges (denoted as C). The alternating chains are interlinked into 2D coordination networks by the tetrapyridinium spacers. Magnetic studies demonstrate that the magnetic coupling through the double EO azide bridges is ferromagnetic and that through mixed azide/carboxylate bridges is antiferromagnetic. The unprecedented F/AF/AF'/AF'/AF coupling sequence along the chain dictates an uncompensated ground spin state (S = 5/2 per Mn5 unit) and leads to one-dimensional topological ferrimagnetism, which features a minimum in the χT versus T plot.