Regimented Charge Transport Phenomena in Semiconductive Self-Assembled Rhenium Nanotubes.

Photoconductivity, a crucial property, determines the potential of semiconductor materials for use in optoelectronic and photocatalytic device applications. The one-dimensional metal-organic nanotube semiconducting material [{Re(CO)3}6(bho)(phpy)6]n (MBT 1, where bho is benzene-1,2,3,4,5,6-hexaoate and phpy is 4-phenylpyridine) reported herein exhibits record photocurrent responses at a broad spectral range. MBT 1 is comprised of a unique nanotube structure that is composed of six rhenium sites, six 4-phenylpyridine ligands, and a benzene-1,2,3,4,5,6-hexaoate unit. The highly organized self-assembled molecular bamboo tube MBT 1 displays semiconducting characteristics with a low activation energy of 1.63 meV. The alternating current (AC) and direct current (DC) conductivities of pellet devices are approximately 10-4 S/cm. For a single-crystal device, DC conductivity was found to be 1.5 S/cm, an unprecedented 10 000 times higher. The bandgap of MBT 1 was determined to be 1.03 eV, consistent with the theoretically estimated value of 1.2 eV. Theoretical calculations suggest that the unique structural architecture of MBT 1 allows for effective charge transport, which is facilitated by the spatial separation of electrons and holes that MBT 1 contains. This also eliminates fast charge recombination. The findings are not only chemically and fundamentally important but also have great potential for applications in innovative nano-optoelectronics.

Thin Film Growth of 3D Sr-based Metal-Organic Framework on Conductive Glass via Electrochemical Deposition.

Integration of metal-organic frameworks (MOFs) as components of advanced electronic devices is at a very early phase of development and the fundamental issues related to their crystal growth on conductive substrate need to be addressed. Herein, we report on the structural characterization of a newly synthesized Sr-based MOF {[Sr(2,5-Pzdc)(H2 O)2 ] ⋅ 3 H2 O}n (1) and the uniform crystal growth of compound 1 on a conducting glass (fluorine doped tin oxide (FTO)) substrate using electrochemical deposition techniques. The Sr-based MOF 1 was synthesized by the reaction of Sr(NO3 )2 with 2,5-pyrazinedicarboxylic acid dihydrate (2,5-Pzdc) under solvothermal conditions. A single-crystal X-ray diffraction analysis revealed that 1 has a 3D structure and crystallizes in the triclinic P 1 ‾ space group. In addition, the uniform crystal growth of this MOF on a conducting glass (FTO) substrate was successfully achieved using electrochemical deposition techniques. Only a handful of MOFs have been reposed to grown on conductive surfaces, which makes this study an important focal point for future research on the applications of MOF-based devices in microelectronics.

Construction of strontium phosphate/graphitic-carbon nitride: A flexible and disposable strip for acetaminophen detection.

A facile technique has been used to synthesize the strontium phosphate interlinked with graphitic carbon nitride nanosheets (SrP/g-CN NSs) nanocomposite for highly selective detection of acetaminophen (AP). The formation of SrP/g-CN NSs nanocomposite is evidenced by several spectroscopic and analytical methods. It was demonstrated that the SrP/g-CN NSs modified screen-printed carbon electrode (SPCE) exhibits excellent catalytic performance with low peak potential towards AP detection than those of pristine SrP-, g-CN NSs-, and bare- SPCEs. The outstanding electrochemical performance can be attributed to the robust synergistic effect between SrP and g-CN NSs. Likewise, g-CN NSs possess a porous multilayer network, which provides a large surface area, fast charge transferability, electrical conductivity, and numerous active sites. Under the optimal conditions, the fabricated sensor could detect AP with a linear relationship range from 0.01 to 370 µM, and the detection limit is calculated to be as low as 2.0 nM. The proposed sensor is successfully used to determine AP in water samples with satisfactory results.

Sonochemical synthesis and fabrication of perovskite type calcium titanate interfacial nanostructure supported on graphene oxide sheets as a highly efficient electrocatalyst for electrochemical detection of chemotherapeutic drug.

In green approaches for electrocatalyst synthesis, sonochemical methods play a powerful role in delivering the abundant surface areas and nano-crystalline properties that are advantageous to electrocatalytic detection. In this article, we proposed the sphere-like and perovskite type of bimetal oxides which are synthesized through an uncomplicated sonochemical procedure. As a yield, the novel calcium titanate (orthorhombic nature) nanoparticles (CaTiO3 NPs) decorated graphene oxide sheets (GOS) were obtained through simple ultrasonic irradiation by a high-intensity ultrasonic probe (Titanium horn; 50 kHz and 60 W). The GOS/CaTiO3 NC were characterized morphologically and chemically through the analytical methods (SEM, XRD, and EDS). Besides, as-prepared nanocomposites were modified on a GCE (glassy carbon electrode) and applied towards electrocatalytic and electrochemical sensing of chemotherapeutic drug flutamide (FD). Notably, FD is a crucial anticancer drug and also a non-steroidal anti-androgen chemical. Mainly, the designed and modified sensor has shown a wide linear range (0.015-1184 µM). A limit of detection was calculated as nanomolar level (5.7 nM) and sensitivity of the electrode is 1.073 µA µM-1 cm-2. The GOS/CaTiO3 modified electrodes have been tested in human blood and urine samples towards anticancer drug detection.

Sonochemical synthesis and fabrication of neodymium sesquioxide entrapped with graphene oxide based hierarchical nanocomposite for highly sensitive electrochemical sensor of anti-cancer (raloxifene) drug.

The ultrasound-assisted synthesis of a novel neodymium sesquioxide nanoparticles (Nd2O5 NPs) decorated graphene oxide (GO) nanocomposite under ultrasonic probe (Ultrasonic processor model-PR 1000; frequency-30 kHz; power of 100 W/cm2) has been reported. After then, SEM, TEM, XRD, EDX and electrochemical impedance spectroscopy characterized was analyzed using Nd2O5 NPs@GO nanomaterial. Furthermore, the nanomaterial modified GCE (glassy carbon electrode) shows excellent electrochemical sensing performance towards anti-cancer drug. Raloxifene is one of the important anti-cancer drug. Moreover, the fabricated electrochemical sensor has showed a wide linear range for raloxifene between 0.03 and 472.5 µM and nanomolar detection limit (18.43 nM). In addition, the Nd2O5 NPs@GO modified sensor has been applied to the determination of raloxifene in human blood and urine samples.

Exploring the promising potential of MoS2-RuS2 binary metal sulphide towards the electrocatalysis of antibiotic drug sulphadiazine.

Benefiting from the rich redox chemistry, high electrical conductivity and synergistic effect from two metal ions, the binary metal sulphides received tremendous attention in various applications. As a result, the MoS2-RuS2 nanomaterial was synthesized through the simple one-pot hydrothermal technique. The electrocatalytic activity of the as-synthesized nanomaterial was exploited towards the electrochemical detection of antibiotic drug sulphadiazine (SDZ). The electrocatalytic oxidation of the SDZ exhibited lowest anodic peak potential and ehanced anodic peak current rather than other modified electrodes. Notably, an excellent electrochemical performance with very lowest limit of detection (LOD) of 0.004 µM, appreciable linear range from 0.01 µM to 598.7 µM and high sensitivity (2.333 µA µM-1 cm-2) was obtained at MoS2-RuS2 modified electrode. Moreover, well anti-interfering property, good operational stability, repeatability and reproducibility was achieved. Facinatingly, the practicability of the modified electrode demonstrated in milk and human serum samples.

Facile sonochemical synthesis of porous and hierarchical manganese(III) oxide tiny nanostructures for super sensitive electrocatalytic detection of antibiotic (chloramphenicol) in fresh milk.

We report the preparation of a porous and hierarchical manganese(III) oxide tiny nanostructures (Mn2O3 TNS) by a simple sonochemical approach. The nanocatalyst was synthesized by a bath-type ultrasound washer (Honda Electronics, W-118T) at 700 W and 300 kHz frequency. The morphology and chemical composition of the nanocatalyst were characterized by X-rays diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive x-rays (EDX), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The electrocatalytic activity (ECA) was monitored by detection of toxic antibiotic drug (chloramphenicol) under phosphate buffer (pH 7.0). A facile sonochemical route was employed to prepare Mn2O3 TNS modified electrode. The screen-printed carbon electrode (SPCE) modified with Mn2O3 TNS was fabricated and applied for the electrochemical determination of chloramphenicol. Compared with bare SPCE, Mn2O3 TNS modified SPCE showed highest current response towards chloramphenicol. Furthermore, the modified sensor exhibits with a sharp peak and two linear ranges by using DPV (i) 0.015-1.28 µM with the sensitivity of 4.167 µA µM-1 cm-2 and (ii) 1.35-566.3 µM with the sensitivity of 7.205 µA µM-1 cm-2. Notably, we achieved a very low-level detection limit of 4.26 nM for the DPV detection of chloramphenicol. Further, the superior practicability of the nanosheets modified sensor can be used for real time sensing of chloramphenicol with good recover ranges.

Integration of a (-Cu-S-)n plane in a metal-organic framework affords high electrical conductivity.

Designing highly conducting metal-organic frameworks (MOFs) is currently a subject of great interest for their potential applications in diverse areas encompassing energy storage and generation. Herein, a strategic design in which a metal-sulfur plane is integrated within a MOF to achieve high electrical conductivity, is successfully demonstrated. The MOF {[Cu2(6-Hmna)(6-mn)]·NH4}n (1, 6-Hmna = 6-mercaptonicotinic acid, 6-mn = 6-mercaptonicotinate), consisting of a two dimensional (-Cu-S-)n plane, is synthesized from the reaction of Cu(NO3)2, and 6,6'-dithiodinicotinic acid via the in situ cleavage of an S-S bond under hydrothermal conditions. A single crystal of the MOF is found to have a low activation energy (6 meV), small bandgap (1.34 eV) and a highest electrical conductivity (10.96 S cm-1) among MOFs for single crystal measurements. This approach provides an ideal roadmap for producing highly conductive MOFs with great potential for applications in batteries, thermoelectric, supercapacitors and related areas.

Elucidating π-π interaction-induced extension effect in sandwich phthalocyaninato compounds.

Electrochemical and theoretical investigations over triple-quadruple-, quintuple-, and sextuple-decker sandwich-type compounds {[(Pc*)Sm][(Pc*)Cd n (Pc*) n ][Sm(Pc*)]} (n = 0-3) elucidate successive π-π interaction-linked extension in the perpendicular direction of the phthalocyanine plane along with increasing the stacked tetrapyrrole number, significantly improving the nonlinear optical properties including effective imaginary third order molecular hyperpolarizability and optical limiting threshold.

Hydrothermal Synthesis of Cr2Se3 Hexagons for Sensitive and Low-level Detection of 4-Nitrophenol in Water.

We report a simple hydrothermal method used for the synthesis of Cr2Se3 hexagons (h-Cr2Se3) and its application towards electrochemical sensing of 4-nitrophenol (4-NP). The formation of h-Cr2Se3 was confirmed by using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The electrochemical activity of the h-Cr2Se3 modified screen-printed carbon electrode (SPCE) towards 4-NP was studied using cyclic voltammetry (CV) and amperometric i-t techniques. Typically, the obtained results were compared with those for a bare SPCE. The CV result clearly reveals that h-Cr2Se3 modified SPCE has higher catalytic activity towards reduction of 4-NP than bare SPCE. Hence, h-Cr2Se3 modified SPCE was concluded as a viable sensor for sensitive determination of 4-NP. Under optimized conditions, h-Cr2Se3 modified SPCE demonstrates the excellent capacity to detect the 4-NP in a linear range from 0.05 µM to 908.0 µM. The LOD and sensitivity in detection of 4-NP were determined at 0.01 µM and 1.24 µAµM-1 cm-2 respectively. The sensor is highly selective and stable and shows reproducible recovery of 4-NP in domestic supply and river water samples.

Structural Transformations of Amino-Acid-Based Polymers: Syntheses and Structural Characterization.

A discrete complex [Zn(tpro)2(H2O)2] (1, Htpro = l-thioproline), and two structural isomers of coordination polymers, a 1D chain of [Zn(tpro)2]n (2) and a layered structure [Zn(tpro)2]n (3), were synthesized and characterized. The discrete complex 1 undergoes a temperature-driven structural transformation, leading to the formation of a 1D helical coordination polymer 2. Compound 3 is comprised of a 2D homochiral layer network with a (4,4) topology. These layers are mutually linked through hydrogen bonding interactions, resulting in the formation of a 3D network. When 1 is heated, it undergoes nearly complete conversion to the microcrystalline form, i.e., compound 2, which was confirmed by powder X-ray diffractions (PXRD). The carboxylate motifs could be activated after removing the coordinated water molecules by heating at temperatures of up to 150 °C, their orientations becoming distorted, after which, they attacked the activation sites of the Zn(II) centers, leading to the formation of a 1D helix. Moreover, a portion of the PXRD pattern of 1 was converted into the patterns corresponding to 2 and 3, and the ratio between 2 and 3 was precisely determined by the simulation study of in-situ synchrotron PXRD expriments. Consequently, such a 0D complex is capable of underdoing structural transformations and can be converted into 1D and/or 2D amino acid-based coordination polymers.

High-κ Samarium-Based Metal-Organic Framework for Gate Dielectric Applications.

The self-assembly of a samarium-based metal-organic framework [Sm2(bhc)(H2O)6]n (1) in good yield was achieved by reacting Sm(NO3)3·6H2O with benzenehexacarboxylic acid (bhc) in a mixture of H2O-EtOH under hydrothermal conditions. A structural analysis showed that compound 1 crystallized in a space group of Pnmn and adopted a 3D structure with (4,8) connected nets. Temperature dependent dielectric measurements showed that compound 1 behaves as a high dielectric material with a high dielectric constant (κ = 45.1) at 5 kHz and 310 K, which is comparable to the values for some of the most commonly available dielectric inorganic metal oxides such as Sm2O3, Ta2O5, HfO2, and ZrO2. In addition, electrical measurements of 1 revealed an electrical conductivity of about 2.15 × 10-7 S/cm at a frequency of 5 kHz with a low leakage current (Ileakage = 8.13 × 10-12 Amm-2). Dielectric investigations of the Sm-based MOF provide an effective path for the development of high dielectric materials in the future.

Reduced thione ligation is preferred over neutral phosphine ligation in diiron biomimics regarding electronic functionality: a spectroscopic and computational investigation.

Sulfur containing ligands with a thiolate-thiyl radical character are much superior than phosphine ligands in the active site modeling of [FeFe]hydrogenase regarding electronic functionality on charge communication and modulation of the electronic structure of the catalytic metal center.

Isorecticular Synthesis of Dissectible Molecular Bamboo Tubes of Hexarhenium(I) Benzene-1,2,3,4,5,6-hexaolate Complexes.

A family of bamboo-like metal-organic nanotubes consisting of in situ synthesized macromolecular blocks (MB) is reported. The MBs are composed of six fac-(CO)3 Re cores, one benzene-1,2,3,4,5,6-hexaolate plate, and six pyridine-derivative pillar ligands, which have a doubly tri-legged geometry and can be mutually assembled, piece by piece. This entire system is characterized as a simple but precise supramolecular complexation of these macromolecular blocks and further introduces an archetypal approach to systematically constructing a tunable form of dissectible molecular bamboo tubes.

Benzene absorption in a protuberant-grid-type zinc(II)-organic framework triggered by the migration of guest water molecules.

The 2D protuberant-grid-type Zn(II)-organic framework consists of unusual racemic interdigitated bilayers and comprises a 3D intersecting channel system. The framework is thermally stable and the channels contain multiple water aggregates. Accompanying the migration of guest water molecules, only the specific channels in the bilayers along the b axis can easily and efficiently absorb guest benzene molecules in a regular manner.

Plasma tau as a window to the brain-negative associations with brain volume and memory function in mild cognitive impairment and early Alzheimer's disease.

Neurofibrillary tangles are associated with cognitive dysfunction, and hippocampal atrophy with increased CSF tau markers. However, the plasma tau levels of Alzheimer's disease (AD) have not been well studied. We investigated plasma tau by using an immunomagnetic reduction assay in 20 patients with mild cognitive impairment (MCI) due to AD, 10 early AD dementia, and 30 healthy elders (HE). All received a 3D-brain MRI scan and a set of cognitive function test. We explored their relationships with both brain structure and cognitive functions. Images were analyzed to determine the brain volumes and gray matter densities. Patients with MCI or early AD had significantly increased plasma tau levels compared with HE. Plasma tau levels were negatively associated with the performance of logical memory, visual reproduction, and verbal fluency; also negatively associated with volume of total gray matter, hippocampus, amygdala; and gray matter densities of various regions. Regression analyses indicated that logical memory explained 0.394 and hippocampus volume predicted .608 of the variance of plasma tau levels, both P < 0.001. Education years were negatively associated with the gray matter densities of the supramarginal (r = -0.407), middle temporal gyrus (r = -0.40) and precuneus (r = -0.377; all P < 0.05) in HE; and negatively associated with plasma tau levels in patients (r = -0.626). We propose that plasma tau may serve as a window to both structure and function of the brain. Higher education is a protective factor against AD and is associated with lower plasma tau levels in patients.

Expression of osteopontin and type I collagen of hFOB 1.19 cells on sintered fluoridated hydroxyapatite composite bone graft materials.

PURPOSE: The biological effect of fluoridated hydroxyapatite (FHA) graft materials has been attributed to their fluoride ion content; but, only few studies have been conducted to explore the osteoblastic cellular response to physicochemical characteristics of them. We hypothesized that the effect of varied sintered FHA composites on osteoblastic behavior would attribute certain specified physicochemical characteristics of apatites. MATERIALS: Sintered FHA composites were prepared by sintering method with varied gravity percentages of calcium fluoride and hydroxyapatite. Scanning electron microscopic, x-ray diffraction, and Fourier-transform infrared analysis were recorded. The human fetal-osteoblast (hFOB 1.19) cells were seeded on the apatites and tissue culture plates. Responses to the apatites were assessed in terms of osteopontin (OPN) and type I collagen, COL I, gene differentiation. RESULTS: We observed the calcined hydroxyapatite (OHAp), sintered F- OHAps, and hydroxy fluorapatites (OH-FAps) with different physicochemical characteristics. The x-ray diffraction analysis showed sintered apatites to be fluorapatites. Otherwise, Fourier-transform infrared spectral patterns could differentiate the sintered F-OHAps from OH-FAps by the existence of OH, OH···F, or OH···F···OH bands. With ≤ 1 wt% CaF2 added, sintered F-OHAp composites expressed both OH and OH···F bands. With >1 wt% CaF2 added, sintered OH-FAp composites expressed both OH···F and OH···F···OH bands. Sintered F-OHAp composites could enhance OPN and COL I gene expression after 6-day culture (P ≤ 0.05). Otherwise, sintered OH-FAp composites inhibited the expression. CONCLUSION: The results revealed that sintered F-OHAp composites with both OH and OH···F bands were bioactive bone graft materials.

Unusual face-to-face pi-pi stacking interactions within an indigo-pillared M3(tpt)-based triangular metalloprism.

A triangular metalloprism, [((CO)3Re(mu-2)Re(CO)3)3(mu3-1)2], self-assembled from Re2(CO)10, 2,4,6-tri-4-pyridyl-1,3,5-triazine (tpt, 1), and indigo (H2(2)), represents a fairly novel example of strong face-to-face pi-pi interactions between the central triazine rings of the tpt ligands that bow significantly inward distorting the prismatic structure.

Ag4L2 nanocage as a building unit toward the construction of silver metal strings.

Self-assembly of AgNO 3 with the semirigid tetratopic ligands 1,2,4,5-tetrakis(benzoimidazol-1-ylmethyl)benzene (TBim) and 1,2,4,5-tetrakis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (TDMBim) afforded compounds [Ag 4(mu 4-TBim) 2(mu 2-eta (2)-NO 3) 2](NO 3) 2. (1)/ 2CH 2Cl 2.2CH 3OH ( 1mu (1)/ 2CH 2Cl 2.2CH 3OH) and [(NO 3 (-)) subset{Ag 4(mu 4-TDMBim) 2}][Ag(NO 3) 2](NO 3) 2.CH 2Cl 2.CH 3OH.4H 2O ( 2.CH 2Cl 2.CH 3OH.4H 2O), respectively. The structures of 1 and 2 were characterized by single-crystal X-ray diffraction analysis. Both compounds adopt a M 4L 2-type tetragonal metalloprismatic cage structure, [Ag 4(mu 4-L) 2] (4+), with strong intramolecular silver-silver contacts. Compound 1 is a discrete species, while compound 2 is a novel infinite chainlike supramolecular array involving silver metal strings assembled from a [Ag 4(mu 4-L) 2] (4+) nanocage and silver linkages. Thermogravimetric analyses of 1. (1)/ 2CH 2Cl 2.2CH 3OH and 2.CH 3OH.4H 2O indicate that the Ag 4L 2-cage structures of 1 and 2 both are thermally stable up to 330 degrees C. Results from an in situ (1)H NMR study of AgNO 3 and TDMBim in different molar ratios unambiguously revealed the successive self-organization process, in which self-organization of the molecular cage takes place initially followed by crystallization of the corresponding supramolecular arrays with silver metal strings.