Molecular Engineering to Boost the Photo-Oxidase Activity of Molecular Rotors in Colorimetric Sensing of Temperatures.

Some organic dyes and photosensitizers with strong visible absorption can behave as photo-responsive oxidase mimics. However, the relationship between the photo-oxidase activity and molecular structure remains unclear to date. In this work, a new type of photosensitizer with the characteristics of molecular rotors, namely DPPy, served as the molecular scaffold for further investigation. To adjust the photocatalytic oxidation ability, DAPy and CBPy were designed and synthesized based on the enhancement and diminishment of the intramolecular charge transfer (ICT) process, respectively. Kinetic studies revealed that DAPy and CBPy both exhibited highly efficient photo-activated oxidase-like activity with 3,3',5,5'-tetramethylbenzidine (TMB) as the substrate, which were in good accordance with their molecular engineering to promote either type I or type II reactive oxygen species (ROS) generation. Impressively a colorimetric method based on the visible light induced oxidase-like activity of molecular rotors was developed to determine the environmental temperature for the first time. Both DAPy and CBPy showed distinct sensitivities toward temperature as compared with several molecular rotors based on the typical fluorimetric detection. This work provides a new strategy for the application of molecular rotors to overcome the non-emissive challenge in temperature sensing.

Formation sequence of solid electrolyte interphases and impacts on lithium deposition and dissolution on copper: an in situ atomic force microscopic study.

Copper is the most widely used substrate for Li deposition and dissolution in lithium metal anodes, which is complicated by the formation of solid electrolyte interphases (SEIs), whose physical and chemical properties can affect Li deposition and dissolution significantly. However, initial Li nucleation and growth on bare Cu creates Li nuclei that only partially cover the Cu surface so that SEI formation could proceed not only on Li nuclei but also on the bare region of the Cu surface with different kinetics, which may affect the follow-up processes distinctively. In this paper, we employ in situ atomic force microscopy (AFM), together with X-ray photoelectron spectroscopy (XPS), to investigate how SEIs formed on a Cu surface, without Li participation, and on the surface of growing Li nuclei, with Li participation, affect the components and structures of the SEIs, and how the formation sequence of the two kinds of SEIs, along with Li deposition, affect subsequent dissolution and re-deposition processes in a pyrrolidinium-based ionic liquid electrolyte containing a small amount of water. Nanoscale in situ AFM observations show that sphere-like Li deposits may have differently conditioned SEI-shells, depending on whether Li nucleation is preceded by the formation of the SEI on Cu. Models of integrated-SEI shells and segmented-SEI shells are proposed to describe SEI shells formed on Li nuclei and SEI shells sequentially formed on Cu and then on Li nuclei, respectively. "Top-dissolution" is observed for both types of shelled Li deposits, but the integrated-SEI shells only show wrinkles, which can be recovered upon Li re-deposition, while the segmented-SEI shells are apparently top-opened due to mechanical stresses introduced at the junctions of the top regions and become "dead" SEIs, which forces subsequent Li nucleation and growth in the interstice of the dead SEIs. Our work provides insights into the impact mechanism of SEIs on the initial stage Li deposition and dissolution on foreign substrates, revealing that SEIs could be more influential on Li dissolution and that the spatial integration of SEI shells on Li deposits is important to improving the reversibility of deposition and dissolution cycling.

Androgen deficit changes the response to antidepressant drugs in tail suspension test in mice.

Depressive symptoms are throughout our life, especially in the older population, the sex hormones reduction link to a high risk of depression. In this study, we investigated whether bilateral orchiectomy (ORX) modifies mice behaviors and antidepressant drugs effects through tail suspension test (TST). We evaluated behavioral changes at 1 week, 2 weeks, 1 month, and up to 2 months after ORX. The behavior responses to doxepin, fluoxetine, and venlafaxine at 1 week, 2 weeks, 1 month, and 2 months after ORX were evaluated. No apparent difference was detected among the durations of immobility of the control group, sham operation group, and ORX group in the TST at 1 week and 2 weeks after ORX. But the immobility time of ORX group was obvious longer than that of both control group and sham operation group at 1 month and 2 months after ORX. Only the antidepressant effect of venlafaxine was observed at 1 week and 2 weeks after ORX, while the antidepressant response to fluoxetine decreased 1 month and 2 months after ORX. The response to antidepressant drugs was strongly modified in ORX mice. Our results suggest that not all antidepressant drugs are suitable for depression with androgen deficiency.HighlightsMice with low androgen were more prone to depression-like behaviors.The response to antidepressants changed under the condition of low androgen in mice.Not all antidepressant drugs are appropriate for patients with low androgen.

Atomically defined angstrom-scale all-carbon junctions.

Full-carbon electronics at the scale of several angstroms is an expeimental challenge, which could be overcome by exploiting the versatility of carbon allotropes. Here, we investigate charge transport through graphene/single-fullerene/graphene hybrid junctions using a single-molecule manipulation technique. Such sub-nanoscale electronic junctions can be tuned by band gap engineering as exemplified by various pristine fullerenes such as C60, C70, C76 and C90. In addition, we demonstrate further control of charge transport by breaking the conjugation of their π systems which lowers their conductance, and via heteroatom doping of fullerene, which introduces transport resonances and increase their conductance. Supported by our combined density functional theory (DFT) calculations, a promising future of tunable full-carbon electronics based on numerous sub-nanoscale fullerenes in the large family of carbon allotropes is anticipated.

Electrical and SERS detection of disulfide-mediated dimerization in single-molecule benzene-1,4-dithiol junctions.

We applied a combination of mechanically controllable break junction (MCBJ) and in situ surface enhanced Raman spectroscopy (SERS) methods to investigate the long-standing single-molecule conductance discrepancy of prototypical benzene-1,4-dithiol (BDT) junctions. Single-molecule conductance characterization, together with configuration analysis of the molecular junction, suggested that disulfide-mediated dimerization of BDT contributed to the low conductance feature, which was further verified by the detection of S-S bond formation through in situ SERS characterization. Control experiments demonstrated that the disulfide-mediated dimerization could be tuned via the chemical inhibitor. Our findings suggest that a combined electrical and SERS method is capable of probing chemical reactions at the single-molecule level.

Designable ultra-smooth ultra-thin solid-electrolyte interphases of three alkali metal anodes.

Dendrite growth of alkali metal anodes limited their lifetime for charge/discharge cycling. Here, we report near-perfect anodes of lithium, sodium, and potassium metals achieved by electrochemical polishing, which removes microscopic defects and creates ultra-smooth ultra-thin solid-electrolyte interphase layers at metal surfaces for providing a homogeneous environment. Precise characterizations by AFM force probing with corroborative in-depth XPS profile analysis reveal that the ultra-smooth ultra-thin solid-electrolyte interphase can be designed to have alternating inorganic-rich and organic-rich/mixed multi-layered structure, which offers mechanical property of coupled rigidity and elasticity. The polished metal anodes exhibit significantly enhanced cycling stability, specifically the lithium anodes can cycle for over 200 times at a real current density of 2 mA cm-2 with 100% depth of discharge. Our work illustrates that an ultra-smooth ultra-thin solid-electrolyte interphase may be robust enough to suppress dendrite growth and thus serve as an initial layer for further improved protection of alkali metal anodes.

Functional status and annual hospitalization in multimorbid and non-multimorbid older adults: a cross-sectional study in Southern China.

BACKGROUND: Hospitalization over the last one year, an indicator of health service utilization, is an important and costly resource in older adult care. However, data on the relationship between functional status and annual hospitalization among older Chinese people are sparse, particularly for those with and without multimorbidity. In this study,we aimed to examine the association between functional status and annual hospitalization among community-dwelling older adults in Southern China, and to explore the independent contributions of socio-demographic variables, lifestyle and health-related factors and functional status to hospitalization in multimorbid and non-multimorbid groups. METHODS: This cross-sectional, community-based survey, studied 2603 older adults aged 60 years and above. Functional status was assessed by Functional Independence Measure (FIM). The outcome variable was any hospitalization over the last one year (annual hospitalization). Clustered logistic regression was used to analyze the independent contributions of FIM domains to annual hospitalization. RESULTS: Only in the multimorbid group, did the risk of annual hospitalization decrease significantly with increasing FIM score in walk domain (adjusted OR = 0.80 per SD increase, 95% CI = 0.70-0.91, P = 0.001) and its independent contribution accounted for 24.62%, more than that of socio-demographic variables (18.46%). However, among individuals without multimorbidity, there were no significant associations between FIM domains and annual hospitalization; thus, no independent contribution to the risk of hospitalization was observed. CONCLUSIONS: There exist some degree of correlation between functional status and annual hospitalization among older adults in Southern China, which might be due to the presence of multimorbidity with advanced age.

Switching of Charge Transport Pathways via Delocalization Changes in Single-Molecule Metallacycles Junctions.

To explore the charge transport through metalla-aromatics building blocks, three metallacycles complexes were synthesized, and their single-molecule conductances were characterized by using mechanically controllable break junction technique. It is found that the conductance of the metallacycles junction with phosphonium group is more than 1 order of magnitude higher than that without phosphonium group. X-ray diffraction and UV-vis absorption spectroscopy suggested that the attached phosphonium group makes metallacycles more delocalized, which shortened the preferred charge transport pathway and significantly enhanced the single-molecule conductance. This work revealed that the delocalization of metalla-aromatics could be used to switch the charge transport pathway of single-molecule junctions and thus tune the charge transport abilities significantly.

Giant single-molecule anisotropic magnetoresistance at room temperature.

We report an electrochemically assisted jump-to-contact scanning tunneling microscopy (STM) break junction approach to create reproducible and well-defined single-molecule spintronic junctions. The STM break junction is equipped with an external magnetic field either parallel or perpendicular to the electron transport direction. The conductance of Fe-terephthalic acid (TPA)-Fe single-molecule junctions is measured and a giant single-molecule tunneling anisotropic magnetoresistance (T-AMR) up to 53% is observed at room temperature. Theoretical calculations based on first-principles quantum simulations show that the observed AMR of Fe-TPA-Fe junctions originates from electronic coupling at the TPA-Fe interfaces modified by the magnetic orientation of the Fe electrodes with respect to the direction of current flow. The present study highlights new opportunities for obtaining detailed understanding of mechanisms of charge and spin transport in molecular junctions and the role of interfaces in determining the MR of single-molecule junctions.

Stretching single atom contacts at multiple subatomic step-length.

This work describes jump-to-contact STM-break junction experiments leading to novel statistical distribution of last-step length associated with conductance of a single atom contact. Last-step length histograms are observed with up to five for Fe and three for Cu peaks at integral multiples close to 0.075 nm, a subatomic distance. A model is proposed in terms of gliding from a fcc hollow-site to a hcp hollow-site of adjacent atomic planes at 1/3 regular layer spacing along with tip stretching to account for the multiple subatomic step-length behavior.

Conductance histogram evolution of an EC-MCBJ fabricated Au atomic point contact.

This work presents a study of Au conductance quantization based on a combined electrochemical deposition and mechanically controllable break junction (MCBJ) method. We describe the microfabrication process and discuss improved features of our microchip structure compared to the previous one. The improved structure prolongs the available life of the microchip and also increases the success rate of the MCBJ experiment. Stepwise changes in the current were observed at the last stage of atomic point contact breakdown and conductance histograms were constructed. The evolution of 1G0 peak height in conductance histograms was used to investigate the probability of formation of an atomic point contact. It has been shown that the success rate in forming an atomic point contact can be improved by decreasing the stretching speed and the degree that the two electrodes are brought into contact. The repeated breakdown and formation over thousands of cycles led to a distinctive increase of 1G0 peak height in the conductance histograms, and this increased probability of forming a single atomic point contact is discussed.

Electrochemically-driven large amplitude pH cycling for acid-base driven DNA denaturation and renaturation.

In this paper, we present an electrochemically driven large amplitude pH alteration method based on a serial electrolytic cell involving a hydrogen permeable bifacial working electrode such as Pd thin foil. The method allows solution pH to be changed periodically up to ±4~5 units without additional alteration of concentration and/or composition of the system. Application to the acid-base driven cyclic denaturation and renaturation of 290 bp DNA fragments is successfully demonstrated with in situ real-time UV spectroscopic characterization. Electrophoretic analysis confirms that the denaturation and renaturation processes are reversible without degradation of the DNA. The serial electrolytic cell based electrochemical pH alteration method presented in this work would promote investigations of a wide variety of potential-dependent processes and techniques.

Revealing the molecular structure of single-molecule junctions in different conductance states by fishing-mode tip-enhanced Raman spectroscopy.

The conductance of single-molecule junctions may be governed by the structure of the molecule in the gap or by the way it bonds with the leads, and the information contained in a Raman spectrum is ideal for examining both. Here we demonstrate that molecule-to-surface bonding may be characterized during electron transport by 'fishing-mode' tip-enhanced Raman spectroscopy (FM-TERS). This technique allows mutually verifiable single-molecule conductance and Raman signals with single-molecule contributions to be acquired simultaneously at room temperature. Density functional theory calculations reveal that the most significant spectral change seen for a gold-4,4'-bipyridine-gold junction results from the deformation of the pyridine ring in contact with the drain electrode at high voltage, and these calculations suggest that a stronger bonding interaction between the molecule and the drain may account for the nonlinear dependence of conductance on bias voltage. FM-TERS will lead to a better understanding of electron-transport processes in molecular junctions.

Electrochemically assisted fabrication of metal atomic wires and molecular junctions by MCBJ and STM-BJ methods.

Atomic wires (point contacts) and molecular junctions are two fundamental units in the fields of nanoelectronics and devices. This Minireview introduces our recent approaches aiming to develop versatile methods to fabricate and characterize these unique metallic and molecular structures reliably. Electrochemical methods are coupled with mechanically controllable break junction (EC-MCBJ) or scanning tunneling microscopy (STM) break junction (EC-STMBJ) methods to fabricate metallic point contacts and metal/molecule/metal junctions. With the designed electrodeposition method, the metal of interest (e.g. Au, Cu, Fe or Pd) is deposited in a controlled way on the original electrode pair, on a chip for MCBJ or on the STM tip, to make the metallic contact. Then, various metal atomic wires and molecular junctions can be fabricated and characterized systematically. Herein, we measured the quantized conductance through the construction of histograms of these metal atomic point contacts and of single molecules including benzene-1,4-dithiol (BDT), ferrocene-bisvinylphenylmethyl dithiol (Fc-VPM), 4,4'-bipyridine (BPY), 1,2-di(pyridin-4-yl)ethene (BPY-EE), and 1,2-di(pyridin-4-yl)ethane (BPY-EA). Finally, we briefly discussed the future of EC-MCBJ and EC-STM for nanoelectronics and devices, for example, for the formation of heterogeneous metal-based atomic point contacts and molecular junctions.

Double layer of Au(100)/ionic liquid interface and its stability in imidazolium-based ionic liquids.

Ring any bells? The differential capacitance curve of Au(100) in neat [BMI]BF(4) (BMI = 1-butyl-3-methylimidazolium) ionic liquid has a bell-shaped feature (see picture). The adsorption of BMI(+) shows a disorder-order transition and depends on the structure of the surface. Ordered adsorption in a micelle-like structure stabilizes the underlying Au surface.

Extending the capability of STM break junction for conductance measurement of atomic-size nanowires: an electrochemical strategy.

The STM break junction (STM-BJ) and mechanically controllable break junction (MCBJ) are the two most widely applied techniques to fabricate atomic-size nanowires for conductance measurement. However, the drawbacks of the mechanical crashing between the two electrodes of the same material in these techniques hamper its capability of application in view of the variety of metals as well as the environment to perform the measurements. In this paper, we present an electrochemical strategy for STM-BJ by establishing a chemically well-defined metallic contact through a jump-to-contact mechanism between the tip and substrate of dissimilar metals, wherein the tip is in situ and electrochemically deposited with a thin film of a foreign metal of interest. The feasibility of the approach is demonstrated by taking Cu as a model system, followed by generalizing to Pd and Fe for which the conductance has been found otherwise difficult to measure at room temperature. The preferential point-contact conductance at 1, 0.9, and 0.86 G0 was measured for Cu, Pd, and Fe, respectively. The strategy present in this work not only extends the capability of STM-BJ to create a variety of metal nanowires including magnetic nanowires for further investigations but also provides opportunities to construct metal-molecule-metal junctions with a variety of choices of metals in the junctions.

[Comparative study of the resistance of bacteriophageT4, PhiX174D, MS2 and f2 to gamma radiation].

OBJECTIVE: To screen the suitable bacteriophage as virus indicator in irradiation sterilization. METHODS: Suspensions of bacteriophage T4, phiX174D, MS2, and f2, Escherichia coli 8099, and Bacillus subtilis var.niger.sp. ATCC9372 were irradiated with (60)Co-gamma ray. The mean log(10) inactivation value (LIV) and killing log value (KL) were calculated. RESULTS: (1) Under 100 Gy of gamma-radiation, the LIV levels of the bacteriophage T4, PhiX174, f2, and MS2 were 6.31, 6.92, 5.74, and 4.46 log(10) respectively, all reaching the disinfection level (LIV >/= 4.00 log(10)), (2) Under the same absorbed dose, the KL of Escherichia coli 8099 was > 7.97 log(10); (3) Under the same absorbed dose, the KL of the Bacillus subtilis var.niger.sp. ATCC9372 was 1.61 log(10). CONCLUSION: The order of resistance of the above six microorganisms to gamma-radiation from the biggest to the smallest is as follows: Bacillus subtilis var. niger. sp. > bacteriophage MS2 > bacteriophage f2 > bacteriophage T4 > bacteriophage phiX 174D > E. coli.

[Comparative study on the resistance of Bacteriophage phi chi 174D, T4 and f2 to an iodophor in laboratory].

BACKGROUND: To screen for the most resistant bacteriophage as indicator in disinfection tests, the resistance of bacteriophage phi chi 174D, T4 and f2 to iodophor were observed in laboratory. METHODS: The virucidal activity of iodophor against bacteriophage phi chi 174D, T4, and f2 were assessed by suspension test. The neutralizer is selected and appraised by testing with neutralizer. Bacteriophage phi chi 174D, T4, and f2 were detected and enumerated by the double-agar-layer plaque technique. RESULTS: (1) With 500 mg/L of available iodine of iodophor solution, within a contact time of 40 min, or 750 mg/L, 10 min, or 1000 mg/L, 5 min, the reduction of bacteriophage phi chi 174D could achieve the "disinfection" level [log10 inactivation value (LIV) or log10 reduction value (LRV) of bacteriophage phi chi 174D (log10 No-log10 Nt) was > or = 4.00 log10]. (2) With 600 mg/L of available iodine of iodophor solution, within a contact time of 40 min, or 700 mg/L, 5 min, the reductions of bacteriophage T4 could achieve the "disinfection" level. (3) With 50 mg/L of available iodine of iodophor solution, within a contact time of 10 min, or 75 mg/L, 10 min, the reductions of bacteriophage f2 could achieve the "disinfection" level. CONCLUSION: The order of resistance of the above three bacteriophages to iodophor from greatest to smallest is as follows: bacteriophage phi chi 174D greater than bacteriophage T4 > bacteriophage f2.

[A comparative study on the resistance of bacteriophage T4, phiXM174D, and f2 to glutaraldehyde in laboratory].

OBJECTIVE: To identify the best indicative bacteriophage in disinfection tests through comparing the resistance of bacteriophage T4, phiX174D, and f2 to glutaraldehyde. METHODS: The virucidal activities of glutaraldehyde against bacteriophage T4, phiX174D, and f2 were assessed with suspension tests along with neutralizer tests. The double-agar-layer plaque technique was used to detect the bacteriophage T4, phiX174D, and f2. RESULTS: (1)In a condition of 3000 mg/L of glutaraldehyde and 20 minutes of contact or 6000 mg/L of glutaraldehyde and 5 minutes of contact, "disinfection" level for bacteriophage T4 was achieved, with the log10 inactivation value (LIV) or log10o reduction value (LRV) (=log10No-log10Nt) > or = 4. 00 log10. (2) In a condition of 2500 mg/L of glutaraldehyde and 20 minutes of contact or 5000 mg/L of glutaraldehyde and 5 minutes of contact, the LIV for bacteriophage phiX174D reached "disinfection" level; (3) In a condition of 4000 mg/L of glutaraldehyde and 40 minutes of contact or 8000 mg/L of glutaraldehyde and 10 minutes of contact, the LIV for bacteriophage f2 reached "disinfection" level. CONCLUSION: Bacteriophage f2 and bacteriophage phiX174D has the strongest and weakest resistance to glutaraldehyde respectively.

[Comparison on resistance of bacteriophages to sodium dichloroisocyanurate in laboratory].

OBJECTIVE: To scan the most resistable bacteriophage as an indicator in disinfection tests, and to study the resistance of bacteriophage T4, Phichi 174D, and f2 to the sodium dichloroisocyanurate (NaDCC) in laboratory. METHODS: The virucidal activity of NaDCC against bacteriophage T4, Phichi 174D, and f2 were assessed by suspension test. The neutralizer was selected and be appraised by test of neutralizer. Bacteriophage T4, Phichi 174D, and f2 were detected and enumerated by the double-agar-layer plaque technique. RESULTS: (1) With 150 mg/L of available chlorine of NaDCC solution, within a contact time of 40 minutes, or 300 mg/L, 5 minutes, the reductions of bacteriophage T4 achieved the "disinfection" level [log(10) inactivation value or log(10) reduction value of bacteriophage T4 (log(10)No-log(10)Nt) > or = 4.00 log(10)]. (2) With 300 mg/L of available chlorine of NaDCC solution, within a contact time of 5 minutes, or 400 mg/L, 3 minutes, the reductions of bacteriophage Phichi 174D achieved the "disinfection" level. (3) With 2000 mg/L of available chlorine of NaDCC solution, within a contact time of 20 minutes, or 4000 mg/L, 5 minutes, the reductions of bacteriophage f2 might achieve the "disinfection" level. CONCLUSION: The order of resistance of the above three bacteriophages to NaDCC from greatest to smallest is as follows: bacteriophage f2 > bacteriophage T4 > bacteriophage Phichi 174D.