Gold Nanoparticles with N-Heterocyclic Carbene/Triphenylamine Surface Ligands: Stable and Electrochromically Active Hybrid Materials for Optoelectronics.

Organic-hybrid particle-based materials are increasingly important in (opto)electronics, sensing, and catalysis due to their printability and stretchability as well as their potential for unique synergistic functional effects. However, these functional properties are often limited due to poor electronic coupling between the organic shell and the nanoparticle. N-heterocyclic carbenes (NHCs) belong to the most promising anchors to achieve electronic delocalization across the interface, as they form robust and highly conductive bonds with metals and offer a plethora of functionalization possibilities. Despite the outstanding potential of the conductive NHC-metal bond, synthetic challenges have so far limited its application to the improvement of colloidal stabilities, disregarding the potential of the conductive anchor. Here, NHC anchors are used to modify redox-active gold nanoparticles (AuNPs) with conjugated triphenylamines (TPA). The resulting AuNPs exhibit excellent thermal and redox stability benefiting from the robust NHC-gold bond. As electrochromic materials, the hybrid materials show pronounced color changes from red to dark green, a highly stable cycling stability (1000 cycles), and a fast response speed (5.6 s/2.1 s). Furthermore, TPA-NHC@AuNP exhibits an ionization potential of 5.3 eV and a distinct out-of-plane conductivity, making them a promising candidate for application as hole transport layers in optoelectronic devices.

Basal actomyosin pulses expand epithelium coordinating cell flattening and tissue elongation.

Actomyosin networks constrict cell area and junctions to alter cell and tissue shape. However, during cell expansion under mechanical stress, actomyosin networks are strengthened and polarized to relax stress. Thus, cells face a conflicting situation between the enhanced actomyosin contractile properties and the expansion behaviour of the cell or tissue. To address this paradoxical situation, we study late Drosophila oogenesis and reveal an unusual epithelial expansion wave behaviour. Mechanistically, Rac1 and Rho1 integrate basal pulsatile actomyosin networks with ruffles and focal adhesions to increase and then stabilize basal area of epithelial cells allowing their flattening and elongation. This epithelial expansion behaviour bridges cell changes to oocyte growth and extension, while oocyte growth in turn deforms the epithelium to drive cell spreading. Basal pulsatile actomyosin networks exhibit non-contractile mechanics, non-linear structures and F-actin/Myosin-II spatiotemporal signal separation, implicating unreported expanding properties. Biophysical modelling incorporating these expanding properties well simulates epithelial cell expansion waves. Our work thus highlights actomyosin expanding properties as a key mechanism driving tissue morphogenesis.

Shear stress enhances anoikis resistance of cancer cells through ROS and NO suppressed degeneration of Caveolin-1.

Circulating tumor cells (CTCs) acquire enhanced anti-anoikis abilities after experiencing flow shear stress in the circulatory system. Our previous study demonstrated that low shear stress (LSS) promotes anoikis resistance of human breast carcinoma cells via caveolin-1 (Cav-1)-dependent extrinsic and intrinsic apoptotic pathways. However, the underlying mechanism how LSS enhanced Cav-1 expression in suspended cancer cells remains unclear. Herein, we found that LSS induced redox signaling was involved in the regulation of Cav-1 level and anoikis resistance in suspension cultured cancer cells. Exposure of human breast carcinoma MDA-MB-231 cells to LSS (2 dyn/cm2) markedly induced ROS and •NO generation, which promoted the cell viability and reduced the cancer cell apoptosis. Furthermore, ROS and •NO scavenging inhibited the upregulation of Cav-1 by interfering ubiquitination, and suppressed the anoikis resistance of suspended tumor cells. These findings provide new insight into the mechanism by which LSS-stimulated ROS and •NO generation increases Cav-1 stabilization in suspended cancer cells through inhibition of ubiquitination and proteasomal degradation, which could be a potential target for therapy of metastatic tumors.

Stress cardiomyopathy: Medical studies and extensive review.

Stress cardiomyopathy (SC) was first reported in the year 1983. It is narrated as critical but quite commutative left ventricular (LV) malfunction mostly caused by poignant or psychological disorder. Numerous variations of SC have been described as well as reverse stress cardiomyopathy (rSC) which is an adaptation identified by the decreased muscle movement related with hyperkinesis that reconciles impetuously. The signature of rSC is a medical demonstration alike to syndrome by an acute coronary, with no obvious difficult coronary artery disease. The occurrence of SC is approximated to be 4% of all victims conferring with gleaned syndrome by acute coronary. The portion of victims conferring with the rSC transfiguration out of all SC patients has been inconstant, varying from 1 to 24%. Reverse stress cardiomyopathy cases are found to be common with young people, less decrease in left ventricular ejection fraction (LVEF) and more neurological disease compared to the SC. While the correct phenomenon of rSC is undetermined, postulated methods comprises of coronary microvasculature impairment, coronary artery spasm, and estrogen deficiency. Patients with rSC typically suffer with chest pain after an emotional or Psychological stressful event. The rSC can also be happened by general anesthesia, or neurological conditions. The diagnosis of rSC demands the presence of new electrocardiogram (EKG) abnormalities or elevated cardiac troponin, and absence of obstructive coronary disease, pheochromocytoma, or myocarditis. The consideration of rSC is quite analogous to that of SC, which is predominantly supportive with the treatment of complications. The recrudescence rate of rSC is around 12%. The most frequent complications of rSC include pericardial effusions, and development of LV thrombi.

Poly(3-hexylthiophene)s Functionalized with N-Heterocyclic Carbenes as Robust and Conductive Ligands for the Stabilization of Gold Nanoparticles.

Recently, N-heterocyclic carbenes (NHCs) are explored as anchor groups to bind organic ligands to colloidal gold (i.e. gold nanoparticles, Au NPs), yet these efforts are confined to non-conjugated ligands so far-that is, focused solely on exploiting the stability aspect. Using NHCs to link Au NPs and electronically active organic components, for example, conjugated polymers (CPs), will allow capitalizing on both the stability as well as the inherent conductivity of the NHC anchors. Here, we report three types of Br-NHC-Au-X (X=Cl, Br) complexes, which, when used as starting points for Kumada polymerizations, yield regioregular poly(3-hexylthiophenes)-NHC-Au (P3HTs-NHC-Au) with narrow molecular weight distributions. The corresponding NPs are obtained via direct reduction and show excellent thermal as well as redox stability. The NHC anchors enable electron delocalization over the gold/CP interface, resulting in an improved electrochromic response behavior in comparison with P3HT-NHC-Au.

Dual-Switching Electrochromism and Electrofluorochromism Derived from Diphenylamine-Based Polyamides with Spirobifluorene/Pyrene as Bridged Fluorescence Units.

Electrochromic (EC)/electrofluorochromic (EFC) bifunctional materials are receiving great attention because of their promising applications in optoelectronic devices. However, the development of ideal EC/EFC bifunctional materials is still a great challenge because of the poor integration of EC/EFC performances (optical contrast, response speed, and switching stability). Herein, we reported two novel diphenylamine-based mixed valence (MV) polyamides (S-HPA and P-HPA) with spirobifluorene (2,7-positions) and pyrene (1,6-positions) as bridged fluorescence units, respectively, showing impressive cyclability and fluorescence contrast with rapid switching. Through the formation of an effective electronic coupling between the two nitrogen centers using spirobifluorene/pyrene bridges, we demonstrated that different bridges have significant effects on the thermal and electrooptical characteristics of polyamides. In addition to lower fluorescence quantum yield and glass transition temperature, the S-HPA exhibited superior cyclability (contrast change <3.4%/14% over 500/300 cycles for EC/EFC switching), higher color/fluorescence contrast (64%/304%), and faster switching time (<2.6 s), mainly owing to the shorter conjugated length and more twisted configuration of the spirobifluorene bridge. The design principle of MV polymers with fluorophore bridges proposed here will be a promising way to realize high-performance EC/EFC devices and will also provide new insights into their future development and applications.

AIE-Active Polyamide Containing Diphenylamine-TPE Moiety with Superior Electrofluorochromic Performance.

Electrofluorochromism has attracted great attention due to the intelligence optoelectronic and sensing applications. The intrinsically switchable fluorophores with high solid-state fluorescence are regarded as key for ideal electrofluorochromic materials. Here, we reported an AIE-active polyamide with diphenylamine and tetraphenylethylene units, showing high fluorescence quantum yield up to 69.1% for the solid polymer film and stable electrochemical cycling stability. The polyamide exhibited reversible color and emission switching even in hundreds of cycles, and the fluorescence on/off contrast ratio was determined up to 417, which is the highest value to our knowledge. Furthermore, as the response time is vital for the real-life applications, to speed up the response of electrofluorochromism, a porous polymer film was readily prepared through a facile method, notably exhibiting high fluorescence contrast, long-term stability and obviously improved response, due to the sharply increased surface area. Therefore, the AIE-functionalization combining the porous structure strategy will synergistically and dramatically improve the electrofluorochromic performance, which will also promote their practical applications in the near future.

Broad-Range Electrically Tunable Plasmonic Resonances of a Multilayer Coaxial Nanohole Array with an Electroactive Polymer Wrapper.

Plasmonic assemblies featuring high sensitivity that can be readily shifted by external fields are the key for sensitive and versatile sensing devices. In this paper, a novel fast-responsive plasmonic nanocomposite composed of a multilayer nanohole array and a responsive electrochromic polymer is proposed with the plasmonic mode appearance vigorously cycled upon orthogonal electrical stimuli. In this nanocomposite, the coaxially stacked plasmonic nanohole arrays can induce multiple intense Fano resonances, which result from the crosstalk between a broad surface plasmon resonance (SPR) and the designed discrete transmission peaks with ultrahigh sensitivity; the polymer wrapper could provide the sensitive nanohole array with real-time-varied surroundings of refractive indices upon electrical stimuli. Therefore, a pronounced pure electroplasmonic shift up to 72 nm is obtained, which is the largest pure electrotuning SPR range to our knowledge. The stacked nanohole arrays here are also directly used as a working electrode, and they ensure sufficient contact between the working electrode (plasmonic structure) and the electroactive polymer, thus providing considerably improved response speed (within 1 s) for real-time sensing and switching.

Covalent functionalization of graphene oxide with porphyrin and porphyrin incorporated polymers for optical limiting.

Porphyrin-graphene composites have attracted increasing attention due to a number of intriguing functions, and their photoelectrical and catalytic performances are expected to be modulated through different approaches. In the present study, a designed polymer based on phenyl sulfone, (p-amino)phenylhydroquinone, and a symmetrical dinaphthylporphyrin were covalently attached to a graphene oxide (GO) sheet. The formation of the nanohybrid was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Raman, ultraviolet-visible (UV-vis) absorption, steady and transient fluorescence spectroscopy techniques. The nonlinear optical and optical limiting performances of the hybrid were investigated using Z-scan measurements at 532 nm and 1064 nm. For comparison, a porphyrin functionalized GO hybrid was synthesized as a reference. At the same linear transmittance, the polymer functionalized GO exhibited a stronger optical limiting response and a larger nonlinear extinction coefficient than the individual GO, porphyrinated polymer, and porphyrin functionalized GO hybrid analogue, and its intrinsic photophysical mechanism was discussed in detail. More importantly, further improvement of its nonlinear optical properties can be achieved by the chemical reduction of the hybrid. The enhanced nonlinear optical performance originated from the effective combination of nonlinear scattering, reverse saturable absorption, and a possible photo-induced electron/energy transfer mechanism from donor porphyrin moieties in the polymer backbone to acceptor graphene. Our result might provide a new avenue for the development of graphene-porphyrin materials in the field of photocatalysis, nonlinear optics, and optoelectronic devices.

Multiple Stimuli-Responsive Fluorescence Behavior of Novel Polyamic Acid Bearing Oligoaniline, Triphenylamine, and Fluorene Groups.

Multiple stimuli-responsive fluorescent materials have gained increasing attention for their fundamental investigation and intelligent applications. In this work, we report design and synthesis of a novel polyamic acid bearing oligoaniline, triphenylamine, and fluorene groups, which served as sensitive units and fluorescence emission unit, respectively. The resulting polymer exhibits multiple stimuli-responsive fluorescence switching behavior triggered by redox species, pH, electrochemical, and pressure stimuli. Every fluorescence switching mechanism upon each stimulus was studied in detail. The interactions and energy transfer between sensitive units and emission unit are largely responsible for this fascinating fluorescent switching behavior. This work provides a deep understanding of the optical switching essence upon these stimuli, opening the way for the development of new fluorescent sensing applications.

Dental practitioner concepts of efficiency related to the use of dental therapists.

OBJECTIVES: Efficiency is concerned with producing maximum output with the minimum input, although what constitutes inputs and outputs within an organization is not always clear. Labour substitution is one method of achieving efficiency gains, although cost savings are found to be context dependent and may not be achieved in some situations. Because dental therapists (DTs) in England are permitted to work in dental practices, we set out to investigate how efficiency with respect to the use of DTs is conceptualized by practitioners to deepen our understanding of the potential for substitution to realize efficiency gains in dental practice. METHODS: Nine dental practices were selected using a purposive sampling methodology to give a range of practice size and DT employment arrangements. Semi-structured interviews were held with 26 dentists. Transcripts were coded and analysed thematically. RESULTS: Efficiency was perceived as optimum use of surgery time to generate intermediate outputs of (i) managing patient flow to give patient satisfaction and business cash flow and (ii) volume of work (procedures and numbers of patients). DT efficiency gains were evaluated according to whether lower labour costs were offset by a slower working pace and higher rate of failed appointments. Patient need and demand, and whether the practice had health improvement goals, influenced whether DTs were deemed to improve efficiency. CONCLUSIONS: Findings are in accord with skill mix reviews in wider health care that substitution may be effective in improving efficiency but this may be limited to particular situations where conditions are conducive. More studies are needed to explore these issues further in other dental practice contexts and with other groups of dental auxiliary.

Translation of remuneration arrangements into incentives to delegate to English dental therapists.

OBJECTIVES: To investigate how changes to the dental remuneration system have translated into disincentives to delegate to dental therapists in dental practices. METHOD: A purposive sample of nine practices was identified incorporating a mix of small, medium and large practices, both with and without dental therapists (DTs). Semi-structured interviews were carried out with 48 principal dentists, associate dentists, DTs, practice managers and dental hygienists. Interview transcripts were analysed using a general inductive approach to identify themes and sub-themes. RESULTS: Four themes were identified: practice finances, productivity, lack of management information relating to the use of DTs, and fairness. DTs were often seen as a 'cost' to the team, rather than part of the team as a whole, within a system where contributions were evaluated according to a cost-volume-profit business model. Thus DTs were expected to be 'self-financing'. The fairness of deducting the salary costs of the DT from associate dentists' income was an issue. CONCLUSIONS: The study reveals that the financial risk sharing model which predominates in dental practice significantly influences how the remuneration system translates into establishing delegation incentives. New organisational forms or a shift in practitioner worldviews of team-working are needed in order for DTs to be fully integrated into dental practice teams.