Water Washable and Flexible Light-Emitting Fibers Based on Electrochemiluminescent Gels.

Herein, a new concept of device architecture to fabricate fibrous light-emitting devices is demonstrated based on an electrochemiluminescence (ECL) material for an electronic textile system. A unique feature of this work is that instead of conventional semiconductor materials, such as organics, perovskites, and quantum dots for fibrous light emitting devices, a solid-state ECL electrolyte gel is employed as a light-emitting layer. The solid-state ECL gel is prepared from a precursor solution composed of matrix polymer, ionic liquid, and ECL luminophore. From this, we successfully realize light-emitting fibers through a simple and cost-effective single-step dip-coating method in ambient air, without complicated multistep vacuum processes. The resulting fiber devices reliably operated under applied AC bias of ±2.5 V and showed luminance of 47 cd m-2. More importantly, the light-emitting fibers exhibited outstanding water resistance without any passivation layers, owing to the water immiscible and hydrophobic nature of the ECL gel. In addition, because of their simple structure, the fiber devices can be easily deformed and woven together with commercial knitwear by hand. Therefore, these results suggest a promising strategy for the development of practical fiber displays and contribute to progress in electronic textile technology.

UHRF1 Induces Methylation of the TXNIP Promoter and Down-Regulates Gene Expression in Cervical Cancer.

DNA methylation, and consequent down-regulation, of tumour suppressor genes occurs in response to epigenetic stimuli during cancer development. Similarly, human oncoviruses, including human papillomavirus (HPV), up-regulate and augment DNA methyltransferase (DNMT) and histone deacetylase (HDAC) activities, thereby decreasing tumour suppressor genes (TSGs) expression. Ubiquitin-like containing PHD and RING finger domain 1 (UHRF1), an epigenetic regulator of DNA methylation, is overexpressed in HPV-induced cervical cancers. Here, we investigated the role of UHRF1 in cervical cancer by knocking down its expression in HeLa cells using lentiviral-encoded short hairpin (sh)RNA and performing cDNA microarrays. We detected significantly elevated expression of thioredoxin-interacting protein (TXNIP), a known TSG, in UHRF1-knockdown cells, and this gene is hypermethylated in cervical cancer tissue and cell lines, as indicated by whole-genome methylation analysis. Up-regulation of UHRF1 and decreased TXNIP were further detected in cervical cancer by western blot and immunohistochemistry and confirmed by Oncomine database analysis. Using chromatin immunoprecipitation, we identified the inverted CCAAT domain-containing UHRF1-binding site in the TXNIP promoter and demonstrated UHRF1 knockdown decreases UHRF1 promoter binding and enhances TXNIP expression through demethylation of this region. TXNIP promoter CpG methylation was further confirmed in cervical cancer tissue by pyrosequencing and methylation-specific polymerase chain reaction. Critically, down-regulation of UHRF1 by siRNA or UHRF1 antagonist (thymoquinone) induces cell cycle arrest and apoptosis, and ubiquitin-specific protease 7 (USP7), which stabilises and promotes UHRF1 function, is increased by HPV viral protein E6/E7 overexpression. These results indicate HPV might induce carcinogenesis through UHRF1-mediated TXNIP promoter methylation, thus suggesting a possible link between CpG methylation and cervical cancer.

Electrochemiluminescent Transistors: A New Strategy toward Light-Emitting Switching Devices.

Light-emitting transistors (LETs) have attracted a significant amount of interest as multifunctional building blocks for next-generation electronics and optoelectronic devices. However, it is challenging to obtain LETs with a high carrier mobility and uniform light-emission because the semiconductor channel should provide both the electrical charge transport and optical light-emission, and typical emissive semiconductors have low, imbalanced carrier mobilities. In this work, a novel device platform that adapts the electrochemiluminescence (ECL) principle in LETs, referred to as an ECL transistor (ECLT) is proposed. ECL is a light-emission phenomenon from electrochemically excited luminophores generated by redox reactions. A solid-state ECL electrolyte consisting of a network-forming polymer, ionic liquid, luminophore, and co-reactant is employed as the light-emitting gate insulator of the ECLT. Based on this construction, high-performance LETs that make use of various conventional non-emissive semiconductors (e.g., poly(3-hexylthiophene), zinc oxide, and reduced graphene oxide) are successfully demonstrated. All the devices exhibit a high mobility (0.9-10 cm2 V-1 s-1 ) and a uniform light-emission. This innovative approach demonstrates a novel LET platform and provides a promising pathway to achieve significant breakthroughs to develop electronic circuits and optoelectronic applications.

Users' Concerns Related to Online HIV Counseling in South Korea: A Descriptive Qualitative Study.

This qualitative descriptive study was designed to identify HIV-related questions frequently asked by online counseling users seeking professional advice. Data were collected via a public online question/answer counseling website operated by the Gyeonggi-do branch of the Korean Association for AIDS Prevention. Data on users' questions regarding HIV were collected between January 1, 2017, and December 31, 2018. The online questions were then analyzed and divided into codes and categories. From the 559 questions submitted, content analysis identified four major categories related to HIV: (a) HIV testing, (b) self-perceived HIV risk and risky sexual behaviors, (c) positive and negative emotional states, and (d) treatment and prevention. This study indicates that online counseling can be used to provide tailored information related to HIV along with emotional and psychosocial support to reach different subgroups and to provide current information such as the use of pre-exposure prophylaxis for those seeking professional advice.

UHRF1 silences gelsolin to inhibit cell death in early stage cervical cancer.

Persistent infection with high-risk strains of human papillomavirus (HPV) is the primary cause of cervical cancer, the fourth most common cancer among women worldwide. Two oncoproteins encoded by the HPV genome, E6 and E7, are required for epigenetic modifications that promote cervical cancer development. We found that knockdown of HPV E6/E7 by siRNA reduced the levels of ubiquitin-like containing PHD and RING finger domain 1 (UHRF1) but increased the levels of gelsolin (GSN) in early stage cervical cancer cells. In addition, we found that UHRF1 levels were increased and GSN levels were decreased in early stage cervical cancer compared with those in normal cervical tissues, as shown by Western blot analysis, immunohistochemistry, and analysis of the Oncomine database. Moreover, knockdown of UHRF1 resulted in increased cell death in cervical cancer cell lines. Treatment of E6/E7-transformed HaCaT (HEK001) cells and HeLa cells with the DNA-hypomethylating agent 5-aza-2'-deoxycytidine and the histone deacetylase inhibitor Trichostatin A increased GSN expression levels. UHRF1 knockdown in HEK001 cells by siRNA or the UHRF1 antagonist thymoquinone increased GSN levels, induced cell cycle arrest and apoptosis, and increased the levels of p27 and cleaved PARP. Those results indicate that upregulation of UHRF1 by HPV E6/E7 causes GSN silencing and a reduction of cell death in early stage cervical cancer, suggesting that GSN might be a useful therapeutic target in early stage cervical cancer.

Ultrahigh-Mobility and Solution-Processed Inorganic P-Channel Thin-Film Transistors Based on a Transition-Metal Halide Semiconductor.

The development of p-channel devices with comparable electrical performances to their n-channel counterparts has been delayed due to the lack of p-type semiconductor materials and device optimization. In this present work, we successfully demonstrated p-channel inorganic thin-film transistors (TFTs) with high hole mobilities similar to the values of n-channel devices. To boost the device performance, the solution-processed copper iodide (CuI) semiconductor was gated by a solid polymer electrolyte. The electrolyte gating could realize electrical double layer (EDL) formation and a three-dimensional carrier transport channel and thus substantially increased charge accumulation in the channel region and realized a high mobility above 90 cm2/(V s) (45.12 ± 22.19 cm2/(V s) on average). In addition, due to the high-capacitance EDL formed by electrolyte gating, the CuI TFTs exhibited a low operation voltage below 0.5 V (Vth = -0.045 V) and a high ON current level of 0.7 mA with an ON/OFF ratio of 1.52 × 103. We also evaluated the operational stabilities of CuI TFTs and the devices showed 80% retention under electrical/mechanical stress. All the active layers of the transistors were fabricated by solution processes at low temperatures (<100 °C), indicating their potential use for flexible, wearable, and high-performance electronic applications.

Sum Frequency Generation Imaging Microscopy of Self-Assembled Monolayers on Metal Surfaces: Factor Analysis of Mixed Monolayers.

Sum frequency generation (SFG) images of microcontact patterned self-assembled alkanethiol monolayers on metal surfaces were analyzed by factor analysis (FA) to determine the spatial distribution of the patterned monolayers over the images. Additionally, each significant abstract factor produced by FA was assessed to determine the information contained within it. These results indicate that FA of the SFG spectra is a promising method to determine the composition and identities of mixed alkanethiol systems that show different vibrational spectra and image contrast. Factor analysis has successfully been applied to SFG images obtained with low signals, which reduces the time required for full spectral SFG imaging.

Poly(1,4-phenylene vinylene) Derivatives with Ether Substituents to Improve Polymer Solubility for Use in Organic Light-Emitting Diode Devices.

New ether-substituted poly(1,4-phenylene vinylene) (PPV) derivatives were synthesized via Horner-Emmons coupling. The structures of the monomers and the resultant oligomers were confirmed by 1H and 13C NMR spectroscopies. The molecular weights of the oligomers were characterized by gel permeation chromatography, giving the number-average and weight-average molecular weights and the corresponding polydispersity indices. Measurements of UV-vis absorption and fluorescence were used to characterize the optical properties of the oligomers. Estimation of the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels and other electrochemical characteristics of the oligomers were investigated by cyclic voltammetry. Dialkyl and dialkoxy PPV oligomers were also prepared and characterized following the same instrumental methods used for the ether-substituted oligomers, providing a known reference system to judge the performance of the new conjugated oligomers. Devices were fabricated to analyze the electroluminescent characteristics of the oligomers in organic light-emitting diodes.

Quaternary Ammonium-Terminated Films Formed from Mixed Bidentate Adsorbates Provide a High-Capacity Platform for Oligonucleotide Delivery.

The exposure of quaternary ammonium groups on surfaces allows self-assembled monolayers (SAMs) to serve as architectural platforms for immobilizing oligonucleotides. The current study describes the preparation of SAMs derived from four unique bidentate adsorbates containing two different ammonium termini (i.e., trimethyl- and triethyl-) and comparison to their monodentate analogs. Our studies found that SAMs derived from the bidentate adsorbates offered considerable enhancements in oligonucleotide binding when compared to SAMs derived from their monodentate analogs. The generated SAMs were analyzed using ellipsometry, X-ray photoelectron spectroscopy, contact angle goniometry, polarization modulation infrared reflection-absorption spectroscopy, and electrochemical quartz crystal microbalance. These analyses showed that the immobilization of oligonucleotides was affected by changes in the terminal functionalities and the relative packing densities of the monolayers. In efforts to enhance further the immobilization of oligonucleotides on these SAM surfaces, we explored the use of adsorbates having aliphatic linkers with systematically varying chain lengths to form binary SAMs on gold. Mixed monolayers with 50:50 ratios of adsorbates showed the greatest oligonucleotide binding. These studies lay the groundwork for oligonucleotide delivery using gold-based nanoparticles and nanoshells.

Broadening the photoresponsive activity of anatase titanium dioxide particles via decoration with partial gold shells.

Titanium dioxide (TiO2) has gained increasing interest in materials research due to its outstanding properties and promising applications in a wide range of fields. From this perspective, we report the synthesis of custom-designed anatase TiO2 submicrometer particles coated with partial Au shells (ATiO2-AuShl). The synthetic strategy used herein yields uniformly shaped monodisperse particles. Amorphous TiO2 core particles were synthesized using template-free oxidation and hydrolysis of titanium nitride (TiN); subsequent hydrothermal treatment generated anatase TiO2 (ATiO2) particles. Coating ATiO2 particles with partial Au shells was accomplished using a simple seeded-growth method. Evaluation of the optical properties of these ATiO2-AuShl particles showed that these submicrometer composites exhibited an intense absorption peak for TiO2 in the UV region (∼326 nm) and a broad extinction band in the visible range (∼650 nm) arising from the incomplete Au shell. These ATiO2-AuShl composite particles provide a unique and effective means for broadening the optical response of TiO2-based nano- and micron-scale materials. The simplicity of our synthetic method should broaden the application of ATiO2-AuShl particles in various visible light-driven technologies.

Quercetin induces cell death in cervical cancer by reducing O-GlcNAcylation of adenosine monophosphate-activated protein kinase.

Hyper-O-GlcNAcylation is a general feature of cancer which contributes to various cancer phenotypes, including cell proliferation and cell growth. Quercetin, a naturally occurring dietary flavonoid, has been reported to reduce the proliferation and growth of cancer. Several reports of the anticancer effect of quercetin have been published, but there is no study regarding its effect on O-GlcNAcylation. The aim of this study was to investigate the anticancer effect of quercetin on HeLa cells and compare this with its effect on HaCaT cells. Cell viability and cell death were determined by MTT and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelling assays. O-GlcNAcylation of AMP-activated protein kinase (AMPK) was examined by succinylated wheat germ agglutinin pulldown and immunoprecipitation. Immunofluorescence staining was used to detect the immunoreactivitiy of O-linked N-acetylglucosamine transferase (OGT) and sterol regulatory element binding protein 1 (SREBP-1). Quercetin decreased cell proliferation and induced cell death, but its effect on HaCaT cells was lower than that on HeLa cells. O-GlcNAcylation level was higher in HeLa cells than in HaCaT cells. Quercetin decreased the expression of global O-GlcNAcylation and increased AMPK activation by reducing the O-GlcNAcylation of AMPK. AMPK activation due to reduced O-GlcNAcylation of AMPK was confirmed by treatment with 6-diazo-5-oxo-L-norleucine. Our results also demonstrated that quercetin regulated SREBP-1 and its transcriptional targets. Furthermore, immunofluorescence staining showed that quercetin treatment decreased the immunoreactivities of OGT and SREBP-1 in HeLa cells. Our findings demonstrate that quercetin exhibited its anticancer effect by decreasing the O-GlcNAcylation of AMPK. Further studies are needed to explore how quercetin regulates O-GlcNAcylation in cancer.

Structure, Wettability, and Thermal Stability of Organic Thin-Films on Gold Generated from the Molecular Self-Assembly of Unsymmetrical Oligo(ethylene glycol) Spiroalkanedithiols.

Organic thin-films on gold were prepared from a set of new, custom-designed bidentate alkanethiols possessing a mixture of normal alkane and methoxy-terminated tri(ethylene glycol) chains. The new unsymmetrical spiroalkanedithiol adsorbates were of the form [CH3O(CH2CH2O)3(CH2)5]-[CH3(CH2)n+1]C[CH2SH]2 where n = 3 and 14; designated EG3C7-C7 and EG3C7-C18, respectively. Their corresponding self-assembled monolayers (SAMs) on gold were characterized and compared with monothiol SAMs derived from an analogous normal alkanethiol (C18SH) and an alkanethiol terminated with an oligo(ethylene glycol) (OEG) moiety (i.e., EG3C7SH). Ellipsometric data revealed reduced film thicknesses for the double-chained dithiolate SAMs, which perhaps arose from the phase-incompatible merger of a hydrocarbon chain with an OEG moiety, contributing to disorder in the films and/or an increase in chain tilt. The comparable wettabilities of the SAMs derived from EG3C7SH and EG3C7-C7, using water as the contacting liquid, are consistent with exposure of the OEG moieties at both interfaces, whereas the lower wettability of the SAM derived from EG3C7-C18 is consistent with exposure of hydrocarbon chains at the interface. The data collected by X-ray photoelectron spectroscopy confirmed the formation of the new OEG-terminated dithiolate SAMs, and also revealed them as less densely packed monolayers due in part to the large molecular cross section of the OEG moieties and to their double-chained structure with dual surface bonds. Mixed SAMs formed from pairs of monothiols having chain compositions analogous to those of the chains of the new dithiols showed that an EG3C7SH/heptanethiol-mixed SAM and the EG3C7-C7 SAM produced almost identical characterization data, revealing the favorable film formation dynamics for adsorbate structures where the alkyl chains can assemble beneath the phase-incompatible OEG termini. For the mixed SAM formed from EG3C7SH/C18SH, the data indicate that the EG3C7SH component failed to incorporate in the film, demonstrating that the blending of phase-incompatible chains is sometimes best accomplished when both chains exist on a single adsorbate structure. Furthermore, the results of solution-phase thermal desorption tests revealed that the OEG-terminated films generated from the bidentate EG3C7-C7 and EG3C7-C18 adsorbates exhibit enhanced thermal stability when compared to the film generated from monodentate EG3C7SH. In a brief study of protein adsorption, the multicomponent SAMs showed a greater ability to resist the adsorption of fibrinogen on their surfaces when compared to the SAM derived from C18SH, but not better than the monolayer derived from EG3C7SH.

Digestive Ripening of Au Nanoparticles Using Multidentate Ligands.

The efficiency of multidentate ligands as digestive ripening (DR) agents for the preparation of monodisperse Au nanoparticles (NPs) was investigated. This systematic investigation was performed using ligands possessing one, two, or three thiol moieties as ligands/DR agents. Our results clearly establish that among the different ligands, monodentate ligands and the use of temperature in the range of 60-120 °C offer the best conditions for DR. In addition, when DR was carried out at lower temperatures (e.g., 60 °C), the NP size increased as the number of thiol groups per ligand increased. However, in the case of ligands possessing two and three thiol moieties, when they were heated with polydispersed particles at higher temperatures (120 or 180 °C), the etching process dominated, which affected the quality of the NPs in terms of their monodispersity. We conclude that the temperature-dependent strength of the interaction between the ligand headgroup and the NP surface plays a vital role in controlling the final particle sizes.

Semifluorinated Alkylphosphonic Acids Form High-Quality Self-Assembled Monolayers on Ag-Coated Yttrium Barium Copper Oxide Tapes and Enable Filamentization of the Tapes by Microcontact Printing.

A custom-designed semifluorinated phosphonic acid, (9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-heptadecafluorohexadecyl)phosphonic acid (F8H8PA), and a normal hexadecylphosphonic acid (H16PA) were synthesized and used to generate self-assembled monolayers (SAMs) on commercially available yttrium barium copper oxide (YBCO) tapes. In this study, we wished to evaluate the effectiveness of these monolayer films as coatings for selectively etching YBCO. Initial films formed by solution deposition and manual stamping using a non-patterned polydimethylsiloxane stamp allowed for a comparison of the film-formation characteristics. The resulting monolayers were characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). To prepare line-patterned (filamentized) YBCO tapes, standard microcontact printing (µ-CP) procedures were used. The stamped patterns on the YBCO tapes were characterized by scanning electron microscopy (SEM) before and after etching to confirm the effectiveness of the patterning process on the YBCO surface and energy-dispersive X-ray spectroscopy (EDX) to obtain the atomic composition of the exposed interface.

Robust Maleimide-Functionalized Gold Surfaces and Nanoparticles Generated Using Custom-Designed Bidentate Adsorbates.

A series of custom-designed alkanethioacetate ligands were synthesized to provide a facile method of attaching maleimide-terminated adsorbates to gold nanostructures via thiolate bonds. Monolayers on flat gold substrates derived from both mono- and dithioacetates, with and without oligo(ethylene glycol) (OEG) moieties in their alkyl spacers, were characterized using X-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy, ellipsometry, and contact angle goniometry. For all adsorbates, the resulting monolayers revealed that a higher packing density and more homogeneous surface were generated when the film was formed in EtOH, but a higher percentage of bound thiolate was obtained in THF. A series of gold nanoparticles (AuNPs) capped with each adsorbate were prepared to explore how adsorbate structure influences aqueous colloidal stability under extreme conditions, as examined visually and spectroscopically. The AuNPs coated with adsorbates that include OEG moieties exhibited enhanced stability under high salt concentration, and AuNPs capped with dithioacetate adsorbates exhibited improved stability against ligand exchange in competition with dithiothreitol (DTT). Overall, the best results were obtained with a chelating dithioacetate adsorbate that included OEG moieties in its alkyl spacer, imparting improved stability via enhanced solubility in water and superior adsorbate attachment owing to the chelate effect.

Entropy-Driven Conformational Control of α,ω-Difunctional Bidentate-Dithiol Azo-Based Adsorbates Enables the Fabrication of Thermally Stable Surface-Grafted Polymer Films.

Thermally stable radical initiator monolayers were prepared from uniquely designed α,ω-difunctional adsorbates with bidentate headgroups for the growth of nanoscale polymer films on metal surfaces. The length of the spacer separating the bidentate headgroups was varied to afford 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercaptomethyl)phenoxy)hexadecyl)-4-cyanopentanamide) (B16), 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercapto-methyl)phenoxy)decyl)-4-cyanopentanamide) (B10), and 4,4'-(diazene-1,2-diyl)bis(N-(4-(3,5-bis(mercaptomethyl)phenoxy)butyl)-4-cyanopentanamide) (B4). The structural features of the self-assembled monolayers (SAMs) derived from B16, B10, and B4 were characterized by X-ray photoelectron spectroscopy (XPS), ellipsometry, and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and compared to those derived from an analogous α,ω-difunctional adsorbate with monodentate headgroups, 4,4'-(diazene-1,2-diyl)bis(4-cyano-N-(16-mercaptohexadecyl)pentanamide (M). These studies demonstrate that the conformation (i.e., hairpin vs standing up) of the bidentate initiator adsorbates on gold surfaces was easily controlled by adjusting the concentration of the adsorbates in solution. The results of solution-phase thermal desorption tests revealed that the radical initiator monolayers generated from B16, B10, and B4 exhibit an enhanced thermal stability when compared to those generated from M. Furthermore, a study of the growth of polymer films was performed to evaluate the utility of these new bidentate adsorbate SAMs as film-development platforms for new functional materials and devices. Specifically, surface-grafted polystyrene films were successfully generated from SAMs derived from B16. In contrast, attempts to grow polystyrene films from SAMs derived from M under a variety of analogous conditions were unsuccessful.

Robust Thick Polymer Brushes Grafted from Gold Surfaces Using Bidentate Thiol-Based Atom-Transfer Radical Polymerization Initiators.

A new bromoisobutyrate-terminated alkanethiol, 16-(3,5-bis(mercaptomethyl)phenoxy)hexadecyl 2-bromo-2-methylpropanoate (BMTBM), was designed as a bidentate adsorbate to form thermally stable bromoisobutyrate-terminated self-assembled monolayers (SAMs) on flat gold surfaces to conduct atom-transfer radical polymerizations (ATRPs). The monolayers derived from BMTBM were characterized by ellipsometry, X-ray photoelectron spectroscopy (XPS), and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and compared to the monolayers formed from 16-mercaptohexadecyl 2-bromo-2-methylpropanoate (MBM), 16-(3-(mercaptomethyl)phenoxy)hexadecyl 2-bromo-2-methyl-propanoate (MTBM), and octadecanethiol (C18SH). In this study, although the monolayer derived from BMTBM was less densely packed than those derived from MBM and MTBM, the bidentate adsorbates demonstrated much higher thermal stability in solution-phase thermal desorption tests, owing to the "chelate effect". The enhanced stability of the BMTBM SAMs ensured the development of thick brushes of poly(methyl methacrylate) and polystyrene at elevated temperatures (60, 90, 105, and 120 °C). In contrast, SAMs derived from MBM and MTBM failed to grow polymer brushes at temperatures above 100 °C.

Surface Dipoles: A Growing Body of Evidence Supports Their Impact and Importance.

Surface dipoles arise from differences in the distribution of electron density of interfacial molecular structures as expressed by charge separation. The direction and magnitude of the associated dipole moments directly impact a variety of interfacial phenomena. For example, the wettability of thin film-coated solid surfaces toward polar contacting liquids can be systematically adjusted by reorienting the direction of an array of interfacial dipoles, while the vector sum total of all of the dipole moments associated with such thin films can be used to tune the work function of a metal. One method of producing such dipole arrays is by coating a surface with a self-assembled monolayer (SAM), which is a thin organic film of amphiphilic adsorbates that spontaneously assemble on a surface. The interfacial properties of SAMs can be menu-selected by choice of adsorbate structure using ω-terminated thiols on gold surfaces as a convenient system for studying and utilizing these properties. In this Account, we describe the impact of an array of oriented surface dipoles upon the interfacial energy of the thin film bearing such an array. Our analysis of these films divides the subject of surface dipole arrays into three types: (1) those directing a well-defined electronegative pole toward the interface, (2) those incorporating an invertable polar group, and (3) those directing a well-defined electropositive pole toward the interface. With regard to the first category, we analyze the impact of permanent dipoles on the wettability of alkanethiolate SAMs generated from adsorbates possessing well-defined transitions between terminal fluorocarbon and underlying hydrocarbon chain segments. The second category covers recent reports of light-responsive SAMs formed from azobenzene-based adsorbates. Finally, the third category explores a unique example of a dipole array that exposes the positive ends of the interfacial dipoles formed from CH3-terminated fluorocarbon tailgroups. Our analysis of the SAMs formed from these carefully crafted adsorbates encompassing several series of fluorocarbon-containing thiols provides support for a conclusion that oriented surface dipoles exert a significant influence on interfacial energetics and wettability. In contrast to the limited distance from the interface that a surface dipole array will have upon contacting liquids, the work function of a thin film reflects the influence of all the polar groups within the film. Therefore, we also explore the change in the substrate work function for n-alkanethiol-modified gold surfaces as a function of molecular length and for other adsorbates as a function of their chemical composition.

Self-Assembled Monolayers Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols.

Self-assembled monolayers (SAMs) were prepared on gold substrates from an unsymmetrical partially fluorinated spiroalkanedithiol adsorbate with the specific structure of [CH3(CH2)7][CF3(CF2)7(CH2)8]C[CH2SH]2 (SADT) and compared to SAMs formed from the semifluorinated monothiol F8H10SH [CF3(CF2)7(CH2)10SH] of analogous chain length and n-octadecanethiol. The adsorbate with two alkyl chains, one terminally fluorinated and the other nonfluorinated, was designed to form monolayers in which the bulky helical fluorocarbon segments assemble on top of an underlying layer of well-packed trans-extended alkyl chains. Different combinations of deposition solvents and temperatures were used to produce the bidentate SAMs. Characterization of the resulting monolayers revealed that SAMs formed in DMF at room temperature allow complete binding of the sulfur headgroups to the surface and exhibit higher conformational order than those produced using alternative solvent/temperature combinations. The reduced film thicknesses and enhanced wettability of the SADT SAMs, as compared to the SAMs generated from F8H10SH, suggest loose packing and an increase in the tilt of the terminal fluorocarbon chain segments. Nevertheless, the density of the underlying hydrocarbon chains of the SADT SAMs was higher than that of the F8H10SH SAMs, owing to the double-chained structure of the new adsorbate. The conformational orders of the SAM systems were observed to decrease as follows: C18SH > F8H10SH > SADT. However, the SAMs formed from this new double-chained bidentate adsorbate in DMF expose a fluorinated interface with a relatively low surface roughness, as determined by contact-angle hysteresis.

Peer supporter experiences of home visits for people with HIV infection.

PURPOSE: This study's purpose was to explore the experiences of peer supporters regarding their work in a home visit program for people with HIV infection. PATIENTS AND METHODS: A qualitative descriptive study was conducted using focus groups. Participants were 12 HIV-positive peer supporters conducting home visits with people living with HIV/AIDS in South Korea. Thematic analysis was used to analyze the data. RESULTS: Six major themes emerged: feeling a sense of belonging; concern about financial support; facing HIV-related stigma and fear of disclosure; reaching out and acting as a bridge of hope; feeling burnout; and need for quality education. The study findings indicate that although peer supporters experience several positive aspects in the role, such as feelings of belonging, they also experience issues that make it difficult to be successful in the role, including the position's instability, work-related stress, and concerns about the quality of their continuing education. CONCLUSION: The findings suggest that to maintain a stable and effective peer supporter program, such positions require financial support, training in how to prevent and manage stress associated with the role, and a well-developed program of education and training.