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Hydrogen Bonds and Molecular Orientations of Supramolecular Structure between Barbituric Acid and Melamine Derivative at the Air/Water Interface Revealed by Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy
摘要： We studied the supramolecular structure between barbituric acid (pyrimidine-2,4,6(1H,3H,5H)-trione, BA) and an amphiphilic melamine derivative at the air/water interface by heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy. HD-VSFG measurements in situ showed a positive broad band from 2300 to 2950 cm?1. By comparing the experimental results with ab initio molecular dynamics (AIMD) simulations, we assigned the broad band to the NH stretching modes of BA strongly hydrogen-bonded to the melamine derivative. In addition, we report in situ HD-VSFG spectra of the interfacial supramolecular structure in the CO stretching region. Two CO stretching bands were identified. On the basis of the signs of the C=O bands, we uniquely determined the orientation of BA. The strong hydrogen bonds and the molecular orientations are direct evidence for the supramolecular structure based on complementary hydrogen bonds at the air/water interface.
关键词： Supramolecular Structure,Molecular Orientations,Barbituric Acid,Melamine Derivative,Hydrogen Bonds,Air/Water Interface,Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy
更新于2025-09-19 17:13:59
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Self-Assembled Monolayers with Embedded Dipole Moments for Work Function Engineering of Oxide Substrates
摘要： Self-assembled monolayers (SAMs) are frequently used for work function (WF) engineering of different materials. For this, typically dipolar groups are attached to the molecule terminus at the SAM?ambient interface, which also influences its chemistry. WF engineering and interface chemistry can, however, be decoupled from one another using embedded dipolar groups, as has been demonstrated before for thiolate SAMs on metals. Herein, we extend this concept to oxide substrates. For this, a series of biphenyl-based molecules with a phosphonic acid (PA) anchoring group was synthesized, with one of the nonpolar phenyl units exchanged for a polar pyrimidine moiety, the dipole moment of which is oriented either toward (“down”) or away (“up”) to/from the PA group and, consequently, to/from the substrate. SAMs of these molecules formed on indium tin oxide (ITO), a frequently used and application-relevant oxide substrate, feature a uniform molecular configuration, dense molecular packing, and an upright molecular orientation. These SAMs exhibit pronounced electrostatic effects associated with the embedded dipolar groups, viz. shifts of the characteristic peaks in the C 1s X-ray photoelectron spectra and WF variations. The latter values were found to be 3.9, 4.85, and 4.4 eV for the up, down, and nonpolar reference SAM-engineered ITO, respectively. Consequently, these SAMs can serve as a powerful tool to monitor WF engineering effects in a variety of device assembles, decoupling these effects from the interface chemistry. The comparably low WF value for the up SAM is particularly important since it extends a rather limited variety of SAMs capable of lowering the WF of ITO.
关键词： Phosphonic acid,Self-assembled monolayers,Work function engineering,Embedded dipolar groups,Indium tin oxide,Oxide substrates
更新于2025-09-19 17:13:59
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Enhanced stability and solar cell performance via π-conjugated Lewis base passivation of organic inorganic lead halide perovskites
摘要： High power conversion efficiency (PCE) and good long-term stability of the perovskite solar cell (PSC) are two important factors on its commercial applications. Here, we propose a simple way to improve the PSC performance by adding 3,3',5,5'-azobenzene-tetracarboxylic acid (H4abtc) into the lead iodide (PbI2) precursor solution with Lewis acid-base adduct via two-step solution method. 24% enhancement of the PCE is achieved for the PSC with 2.0% H4abtc comparing with the pure PSC without H4abtc. Further research suggests that the H4abtc can passivate grain boundaries of perovskite film by reacting with the lead cation, therefore leading to good thermal stability and anti-moisture of perovskite films. The paper provides a new method to prepare a stable and efficient PSC by employing a novel Lewis base to passivate grain boundaries and gain high-quality perovskite films.
关键词： Perovskite solar cell,Additive,Two-step solution method,Lewis acid-base adduct
更新于2025-09-19 17:13:59
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[IEEE 2020 8th International Winter Conference on Brain-Computer Interface (BCI) - Gangwon, Korea (South) (2020.2.26-2020.2.28)] 2020 8th International Winter Conference on Brain-Computer Interface (BCI) - Implementation of multi-connected single-channel functional near-infrared spectroscopy system for hyperscanning study
摘要： A drug delivery system is used for targeting drugs to specific cells. Various drug carriers, that also reduce the side effects of unbound drugs, have been introduced and commercialized in the pharmaceutical field. Among them, synthetic biodegradable polymers have received much attention attributed to their low toxicity, controllable biodegradation rates, manufacturability, and low costs. This paper reviews the salient characteristics of biodegradable polymers as drug carriers and their microfabrication methods. The reviewed microfabrication methods include laser micromachining, rapid prototyping, replication, emulsification, microfluidic fabrication, and X-ray-lithography-based methods. For these microfabrication methods, critical dimensions, feature variety, solvent compatibility, production throughput, and tooling requirements are also summarized.
关键词： poly-capro-lactone (PCL),laser micromachining,emulsification,microfluidics,poly(lactic-co-glycolic acid) (PLGA),biodegradable polymers,Drug delivery systems (DDS),rapid prototyping,replication,x-ray-lithography,microfabrication,drug carriers
更新于2025-09-19 17:13:59
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Performances of ionic liquid matrices with butyl ammonium counterion for matrix-assisted laser desorption/ionization mass spectrometric detection and analysis of sucralfate
摘要： In this work, the performances of two ionic liquid matrices (ILMs) with the same ammonium counterpart for mass spectrometric analysis of the insoluble and soluble sucralfate were compared. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) was performed assisted by the butylammonium salts of a-cyano-hydroxycinnamic acid (CHCAB) and 2,5-dihydroxybenzoic acid (DHBB). CHCAB has a higher IE than DHBB, but better optical properties. CHCAB is more suitable for the analysis of sucralfate, although molecular ions of both compounds were detectable only with low intensities. Thus, optical properties of ILMs are crucial to enhance the sensitivity of MALDI MS detection of polysulfated oligosaccharides.
关键词： sucralfate,a-cyano-hydroxycinnamic acid,Ionic liquid matrices,2,5-dihydroxybenzoic acid,matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
更新于2025-09-16 10:30:52
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Bionanosensor based on N-doped graphene quantum dots coupled with CoOOH nanosheets and their application for in vivo analysis of ascorbic acid
摘要： Herein, we employ 3D nitrogen-doped porous graphene frameworks (3D NPG) as raw material to prepare emissive nitrogen doped graphene quantum dots (r-NGQDs) via chemical oxidation method. The as-prepared fluorescent r-NGQDs was integrated with CoOOH nanosheets to construct a sensing platform for in vivo ascorbic acid (AA) analysis. Initially, the fluorescence emission intensity of r-NGQDs was quenched by CoOOH nanosheets based on the inner filter effect (IFE). Then the quenched intensity of r-NGQDs and CoOOH nanosheets system was enlightened by the addition of AA, since AA could consume CoOOH nanosheets through redox reaction, leading to the release of r-NGQDs and fluorescence restoration. Moreover, the restored fluorescence intensity of r-NGQDs is highly dependent on the concentration of AA which endows them as a quantitative analysis of AA with a limit of detection (LOD) reach up to1.85 μM (n = 3) in aqueous solution. Finally, the as constructed bionanosensor was further employed for in vivo analysis of AA in living rat brain microdialysate with basal value up to 9.4 ± 1.4 μM (n = 3).
关键词： Nitrogen-doped porous graphene,Graphene quantum dots,Ascorbic acid,In vivo,CoOOH nanosheets
更新于2025-09-16 10:30:52
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Two topologically different 3D Cu <sup>II</sup> metal–organic frameworks assembled from the same ligands: control of reaction conditions
摘要： Bifunctional ligands containing both carboxylic and sulfonate groups can adopt versatile coordination modes to produce novel metal–organic frameworks (MOFs) with high-dimensional networks and interesting topologies. Using 2,20-disulfonylbiphenyl-4,40-dicarboxylic acid (H4L) as a linker and 4,40-bipyridine (4,40-bpy) as a co-ligand, two novel 3D CuII MOFs, {[Cu2(L)(4,40-bpy)2.5(H2O)](cid:2)1.7H2O}n, (1), and {[Cu2(L)(4,40-bpy)2](cid:2)DMA(cid:2)3H2O}n, (2), have been synthesized and structurally characterized by X-ray crystallography (DMA is N,N-dimethylacetamide). MOF (1) shows an unprecedented trinodal 4,4,5-connected network with the Schla¨ ?i symbol (4.62.73)(43.65.7.8)(6.73.8.10), while MOF (2) indicates a binodal 4,6-connected fsc network with the Schla¨ ?i symbol (44.610.8)(44.62). MOFs (1) and (2) were further characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction and thermogravimetric analysis. MOF (1) shows a high water and chemical stability. The proton conductivity of (1) and CO2 adsorption of (2) were also investigated.
关键词： 4,4,5-connected network,topology,structural diversity,2,20-disulfonylbiphenyl-4,40-dicarboxylic acid,water and chemical stability,crystal engineering
更新于2025-09-16 10:30:52
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DC-biased optofluidic biolaser for uric acid detection
摘要： Optofluidic biolaser is an emerging technology for chemical and biomedical sensing. However, the sensitivity of optofluidic laser is still limited by the laser threshold condition. In this paper we report a DC-biased optofluidic biolaser for uric acid (UA) detection. Inside a Fabry-Perot laser cavity, a coupled enzyme reaction was employed to transform the detection of UA into the detection of analyte-converted hydrogen peroxide (H2O2). The fluorescent product of the enzyme-catalyzed reaction, resorufin, was employed as gain medium for optofluidic lasing. An optimized concentration of H2O2 was pre-added as a DC bias to counterbalance the requirement of high analyte concentration for lasing. UA detection with a limit of detection of 3.63 μM was achieved with a low sample volume as small as 10 μl. This work provides a sensitive technology using optofluidic biolaser for the detection of substance in human body fluids that can be converted into H2O2.
关键词： Optofluidic laser,uric acid,enzyme catalytic reaction,optical biosensing
更新于2025-09-16 10:30:52
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SERS detection of sodium thiocyanate and benzoic acid preservatives in liquid milk using cysteamine functionalized core-shelled nanoparticles
摘要： A cysteamine functionalized core shelled nanoparticles (Au@Ag-CysNPs) was presented for simultaneous and rapid detection of sodium thiocyanate (STC) and benzoic acid (BA) preservatives in liquid milk using surface-enhanced Raman spectroscopy (SERS) technique. A spectrum covering 350-2350 cm-1 region was selected to detect STC with concentrations ranging from 0.5 to 10 mg/L and BA with concentrations ranging from 15 to 240 mg/L in milk samples. Characterization of nanoparticles using high-resolution TEM confirmed that the successful synthesis of Au@AgNPs with core (gold) size of 28 nm and shell (silver) thickness of about 5 nm was grafted with 120 μL of 0.1 nM cysteamine hydrochloride. Results showed that Au@Ag-CysNPs could be used to detect STC up to 0.03 mg/L with a limit of quantification (LOQ) of 0.039 mg/L and a coefficient of determination (R2) of 0.9833 in the milk sample. For detecting BA, it could be screened up to 9.8 mg/L with LOQ of 10.2 mg/L and R2 of 0.9903. The proposed substrate was also highly sensitive and the employed method involved only minor sample pretreatment steps. It is thus hoped that the new substrate could be used in the screening of prohibited chemicals in complex food matrices in future studies.
关键词： SERS,milk adulteration,sodium thiocyanate,nanoparticles,benzoic acid
更新于2025-09-16 10:30:52
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Inorganic perovskite engineering through incorporation of a carboxylic acid containing ligand for performance enhancement in perovskite light-emitting diodes
摘要： Inorganic cesium lead halide perovskites (such as CsPbBr3) are emerging as one kind of promising optoelectronic material with good stability, narrow color spectrum and facile bandgap tunability. However, the morphology issue of CsPbBr3 film limits its applications in perovskite light-emitting diodes (PeLEDs). Here, we present an effective strategy of perovskite structure engineering by incorporating a long chain cation ligand (HOOC-PMA-Br) into CsPbBr3, aiming to optimize perovskite morphology and thereby improve device performance. It is found that the HOOC-PMA-Br ligand plays a key role in controlling the dimension and crystal growth of perovskites, attributed to the formation of hydrogen bond networks induced by the carboxylic acid unit. With an optimized doping ratio of HOOC-PMA-Br, (HOOC-PMA)2CsPb2Br7 perovskite not only maintains a 3D structure but also presents excellent morphology with a uniform distribution of smaller grain size, smoother surface and better coverage like that of a quasi-2D structure, along with a much higher photoluminescence quantum yield than that of pure CsPbBr3. Significantly, (HOOC-PMA)2CsPb2Br7 endows PeLEDs with remarkably higher luminance and efficiencies than that of CsPbBr3 based devices.
关键词： morphology,inorganic perovskite,carboxylic acid,performance enhancement,light-emitting diodes
更新于2025-09-16 10:30:52