- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Self-Assembled Monolayers with Distributed Dipole Moments Originating from Bipyrimidine Units
摘要： The concept of distributed dipoles in monomolecular self-assembly on solid substrates was tested for the example of thiolate self-assembled monolayers (SAMs) on Au(111) containing dipolar 2,5?-bipyrimidine units. These were attached to a thiol anchoring group either directly or via a phenylene-methylene spacer, with the spacer decoupling the dipolar moiety from the substrate and promoting layer formation. As expected, the SAMs containing spacer groups exhibited a higher quality, including a higher packing density and nearly upright molecular orientation. The electrostatic effects of the dipolar bipyrimidine moieties were tested through C 1s and N 1s photoemission spectra, where electrostatic core-level shifts impact the shapes of the spectra. Additionally, changing the orientation of the dipoles allows a variation of the work function over a range of ~1.35 eV. The experiments were complemented by density-functional theory calculations. The work function tuning range was reasonably high, but smaller than expected considering that for SAMs with a single embedded pyrimidine group per molecule work-function changes already amounted to ~1.0 eV. This behavior is rooted in an asymmetry of the studied SAMs: For dipoles pointing away from the substrate, the expected doubling of the work function change between monopyrimidine and bipyrimidine SAMs essentially occurs. Conversely, for the downward-oriented pyrimidine dipoles, the second polar ring has hardly any effect. Consistent observations were made for the core-level shifts. We discuss several factors, which are potentially responsible for this asymmetry, like disorder, depolarization, or Fermi-level pinning. Of these, the most likely explanation is the adsorption of airborne contaminants interacting with the nitrogen atoms in the immediate vicinity of the outer surface, which are present only in films with downward oriented dipoles. In spite of these complications, some of the introduced distributed dipole SAMs serve as important model systems for understanding electrostatic effects at interfaces. They are also of interest for controlling carrier-injection barriers in organic (opto)electronic devices.
关键词： Bipyrimidine Units,Distributed Dipole Moments,Self-Assembled Monolayers,Organic (Opto)electronic Devices,Work Function Tuning
更新于2025-09-12 10:27:22
-
High-selectivity NOx sensors based on an Au/InGaP Schottky diode functionalized with self-assembled monolayer of alkanedithiols
摘要： This work was devoted to fabricating high-selectivity NOx gas sensors based on an Au/InGaP Schottky diode. In order to enhance the sensing selectivity and sensing response, a self-assembled monolayer (SAM) of alkanedithiol was used to modify the Schottky contact with an S-Au covalent bond based on the self-assembled property and terminal functional group. The studied SAM/Au/InGaP Schottky diodes were fabricated by semiconductor processes and immersion treatment. The effects of the carbon number (CN) of SAM, the SAM immersion time, and immersion dithiol concentrations were comprehensively studied in this work. In addition, the selectivity and sensing performance of dithiol functionalized Au/InGaP Schottky diodes under different temperatures and NOx concentrations were studied for comparison. In order to obtain the optimal NOx sensing performance, cyclic voltammetry (CV) was employed to study the self-assembled performance of the dithiol monolayer on the Au surface. The sensing responses of 16.5 and 7.2 were obtained under 100 ppm NO2/N2 and NO/N2 at 30oC, respectively, for the studied 1,10-decanedithiol (DDT)/Au/InGaP device. Moreover, compared to other sensing gases, the DDT/Au/InGaP sensing device showed high selectivity toward NOx gas. Furthermore, the theoretical first-order kinetic and thermodynamic theoretical analysis were consistent with the experimental transient and steady-state sensing results. Therefore, the studied SAM/Au/InGaP Schottky diode demonstrated promising results for NOx sensing applications.
关键词： Nitrogen oxides,Gas sensors,Schottky diode,Self-assembled monolayers (SAM),InGaP,Alkanedithiol
更新于2025-09-12 10:27:22
-
Polarization nano-tomography of tightly focused light landscapes by self-assembled monolayers
摘要： Recently, four-dimensional (4D) functional nano-materials have attracted considerable attention due to their impact in cutting-edge fields such as nano-(opto)electronics, -biotechnology or -biomedicine. Prominent optical functionalizations, representing the fourth dimension, require precisely tailored light fields for its optimal implementation. These fields need to be like-wise 4D, i.e., nano-structured in three-dimensional (3D) space while polarization embeds additional longitudinal components. Though a couple of approaches to realize 4D fields have been suggested, their breakthrough is impeded by a lack of appropriate analysis techniques. Combining molecular self-assembly, i.e., nano-chemistry, and nano-optics, we propose a polarization nano-tomography of respective fields using the functional material itself as a sensor. Our method allows a single-shot identification of non-paraxial light fields at nano-scale resolution without any data post-processing. We prove its functionality numerically and experimentally, elucidating its amplitude, phase and 3D polarization sensitivity. We analyze non-paraxial field properties, demonstrating our method’s capability and potential for next generation 4D materials.
关键词： four-dimensional (4D) functional nano-materials,nano-optics,non-paraxial light fields,self-assembled monolayers (SAMs),polarization nano-tomography
更新于2025-09-12 10:27:22
-
Towards scalable fabrication of atomic wires in silicon by nano-patterning self-assembled molecular monolayers
摘要： Developing a scalable method to fabricate atomic wires is an important step for building solid-state semiconductor quantum computers. In this work, we developed a selective doping strategy by patterning the self-assembled monolayer to a few nanometers using standard nanofabrication processes, which significantly improves the lateral doping resolution of monolayer doping (MLD) from microscale to nanoscale. Using this method, we further explore the possibility to fabricate phosphorus wires in silicon by patterning self-assembled diethyl vinylphosphonate monolayers into lines with a width ranging from 500 nm to 10 nm. The phosphorus dopants are driven into silicon by rapid thermal annealing, forming dopant wires. Four-probe and Hall effect measurements are employed to characterize the dopant wires. The results show that the conductance is linear with the width for the wires, showing the success of the monolayer patterning process to nanoscale. To fabricate atomic wires made of one or a few lines of phosphorus atoms, we need to significantly shorten the thermal diffusion length and increase the dopant incorporation rate at the same time. Pulsed laser annealing may be a promising solution. The present work provides a promising pathway for mass fabrication of atomic wires in silicon that may find important applications in quantum computing.
关键词： atomic wires,semiconductors,nanoelectronics,Monolayer doping,self-assembled monolayers
更新于2025-09-12 10:27:22
-
Combined SERS/DFT studies of push–pull chromophore self-assembled monolayers: insights into their surface orientation
摘要： Having clear and deep information on the surface/interface of deposited molecules is of crucial importance for the development of efficient optoelectronic devices. This paper reports on a joint experimental/theoretical hybrid approach based on Raman spectroscopy in order to provide information on the orientation of push–pull chromophores deposited onto a gold surface. In addition, several parameters can strongly control or impede the orientation of such molecules on the surface such as: the molecular structure, the surface itself, the method of deposition and the solvents used. From this approach, additional information has been highlighted such as perpendicularly depositing the molecule on the surface, the bithiophene compounds displaying more solvent effects compared to terthiophene molecules and so on. According to the results, the joint SERS/DFT study proves to be an effective tool for probing the arrangement of push–pull chromophores and selecting the right experimental conditions to tune the surface properties.
关键词： SERS,DFT,push–pull chromophores,surface orientation,self-assembled monolayers
更新于2025-09-12 10:27:22
-
Vibrational Spectra of Thiolate-Protected Gold Nanocluster with Infrared Reflection Absorption Spectroscopy: Size- and Temperature-Dependent Ordering Behavior of Organic Monolayer
摘要： Vibrational spectra of thiolate-protected gold nanoclusters, prepared in a monolayer manner using the Langmuir?Blodgett method, were measured by means of infrared re?ection absorption spectroscopy (IRAS). A transferred monolayer of gold nanoclusters ligated by dodecanethiolate or 2-phenylethane-1-thiolate onto a single-crystal gold (Au) surface of Au(111) exhibits worthy IRAS spectra that reveal temperature-dependent behaviors from 100 to 340 K as well as comprehensive peak assignments based on density functional theory calculations: the conformation change in ligands between all trans and gauche defect forms with temperature. In addition to the temperature dependence, the cluster size dependence of alkyl and phenyl moieties is discussed, compared with the IRAS spectra of the corresponding self-assembled monolayers (SAMs) on Au(111). Ligands spreading three-dimensionally from the Au core determine the coordination structure of the ligated Au nanoclusters.
关键词： self-assembled monolayers,density functional theory calculations,Langmuir?Blodgett method,thiolate-protected gold nanoclusters,Vibrational spectra,temperature-dependent behaviors,infrared re?ection absorption spectroscopy
更新于2025-09-12 10:27:22
-
Formation of Highly Ordered Terminal Alkyne Self-Assembled Monolayers on the Au{111} Surface through Substitution of 1-Decaboranethiolate
摘要： The reaction aimed at completing and closing the open cages of 1-decaboranethiol self-assembled monolayers (SAMs) on Au{111} with 4-phenyl-1-butyne results in highly ordered monolayers of 4-phenyl-1-butyne. The initially disordered 1-decaboranethiolate changed into ordered (√3×√3)R 30° lattices on Au{111} typical of alkyne SAMs, indicating the complete substitution of 1-decaboranethiolate moieties, as determined by nanoscale imaging with scanning tunneling microscopy and X-ray photoelectron spectroscopy. Vibrational spectroscopy results indicate that the process happens gradually and that alkynyl groups are not totally oxidized in the ordered 4-phenyl-1-butyne monolayer.
关键词： Au{111},self-assembled monolayers,vibrational spectroscopy,scanning tunneling microscopy,X-ray photoelectron spectroscopy,4-phenyl-1-butyne,1-decaboranethiol
更新于2025-09-11 14:15:04
-
Multiwalled carbon nanotube based aromatic volatile organic compound sensor: sensitivity enhancement through 1-hexadecanethiol functionalisation
摘要： Aromatic volatile organic compound (VOC) sensors are attracting growing interest as a response to the pressing market need for sensitive, fast response, low power consumption and stable sensors. Benzene and toluene detection is subject to several potential applications such as air monitoring in chemical industries or even biosensing of human breath. In this work, we report the fabrication of a room temperature toluene and benzene sensor based on multiwall carbon nanotubes (MWCNTs) decorated with gold nanoparticles and functionalised with a long-chain thiol self-assembled monolayer, 1-hexadecanethiol (HDT). High-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR) were performed to characterize the gold nanoparticle decoration and to examine the thiol monolayer bonding to the MWCNTs. The detection of aromatic vapours using Au-MWCNT and HDT/Au-MWCNT sensors down to the ppm range shows that the presence of the self-assembled layer increases the sensitivity (up to 17 times), selectivity and improves the response dynamics of the sensors.
关键词： multiwall carbon nanotubes (MWCNTs),vapour sensor,sensitivity,gold-decorated MWCNTs,self-assembled monolayers (SAMs),selectivity
更新于2025-09-11 14:15:04
-
Handbook of Graphene || Self‐Assembled Thin Films of Graphene Materials for Sensors
摘要： It is well known that graphene and its derivatives exhibit unique optical, electrical, mechanical, and chemical properties, which are valuable for sensing applications. However, the chosen methods to synthesize and process graphene to form the sensing unit are critical steps defining the real property of the final sensor. Instead of a physical mixture of graphene in a bulk support, different immobilization techniques have been investigated to take advantage of the outstanding properties of graphene and graphene-based materials, such as linkage to the self-assembled monolayers, layer-by-layer, and Langmuir–Blodgett techniques. Such techniques lead to a new concept of nanoarchitectonics allowing to take a synergistic effect on mixing distinct properties with various materials in a unique device. Examples of these approaches on developing electrochemical, electric, and optical sensors are discussed in an overview.
关键词： chemical synthesis,self-assembled monolayers,Sensors,layer-by-layer,Langmuir–Blodgett,biosensors
更新于2025-09-11 14:15:04
-
Fabrication of rhodanine self-assembled monolayer thin films on copper: Solvent optimization and corrosion inhibition studies
摘要： Rhodanine self-assembled monolayer (Rh-SAM) films were prepared on copper specimens in different solvents. The assembled films were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR) and contact angle measurements. The inhibition efficiency of the films against copper corrosion in 3.5% NaCl solution was studied using electrochemical impedance spectroscopy (EIS), potantodynamic polarization (PP) and linear polarization resistance (LPR) techniques. It was found that very well-ordered and almost homogenously distributed Rh-SAM films were assembled on the copper surface. The appearance, electrochemical and physical properties of the films were depending on preparation conditions. The SAM films reduce greatly the corrosion rate of copper in 3.5% NaCl solution. Their protection ability depends on the type of solvent. The best film for this aim was obtained in 10 mM Rh after 24 h film formation time when methanol was used as solvent. The high corrosion protection ability of the films was assigned to the formation of a compact and protective structure over the copper surface. Assembling SAM films of this healthy compound and their application for corrosion protection has not been reported yet and is very original.
关键词： Copper,Rhodanine,Self-assembled monolayers,Corrosion inhibition
更新于2025-09-10 09:29:36