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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
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Near-Infrared Microlasers from Self-assembled Spiropyrane-Based Microsphercial Caps
摘要： Near-infrared (NIR) microlasers play a significant role in telecommunication and biomedical tissue imaging. However, it remains a big challenge to realize NIR microlasers due to the difficulty in preparing highly efficient NIR luminescent materials and perfect optical resonators. Here we propose a molecular design strategy to creatively realize the first spiropyrane-based NIR microlasers with low threshold from self-assembled microsphercial caps. Tetraphenylethylene (TPE) moiety with a highly twisted conformation provides a large free volume to facilitate the photoisomerization process of spiropyrane (SP) and enhance NIR emission of merocyanine in the solid state. Moreover, self-assembled TPE-SP microsphercial caps simultaneously serve as gain media and resonating microcavities, providing optical gain and feedback for NIR laser oscillations with a low threshold (3.68 μJ/cm2). These results are beneficial for deeply understanding the SP microstructures-lasing emission characteristic relationship and provide a useful guideline for the rational molecular design of NIR microlasers with special functionalities.
关键词： tetraphenylethylene twisted conformation,spiropyrane,enhanced quantum yield,self-assembled microsphercial cap,NIR microlaser
更新于2025-09-11 14:15:04
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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
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The Porter-Whitesides Discrepancy: Revisiting Odd-Even Effects in Wetting Properties of n-Alkanethiolate SAMs
摘要： This review discusses the Porter-Whitesides discrepancy in wetting properties of n-alkanethiolate self-assembled monolayers (SAMs). About 25 years ago, Whitesides and coworker failed to observe any odd-even effect in wetting, however, Porter and his coworker did, albeit in select cases. Most previous studies agreed with Whitesides’ results, suggesting the absence of the odd-even effect in hydrophobicity of n-alkanethiolate SAMs. Recent reports have, however, found the odd-even effect in hydrophobicity of n-alkanethiolate SAMs on smooth substrates, indicating that hydrophobicity, and analogous interfacial properties, of n-alkanethiolate SAMs significantly depends on the properties of substrate. Unfortunately, the Whitesides and Porter papers do not report on the quality of the surfaces used. Based on recent work, we inferred that the original discrepancy between Whitesides and Porter can be attributed to the quality of the surface. Odd-even effect of SAMs in charge transport, capacitance, friction, and SAM structure are also discussed in this review to inform the general discussion. The discrepancy between Porter's group and Whitesides’ group could be due to surface roughness, morphology, oxidation, and adventitious contaminants.
关键词： hydrophobicity,roughness,odd-even effect,self-assembled monolayer
更新于2025-09-09 09:28:46
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Facile Preparation of Functional Group Gradient Surfaces by Desorption and <i>Re</i> -Adsorption of Alkanethiols on Gold
摘要： Many organisms live in various stimuli-responsive milieus of signaling components in gradient forms which are known to be closely related to biological phenomena including embryonic development, wound repair, and tumor metastasis. In addition, the physicochemical properties of gradient surfaces, i.e., a continuous spatial variation of gradient components, enable various types of biological/biochemical research such as cell proliferation/migration and tissue engineering. Various techniques have been reported for the preparation of gradient surfaces, including laminar flow mixing in microfluidic channels, cross-diffusion of alkanethiols, microfluidic permeation printing, oblique deposition and template coating, controlled polymerization on substrates, and controlled UV irradiation on photo-responsive substrates. Previously, we reported a simple method for the generation of multi-component gradient surfaces on self-assembled monolayers (SAMs) on gold. The monolayers consisted of quinone derivatives which reacted with reducing agents in a predictable manner to produce amine gradient surfaces. Recently, desorption and re-adsorption-based methods on SAMs have gained attention, in which alkanethiolates on gold surfaces were desorbed in order to provide an empty space gradient, following which other types of alkanethiols filled up the empty space, leading to an end group gradient of alkanethiolates. For example, Kim et al. reported a simple and flexible method for preparing cell adhesion ligand patterns on SAMs by using a laser beam equipped in a matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer. Similarly, Meyyappan et al. demonstrated that a surface gradient can be achieved by irradiating a focused laser beam on SAMs with subsequent re-adsorption of a second alkanethiol. Fioravanti et al. reported on a new method to fabricate surface chemical gradients of alkanethiols through combining reductive electrochemical desorption and partial re-adsorption of alkanethiolates. Recently, we found that tetrahydrofuran (THF) highly compromises the stability of SAMs on gold, and thus induces unusually fast exchange of alkanethiolates of SAMs with other alkanethiols in the solution. In this study, we harnessed this desorption capability of THF for the preparation of functional group gradient surfaces. In our strategy, a monolayer of alkanethiolates was exposed to THF in a time-dependent manner followed by immersion in a solution of other functional group-terminated alkanethiols, leading to functional group gradient surfaces. The functional group then played a role of a chemical handle to conjugate various functional molecules for the formation of gradients of those components.
关键词： Gradient surfaces,Alkanethiols,Desorption,Self-assembled monolayers,Tetrahydrofuran
更新于2025-09-09 09:28:46
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Enhanced Signal Amplification in a TLR-4 Biosensor Utilizing Ferrocene-Terminated Mixed Monolayers
摘要： A major challenge in effectively treating infections is to provide timely diagnosis of a bacterial or viral agent. Current cell culture methods require >24 hours to identify the cause of infection. The Toll-Like Receptor (TLR) family of proteins can identify classes of pathogens and has been shown to work well in an impedance-based biosensor, where the protein is attached to an electrode via a self-assembled monolayer (SAM). While the sensitivity of these sensors has been good, they contain a high resistance (>1 kΩ) SAM, generating relatively small signals and requiring longer data collection, which is ill-suited to implementation outside of a laboratory. Here, we describe a novel approach to increase the signal magnitude and decrease the measurement time of a TLR-4 biosensor by inserting a redox-active ferrocenyl-terminated alkane thiol into a mixed SAM containing hydroxyl- and carboxyl-terminated alkane thiols. The SAM formation and modification was confirmed via contact angle and X-ray photoelectron spectroscopy measurements, with TLR-4 immobilization demonstrated through a modified immunosorbent assay. It is shown that these TLR-4 biosensors respond selectively to their intended target, Gram-negative bacteria at levels between 100 and 105 lysed cells/mL, while remaining insensitive to Gram-positive bacteria or viral particles at up to 105 particles/mL. Furthermore, the signal enhancement due to the addition of ferrocene decreased the measurement time to less than one minute and has enabled this sensor to be used with an inexpensive, portable, handheld potentiostat that could be easily implemented in field settings.
关键词： TLR-4,Toll-Like Receptor biosensor,Gram-negative bacteria,ferrocene.,Mixed self-assembled monolayers
更新于2025-09-04 15:30:14
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Carbon Nanomembranes
摘要： This chapter describes the formation and properties of one nanometer thick carbon nanomembranes (CNMs), made by electron induced cross-linking of aromatic self-assembled monolayers (SAMs). The cross-linked SAMs are robust enough to be released from the surface and placed on solid support or over holes as free-standing membranes. Annealing at ~1000K transforms CNMs into graphene accompanied by a change of mechanical stiffness and electrical resistance. The developed fabrication approach is scalable and provides molecular level control over thickness and homogeneity of the produced CNMs. The mechanisms of electron-induced cross-linking process are discussed in details. A variety of polyaromatic thiols: oligophenyls as well as small and extended condensed polycyclic hydrocarbons have been successfully employed, demonstrating that the structural and functional properties of the resulting nanomembranes are strongly determined by the structure of molecular monolayers. The mechanical properties of CNMs (Young’s modulus, tensile strength and prestress) are characterized by bulge testing. The interpretation of the bulge test data relates the Young’s modulus to the properties of single molecules and to the structure of the pristine SAMs. The gas transport through the CNM is measured onto polydimethylsiloxane (PDMS) - thin film composite membrane. The established relationship of permeance and molecular size determines the molecular sieving mechanism of permeation through this ultrathin sheet.
关键词： Helium Ion Microscopy,radiation induced cross-linking,Self-Assembled Monolayer,Carbon Nanomembrane (CNM),Graphene
更新于2025-09-04 15:30:14