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1,408 result(s) for "self-assembled monolayer"
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Surface NMR using quantum sensors in diamond
NMR is a noninvasive, molecular-level spectroscopic technique widely used for chemical characterization. However, it lacks the sensitivity to probe the small number of spins at surfaces and interfaces. Here, we use nitrogen vacancy (NV) centers in diamond as quantum sensors to optically detect NMR signals from chemically modified thin films. To demonstrate the method’s capabilities, aluminum oxide layers, common supports in catalysis and materials science, are prepared by atomic layer deposition and are subsequently functionalized by phosphonate chemistry to form self-assembled monolayers. The surface NV-NMR technique detects spatially resolved NMR signals from the monolayer, indicates chemical binding, and quantifies molecular coverage. In addition, it can monitor in real time the formation kinetics at the solid–liquid interface. With our approach, we show that NV quantum sensors are a surface-sensitive NMR tool with femtomole sensitivity for in situ analysis in catalysis, materials, and biological research.
Molecular surface coverage standards by reference-free GIXRF supporting SERS and SEIRA substrate benchmarking
Non-destructive reference-free grazing incidence X-ray fluorescence (RF-GIXRF) is proposed as a highly effective analytical technique for extracting molecular arrangement density in self-assembled monolayers. The establishment of surface density standards through RF-GIXRF impacts various applications, from calibrating laboratory XRF setups to expanding its applicability in materials science, particularly in surface coating scenarios with molecular assemblies. Accurate determination of coverage density is crucial for proper functionalization and interaction, such as in assessing the surface concentration of probes on plasmonic nanostructures. However, limited synchrotron radiation access hinders widespread use, prompting the need for molecular surface density standards, especially for benchmarking substrates for surface-enhanced Raman and infrared absorption spectroscopies (SERS and SEIRA) as well as associated surface-enhanced techniques. Using reproducible densities on gold ensures a solid evaluation of the number of molecules contributing to enhanced signals, facilitating comparability across substrates. The research discusses the importance of employing molecular surface density standards for advancing the field of surface-enhanced spectroscopies, encouraging collaborative efforts in protocol development and benchmarking in surface science.
Co-deposition of hole-selective contact and absorber for improving the processability of perovskite solar cells
Simplifying the manufacturing processes of renewable energy technologies is crucial to lowering the barriers to commercialization. In this context, to improve the manufacturability of perovskite solar cells (PSCs), we have developed a one-step solution-coating procedure in which the hole-selective contact and perovskite light absorber spontaneously form, resulting in efficient inverted PSCs. We observed that phosphonic or carboxylic acids, incorporated into perovskite precursor solutions, self-assemble on the indium tin oxide substrate during perovskite film processing. They form a robust self-assembled monolayer as an excellent hole-selective contact while the perovskite crystallizes. Our approach solves wettability issues and simplifies device fabrication, advancing the manufacturability of PSCs. Our PSC devices with positive–intrinsic–negative (p-i-n) geometry show a power conversion efficiency of 24.5% and retain >90% of their initial efficiency after 1,200 h of operating at the maximum power point under continuous illumination. The approach shows good generality as it is compatible with different self-assembled monolayer molecular systems, perovskites, solvents and processing methods. Improving the manufacturability of perovskite solar cells is key to their deployment. Zheng et al. report a one-step deposition of the hole-selective and absorber layers that addresses wettability issues and simplifies the fabrication process.
Low-temperature and high-rate-charging lithium metal batteries enabled by an electrochemically active monolayer-regulated interface
Stable operation of rechargeable lithium-based batteries at low temperatures is important for cold-climate applications, but is plagued by dendritic Li plating and unstable solid–electrolyte interphase (SEI). Here, we report on high-performance Li metal batteries under low-temperature and high-rate-charging conditions. The high performance is achieved by using a self-assembled monolayer of electrochemically active molecules on current collectors that regulates the nanostructure and composition of the SEI and deposition morphology of Li metal anodes. A multilayer SEI that contains a lithium fluoride-rich inner phase and amorphous outer layer effectively seals the Li surface, in contrast to the conventional SEI, which is non-passive at low temperatures. Consequently, galvanic Li corrosion and self-discharge are suppressed, stable Li deposition is achieved from −60 °C to 45 °C, and a Li | LiCoO 2 cell with a capacity of 2.0 mAh cm −2 displays a 200-cycle life at −15 °C with a recharge time of 45 min. In addition to high energy, batteries need to possess high power and to be able to operate in all climates. Here, the authors present an electrochemically active monolayer-coated current collector that is used to produce high-performance Li metal batteries under low-temperature and high-rate-charging conditions.
Bioactive Coatings on Titanium: A Review on Hydroxylation, Self-Assembled Monolayers (SAMs) and Surface Modification Strategies
Titanium (Ti) and its alloys have been demonstrated over the last decades to play an important role as inert materials in the field of orthopedic and dental implants. Nevertheless, with the widespread use of Ti, implant-associated rejection issues have arisen. To overcome these problems, antibacterial properties, fast and adequate osseointegration and long-term stability are essential features. Indeed, surface modification is currently presented as a versatile strategy for developing Ti coatings with all these challenging requirements and achieve a successful performance of the implant. Numerous approaches have been investigated to obtain stable and well-organized Ti coatings that promote the tailoring of surface chemical functionalization regardless of the geometry and shape of the implant. However, among all the approaches available in the literature to functionalize the Ti surface, a promising strategy is the combination of surface pre-activation treatments typically followed by the development of intermediate anchoring layers (self-assembled monolayers, SAMs) that serve as the supporting linkage of a final active layer. Therefore, this paper aims to review the latest approaches in the biomedical area to obtain bioactive coatings onto Ti surfaces with a special focus on (i) the most employed methods for Ti surface hydroxylation, (ii) SAMs-mediated active coatings development, and (iii) the latest advances in active agent immobilization and polymeric coatings for controlled release on Ti surfaces.
Self‐assembled monolayers (SAMs) in inverted perovskite solar cells and their tandem photovoltaics application
Self‐assembled monolayers (SAMs) employed in inverted perovskite solar cells (PSCs) have achieved groundbreaking progress in device efficiency and stability for both single‐junction and tandem configurations, owing to their distinctive and versatile ability to manipulate chemical and physical interface properties. In this regard, we present a comprehensive review of recent research advancements concerning SAMs in inverted perovskite single‐junction and tandem solar cells, where the prevailing challenges and future development prospects in the applications of SAMs are emphasized. We thoroughly examine the mechanistic roles of diverse SAMs in energy‐level regulation, interface modification, defect passivation, and charge transportation. This is achieved by understanding how interfacial molecular interactions can be finely tuned to mitigate charge recombination losses in inverted PSCs. Through this comprehensive review, we aim to provide valuable insights and references for further investigation and utilization of SAMs in inverted perovskite single‐junction and tandem solar cells. The self‐assembled monolayer plays a pivotal role in inverted single‐junction and tandem perovskite solar cells due to its distinctive and versatile ability to manipulate chemical and physical interface properties, serving as a key factor in charge transport, interface modification, energy‐level modulation, and defect passivation.
Repairing Interfacial Defects in Self‐Assembled Monolayers for High‐Efficiency Perovskite Solar Cells and Organic Photovoltaics through the SAM@Pseudo‐Planar Monolayer Strategy
Lately, carbazole‐based self‐assembled monolayers (SAMs) are widely employed as effective hole‐selective layers (HSLs) in inverted perovskite solar cells (PSCs). Nevertheless, these SAMs tend to aggregate in solvents due to their amphiphilic nature, hindering the formation of a monolayer on the ITO substrate and impeding effective passivation of deep defects in the perovskites. In this study, a series of new SAMs including DPA‐B‐PY, CBZ‐B‐PY, POZ‐B‐PY, POZ‐PY, POZ‐T‐PY, and POZ‐BT‐PY are synthesized, which are employed as interfacial repairers and coated atop CNph SAM to form a robust CNph SAM@pseudo‐planar monolayer as HSL in efficient inverted PSCs. The CNph SAM@pseudo‐planar monolayer strategy enables a well‐aligned interface with perovskites, synergistically promoting perovskite crystal growth, improving charge extraction/transport, and minimizing nonradiative interfacial recombination loss. As a result, the POZ‐BT‐PY‐modified PSC realizes an impressively enhanced solar efficiency of up to 24.45% together with a fill factor of 82.63%. Furthermore, a wide bandgap PSC achieving over 19% efficiency. Upon treatment with the CNph SAM@pseudo‐planar monolayer, also demonstrates a non‐fullerene organic photovoltaics (OPVs) based on the PM6:BTP‐eC9 blend, which achieves an efficiency of 17.07%. Importantly, these modified PSCs and OPVs all show remarkably improved stability under various testing conditions compared to their control counterparts. A new series of SAMs from DPA‐B‐PY to POZ‐BT‐PY, employed as interfacial repairers, are coated atop CNph SAM to form a robust CNph SAM@pseudo‐planar monolayer as HSL in inverted PSCs. The CNph SAM@pseudo‐planar monolayer strategy enables a well‐aligned interface with perovskites, synergistically promoting perovskite crystal growth, improving charge extraction/transport, and minimizing nonradiative interfacial recombination loss.
Gas‐Assisted Spray Coating of Perovskite Solar Cells Incorporating Sprayed Self‐Assembled Monolayers
Self‐assembled monolayers (SAMs) are becoming widely utilized as hole‐selective layers in high‐performance p‐i‐n architecture perovskite solar cells. Ultrasonic spray coating and airbrush coating are demonstrated here as effective methods to deposit MeO‐2PACz; a carbazole‐based SAM. Potential dewetting of hybrid perovskite precursor solutions from this layer is overcome using optimized solvent rinsing protocols. The use of air‐knife gas‐quenching is then explored to rapidly remove the volatile solvent from an MAPbI3 precursor film spray‐coated onto an MeO‐2PACz SAM, allowing fabrication of p‐i‐n devices with power conversion efficiencies in excess of 20%, with all other layers thermally evaporated. This combination of deposition techniques is consistent with a rapid, roll‐to‐roll manufacturing process for the fabrication of large‐area solar cells. Carbazole‐based self‐assembled monolayers are becoming a dominant hole‐transporting layer in p‐i‐n perovskite solar cells, combining stability, efficiency, and low‐cost. Here, spray coating and airbrush pen coating of MeO‐2PACz are used to fabricate high‐quality transport layers. This is combined with gas‐quenched spray‐coated perovskite layers, to realize solar cells with power conversion efficiencies in excess of 20%.
Effects of Alkyl Spacer Length in Carbazole‐Based Self‐Assembled Monolayer Materials on Molecular Conformation and Organic Solar Cell Performance
Carbazole‐based self‐assembled monolayer (SAM) materials as hole transport layers (HTL) have led organic solar cells (OSCs) to state‐of‐the‐art photovoltaic performance. Nonetheless, the impact of the alkyl spacer length of SAMs remains inadequately understood. To improve the knowledge, four dichloride‐substituted carbazole‐based SAMs (from 2Cl‐2PACz to 2Cl‐5PACz) with spacer lengths of 2–5 carbon atoms is developed. Single crystal analyses reveal that SAMs with shorter spacers exhibit stronger intermolecular interactions and denser packing. The molecular conformation of SAMs significantly impacts their molecular footprint and coverage on ITO. These factors result in the highest coverage of 2Cl‐2PACz and the lowest coverage for 2Cl‐3PACz on ITO. OSCs based on PM6:L8‐BO with 2Cl‐2PACz as HTL achieved high efficiencies of 18.95% and 18.62% with and without methanol rinsing of the ITO/SAMs anodes, corresponding to monolayer and multilayer structures, respectively. In contrast, OSCs utilizing the other SAMs showed decreased efficiencies as spacer length increased. The superior performance of 2Cl‐2PACz can be attributed to its shorter spacer, which reduces series resistance, hole tunneling distance, and barrier. This work provides valuable insights into the design of SAMs for high‐performance OSCs. The spacer length in carbazole‐based self‐assembled monolayer (SAM) hole‐transport layer materials significantly influences the hole tunneling distance, which in turn affects the efficiency of organic solar cells. Additionally, spacer length impacts the molecular conformation, as revealed by single crystal analysis, resulting in varied coverage on indium tin oxide (ITO) surfaces.
Aromatic‐Substituted Carbazole Monolayers: Self‐Assembly Optimization for Efficient Inverted Perovskite Solar Cells
Self‐assembled monolayers (SAMs) offer transformative potential as hole‐transporting layers (HTLs) in inverted perovskite solar cells (IPSCs) through lossless contact engineering and suppressed interfacial recombination. To address persistent challenges of molecular aggregation, inadequate wettability, and limited durability, we pioneered a groundbreaking fluorine‐substituted aromatic carbazole‐based SAM molecule: (3‐(3,6‐bis(3‐fluoro‐4‐methoxy‐phenyl)‐9H‐carbazol‐9‐yl)‐propyl)phosphonic acid (F‐MeO‐3PABCz). This design achieves three breakthroughs: (1) defect passivation via optimized perovskite crystallization and energy‐level alignment, eliminating nonradiative recombination at the buried interface; (2) enhanced hole extraction/transport through directed molecular assembly; and (3) superior stability via fluorine‐induced hydrophobicity and aggregation resistance. The result is an impressive‐breaking champion power conversion efficiency (PCE) of 26.21% (certified 25.76%), surpassing commercial 4PACz‐based devices (24.37%) by a significant margin. Accelerated aging tests confirm F‐MeO‐3PABCz's exceptional operational longevity, outperforming conventional HTLs under thermal and humidity stress. This work establishes a paradigm for SAM engineering by integrating fluorine substitution, aromatic rigidity, and phosphonic acid anchoring, paving the way for next‐generation high‐efficiency IPSCs with industrial‐grade durability.