Water-Ion Interaction Determines the Mobility of Ions in Highly Concentrated Aqueous Electrolytes.

Solvation engineering plays a critical role in tailoring the performance of batteries, particularly through the use of highly concentrated electrolytes, which offer heterogeneous solvation structures of mobile ions with distinct electrochemical properties. In this study, we employed spectroscopic techniques and molecular dynamics simulations to investigate mixed-cation (Li+/K+) acetate aqueous electrolytes. Our research unravels the pivotal role of water in facilitating ion transport within a highly viscous medium. Notably, Li+ cations primarily form ion aggregates, predominantly interacting with acetate anions, while K+ cations emerge as the principal charge carriers, which is attributed to their strong interaction with water molecules. Intriguingly, even at a concentration as high as 40 m, a substantial amount of water molecules persistently engages in hydrogen bonding with one another, creating mobile regions rich in K+ ions. Our observations of a redshift of the OH stretching band of water suggest that the strength of the hydrogen bond alone cannot account for the expansion of the electrochemical stability window. These findings offer valuable insights into the cation transfer mechanism, shedding light on the contribution of water-bound cations to both the ion conductivity and the electrochemical stability window of aqueous electrolytes for rechargeable batteries. Our comprehensive molecular-level understanding of the interplay between cations and water provides a foundation for future advances in solvation engineering, leading to the development of high-performance batteries with improved energy storage and safety profiles.

Revisiting Ultrafast Dynamics in Carbonate-Based Electrolytes for Li-Ion Batteries: Clarifying 2D-IR Cross-Peak Interpretation.

Understanding chemical exchange in carbonate-based electrolytes employed in Li-ion batteries (LIBs) is crucial for elucidating ion transport mechanisms. Ultrafast two-dimensional (2D) IR spectroscopy has been widely used to investigate the solvation structure and dynamics of Li-ions in organic carbonate-based electrolytes. However, the interpretation of cross-peaks observed in picosecond carbonyl stretch 2D-IR spectra has remained contentious. These cross-peaks could arise from various phenomena, including vibrational couplings between neighboring carbonyl groups in the first solvation shell around Li-ions, vibrational excitation transfers between carbonyl groups in distinct solvation environments, and local heating effects. Therefore, it is imperative to resolve the interpretation of 2D-IR cross-peaks to avoid misinterpretations regarding ultrafast dynamics found in LIB carbonate-based electrolytes. In this study, we have taken a comprehensive investigation of carbonate-based electrolytes utilizing 2D-IR spectroscopy and molecular dynamics (MD) simulations. Through meticulous analyses and interpretations, we have identified that the cross-peaks observed in the picosecond 2D-IR spectra of LIB electrolytes predominantly arise from intermolecular vibrational excitation transfer processes between the carbonyl groups of Li-bound and free carbonate molecules. We further discuss the limitations of employing a picosecond 2D-IR spectroscopic technique to study chemical exchange and intermolecular vibrational excitation transfer processes, particularly when the effects of the molecular photothermal process cannot be ignored. Our findings shed light on the dynamics of LIB electrolytes and resolve the controversy related to 2D-IR cross-peaks. By discerning the origin of these features, we could provide valuable insights for the design and optimization of next-generation Li-ion batteries.

In-plane anisotropy of graphene by strong interlayer interactions with van der Waals epitaxially grown MoO3.

van der Waals (vdW) epitaxy can be used to grow epilayers with different symmetries on graphene, thereby imparting unprecedented properties in graphene owing to formation of anisotropic superlattices and strong interlayer interactions. Here, we report in-plane anisotropy in graphene by vdW epitaxially grown molybdenum trioxide layers with an elongated superlattice. The grown molybdenum trioxide layers led to high p-doping of the underlying graphene up to p = 1.94 × 1013 cm-2 regardless of the thickness of molybdenum trioxide, maintaining a high carrier mobility of 8155 cm2 V-1 s-1. Molybdenum trioxide-induced compressive strain in graphene increased up to -0.6% with increasing molybdenum trioxide thickness. The asymmetrical band distortion of molybdenum trioxide-deposited graphene at the Fermi level led to in-plane electrical anisotropy with a high conductance ratio of 1.43 owing to the strong interlayer interaction of molybdenum trioxide-graphene. Our study presents a symmetry engineering method to induce anisotropy in symmetric two-dimensional (2D) materials via the formation of asymmetric superlattices with epitaxially grown 2D layers.

Ultrafast Continuum IR Generation and Its Application in IR Spectroscopy.

The spectral range of femtosecond time-resolved infrared spectroscopy is limited by the bandwidth of mid-IR pulses (100~400 cm-1) generated from the combination of Ti:Sapphire amplifier, Optical Parametric Amplifier (OPA), and Difference Frequency Generation (DFG). To overcome this limitation, we implement a compact continuum mid-IR source producing ultrafast pulses that span the frequency range from 1000 to 4200 cm-1 (from 10 to 2.4 µm), which utilize the mixing of fundamental, second-harmonic, and third-harmonic of 800 nm pulse in the air. After building an IR spectrometer with continuum IR and a monochromator, we found that the distortion of the measured IR spectrum originated from the contamination of higher-order diffraction. We used bandpass filters to eliminate the higher-order contributions and correct the measured IR spectrum. We further characterized the spectral properties of fundamental, second-harmonic, and third-harmonic fields after the plasmonic filamentation process, which helps to improve the efficiency of the continuum IR generation. Using the generated continuum IR pulses, we measured the IR absorption spectrum of a water-benzonitrile mixture, which was found to be consistent with the spectrum obtained with a commercial FT-IR spectrometer. The present work will be useful for the efficient generation of continuum IR pulses for IR pump-probe and two-dimensional IR spectroscopy experiments in the future.

Optical Imaging of Redox and Molecular Diffusion in 2D van der Waals Space.

Understanding charge transfer (CT) between two chemical entities and the subsequent change in their charge densities is essential not only for molecular species but also for various low-dimensional materials. Because of their extremely high fraction of surface atoms, two-dimensional (2-D) materials are most susceptible to charge exchange and exhibit drastically different physicochemical properties depending on their charge density. In this regard, spontaneous and uncontrollable ionization of graphene in the ambient air has caused much confusion and technical difficulty in achieving experimental reproducibility since its first report in 2004. Moreover, the same ambient hole doping was soon observed in 2-D semiconductors, which implied that a common mechanism should be operative and apply to other low-dimensional materials universally. Notably, a similar CT reaction has long been known for carbon nanotubes but is still controversial in its mechanism.In this Account, we review our breakthroughs in unraveling the chemical origin and mechanistic requirements of the hidden CT reactions using 2-D crystals. As a first step, we have developed in situ optical methods to quantify charge density using Raman and photoluminescence (PL) spectroscopy and imaging. To overcome the multimodal sensitivity of Raman frequencies, we established a novel analytical method based on theory and experiments with excellent resolution for the charge density (∼1 × 1012 cm-2) and lattice strain (∼0.02%) of graphene. For 2-D transition-metal dichalcogenides, PL spectroscopy and imaging provided a high precision and sensitivity that enabled rapid kinetic measurements in a spatially resolved manner.Using gas- and temperature-controlled in situ measurements, we revealed that the electrical holes are injected by the oxygen reduction reaction (ORR) O2 + 4H+ + 4e- ⇄ 2H2O, which was independently verified by the pH dependence in HCl solutions. In addition to oxygen and water vapor, the overall CT reaction requires hydrophilic dielectric substrates, which assist the hydration of the sample-substrate interface. We also found that the CT reaction is substantially enhanced when samples are thermally annealed. The amplification is due to the interfacial hydrophilicity increased by the thermal hydroxylation of substrates, which indicates that the CT reaction is localized at the interface and boosted by interfacial water.The interface-localized CT allowed us to study and control molecular diffusion through the 2-D van der Waals space between samples and substrates. Wide-field PL imaging showed how fast oxygen molecules diffuse through the interfacial space, subsequently inducing the CT reaction. By increasing the 2-D gap spacing, the diffusion kinetics could be accelerated. The rate of CT could also be enhanced by introducing defects on the basal plane of 2-D crystals, which demonstrates the decisive role of defects as CT centers.Because of their unique geometry, low-dimensional materials are highly susceptible to external perturbation including charge exchange. Because the vulnerability can be exploited to modify material properties, the complete mechanism of the fundamental charge exchange summarized in this Account will be essential to exploring material and device properties of other low-dimensional materials.

Adsorbed Water Structure on Acrylate-Based Biocompatible Polymer Surface.

The role of water in the excellent biocompatibility of the acrylate-based polymers widely used for antibiofouling coating material has been realized previously. Here, we report femtosecond mid-infrared pump-probe spectroscopy of the OD stretch band of HOD molecule adsorbed on highly biocompatible poly(2-methoxyethyl) acrylate [PMEA] and poorly biocompatible poly(2-phenoxyethyl) acrylate [PPEA], both of which reveal that there are two water species with significantly different vibrational lifetime. PMEA interacts more strongly with water than PPEA through the H-bonding interaction between carbonyl (C═O) and water. The vibrational lifetime of the OD stretch in PPEA is notably longer by factors of 3 and 7 than those in PMEA and bulk water, respectively. The IR-pump visible-probe photothermal imaging further unravels substantial spatial overlap between polymer CO group and water for hydrated PMEA and a significant difference in surface morphology than those in PPEA, which exhibits the underlying relationships among polymer-water interaction, surface morphology, and biocompatibility.

Surface Stabilization of a Formamidinium Perovskite Solar Cell Using Quaternary Ammonium Salt.

Dimensionality engineering is an effective approach to improve the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). A two-dimensional (2D) perovskite assembled from bulky organic cations to cover the surface of three-dimensional (3D) perovskite can repel ambient moisture and suppress ion migration across the perovskite film. This work demonstrates how the thermal stability of the bulky organic cation of a 2D perovskite affects the crystallinity of the perovskite and the optoelectrical properties of perovskite solar cells. Structural analysis of (FAPbI3)0.95(MAPbBr3)0.05 (FA = formamidinium ion, MA = methylammonium ion) mixed with a series of bulky cations shows a clear correlation between the structure of the bulky cations and the formation of surface defects in the resultant perovskite films. An organic cation with primary ammonium structure is vulnerable to a deprotonation reaction under typical perovskite-film processing conditions. Decomposition of the bulky cations results in structural defects such as iodide vacancies and metallic lead clusters at the surface of the perovskite film; these defects lead to a nonradiative recombination loss of charge carriers and to severe ion migration during operation of the device. In contrast, a bulky organic cation with a quaternary ammonium structure exhibits superior thermal stability and results in substantially fewer structural defects at the surface of the perovskite film. As a result, the corresponding PSC exhibits the PCE of 21.6% in a reverse current-voltage scan and a stabilized PCE of 20.1% with an excellent lifetime exceeding 1000 h for the encapsulated device under continuous illumination.

Enhancing Thermoelectric Power Factor of 2D Organometal Halide Perovskites by Suppressing 2D/3D Phase Separation.

Organometal halide perovskites (OHPs) exhibit superior charge transport characteristics and ultralow thermal conductivities. However, thermoelectric (TE) applications of OHPs have been limited because of difficulties in controlling their carrier concentration, which is a key to optimizing their TE properties. Here, facile control of the carrier concentration in Sn-based OHPs is achieved by developing 2D crystal structures. The 2D OHP crystals are laterally oriented using a mixed solvent, and the morphology and crystal structure of the coexisting 2D/3D hybrid structures are systematically controlled via doping with methylammonium chloride. The effective number neff of inorganic octahedron layers in the 2D OHPs shows a strong positive correlation with the carrier concentration. Moreover, the 2D structure induces the quantum confinement effect, which enhances both the Seebeck coefficient and the electrical conductivity. A 2D OHP shows a high power factor of 111 µW m-1 K-2 , which is an order of magnitude greater than the power factor of its 3D counterpart.

Graphene Nanoribbon Grids of Sub-10 nm Widths with High Electrical Connectivity.

Quasi-one-dimensional (1D) graphene nanoribbons (GNRs) have finite band gaps and active edge states and therefore can be useful for advanced chemical and electronic devices. Here, we present the formation of GNR grids via seed-assisted chemical vapor deposition on Ge(100) substrates. Nucleation seeds, provided by unzipped C60, initiated growth of the GNRs. The GNRs grew toward two orthogonal directions in an anisotropic manner, templated by the single crystalline substrate, thereby forming grids that had lateral stitching over centimeter scales. The spatially uniform grid can be transferred and patterned for batch fabrication of devices. The GNR grids showed percolative conduction with a high electrical sheet conductance of ∼2 µS·sq and field-effect mobility of ∼5 cm2/(V·s) in the macroscopic channels, which confirm excellent lateral stitching between domains. From transconductance measurements, the intrinsic band gap of GNRs with sub-10 nm widths was estimated as ∼80 meV, similar to theoretical expectation. Our method presents a scalable way to fabricate atomically thin elements with 1D characteristics for integration with various nanodevices.

Two-dimensional infrared spectroscopic study of cytochrome c peroxidase activity in deep eutectic solvent.

Deep eutectic solvents (DESs) prepared by mixing hydrogen-bond donor and acceptor molecules have been found to be of use in several applications. Recently, it was shown that DESs can enhance the peroxidation activity of cytochrome c. Here, to elucidate the effects of DESs on the peroxidase activity of cytochrome c, we carried out linear and nonlinear infrared spectroscopic studies of the CO stretch mode of carbon monoxide cytochrome c (COCytc) in ethylammonium chloride (EAC)/urea DES. The FTIR spectrum of COCytc shows a significant spectral shift upon addition of the DES. The broadening and red-shifting of the CO band are observed in both urea and DES solutions, which are induced by the change of the distal ligands around the heme. Although the FTIR study is sensitive to structural changes in the active site, it does not provide quantitative information about structural dynamics related to the catalytic activity itself. Thus, we carried out two-dimensional IR spectroscopy of the CO mode, which suggests that there is a different conformer that could be related to the enhanced catalytic activity in DES. In particular, the spectral diffusion dynamics of that conformer exhibits quite different behavior. The experimental results lead us to propose a hypothesis that the DES increases the population of the conformer with distal ligand lysines close to the reaction center through the combining effect of urea and EAC, which results in the enhancement of the peroxidase activity of cytochrome c. We anticipate that the present experimental work stimulates future investigations of the effects of DES on biocatalysis.

Redox-governed charge doping dictated by interfacial diffusion in two-dimensional materials.

Controlling extra charge carriers is pivotal in manipulating electronic, optical, and magnetic properties of various two-dimensional materials. Nonetheless, the ubiquitous hole doping of two-dimensional materials in the air and acids has been controversial in its mechanistic details. Here we show their common origin is an electrochemical reaction driven by redox couples of oxygen and water molecules. Using real-time photoluminescence imaging of WS2 and Raman spectroscopy of graphene, we capture molecular diffusion through the two-dimensional nanoscopic space between two-dimensional materials and hydrophilic substrates, and show that the latter accommodate water molecules also serving as a hydrating solvent. We also demonstrate that HCl-induced doping is governed by dissolved O2 and pH in accordance with the Nernst equation. The nanoscopic electrochemistry anatomized in this work sets an ambient limit to material properties, which is universal to not only 2D but also other forms of materials.

Two-Dimensional Infrared Spectroscopy and Molecular Dynamics Simulation Studies of Nonaqueous Lithium Ion Battery Electrolytes.

Lithium ion battery (LIB) technology is undoubtedly indispensable to modern life. However, despite enormous and extended effort to improve LIB performance, our understanding of the underlying principles and mechanisms of lithium ion transport in nonaqueous LIB electrolytes remained limited until recently. There is a particular lack of knowledge of the microscopic solvation structures and fluctuation dynamics around charge carriers in real electrolytes. Typical electrolytes found in commercially available LIBs consist of lithium salts and mixed carbonate solvents, with the latter playing an essential role in promoting lithium ion transport and forming an electrically stable solid electrolyte interphase. Although a number of linear spectroscopic studies of LIB electrolytes aiming at understanding the complex nature of lithium ion solvation processes have been reported, the notion that each lithium ion is strongly solvated by carbonate molecules to form a long-lasting solvation sheath structure has remained the subject of intense debate. Here, we present the results of FTIR, fs IR pump-probe, two-dimensional IR spectroscopy, and molecular dynamics simulations reported by us and others and discuss the possible interplay of picosecond solvation dynamics and macroscopic ion transport processes within the framework of the fluctuation-dissipation relationship. Further, by measuring the time-dependent fluctuations and spectral diffusions of carbonate carbonyl stretch modes that act as excellent infrared probes for the local electrostatic environment, we show that lithium cations are not only solvated by carbonate molecules but also interact with counteranions at equilibrium depending on solvent composition. Molecular dynamics simulations support the notion that rapid chemical exchanges between carbonate solvent molecules in the first and outer solvation shells are critical for describing mobile lithium ion transport phenomena. We thus anticipate that time-resolved coherent multidimensional vibrational spectroscopy is capable of providing decisive evidence on the ultrafast solvent dynamics of various electrolytes, which is potentially helpful for designing improved and more efficient LIB electrolytes in the future.

Rational Design of an Acetylenic Infrared Probe with Enhanced Dipole Strength and Increased Vibrational Lifetime.

Developing infrared (IR) probes is of great interest in biomolecular imaging and spectroscopy. We report our attempt to improve the IR properties of alkyne-derivatized compounds. The vibrational properties of the alkyne (C≡C) stretch mode of aromatic silylacetylene 1 and aliphatic silylacetylene 2 were studied using Fourier transform infrared and femtosecond IR pump-probe spectroscopies. We find that the insertion of silicon at the position adjacent to the alkyne group, separating it from the compound's main body, causes an approximately 10-fold increase in the dipole strength of the C≡C stretch mode and a lengthening of its vibrational lifetime from 5.6 ps for the acetylenic compound without a silicon atom acting like a thermal insulator to 50.6 and 50.4 ps for 1 and 2, respectively. The enhanced dipole strength and the increased lifetime of 1 allowed us to measure the 2D IR spectra for long waiting times up to 450 ps, which suggests that the dynamic observation range of 2D IR spectroscopy with these IR probes can be extended into the subnanosecond range where protein skeletal movements occur.

Nanometric Water Channels in Water-in-Salt Lithium Ion Battery Electrolyte.

Lithium-ion batteries (LIBs) have been deployed in a wide range of energy-storage applications and helped to revolutionize technological development. Recently, a lithium ion battery that uses superconcentrated salt water as its electrolyte has been developed. However, the role of water in facilitating fast ion transport in such highly concentrated electrolyte solutions is not fully understood yet. Here, femtosecond IR spectroscopy and molecular dynamics simulations are used to show that bulk-like water coexists with interfacial water on ion aggregates. We found that dissolved ions form intricate three-dimensional ion-ion networks that are spontaneously intertwined with nanometric water hydrogen-bonding networks. Then, hydrated lithium ions move through bulk-like water channels acting like conducting wires for lithium ion transport. Our experimental and simulation results indicate that water structure-breaking chaotropic anion salts with a high propensity to form ion networks in aqueous solutions would be excellent candidates for water-based LIB electrolytes. We anticipate that the present work will provide guiding principles for developing aqueous LIB electrolytes.

Does Bowstringing Affect Hand Function in Patients Treated With A1 Pulley Release for Trigger Fingers?: Comparison Between Percutaneous Versus Open Technique.

We aimed to inspect bowstringing after percutaneous and open release of the A1 pulley for trigger digits and its influence on hand function. Sixty-two patients with a resistant trigger digit were randomized to undergo either open release or percutaneous release of the A1 pulley. We quantified bowstringing of the digit using ultrasonography preoperatively and at 12 and 24 weeks after surgery. Pain on a visual analog scale; Disabilities of the Arm, Shoulder, and Hand questionnaire; pinch power; and grip strength were assessed. Bowstringing was significantly increased at 12 weeks after surgery in both groups, and the mean value of the open release group was significantly greater than that of the percutaneous group (2.30 ± 0.58 mm vs 1.46 ± 0.51 mm, respectively; P = 0.035). However, the bowstringing was decreased at 24 weeks without showing significant difference between the 2 groups. The clinical outcomes of each cohort improved significantly, with no difference between the groups at final follow-up. No association was found between bowstringing and any clinical outcome measure. Bowstringing occurred by A1 pulley release with either the percutaneous or open technique does not affect clinical hand function in patients with trigger fingers.

Comparison of outcomes of osteosynthesis in type II accessory navicular by variable fixation methods.

BACKGROUND: To compare the outcomes of fixation methods for osteosynthesis of a type II symptomatic accessory navicular between screw and tension band wiring. METHODS: Forty-four patients (mean age, 29.2 years; range, 13-54 years; 21 males and 23 females) who had undergone operative treatment after failed conservative treatment were chosen for the study between 2007 and 2014. The patients were divided into two groups by the method of osteosynthesis: group 1 (screw) and group 2 (tension band wiring). Pre and postoperative evaluations were performed, using the midfoot scale from the American Orthopaedic Foot and Ankle Society (AOFAS), a visual analog scale, time to return to social activities, and plain radiography. RESULTS: The AOFAS midfoot and visual analog scale scores of both groups were improved at the last postoperative follow-up. The time to return to social activities was 12.3 weeks in the screw group and 11.9 weeks in the tension band wiring group (p=0.394). A broken screw was observed in one case in the screw group and a broken k-wire was detected in two cases in the tension band wiring group. Nonunion was observed in two cases in each group. CONCLUSION: The tension band wiring technique could be another treatment choice of osteosynthesis for fixation of the accessory navicular bone. LEVEL OF EVIDENCE: Level III, Retrospective Case Control Study.

Determination of chlorogenic acids and caffeine in homemade brewed coffee prepared under various conditions.

Coffee, a complex mixture of more than 800 volatile compounds, is one of the most valuable commodity in the world, whereas caffeine and chlorogenic acids (CGAs) are the most common compounds. CGAs are mainly composed of caffeoylquinic acids (CQAs), dicaffeoylquinic acids (diCQAs), and feruloylquinic acids (FQAs). The major CGAs in coffee are neochlorogenic acid (3-CQA), cryptochlorogenic acid (4-CQA), and chlorogenic acid (5-CQA). Many studies have shown that it is possible to separate the isomers of FQAs by high-performance liquid chromatography (HPLC). However, some authors have shown that it is not possible to separate 4-feruloylquinic acid (4-FQA) and 5-feruloylquinic acid (5-FQA) by HPLC. Therefore, the present study was designated to investigate the chromatographic problems in the determination of CGAs (seven isomers) and caffeine using HPLC-DAD. The values of determination coefficient (R2) calculated from external-standard calibration curves were >0.998. The recovery rates conducted at 3 spiking levels ranged from 99.4% to 106.5% for the CGAs and from 98.8% to 107.1% for the caffeine. The precision values (expressed as relative standard deviations (RSDs)) were <7% and <3% for intra and interday variability, respectively. The tested procedure proved to be robust. The seven CGAs isomers except 4-FQA and 5-FQA were well distinguished and all gave good peak shapes. We have found that 4-FQA and 5-FQA could not be separated using HPLC. The method was extended to investigate the effects of different brewing conditions such as the roasting degree of green coffee bean, coffee-ground size, and numbers of boiling-water pours, on the concentration of CGAs and caffeine in homemade brewed coffee, using nine green coffee bean samples of different origins. It was reported that medium-roasted, fine-ground coffees brewed using three pours of boiling water were the healthiest coffee with fluent CGAs.

Ultrafast fluxional exchange dynamics in electrolyte solvation sheath of lithium ion battery.

Lithium cation is the charge carrier in lithium-ion battery. Electrolyte solution in lithium-ion battery is usually based on mixed solvents consisting of polar carbonates with different aliphatic chains. Despite various experimental evidences indicating that lithium ion forms a rigid and stable solvation sheath through electrostatic interactions with polar carbonates, both the lithium solvation structure and more importantly fluctuation dynamics and functional role of carbonate solvent molecules have not been fully elucidated yet with femtosecond vibrational spectroscopic methods. Here we investigate the ultrafast carbonate solvent exchange dynamics around lithium ions in electrolyte solutions with coherent two-dimensional infrared spectroscopy and find that the time constants of the formation and dissociation of lithium-ion···carbonate complex in solvation sheaths are on a picosecond timescale. We anticipate that such ultrafast microscopic fluxional processes in lithium-solvent complexes could provide an important clue to understanding macroscopic mobility of lithium cation in lithium-ion battery on a molecular level.

The Outcomes of Arthroscopic Repair Versus Debridement for Chronic Unstable Triangular Fibrocartilage Complex Tears in Patients Undergoing Ulnar-Shortening Osteotomy.

PURPOSE: The aim of this study was to compare the results of arthroscopic peripheral repair (AR) and arthroscopic debridement (AD) for the treatment of chronic unstable triangular fibrocartilage complex (TFCC) tears in ulnar-positive patients undergoing ulnar-shortening osteotomy (USO). METHODS: A total of 31 patients who underwent arthroscopic treatments combined with USO for unstable TFCC tears and were followed-up at a minimum of 24 months were included in this retrospective cohort study. Fifteen patients were treated with AR, and 16 patients were treated with AD while at the same time undergoing a USO. Outcome measures included wrist range of motion, grip strength, Disabilities of the Arm, Shoulder, and Hand (DASH) and Patient-Rated Wrist Evaluation (PRWE) scores, and overall outcomes according to the modified Mayo wrist scoring system. In addition, a stress test to assess distal radioulnar joint (DRUJ) stability was performed before and after surgery to compare the 2 cohorts. RESULTS: Both respective cohorts showed significant improvements in grip strength and subjective scores at the final follow-up. Grip strength, DASH, and PRWE scores were better in the AR group than in the AD group. The recovery rate from DRUJ instability observed during the preoperative examination was superior in the AR group. CONCLUSIONS: Both AD and AR of the TFCC combined with USO are reliable procedures with satisfactory clinical outcomes for unstable TFCC tears in ulnar-positive patients. However, AR of the TFCC is suggested if DRUJ stability is concomitantly compromised. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

ß-Isocyanoalanine as an IR probe: comparison of vibrational dynamics between isonitrile and nitrile-derivatized IR probes.

An infrared (IR) probe based on isonitrile (NC)-derivatized alanine 1 was synthesized and the vibrational properties of its NC stretching mode were investigated using FTIR and femtosecond IR pump-probe spectroscopy. It is found that the NC stretching mode is very sensitive to the hydrogen-bonding ability of solvent molecules. Moreover, its transition dipole strength is larger than that of nitrile (CN) in nitrile-derivatized IR probe 2. The vibrational lifetime of the NC stretching mode is found to be 5.5 ± 0.2 ps in both D2O and DMF solvents, which is several times longer than that of the azido (N3) stretching mode in azido-derivatized IR probe 3. Altogether these properties suggest that the NC group can be a very promising sensing moiety of IR probes for studying the solvation structure and dynamics of biomolecules.