98%
921
2 minutes
20
The origin of the sum-frequency generation (SFG) signal of the water bending mode has been controversially debated in the past decade. Unveiling the origin of the signal is essential, because different assignments lead to different views on the molecular structure of interfacial water. Here, we combine collinear heterodyne-detected SFG spectroscopy at the water-charged lipid interfaces with systematic variation of the salt concentration. The results show that the bending mode response is of a dipolar, rather than a quadrupolar, nature and allows us to disentangle the response of water in the Stern and the diffuse layers. While the diffuse layer response is identical for the oppositely charged surfaces, the Stern layer responses reflect interfacial hydrogen bonding. Our findings thus corroborate that the water bending mode signal is a suitable probe for the structure of interfacial water.
Download full-text PDF |
Source |
---|---|
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8279539 | PMC |
http://dx.doi.org/10.1021/acs.jpcb.1c03258 | DOI Listing |
Phys Chem Chem Phys
September 2025
Department of Chemistry and Sustainable Technology, University of Eastern Finland, Joensuu Campus, Yliopistokatu 7, FI-80100, Joensuu, Finland.
Accurate thermodynamic calculations for aluminum alkyls require proper treatment of low-frequency vibrations poorly described by the harmonic approximation (HA). Here, we present a systematic investigation of hindered rotation and out-of-plane bending in aluminum trichloride (ATC) and its methyl derivatives, employing advanced computational methods to perform anharmonic entropy corrections, such as torsional eigenvalue summation (TES), the extended two-dimensional torsion method (E2DT), the multi-structural approximation with torsional anharmonicity (MS-T), and Fourier grid Hamiltonian (FGH). Our results reveal distinct structure-dependent behaviors: monomers exhibit near-free methyl rotations where the HA overestimates entropy by 20-30 J K mol, while dimers show more hindered rotations adequately described by the HA around room temperature.
View Article and Find Full Text PDFChem Sci
August 2025
State Key Laboratory of Chemical Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
We report time-sliced velocity map imaging studies of the methyl (CH) and electronically excited sulfur (S(D)) fragments formed following the photoexcitation of jet-cooled CHSH molecules in the 2A'' ← X̃ A' absorption band (. at wavelengths in the range 190 ≤ ≤ 210 nm). Analyses of images of CH fragments in their = 0, 1 and 2 vibrational levels confirm the perpendicular parent transition dipole moment and prompt bond fission and show that the ground state SH(X) partners are formed with an inverted vibrational population distribution, peaking at = 2 at the shortest excitation wavelengths investigated.
View Article and Find Full Text PDFHip Pelvis
September 2025
Department of Radiology & Diagnostic Imaging, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, AB, Canada.
Purpose: Through the measurement of Graf's alpha (α) angle, the Graf method uses two-dimensional ultrasound (US) to diagnose developmental dysplasia of the hip (DDH) in infants. However, this unidimensional index cannot fully reflect anatomic shape features and variations of iliac wing and bony acetabular roof (IW-AR) coronal outlines that may influence DDH. This study aimed to analyze the shapes of IW-AR outlines by revealing their mean shape, possible shape variations, and the impact of these variations on the α angle variability.
View Article and Find Full Text PDFAdv Mater
September 2025
School of Fashion and Textiles, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, 999077, P. R. China.
Fiber-reinforced polymer composite mechanical metamaterials have emerged as promising candidates for multifunctional structural applications owing to their exceptional strength-to-weight ratios. However, achieving concurrent high stiffness, high strength, and large recoverable strain in such structures remains challenging due to inherent trade-offs between these properties. To address this limitation, a novel Möbius-inspired metamaterial through optimized fiber orientation design is developed.
View Article and Find Full Text PDFSensors (Basel)
August 2025
School of Physics and Technology, University of Jinan, Jinan 250022, China.
A respiratory monitoring sensor based on a balloon-shaped optical fiber is proposed. The sensor consists of a single-mode fiber (SMF) coated with polydimethylsiloxane (PDMS) bent into a balloon shape to form a fiber optic Mach-Zehnder interferometer. The sensor's sensitivity to temperature enables monitoring of breathing status by recognizing the temperature changes that occur during human respiration.
View Article and Find Full Text PDF