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Abstract The creation of next‐generation flexible and conformable magneto‐optic (MO) materials with dramatically enhanced Verdet constant will significantly advance technologies, including optical isolation, magnetic quantum spin fluctuation measurements, and cold atom spin coherence probes, while opening new possibilities for mapping weakly emanating magnetic fields from sources, including microelectronics or brain activity. The results presented here show that the natural coupling of electric and magnetic dipoles in a chiral polymer with large optical activity (circular birefringence) is significantly enhanced by combined plasmonic field and magnetic interactions of plasmonic nanostars and magnetic nanoparticles to yield a dramatically increased Verdet constant within an optical path of a few hundred nanometers. A 175 ± 10 nm film of this material produces up to 600 mdeg of relative MO rotation at 510 nm, which translates to a record‐high Verdet constant of 3.1 × 10⁷deg T⁻¹m⁻¹at 93 K, more than two orders of magnitude higher than the current state of the art MO garnet crystals. The room temperature Verdet constant substantially exceeds that of other thin film nanocomposites reported to date. Manipulation of electric and magnetic coupling offers an unprecedented opportunity to tailor the magnitude, sign, and spectral dispersion of the Verdet constant over a broad range of wavelengths. 

Experimental methods capable of selectively probing water at the DNA minor groove, major groove, and phosphate backbone are crucial for understanding how hydration influences DNA structure and function. Chiral-selective sum frequency generation spectroscopy (chiral SFG) is unique among vibrational spectroscopies because it can selectively probe water molecules that form chiral hydration structures around biomolecules. However, interpreting chiral SFG spectra is challenging since both water and the biomolecule can produce chiral SFG signals. Here, we combine experiment and computation to establish a theoretical framework for the rigorous interpretation of chiral SFG spectra of DNA. We demonstrate that chiral SFG detects the N–H stretch of DNA base pairs and the O–H stretch of water, exclusively probing water molecules in the DNA first hydration shell. Our analysis reveals that DNA transfers chirality to water molecules only within the first hydration shell, so they can be probed by chiral SFG spectroscopy. Beyond the first hydration shell, the electric field-induced water structure is symmetric and, therefore, precludes chiral SFG response. Furthermore, we find that chiral SFG can differentiate chiral subpopulations of first hydration shell water molecules at the minor groove, major groove, and phosphate backbone. Our findings challenge the scientific perspective dominant for more than 40 years that the minor groove “spine of hydration” is the only chiral water structure surrounding the DNA double helix. By identifying the molecular origins of the DNA chiral SFG spectrum, we lay a robust experimental and theoretical foundation for applying chiral SFG to explore the chemical and biological physics of DNA hydration. 

Abstract Polymer‐based chiral materials with exceptional optical activity can dramatically impact integrated chiral photonics due to the tunability of their optical responses coupled with ease of fabrication. Realizing these applications requires increasing the absorbance dissymmetry factor. Here, in situ, the synthesis of gold nanostars is introduced in a chiral polymer medium to produce chiral polymer‐anisotropic plasmonic nanocrystal nanocomposites. The optimized nanocomposite shows a tenfold enhancement of dissymmetry factor,g_abs(up to 0.64) and a corresponding 46‐fold augmented circular dichroism (CD) value upon annealing, relative to the annealed pure chiral polymer film. Moreover, the enhancement relative to the non‐annealed polymer‐gold nanostar nanocomposite is strikingly higher: a 35‐fold increase ing_absand a 4272‐fold increase in CD. Based on computational analysis, it is concluded that the local plasmon field enhancement around the crevices and tips of nanostars is mainly responsible for the observed effect which is further supported by a signal enhancement in Surface Enhanced Raman Scattering (SERS). Thus, this study underscores the significant role of close‐range plasmon interactions in altering the chiroptical response of nanocomposite materials and a practical pathway toward the realization of next‐generation integrated photonics and optoelectronic circuitry with photon spin control. 

Materials recovery facilities (MRFs) require new automated technologies if growing recycling demands are to be met. Current optical screening devices use visible (VIS) and near-infrared (NIR) wavelengths, frequency ranges that can experience challenges during the characterization of postconsumer plastic waste (PCPW) because of the overly-absorbing spectral bands from dyes and other polymer additives. Technological bottlenecks such as these contribute to 91% of plastic waste never actually being recycled. The mid-infrared (MIR) region has attracted recent attention due to inherent advantages over the VIS and NIR. The fundamental vibrational modes found therein make MIR frequencies promising for high fidelity machine learning (ML) classification. To-date, there are no ML evaluations of extensive MIR spectral datasets reflecting PCPW that would be encountered at MRFs. This study establishes quantifiable metrics, such as model accuracy and prediction time, for classification of a comprehensive MIR database consisting of five PCPW classes that are of economic interest: polyethylene terephthalate (PET #1), high-density polyethylene (HDPE #2), low-density polyethylene (LDPE #4), polypropylene (PP #5), and polystyrene (PS #6). Autoencoders, an unsupervised ML algorithm, were applied to the random forest (RF), k-nearest neighbor (KNN), support vector machine (SVM), and logistic regression (LR) models. The RF model achieved accuracies of 100.0% in both the C–H stretching region (2990–2820 cm −1 ) and molecular fingerprint region (1500–650 cm −1 ). The C–H stretching region was found to be free from additives that were responsible for misclassification in other regions, making it a fruitful frequency range for future PCPW sorting technologies. The MIR classification of black plastics and polyethylene PCPW using ML autoencoders was also evaluated for the first time. 

Oxygen plasma treatment of polydimethylsiloxane (PDMS) induces an ultrathin polyorganosilica (POSi) layer (< 10 nm) on top of a PDMS membrane, leading to excellent H2/gas separation properties and providing a rapid and scalable way to fabricate robust silica membranes compared with conventional high-temperature and time-consuming sol-gel methods. Here, we thoroughly investigate POSi membranes derived from poly(dimethylsiloxane-co-methylhydroxidesiloxane) (poly(DMS-co-MHOS)) containing -SiOH groups that can be more easily converted to silica networks than the -SiCH3 in PDMS. The effect of the polysiloxane structure and plasma treatment conditions (including plasma generating powers, oxygen flowrate, chamber pressure, and treatment time) on the silica chemistry, structure, and H2/CO2 separation properties are systematically determined to derive structure/property relationships. An optimized membrane exhibits H2 permeance of 880 GPU and H2/CO2 selectivity of 67 at 150 ℃, superior to state-of-the-art polymeric membranes. The membrane retains H2/CO2 selectivity as high as 46 when challenged with simulated syngas containing 2.8 mol% water vapor at 150 ℃, demonstrating the potential of these POSi membranes for practical applications. 

ABSTRACT Elucidating the crystalline‐amorphous interface during decrystallization processes in semi‐crystalline polyethylene (PE) is crucial for the advancement of polymer theory and plastic‐to‐plastic recycling technologies. In this study, we carried out an in‐depth investigation of PE thin films undergoing melting or dissolution using a temperature‐controlled liquid flow‐cell experimental setup which provided in situ mid‐infrared (MIR, 4000–700 cm⁻¹) and near‐infrared (NIR, 6000–4000 cm⁻¹) spectra in real time. The spectroscopic results yielded molecular‐level information regarding PE decrystallization and chain disentanglement via fundamental vibrations, combination bands, and overtones which were correlated using hetero‐spectral two‐dimensional correlation spectroscopy (2D‐COS). A quantitative procedure for the calculation of PE degree of crystallinity was developed to track transformations of crystalline domains during melting and dissolution. This semi‐empirical model achieved a strong linear correlation of at least +0.93 in four spectral regions: 750–700 cm⁻¹, 1500–1400 cm⁻¹, 3000–2800 cm⁻¹, and 4400–4200 cm⁻¹. This analysis revealed important spectral trends about the interfacial solvation environment during these processes. Lastly, the time evolution of the unraveling, terminal methyl (CH₃) groups of PE cilia was examined in relation to the decrystallization mechanism of PE. The insights obtained from this study advance the fundamental understanding necessary for developing new depolymerization and dissolution‐precipitation recycling strategies.