Nearby Molecules Research Articles

Solvent Mediated Interactions on Alkene Epoxidations in Ti-MFI: Effects of Solvent Identity and Silanol Density

Selective alkene oxidation rates within zeolite pores reflect differences in contributions from thermodynamic nonidealities introduced by noncovalent interactions at solid–liquid interfaces and spatial constraints enforced by the zeolite topology. Epoxidation turnover rates for 1-hexene in Ti-MFI zeolite differ by 1000-fold across 10 combinations of solvents, including alcohols and acetonitrile, over Ti-MFI with distinct silanol defect densities. Solvent mediated noncovalent interactions persist across an extended binding environment that influences the stability of epoxidation transition states. Apparent activation enthalpies (ΔHApp⧧) and entropies (ΔSApp⧧) span 80 kJ mol–1 and 200 J mol–1 K–1, respectively, with the most positive values for both appearing in methanol. Hydrophilic (i.e., (SiOH)x defect rich) Ti-MFI-OH catalysts in methanol give the greatest turnover rates because entropic gains associated with the disruption of hydrogen-bonded networks of intrapore methanol and water dominate activation free energies. In situ infrared spectra show that the adsorption of 1,2-epoxyhexane to Ti sites disturbs the equilibrium solvent structure within pores in ways that reflect the density of the hydrogen bond donor and acceptors near active sites. This interpretation agrees with measured enthalpies for adsorption of 1,2-epoxyhexane to Ti active sites within solvent filled pores that correlate with ΔHApp⧧ across solvent and catalyst combinations. The displacement of solvent molecules and the associated rupture and formation of hydrogen bonds among solvents, pore walls, and nearby reactive molecules during catalysis and adsorption events incur substantial excess contributions that govern the reaction rates and barriers. These realizations explain the particular success of alkene epoxidations in mixtures of H2O2 and methanol over hydrophilic forms of Ti-MFI in industrial processes (e.g., the hydrogen peroxide–propylene oxide process). These findings demonstrate the gains achieved by appropriately pairing organic solvents with microporous catalysts to manipulate the intrinsic kinetics of reactions and the thermodynamics of adsorption at solid–liquid interfaces.

AMOEBA Force Field Predicts Accurate Hydrogen Bond Counts of Nitriles in SNase by Revealing Water-Protein Interaction in Vibrational Absorption Frequencies.

Precisely quantifying the magnitude and direction of electric fields in proteins has long been an outstanding challenge in understanding biological functions. Nitrile vibrational Stark effect probes have been shown to be minimally disruptive to the protein structure and can be better direct reporters of local electrostatic field in the native state of a protein than other measures such as pKa shifts of titratable residues. However, interpretations of the connection between measured vibrational energy and electric field rely on the accurate molecular understanding of interactions of the nitrile group and its environment, particularly from hydrogen bonding. In this work, we compared the extent of hydrogen bonding calculated in two common force fields, the fixed charge force field Amber03 and polarizable force field AMOEBA, at 10 locations of cyanocysteine (CNC) in staphylococcal nuclease (SNase) against the experimental nitrile absorption frequency in terms of full width at half-maximum (FWHM) and frequency temperature line slope (FTLS). We observed that the number of hydrogen bonds correlated well in AMOEBA trajectories with respect to both the FWHM (r = 0.88) and the FTLS (r = -0.85), whereas the correlation of Amber03 trajectories was less reliable because the Amber03 force field predicted more hydrogen bonds in some mutants. Moreover, we demonstrated that contributions from the interactions between CNC and nearby water molecules were significant in AMOEBA trajectories but were not predicted by Amber03. We conclude that although the nitrile absorption peak shape could be qualitatively predicted by the fixed charge Amber03 force field, the detailed electrostatic environment measured by the nitrile probe in terms of the extent of hydrogen bonding could only be accurately observed in the AMOEBA trajectories, where the permanent dipole, quadrupole, and dipole-induced-dipole polarizable interactions were all taken into account. The significance of this finding to the goal of accurately predicting electric fields in complex biomolecular environments is discussed.

Double-ring-disk hybrid nanostructures with slits for electric field enhancement.

Although noble metal nanoantennas have distinctive optical properties and local electric field enhancement, considerable non-radiative ohmic losses occur at the optical frequencies, consequently creating significant absorption and unwanted heating. Combining the plasmon mode of metal nanoantennas with the anapole mode of high refractive index dielectric materials offers a promising alternative to increase the electric field strength with minimal loss. Herein, a silicon disk with slots and two Au rings with a coupling mechanism are described. To elucidate the field enhancement mechanism, the near-field enhancement features and near-field electric field distributions are explored by a numerical simulation and multipole decomposition analysis. By opening the slit to generate high-intensity hot spots inside the disk, the electric field can be enhanced significantly, and nearby molecules can directly contact these hot spots. The resulting large field enhancement suggests significant applications to strong photon-exciton coupling and nonlinear photonics.

Near-Field-Induced Ionization on Photo-Excited Gold Nanoparticles

Gold nanoparticles (AuNPs) have been widely utilized as an effective substrate for triggering molecular ionization upon photoexcitation. However, its underlying mechanism(s) remains unclear. Here, by blocking heat transfer and electron transfer on photo-excited AuNPs with a thin layer of silica shell (i.e., Au@SiO2 NPs), the critical role of the enhanced E-field in ionizing nearby molecules was evidenced. The enhanced E-field of the Au core could enhance the protonation of amino acids (via short-range interaction) by polarizing the analyte molecules. In contrast, the polarizability of the Au core showed a more pronounced effect to enhance the metal cationization process (Na+ and K+ adduction via long-range interaction) by polarizing both the analyte molecules and metal ions and was successfully applied to the sensitive analysis of amino acids in human serum.

FRET Based Biosensor: Principle Applications Recent Advances and Challenges.

Förster resonance energy transfer (FRET)-based biosensors are being fabricated for specific detection of biomolecules or changes in the microenvironment. FRET is a non-radiative transfer of energy from an excited donor fluorophore molecule to a nearby acceptor fluorophore molecule. In a FRET-based biosensor, the donor and acceptor molecules are typically fluorescent proteins or fluorescent nanomaterials such as quantum dots (QDs) or small molecules that are engineered to be in close proximity to each other. When the biomolecule of interest is present, it can cause a change in the distance between the donor and acceptor, leading to a change in the efficiency of FRET and a corresponding change in the fluorescence intensity of the acceptor. This change in fluorescence can be used to detect and quantify the biomolecule of interest. FRET-based biosensors have a wide range of applications, including in the fields of biochemistry, cell biology, and drug discovery. This review article provides a substantial approach on the FRET-based biosensor, principle, applications such as point-of-need diagnosis, wearable, single molecular FRET (smFRET), hard water, ions, pH, tissue-based sensors, immunosensors, and aptasensor. Recent advances such as artificial intelligence (AI) and Internet of Things (IoT) are used for this type of sensor and challenges.

Water-assisted electron capture exceeds photorecombination in biological conditions.

A decade ago, an electron-attachment process called interatomic Coulombic electron capture has been predicted to be possible through energy transfer to a nearby neighbor. It has been estimated to be competitive with environment-independent photorecombination, but its general relevance has yet to be established. Here, we evaluate the capability of alkali and alkaline earth metal cations to capture a free electron by assistance from a nearby water molecule. We introduce a characteristic distance rIC for this energy transfer mechanism in equivalence to the Förster radius. Our results show that water-assisted electron capture dominates over photorecombination beyond the second hydration shell of each cation for electron energies above a threshold. The assisted capture reaches distances equivalent to a fifth to seventh solvation shell for the studied cations. The far reach of the assisted electron capture is of significant general interest to the broad spectrum of research fields dealing with low-energy electrons, in particular radiation-induced damage of biomolecules. The here introduced distance measure will enable quantification of the role of the environment for assisted electron attachment.

Theoretical Investigations on the Plasmon-Mediated Dissociation of Small Molecules in the Presence of Silver Atomic Wires.

Plasmonic nanoparticles can promote bond activation in adsorbed molecules under relatively benign conditions via excitation of the nanoparticle's plasmon resonance. As the plasmon resonance often falls within the visible light region, plasmonic nanomaterials are a promising class of catalysts. However, the exact mechanisms through which plasmonic nanoparticles activate the bonds of nearby molecules are still unclear. Herein, we evaluate Ag8-X2 (X = N, H) model systems via real-time time-dependent density functional theory (RT-TDDFT), linear response time-dependent density functional theory (LR-TDDFT), and Ehrenfest dynamics in order to better understand the bond activation processes of N2 and H2 facilitated by the presence of the atomic silver wire under excitation at the plasmon resonance energies. We find that dissociation is possible for both small molecules at high electric field strength. Activation of each adsorbate is symmetry- and electric field-dependent, and H2 activates at lower electric field strengths than N2. This work serves as a step toward understanding the complex time-dependent electron and electron-nuclear dynamics between plasmonic nanowires and adsorbed small molecules.

Molecular Dynamics Simulation of CO2 Hydrate Growth in NaCl Aqueous Solution

Summary Climate change has brought enormous adverse outcomes to biological activities around the world. The main reason is that too much CO2 has been released into the atmosphere. In recent years, storing CO2 in the form of CO2 hydrate is a research hotspot, the main purpose of which is to reduce carbon emissions to mitigate the greenhouse effect. In this work, we use the molecular dynamics simulation method to study the growth of CO2 hydrate in NaCl aqueous solution with the assumption of induction of CO2 sequestration in the ocean. The temperature is 275 K and the pressure is 10 MPa in this work. Under these conditions, stucture I type (sI-type) CO2 hydrate with a density of about 1150 kg/m3 formed within a very short period of time. The simulation results show that during hydrate growth, Na+ and Cl− are “driven” together and the water molecules remain liquid in this region, where they are near Na+ and Cl−. From the independent gradient model (IGM) based on Hirshfeld partition (IGMH) analysis, Na+ does not bond with any ions/molecules, which hinders the formation of water cages and thus inhibits hydrate growth; Cl− forms multiple H-bonds with neighboring H2O molecules and can participate in the formation of water cages. However, it is worth noting that not all Cl– and the nearby water molecules can form either a five-membered ring or a four-membered ring; even some water molecules and Cl− cannot form a closed ring. Therefore, it is impossible to determine whether the water molecules near the Cl− are all in liquid or solid state.

Optical method for quantifying the potential of zero charge at the platinum-water electrochemical interface.

When an electrode contacts an electrolyte, an interfacial electric field forms. This interfacial field can polarize the electrode's surface and nearby molecules, but its effect can be countered by an applied potential. Quantifying the value of this countering potential ('potential of zero charge' (pzc)) is, however, not straightforward. Here we present an optical method for determining the pzc at an electrochemical interface. Our approach uses phase-sensitive second-harmonic generation to determine the electrochemical potential where the interfacial electric field vanishes at an electrode-electrolyte interface with Pt-water as a model experiment. Our method reveals that the pzc of the Pt-water interface is 0.23 ± 0.08 V versus standard hydrogen electrode (SHE) and is pH independent from pH 1 to pH 13. First-principles calculations with a hybrid explicit-implicit solvent model predict the pzc of the Pt(111)-water interface to be 0.23 V versus SHE and reveal how the interfacial water structure rearranges as the electrode potential is moved above and below the pzc. We further show that pzc is sensitive to surface modification; deposition of Ni on Pt shifts the interfacial pzc in the cathodic direction by ~360 mV. Our work demonstrates a materials-agnostic approach for quantifying the interfacial electrical field and water orientation at an electrochemical interface without requiring probe molecules and confirms the long-held view that the interfacial electric field is more intense during hydrogen electrocatalysis in alkaline than in acid.

Structural and Spectroscopic Studies of Steric and Electronic Substituent Effects in a Series of Magnesium Aminodiboranates Mg[(BH3)2NMeR]2.

The magnesium N,N-dimethylaminodiboranate compound Mg[(BH3)2NMe2]2, the most volatile compound of magnesium known, serves as an excellent chemical vapor deposition (CVD) precursor for the growth of thin films such as the dielectric material MgO. To explore how the thermal stability and physical properties of magnesium aminodiboranates depend on the steric and electronic properties of the nitrogen-bound substituents, we have made a series of analogues of Mg[(BH3)2NMe2]2, in which one of the two methyl substituents on nitrogen is replaced with an ethyl, iso-propyl, or tert-butyl group. In the crystal structure of Mg[(BH3)2NMe(t-Bu)]2, the magnesium center is coordinated to two chelating (BH3)2NMe(t-Bu) ligands, each of which binds in a κ2,κ2 fashion so that the magnesium center forms eight Mg-H contacts. Unlike Mg[(BH3)2NMe2]2, however, which has a linear N···Mg···N angle and is an isolated molecule in the solid state, the N···Mg···N angle in Mg[(BH3)2NMe(t-Bu)]2 is distinctly nonlinear (149.9°) because hydrogen atoms of BH3 groups of nearby molecules form two additional Mg-H contacts with the magnesium center. When the complexes are heated in toluene solution, the (BH3)2NMeR- groups reversibly undergo B-N bond cleavage (with concomitant migration of a hydrogen atom) to release the aminoborane BH2═NMeR and form magnesium borohydride, Mg(BH4)2. For the methyl, ethyl, and iso-propyl derivatives, the equilibrium strongly favors Mg[(BH3)2NMeR]2. In contrast, for the tert-butyl derivative, the equilibrium strongly favors BH2═NMe(t-Bu) and Mg(BH4)2. The results suggest that more strongly electron-donating groups slightly strengthen the B-N bonds and disfavor B-N bond cleavage, provided that the groups are not too large. In contrast, sterically bulky ligands disfavor B-N bond reformation, thus promoting the dissociative equilibrium that involves B-N bond cleavage. Interestingly, the rates at which the complexes approach equilibrium depend only weakly on the nature of the R group, at least within the series studied. These findings are relevant to the potential use of magnesium aminodiboranates as CVD precursors to the superconducting phase MgB2.

Mechanistic Insight into Peptidyl-Cysteine Oxidation by the Copper-Dependent Formylglycine-Generating Enzyme.

The copper-dependent formylglycine-generating enzyme (FGE) catalyzes the oxygen-dependent oxidation of specific peptidyl-cysteine residues to formylglycine. Our QM/MM calculations provide a very likely mechanism for this transformation. The reaction starts with dioxygen binding to the tris-thiolate CuI center to form a triplet CuII -superoxide complex. The rate-determining hydrogen atom abstraction involves a triplet-singlet crossing to form a CuII -OOH species that couples with the substrate radical, leading to a CuI -alkylperoxo intermediate. This is accompanied by proton transfer from the hydroperoxide to the S atom of the substrate via a nearby water molecule. The subsequent O-O bond cleavage is coupled with the C-S bond breaking that generates the formylglycine and a CuII -oxyl complex. Moreover, our results suggest that the aldehyde oxygen of the final product originates from O2 , which will be useful for future experimental work.

Mechanistic Insight into Peptidyl‐Cysteine Oxidation by the Copper‐Dependent Formylglycine‐Generating Enzyme

AbstractThe copper‐dependent formylglycine‐generating enzyme (FGE) catalyzes the oxygen‐dependent oxidation of specific peptidyl‐cysteine residues to formylglycine. Our QM/MM calculations provide a very likely mechanism for this transformation. The reaction starts with dioxygen binding to the tris‐thiolate CuI center to form a triplet CuII‐superoxide complex. The rate‐determining hydrogen atom abstraction involves a triplet‐singlet crossing to form a CuII−OOH species that couples with the substrate radical, leading to a CuI‐alkylperoxo intermediate. This is accompanied by proton transfer from the hydroperoxide to the S atom of the substrate via a nearby water molecule. The subsequent O−O bond cleavage is coupled with the C−S bond breaking that generates the formylglycine and a CuII‐oxyl complex. Moreover, our results suggest that the aldehyde oxygen of the final product originates from O2, which will be useful for future experimental work.

ANALYSIS OF THE CRYSTAL STRUCTURE AND ENERGY FRAMEWORKS OF 5-ACETIL-1,3-DIMETHYL BARBITURIC ACID

C8H9N2O4 was prepared via acetylation of 1,3-dimethyl barbituric acid. The atomic and crystalline structures were determined using single crystal analysis (X-ray). It is a member of the monoclinic system P 21/c group of space with a = 8.6056 (3) Å, b = 9.1602 (3) Å, c = 11.9601 (4) Å, β = 109.410 (3)°, Z = 4 and V = 889.22 (5) Å3. π–π interactions between circles of nearby molecules with intercentroid distances of 3.4300 (11) aid in the stability of the structure by keeping the crystals in place. The Hirshfeld surface (HS) analysis of the crystal structure reveals that the H... O/O... H (45.9%) and H... H (32.9%) interactions contribute the most to crystal packing. The most essential interactions in crystal packing are hydrogen bonding and van der Waals interactions. According to the dispersion, electrostatic and overall energy frameworks, the contribution of dispersion energy dominates the stability.

Identification of a Cardiac Glycoside Exhibiting Favorable Brain Bioavailability and Potency for Reducing Levels of the Cellular Prion Protein.

Several strands of investigation have established that a reduction in the levels of the cellular prion protein (PrPC) is a promising avenue for the treatment of prion diseases. We recently described an indirect approach for reducing PrPC levels that targets Na,K-ATPases (NKAs) with cardiac glycosides (CGs), causing cells to respond with the degradation of these pumps and nearby molecules, including PrPC. Because the therapeutic window of widely used CGs is narrow and their brain bioavailability is low, we set out to identify a CG with improved pharmacological properties for this indication. Starting with the CG known as oleandrin, we combined in silico modeling of CG binding poses within human NKA folds, CG structure-activity relationship (SAR) data, and predicted blood-brain barrier (BBB) penetrance scores to identify CG derivatives with improved characteristics. Focusing on C4'-dehydro-oleandrin as a chemically accessible shortlisted CG derivative, we show that it reaches four times higher levels in the brain than in the heart one day after subcutaneous administration, exhibits promising pharmacological properties, and suppresses steady-state PrPC levels by 84% in immortalized human cells that have been differentiated to acquire neural or astrocytic characteristics. Finally, we validate that the mechanism of action of this approach for reducing cell surface PrPC levels requires C4'-dehydro-oleandrin to engage with its cognate binding pocket within the NKA α subunit. The improved brain bioavailability of C4'-dehydro-oleandrin, combined with its relatively low toxicity, make this compound an attractive lead for brain CG indications and recommends its further exploration for the treatment of prion diseases.

Waveguide-Enhanced Raman Spectroscopy (WERS): An Emerging Chip-Based Tool for Chemical and Biological Sensing.

Photonic chip-based methods for spectroscopy are of considerable interest due to their applicability to compact, low-power devices for the detection of small molecules. Waveguide-enhanced Raman spectroscopy (WERS) has emerged over the past decade as a particularly interesting approach. WERS utilizes the evanescent field of a waveguide to generate Raman scattering from nearby analyte molecules, and then collects the scattered photons back into the waveguide. The large interacting area and strong electromagnetic field provided by the waveguide allow for significant enhancements in Raman signal over conventional approaches. The waveguide can also be coated with a molecular class-selective sorbent material to concentrate the analyte, thus further increasing the Raman signal. This review provides an overview of the historical development of WERS and highlights recent theoretical and experimental achievements with the technique.

Effect of Protonation and Deprotonation on Electron Transfer Mediated Decay and Interatomic Coulombic Decay.

Electronically excited atoms or molecules in an environment are often subject to interatomic/intermolecular Coulombic decay (ICD) and/or electron transfer mediated decay (ETMD) mechanisms. A few of the numerous variables that can impact these non-radiative decay mechanisms include bond distance, the number of nearby atoms or molecules, and the polarisation effect. In this paper, we have studied the effect of protonation and deprotonation on the ionization potential (IP), double ionization potential (DIP), and lifetime (or decay width) of the temporary bound state in these non-radiative decay processes. We have chosen LiH-NH3 and LiH-H2 O as test systems. The equation of motion coupled cluster singles and doubles method augmented by complex absorbing potential (CAP-EOM-CCSD) has been used in calculating the energetic position of the decaying state and the system's decay rate. Deprotonation of LiH-NH3 /LiH-H2 O either from the metal center (LiH) or from ammonia/water lowers the IP and DIP compared to the neutral systems. In contrast, protonation increases these quantities compared to neutral systems. The protonation closes the inner valence state relaxation channels for ICD/ETMD. For example, the decay of the O-2s/N-2s state stops in protonated systems (LiH2 + -H2 O, LiH2 + -NH3 , and LiH-NH4 + ). Our study also shows that the efficiency, i. e., the rate of ICD/ETMD, can be altered by protonation and deprotonation. It is expected to have implications for chemical and biological systems.

Potential of Zero Charge Measurement By Second Harmonic Generation

When an electrode contacts an electrolyte, an interfacial electric field forms. This interfacial field can polarize the electrode’s surface and nearby molecules, but its effect can be countered by applying countering potential. We present an optical method for quantifying the value of this countering potential (“potential of zero charge”, pzc). Our approach uses phase-sensitive second harmonic generation to determine the potential where the interfacial electric field vanishes, using Pt-water interface as a model system. Our experiment reveals that the value of the pzc of the Pt/water interface and further shows that it is pH-independent from pH 1 to 13 on an absolute potential scale. We will discuss this result from the consideration of the solid-liquid interface, including the electrode materials and interfacial water structure. Our work provides a materials-agnostic tool for quantifying the interfacial electrical field at a solid-liquid interface and confirms the view that the interfacial electric field during hydrogen electrocatalysis is more intense in alkaline than acid.

Insights into binding molecular mechanism of hemagglutinin H3N2 of influenza virus complexed with arbidol and its derivative: A molecular dynamics simulation perspective

Recently, the H3N2 influenza outbreak has caused serious global public health concern for future control of the next influenza pandemic. Since using current anti-influenza drugs targeting neuraminidase (oseltamivir and zanamivir) and the proton M2 channel (amantadine and rimantadine) leads to drug resistance, it is essential to seek new anti-viral agents that act on additional viral targets. Hemagglutinin (HA), a glycoprotein embedded in the viral surface and playing a critical role in influenza the viral replication cycle has become an attractive target. This work investigates the molecular binding mechanism of HA H3N2 of influenza virus complexed with the fusion inhibitor, arbidol and its derivative (der-arbidol), by means of molecular dynamics simulation. The result showed that the arbidol derivative could form many and strong hydrogen bonds with the HA surrounding amino acids comprising GLU1032(1), LYS3071(1) and LYS3102(1) while arbidol makes this type of interaction with only LYS582(1). The introduction of hydroxyl group at the meta-position of the thiophenol ring was detected to replace the nearby water molecule, thus allowing the direct hydrogen bond formation between der-arbidol and GLU1032(1) of HA residue. Furthermore, the salt bridge networks established among residues GLU572(1)···ARG542(1)···GLU972(2) were considerably more stable in HA-Der-arbidol than that found in HA-Arbidol. The predicted protein-ligand binding free energies were in agreement with experimental data indicating that der-arbidol exhibits higher inhibitory potency against HA H3N2 of influenza virus. Detailed information could be useful for further designing and optimizing HA fusion inhibitors with improved efficiency.

Azide Photochemistry in Acrylic Copolymers for Ultraviolet Cross-Linkable Pressure-Sensitive Adhesives: Optimization, Debonding-on-Demand, and Chemical Modification.

Pressure-sensitive adhesives (PSAs) are usually made from viscoelastic, high-molecular-weight copolymers, which are fine-tuned by adjusting the comonomer ratios, molecular weights, and cross-link densities to optimize the adhesion properties for the desired end-use. To create a lightly cross-linked network, an ultraviolet (UV) photoinitiator can be incorporated. Here, we present the first use of perfluorophenylazide chemistry to control precisely a polyacrylate network for application as a PSA. Upon UV irradiation, the highly reactive nitrene from the azide moiety reacts with nearby molecules through a C–H insertion reaction, resulting in cross-linking via covalent bonding. This approach offers three benefits: (1) a means to optimize adhesive properties without the addition of an external photoinitiator; (2) the ability to switch off the tack adhesion on demand via a high cross-linking density; and (3) a platform for additional chemical modification. A series of poly(n-butyl acrylate-co-2,3,4,5,6-pentafluorobenzyl acrylate) or poly(PFBA-co-BA) copolymers were synthesized and modified post-polymerization into the photo-reactive poly(n-butyl acrylate-co-4-azido-2,3,5,6-tetrafluorobenzyl acrylate) [azide-modified poly(PFBA-co-BA)] with various molar contents. When cast into films, the azide-modified copolymers with a high azide content achieved a very high shear resistance after UV irradiation, whereas the tack and peel adhesion decreased strongly with the increase in azide content, indicating that excessive cross-linking occurred. These materials are thus photo-switchable. However, in the low range of azide content, an optimum probe tack adhesion energy was obtained in films with a 0.3 mol % azide content, where a long stress plateau (indicating good fibrillation) with a high plateau stress was observed. An optimum peel adhesion strength was achieved with 0.5 mol % azide. Thus, the adhesion was finely controlled by the degree of cross-linking of the PSA, as determined by the azide content of the copolymer chain. Finally, as a demonstration of the versatility and advantages of the material platform, we show an azide–aldehyde–amine multicomponent modification of the azide copolymer to make a dye-functionalized film that retains its adhesive properties. This first demonstration of using azide functionality has enormous potential for functional PSA design.

Triplet Energy Transfer from Lead Halide Perovskite for Highly Selective Photocatalytic 2 + 2 Cycloaddition.

Triplet excitons are generally confined within a semiconductor. Hence, solar energy utilization via direct triplet energy transfer (TET) from semiconductors is challenging. TET from lead halide perovskite semiconductors to nearby organic molecules has been illustrated with ultrafast spectroscopy. Direct utilization of solar energy, i.e., visible light, via TET for photocatalysis is an important route but has not yet been demonstrated with lead halide perovskite semiconductors. Here, we show that a photocatalytic reaction, focusing on a 2 + 2 cycloaddition reaction, can been successfully demonstrated via TET from lead halide perovskite nanocrystals (PNCs). The triplet excitons are shown to induce a highly diastereomeric syn-selective 2 + 2 cycloaddition starting from olefins. Such photocatalytic reactions probe the TET process previously only observed spectroscopically. Moreover, our observation demonstrates that bulk-like PNCs (size, >10 nm; PL = 530 nm), in addition to quantum-confined smaller PNCs, are also effective for TET. Our findings may render a new energy conversion pathway to employ PNCs via direct TET for photocatalytic organic synthesis.