This review presents the feasibility of evanescent field-based fiber optic sensors across a wide range of applications. We evaluated two distinct sensing platforms based on localized surface plasmon resonance (LSPR) and a metal-free porphyrin-based fiber optic sensor. To maximize evanescent field penetration depth and sensitivity, U-bent and D-shaped fiber probe geometries were employed. For LSPR-based U-bent sensors, nanoparticle distribution was optimized, which is essential for controlling plasmonic coupling and maximizing sensitivity. Further, these probes are used for various applications, including the field of biosensing, water safety monitoring, and clinical diagnostics. Additionally, the review explores the unique potential of these platforms for monitoring ultrafast thermal dynamics of materials. In parallel, porphyrinimmobilized optical fiber probes were reviewed as powerful spectroscopic sensing platforms by monitoring UV-Vis absorption changes in Soret and Q bands, enabling selective detection of volatile gases and metal ions. The spectral feature changes during various analyte interactions produce high-dimensional data that necessitate advanced analysis techniques. These were analyzed using both unsupervised and supervised algorithms for spectral classification and analyte identification, with a focus on the critical role of spectral preprocessing in enhancing classification accuracy. Collectively, these platforms provide a comprehensive framework for next-generation, stable, and remote fiber-optic sensing systems. The graphical abstract depicts two distinct evanescent-fi eld-based optical fiber sensing platforms. One platform employs a metal-nanoparticle-based fiber-optic probe, in which analyte binding to the fiber core surface induces changes in the LSPR absorption spectrum. The other utilizes porphyrin-immobilized optical fiber probes, where analyte interactions induce characteristic changes in the Soret and Q bands of the porphyrin absorption spectrum. These spectral changes enable analyte identification through machine learning-assisted spectral analysis.
A new Mn(II) incorporated kaolinite was designed and synthesized via the impregnation method followed by calcination at 723 K for 360 min, then characterized with AAS, XRD, surface area, SEM, and FTIR measurements. Catalytic wet peroxide oxidations (CWPO) of 2–chlorophenol (2–CP) and 4–chlorophenol (4–CP) were assigned to probe the reactivity and activity of the catalyst prepared. The results showed that Mn(II) could be successfully incorporated into the interlayer of kaolinite, where surface area and the intensity of basal space of kaolinite were slightly altered to 7.02 A° and 24.96 m2/g. The heterogeneous catalyst exhibited first-order kinetics, with 87.9
A novel Tröger’s base amide-functionalized chitosan polymer (TB_CONH@CS) was synthesized via EDC/NHS-mediated carbodiimide coupling, forming stable amide linkages. Comprehensive characterization by FT-IR, PXRD, 1H NMR, DLS, zeta potential, and FE-SEM confirmed successful conjugation, spherical morphology of the blank conjugate (371 nm, +43.6 ± 6.91 mV), and rod-shaped morphology upon curcumin loading (426 nm, +38.3 ± 6.36 mV) and the degree of substitution, DS ≈15.6
Molecular self-assemblies, particularly amyloid fibrils at the micro- and nanoscale, play a crucial role in understanding biomolecular functions of peptides. Recent efforts show that selenopeptides are being studied to understand the role of selenium (Se) in molecular self-assemblies. In this context, this study reports the synthesis of a Se-containing tripeptide, Sec(C6H5)-Sec(C6H5)-Sec(C6H5)-NH2 (1), through solid-phase peptide synthesis (SPPS). Oxidation of 1 with hydrogen peroxide (H2O2), followed by in-situ thiophenol (PhSH) ligation, produced the corresponding S-tripeptide, Cys(C6H5)-Cys(C6H5)-Cys(C6H5)-NH2 (2). Both tripeptides were characterized using NMR, FT-IR, HR-MS, RP-HPLC, CD spectroscopy, fluorescence spectroscopy and fiber X-ray diffraction. Their molecular self-assemblies were investigated by SEM, TEM, and AFM. Se-tripeptide 1 formed amyloid-like fibrils, which, upon oxidative deselenization and thiol ligation, transformed into flower-like microstructures of S-tripeptide 2. Findings highlight the role of Se in selenopeptide self-assembly and its tunability through chemical modification. A selenium-containing tripeptide was synthesized by SPPS method and transformed into its sulfur analogue through oxidative deselenization followed by in situ thiophenol ligation. This chemical modification induced a transition in self-assembly from amyloid-like fibrils to flower-like microstructures, demonstrating the critical role of selenium in regulating peptide supramolecular architecture.
Plastic pollution is a significant environmental issue in the 21st century, and polyoxymethylene (POM) is a key component that needs upcycling into useful chemicals. POM undergoes depolymerization to produce a toxic chemical, formaldehyde. In a notable advancement, Ruquan Ye and co-workers demonstrated a one-pot electrochemical process that converts formaldehyde into formic acid at the anode and methanol at the cathode, utilizing Pt2Ru and a hydrophobic CuTAPc-layer catalysts, respectively with exceptional Faradaic efficiencies. Ruquan Ye and co-workers report one-pot depolymerisation of polyoxymethylene (POM) to formaldehyde in an acidic solution, and, in the same acidic medium, electrochemical conversion of formaldehyde to methanol (cathode) and formic acid (anode) in a single electrochemical cell, with remarkable Faradaic efficiencies.
Employing density functional theory (DFT), the potential energy curve (PEC) of encapsulated beryllium dimer (Be2@C60) and isolated beryllium dimer have been generated to study the effects of C60 Fullerene’s encapsulation on the PEC of beryllium dimer to analyze the dimer’s stability inside a constrained C60 fullerene. The stability of the dimer is numerically gauged by the analysis of equilibrium position, difference of energy between 6 Å point and the point representing equilibrium position (activation energy) and the steepness of the PEC of the dimer under encapsulation. The PECs for both systems are drawn at the mPW2PLYP/cc-pVTZ level of theory. The PEC for Be2@C60 is drawn by considering both D5d and D3d symmetry and considering fullerene as a rigid cage with only relaxation of beryllium atoms inside the fullerene. To ensure the computational accuracy of each single point energy calculation, energy tolerance of 10–9 Eh, integral cutoffs of 10–12, and large DFT Grid are used. Further, the second order converger (TRAH SCF) is used selectively. Numerical analysis of the PECs of both systems resulted in a shift of equilibrium position towards longer bond length of the dimer, immense increase in activation energy, and a steeper PEC in case of encapsulation in comparison to isolated beryllium dimer. Large activation energy and a steeper PEC reflects the stability of the dimer under encapsulation. These results are further supported by the topological analysis of electron density distribution.
We employ a fully close-coupled three-dimensional time-dependent wavepacket (FCC-3D-TDWP) approach in hyperspherical coordinates to investigate the H + H _2 exchange reaction on recently constructed ground adiabatic as well as Beyond Born–Oppenheimer (BBO)-based three-state diabatic potential energy surfaces (J. Phys. Chem. A 2025 129 6315–6332). For the reaction, H + H _2 ( v=0 , j=0 ) → H _2 ( v' , j' ) + H over the total energy range 0.6 ≤ E_tot≤ 4.5 eV, adiabatic state-to-state reaction probabilities, cross-sections, and product rotational distributions are calculated for total angular momenta up to J=50 , whereas for the diabatic case, state-to-state and total reaction probabilities are computed at J=0 . Calculated adiabatic and diabatic reaction attributes are compared with earlier theoretical results. Though the reaction probabilities as well as cross-sections calculated on adiabatic potential energy surface are qualitatively close to the earlier theoretical profiles, the reaction probability at J=0 on diabatic surfaces is substantially different from existing theoretical ones. The difference originates from the inclusion of ab initio computed non-adiabatic coupling terms in the construction of diabatic Hamiltonian and thereafter, in dynamical calculations.
Molecular recognition within the crowded cellular milieu requires biomolecules to navigate complex and dynamic energy landscapes. Such a challenge is particularly acute during biogenesis of bacterial ribosomes, where the erythromycin resistance methyltransferase (Erm) modifies nascent ribosomal RNA to confer antibiotic resistance. Recently, it has been shown that the head domain of Erm binds to a helical cleft of the precursor (immature) ribosome, which allows the catalytic domain to access the target helix where the methylation substrate (adenine) is located. While Cryo-EM structures of the enzyme-substrate complex suggest an ‘anchor-and-sway’ mechanism for Erm, static reconstructions are unable to capture the stochastic dynamics that the enzyme has to undergo to locate the target site on a flexible ribosomal precursor. Here, we resolve the real-time conformational landscape of the Erm-precursor complex using variability analysis of individual single-molecule FRET (smFRET) efficiency trajectories. Our analyses reveal that the enzyme's C-terminal anchor domain is not very rigidly fixed to a transient helical cleft of the immature ribosome; rather, its motion acts as a sensor for the intrinsic ‘breathing’ dynamics of the precursor binding cleft. In contrast, the catalytic N-terminal domain vacillates between catalytically poised states and a distinct, high-entropy conformation characterised by anomalous spatial flexibility (> 3 Å). Our results support a 'tethered search' model wherein the anchoring domain prevents dissociation, enabling the catalytic domain to sample the local free-energy landscape, thereby preventing kinetic trapping. This study reaffirms site-specific recognition not as a deterministic lock-and-key event, but as a dynamic search process, offering a quantitative framework to resolve the rigid-to-fluid continuum in bio-macromolecular assemblies. Variability analyses of Single-molecule FRET demonstrate that Erm employs a 'tethered search' mechanism to navigate the dynamic surface of the precursor ribosome. While its C-terminal head domain anchors to a transient cleft to maintain a high local concentration, the catalytic domain retains the conformational freedom necessary to scan for the target methylation site, preventing kinetic trapping
Single-molecule toroics (SMTs) hold great promise for quantum information science and multiferroics due to their magnetically silent, electric-field-controllable ground states. However, in conventional systems, opposite toroidal handedness (clockwise and anticlockwise spin vortices) degenerate, resulting in a racemic mixture that cancels out macroscopically. Recently, in Nature Chemistry, Tang and co-workers reported a major breakthrough by synthesising enantiopure triangular dysprosium Dy3 complexes, in which axial chirality in the organic ligand framework lifts the toroidal degeneracy. This structural symmetry-breaking resulted in a single, homochiral toroidal spin state at both the molecular and unit-cell levels. Probed through single-crystal micro-SQUID magnetometry and magneto-chiral dichroism (MChD) spectroscopy, this work marks the first realisation of a structurally sealected homochiral toroidal ground state, laying the foundation for macroscopic, field-switchable Toroidic and Ferrotoroidic materials. Molecular chirality breaks spin degeneracy, enabling controllable homochiral toroidal states and opening new opportunities for quantum information and magnetoelectric molecular materials.
Carbohydrate chemistry continues to provide versatile routes toward new bioactive compounds, yet limited solubility often restricts their broader applications. In the present study, N-fluoroamide thioglycoside derivatives were synthesized in a short and mild process starting from 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-β-D-glucopyranose hydrochloride. The transformation employed a fluorous acylating agent in the presence of potassium carbonate and thiophenol, affording the desired products in excellent yields (82–95
We have demonstrated dual hollow zeolites encapsulating single gold nanoparticle. The dual hollow zeolites taken for research are ZSM-5 and MCM-22. The dual hollow zeolites comprise inner shell as ZSM-5, encapsulating single gold nanoparticles and outer shell comprises of MCM-22. Hierarchical hollow zeolites encapsulating gold nanoparticle facilitates shape selectivity, reduced poisoning/sintering/ agglomeration/leaching of metallic core catalyst by the dual hollow zeolite shells. Additionally, dual hollow zeolites also achieve hierarchical porosity, acidity and additional thermal stability. The oxidation of cyclohexane was selected for evaluation of current catalyst. The catalytic activity was compared with single shell hollow zeolites encapsulating gold nanoparticles for oxidation of cyclohexane to cyclohexanol and cyclohexanone. Higher conversion (65
A [Cu]-catalyzed cascade reaction involving self-condensation and cyclization of tert-propargylic alcohols affording 1H-cyclopenta[b]naphthalenes and dihydro-indenopyrans has been developed. While the 2-methyl substituted propargylic alcohols led to 1H-cyclopenta[b]naphthalenes, 2-diaryl substituted propargylic alcohols furnished dihydro-indenopyrans in moderate to good yields. The transformation proceeded under mild conditions using Cu(OTf)2 and p-toluenesulfonic acid (p-TsOH) as cooperative catalysts. The scope, mechanism, and synthetic potential of this cyclization are discussed. Tert-propargyl alcohols bearing a 2-methyl or 2-diaryl group undergo self-condensation to afford cyclopenta[b]naphthalenes or dihydro-indenopyrans.
The standard paradigm of ‘weak values’ is outlined, and examples leading to several pathological situations are summarized. A few apparently disturbing features are rationalized via explicit links with eigenvalues and the average values. Specifically, we have found it expedient to choose a complete orthonormal set of post-selected states, and hence a full set of weak values, for discussion in a stationary framework. As an illustrative example, a qubit is chosen to avoid any complex number. Inflation and deflation of quantum ‘weak’ values, respectively beyond the highest and lowest eigen values of a Hermitian operator, are studied for qubits with fixed post-selected and varying preselected states to enrich our understanding.
Reported here are the infrared absorption and infrared vibrational circular dichroism (VCD) spectra of a binary complex of trifluoroacetic acid (TFAA) with two enantiomers of camphor in carbon tetrachloride (CCl4) solution. The spectral analysis reveals formation of two distinct isomeric complexes in the liquid at room temperature. The measured VCD spectra of the binary complex shows distinct transitions with respect to selected vibrational modes of the TFAA moiety. The observations have been corroborated by the predictions of density functional theory (DFT) calculations. The results demonstrate the occurrence of chirality induction in an achiral counterpart in the non-covalent complex of a chiral molecule. Synopsis. The graphical abstract illustrates that due to the formation of a hydrogen-bonded binary complex between trifluoroacetic acid and the two enantiomers of camphor, chirality is induced in the otherwise achiral trifluoroacetic acid molecule. This induced chirality is evidenced by both experimental and theoretical vibrational circular dichroism spectra of the complex.
A previously reported Schiff base receptor (H2L) showed strong sensitivity for lanthanum ions (Ka = 2.09×107 M−1, LOD = 5.89×10−8 M). To improve performance, H2L was hybridized with silver (Ag) and zinc (Zn) nanoparticles, forming Ag@H2L and Zn@H2L. These hybrids were characterized by TEM, DLS, UV-vis, fluorescence, and optical analysis. Ag@H2L displayed exceptional sensitivity and selectivity (Ka = 2×109 M−1, LOD = 2.8×10−10 M), surpassing both H2L and Zn@H2L (Ka = 1.47×107 M−1, LOD = 1.41×10−7 M). Results confirm that nanoparticle hybridization, especially with Ag, greatly enhances chemosensory efficiency for lanthanum ion detection. A Schiff base receptor (H2L) and its nanoparticle-based hybrids, Ag@H2L and Zn@H2L, were developed for selectivelanthanum (La3+) ion sensing. Hybridization with Ag nanoparticles significantly enhanced fluorescence intensity, binding affinity, and detection sensitivity due to π-conjugation and surface effects, resulting in superior sensingperformance (Ka = 2×109 M−1, LOD = 2.8×10−10 M) compared to H2L and Zn@H2L.
Azeotropes are constant-boiling mixtures in which the liquid and vapor phases share the same composition. Previous work on the water–ethanol system proposed that, at the azeotropic condition, water and ethanol exhibit identical diffusion distributions as a dynamical signature. However, whether this dynamical behavior plays a causal role in azeotrope formation remains unresolved. In this work, we performed computational estimations of key thermodynamic quantities to probe the origin of the azeotropic behavior in the water–ethanol mixture at the azeotropic composition and temperature. We examined the composition dependence of the total Gibbs free energy of mixing ( ΔG_mix ) and found no distinctive feature at the azeotropic composition. A similar non-unique trend is observed for the entropic contribution ( ΔS_mix ). In contrast, the enthalpy of mixing ( ΔH_mix ) exhibits a distinctive signature at the azeotropic point compared to other compositions at the same temperature ( T_aze= 351 K ). It is observed that, ΔH_mix remains negative until the azeotropic composition is crossed, after which it abruptly changes to become positive. This enthalpic signature underscores the critical importance of intermolecular interactions in establishing the unique azeotropic condition for water–ethanol mixture, though the universality of this feature is not tested. In search of any thermodynamic signature at the azeotropic condition (Xaze, Taze), computational calculation of ΔG_mix , ΔS_mix and ΔH_mix is carried out. Neither ΔG_mix nor ΔS_mix exhibited any anomalous behavior. Interestingly, ΔH_mix gives composition-dependent signature as it shows abrupt change on crossing Xaze, suggesting crucial role of intermolecular interactions.
We have presented a unified theoretical framework for the turnover of stochastic kinetics and non-equilibrium thermodynamics of phosphorylation–dephosphorylation cycles (PdPc) and their extension to cascade signaling networks. Starting from the chemical master equation, we have employed a large deviation ansatz to recast the dynamics into the Hamilton–Jacobi formalism, yielding an explicit Hamiltonian with species concentrations and their conjugate momenta as canonical variables. This formulation provides a systematic evaluation of reaction velocities, fluctuation-induced diffusion, and entropy production rates (EPR). Our results reveal hallmark features of ultrasensitivity: in PdPc, sharp switch-like transitions are reflected in the slope of the EPR, which steepens with increasing chemical potential difference. In a typical PdPc cascade circuits within mitogen-activated protein kinase (MAPK), cooperative enzymatic interactions amplify these effects, optimized at a critical size of the cycle number. An unidirectional signaling cascade is illustrated where receptor activation triggers sequential downstream cycles. Time-series and steady-state analyses show a sharp transition beyond the third cycle, highlighting cycle three as optimal. Increasing cycle numbers enhance cooperativity, sharpening transitions in system velocity and entropy production, indicating critical behavior in the cascade dynamics.
The synthesis of 2-oxazolines typically relies on homogeneous zinc salts, which offer high activity but suffer from poor recyclability and metal contamination. Here, we demonstrate that commercially available zinc oxide (ZnO) functions as an efficient and reusable heterogeneous catalyst for the cyclodehydration of amino alcohols with nitriles under solvent-free conditions. Time-resolved 1H NMR kinetics were recorded for the formation of five products (MeOx, EtOx, iPrOx, BuOx, PhOx), revealing a characteristic sigmoidal conversion profile. Classical kinetic models, including first-order, power-law and Langmuir-type expressions, failed to describe the data, while a logistic kinetic model provided excellent fits for all the product formation, capturing the induction phase, rapid cooperative acceleration and late-stage saturation. This behavior is rationalized by progressive surface activation, evolving adsorption equilibria, and partial ZnO site blocking during the course of the reaction. Scanning electron microscopy and powder X-ray diffraction analyses confirm that the catalyst retains its wurtzite structure and morphology and can be reused without loss of integrity. This work highlights logistic kinetics as a useful descriptor for heterogeneous Lewis-acid catalysis and establishes ZnO as a low-cost, recyclable platform for oxazoline synthesis. Graphical abstract illustrates the solvent-free cyclodehydration of nitriles and amino alcohols to synthesize 2-oxazolines using a reusable heterogeneous zinc oxide catalyst. Time-resolved 1H NMR kinetics demonstrate a distinct sigmoidal conversion profile accurately described by a logistic kinetic model rather than classical rate expressions.
We developed a transparent, low-viscosity molten mixture employing sorbitol, urea and water, and investigated its physical properties, molecular-level interactions and dynamics through different experiments. The measured viscosity coefficient ( η ) of the molten mixture varies from 73 to 8 cP within the temperature range 288 K ≤ T≤ 338 K. Temperature dependent (303 K ≤ T≤ 343 K) dielectric relaxation (DR) measurements in the frequency window 0.2≤ν / GHz≤ 50 reveals presence of multi-Debye relaxation dynamics in this medium with average relaxation time spanning from 400 to 100 ps within this temperature range. The high static dielectric constant (ε_s∼ 80) of the molten mixture, like water, makes it excellent at dissolving things, even though its dynamics are much slower than water. Steady-state emission studies using fluorescent dyes coumarin 153 (C153) and coumarin 343 (C343) demonstrate spatial homogeneity in the medium, though signs of mild dynamic heterogeneity are evident from the fractional viscosity dependency of the rotational dynamics of the dye molecules ( τ_r∝[η/T]^pwith p≈ 0.7) . In contrast, DR dynamics captures less dynamical heterogeneity of the system, with τ_r∝[η/T]^pwhere p ≈ 0.87 . Further, the rotational dynamics exhibit an Arrhenius-type temperature dependence. The obtained activation energy for C153 and C343 rotation are 30 kJ mol–1 and 26 kJ mol–1, respectively, whereas the viscosity and average DR times activation energies are 36 kJ mol–1 and 32 kJ mol–1. These results indicate that the reorientation of dipolar molecules of the molten mixture felt higher friction than the rotation of C153 and C343 in the same medium. The graphical abstract presents the dielectric relaxation response of the (sorbitol + urea + water) molten mixture over a frequency range 0.2≤ν / GHz≤ 50 at various temperatures. The spectra reveal multiple relaxation modes arising from complex molecular motions and hydrogen-bond rearrangements. Decomposition of the dielectric loss profiles highlights cooperative dipolar dynamics, while the medium maintains high polarity together with comparatively low viscosity.
Chemical dynamics simulations were carried out to investigate the association and dissociation of the benzene–hexachlorobenzene (Bz–HCB) complex at 1000–2000 K with impact parameters up to 10 Å. Two classes of complexes, short- and long-lived, were identified based on distance and lifetime criteria. Association probability decreased from 40
