Effect of salt addition on a triblock copolymer-zwitterionic surfactant assembly: insight from excited-state proton transfer.

Copolymer-surfactant assemblies are frequently utilized across various fields, from medicine to nanotechnology. Understanding the organization of the mixed assemblies in a saline environment will further expand their application horizons, especially under physiological conditions. Excited-state proton transfer (ESPT) can provide insight into the hydration nature and organization of the non-toxic assembly of a triblock copolymer F127 (poly-(ethylene oxide)101 (PEO101)-poly(propylene oxide)56 (PPO56)-PEO101)) and a zwitterionic sulfobetaine surfactant N-dodecyl-N,N-dimethyl-3-ammoniopropane sulfonate (SB12). Here, we present a comprehensive investigation of the compactness and hydration nature of the F127-SB12 mixed assemblies at different salt concentrations using the ESPT of 8-hydroxy pyrene-1,3,6-trisulfonate (HPTS). In the absence of salts, gradual SB12 addition to a premicellar (0.4 mM) or a post-micellar (4 mM) F127 solution leads to an anomalous modulation of the protonated and deprotonated emission bands. The emission intensity ratio (protonated/deprotonated) first increases to a maximum at a particular SB12 concentration (6 mM and 35 mM for the premicellar and post-micellar F127 assemblies, respectively), and then the ratio decreases with a further increase in the surfactant concentration. Since the intensity ratio is an indicator of the retardation of the ESPT process, the mixed micellar configuration displaying a maximum intensity ratio represents the most compact and least hydrated state. Salt addition to this configuration lowers the intensity ratio, signifying an enhanced ESPT process. Dynamic light scattering (DLS) results indicate that the size of the mixed assembly remains almost unaltered with the addition of salts. Thus, salinity enhances the ESPT process inside the F127-SB12 mixed assemblies without significantly altering the hydrodynamic radius.

Extreme rotational events in a forced-damped nonlinear pendulum.

Since Galileo's time, the pendulum has evolved into one of the most exciting physical objects in mathematical modeling due to its vast range of applications for studying various oscillatory dynamics, including bifurcations and chaos, under various interests. This well-deserved focus aids in comprehending various oscillatory physical phenomena that can be reduced to the equations of the pendulum. The present article focuses on the rotational dynamics of the two-dimensional forced-damped pendulum under the influence of the ac and dc torque. Interestingly, we are able to detect a range of the pendulum's length for which the angular velocity exhibits a few intermittent extreme rotational events that deviate significantly from a certain well-defined threshold. The statistics of the return intervals between these extreme rotational events are supported by our data to be spread exponentially at a specific pendulum's length beyond which the external dc and ac torque are no longer sufficient for a full rotation around the pivot. The numerical results show a sudden increase in the size of the chaotic attractor due to interior crisis, which is the source of instability that is responsible for triggering large amplitude events in our system. We also notice the occurrence of phase slips with the appearance of extreme rotational events when the phase difference between the instantaneous phase of the system and the externally applied ac torque is observed.

Exploring cationic polyelectrolyte-micelle interaction via excited-state proton transfer. Signatures of probe transfer.

Excited-state proton transfer (ESPT) is a sensitive tool for the delicate monitoring of structural reorganization, hydration level, and confinement within surfactant and polymer assemblies. Here, we investigate the interaction of a cationic polyelectrolyte, poly(diallyl dimethylammonium chloride) (PDADMAC), with micelles of differently charged surfactants using 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) as an ESPT probe. We used three surfactants: anionic sodium dodecyl sulfate (SDS), cationic dodecyl trimethylammonium bromide (DTAB), and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB12), possessing the same alkyl (dodecyl) chain but varying headgroup charges. The fluorescence of HPTS residing initially within the micellar medium modulates differently in the presence of PDADMAC. For the anionic SDS and cationic DTAB micelles, the emission spectrum of HPTS does not alter significantly; however, for SB12 micelles, the emission spectrum undergoes a strong modulation upon adding the polyelectrolyte. The emission intensities quench strongly at a low concentration of PDADMAC but recover at a higher concentration. The emission intensity ratio of the two emission bands also changes significantly, implying strong modulation of the ESPT process with varying PDADMAC concentrations. The time-resolved area normalized emission spectra (TRANES) disclose single isoemissive points in the SB12 micelle at low and high concentrations of PDADMAC but two different isoemissive points (one characteristic of the SB12 micelle at 500 nm and another characteristic of the PDADMAC interface at 480 nm) in the mixed assembly at an intermediate concentration. Detailed analysis suggests that the polyelectrolyte can enforce the transfer of the anionic probe HPTS from the zwitterionic micelle to the PDADMAC assembly above a specific PDADMAC concentration. The transfer of the molecular probe between two assemblies resembles a drug sequestration event, and the study reveals necessary emission signatures.

Fabrication, Characterization, and Modeling of an Aluminum Oxide-Gate Ion-Sensitive Field-Effect Transistor-Based pH Sensor.

The ion-sensitive field-effect transistor (ISFET) is a popular technology utilized for pH sensing applications. In this work, we have presented the fabrication, characterization, and electrochemical modeling of an aluminum oxide (Al2O3)-gate ISFET-based pH sensor. The sensor is fabricated using well-established metal-oxide-semiconductor (MOS) unit processes with five steps of photolithography, and the sensing film is patterned using the lift-off process. The Al2O3 sensing film is deposited over the gate area using pulsed-DC magnetron-assisted reactive sputtering technique in order to improve the sensor performance. The material characterization of sensing film has been done using x-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray photoelectron spectroscopy techniques. The sensor has been packaged using thick-film technology and encapsulated by a dam-and-fill approach. The packaged device has been tested in various pH buffer solutions, and a sensitivity of nearly 42.1 mV/pH has been achieved. A simulation program with integrated circuit emphasis (SPICE) macromodel of the Al2O3-gate ISFET is empirically derived from the experimental results, and the extracted electrochemical parameters have been reported. The drift and hysteresis characteristics of the Al2O3-gate ISFET were also studied, and the obtained drift rates for different pH buffer solutions of 4, 7, and 10 are 0.136 µA/min, 0.124 µA/min, and 0.108 µA/min, respectively. A hysteresis of nearly 5.806 µA has been obtained. The developed sensor has high sensitivity along with low drift and hysteresis.

Anomalous Variation of Excited-State Proton Transfer Dynamics inside a Triblock Copolymer-Cationic Surfactant Mixed Micelle.

Mixed micelles formed by triblock copolymers [poly(ethylene oxide)m (EOm)-poly(propylene oxide)n (POn)-EOm] with various surfactants have widespread applications. Molecular-level understanding of the composition, interfacial organization, and hydration of the copolymer-surfactant mixed micelle is greatly necessary from application perspectives. Here, we applied 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) to probe the mixed micelle of a triblock copolymer F127 (EO101-PO56-EO101) and a cationic surfactant dodecyltrimethylammonium bromide (DTAB) at various compositions. The emission spectrum of HPTS modulates anomalously with the variation of DTAB concentration, displaying at least four regimes. The ratio of the emission intensities of the two bands (protonated/deprotonated) (1) first increases steeply in the low-concentration range (0.1-6 mM), (2) remains almost steady at the intermediate concentration (8-20 mM), (3) decreases at high concentration (20-80 mM), and (4) finally, remains almost constant at a very high concentration (100-400 mM) of DTAB. Time-resolved measurements confirm that excited-state proton transfer dynamics varies unusually with the concentration of DTAB in the mixed micelle; substantial retardation is observed up to ∼12 mM, but after that, the dynamics becomes somewhat faster upon further addition. The rotational dynamics of a methoxy analogue of HPTS, 8-methoxypyrene-1,3,6-trisulfonate, becomes slower up to ∼12 mM DTAB and after that becomes faster at higher concentration. Moreover, dynamic light scattering measurements showed that the size of the mixed micelle decreases sharply in the low-concentration region (<20 mM DTAB) but decreases moderately at high concentration. Thus, the nature of the mixed micelle is very different at low and high concentrations of DTAB. At low concentration, the incorporation of DTAB results in a more compact and less hydrated mixed micelle, whereas a more hydrated and less organized assembly is formed at high concentration of DTAB.

Regioselective Synthesis of Fused Furans by Decarboxylative Annulation of α,ß-Alkenyl Carboxylic Acid with Cyclic Ketone: Synthesis of Di-Heteroaryl Derivatives.

α,ß-Alkenyl carboxylic acids undergo CuII -mediated decarboxylative annulation reactions with aliphatic cyclic ketones to provide synthetically valuable di-heterocycles. The annulation process tolerates a variety of aliphatic ketones and heterocyclic alkenyl carboxylic acids, producing substituted fused furan derivatives with complete regioselectivity. The current protocol offers a synthetically applicable pathway to construct a variety of oligo-heterocycles through Cu-mediated single-electron transfer and decarboxylation. Notably, synthesis of relatively inaccessible di-heterocycles has been achieved successfully using this protocol.

Palladium-Catalyzed Template Directed C-5 Selective Olefination of Thiazoles.

An efficient method has been developed to afford highly C-5 selective olefination of thiazole derivatives utilizing a bifunctional template in an intermolecular fashion. Coordinative interaction between the substrates and the metal chelated template backbone plays a crucial role in high C-5 selectivity. Excellent selectivity for the C-5 position was observed while mono substituted (2- or 4-) or even more challenging unsubstituted thiazoles were employed.

Regiocontrolled Remote C-H Olefination of Small Heterocycles.

Achieving site-selective C-H functionalization of arene is a fundamental challenge, as it is mainly controlled by the electronic nature of the molecules. A chelation-assisted C-H functionalization strategy overcomes the selectivity issues by utilizing distance and geometry of covalently attached directing groups (DGs). This strategy requires stoichiometric DG installation/removal and a suitable functional group on which to tether the DG. Such strategies are ineffective for small heterocycles unless suitable functional groups are added. Moreover, heterocycles are not the judicious choice as substrates owing to the possibilities of catalyst deactivation. Inspired by recent developments, this work demonstrates the utilization of a chelating template backbone bearing covalently attached directing groups, which enables site-selective remote C-H functionalization of heterocycles. The observed selectivity is the outcome of non-covalent interactions between the heterocycles and bifunctional template backbone.

A New Phase Transfer Strategy to Convert Protein-Capped Nanomaterials into Uniform Fluorescent Nanoclusters in Reverse Micellar Phase.

A new phase transfer strategy to convert aqueous phase protein-protected nanomaterials into fluorescent nanoclusters in the reverse micellar environment is introduced using bovine serum albumin (BSA)-protected silver nanoclusters (AgNCs) and nanoparticles (AgNPs) as an example. The basic pH employed in the fabrication of protein-protected nanoclusters induces the the protein capping to be negatively charged and facilitates the transfer process of the nanomaterials from aqueous phase to a cationic gemini surfactant (16-2-16)/hexane/hexanol/water reverse micelle (RM) phase. The original fluorescence characteristics of the seed nanocluster is retained after the transfer process. Strikingly, when both the nanomaterials (AgNCs and AgNPs) coexist in the aqueous feed solution, they are exclusively converted into uniform nanoclusters in the RM extract with enhanced fluorescence intensity.

Design and characterization of diclofenac diethylamine transdermal patch using silicone and acrylic adhesives combination.

BACKGROUND AND PURPOSE OF THE STUDY: The objective of the study was to develop and characterize Diclofenac Diethylamine (DDEA) transdermal patch using Silicone and acrylic adhesives combination. METHODS: Modified solvent evaporation method was employed for casting of film over Fluoropolymer coated polyester release liner. Initial studies included solubilization of drug in the polymers using solubilizers. The formulations with combination of adhesives were attempted to combine the desirable features of both the adhesives. The effect of the permeation enhancers on the drug permeation were studied using pig ear skin. All the optimized patches were subjected to adhesion, dissolution and stability studies. A 7-day skin irritancy test on albino rabbits and an in vivo anti-inflammatory study on wistar rats by carrageenan induced paw edema method were also performed. RESULTS: The results indicated the high percent drug permeation (% CDP-23.582) and low solubility nature (1%) of Silicone adhesive and high solubility (20%) and low% CDP (10.72%) of acrylic adhesive. The combination of adhesives showed desirable characteristics for DDEA permeation with adequate % CDP and sufficient solubility. Release profiles were found to be dependent on proportion of polymer and type of permeation enhancer. The anti-inflammatory study revealed the sustaining effect and high percentage inhibition of edema of C4/OLA (99.68%). The acute skin irritancy studies advocated the non-irritant nature of the adhesives used. CONCLUSION: It was concluded that an ideal of combination of adhesives would serve as the best choice, for fabrication of DDEA patches, for sustained effect of DDEA with better enhancement in permeation characteristics and robustness.