Maximum Wavelength Research Articles

Synthesis and application of Schiff base as a dual-mode chemosensor for optical determination of aluminium ion content in water samples

Aluminium is highly abundant in the earth's crust and has played a pivotal role in various industries for centuries. Its versatility and abundance have led to its widespread use in everything from food packaging to construction materials. However, this extensive use has also raised concerns about its potential impact on human health and the environment. This study aimed to synthesize and apply a Schiff base molecule, N-(2-hydroxy-1-naphthylmethylidene)-o-aminoacetophenone (N-HyNA), as an optical sensor for aluminium ion (Al3+) determination. The synthesis of N-HyNA was achieved with a high yield of 85% through the reaction of 2-Hydroxy-1-naphthaldehyde and 2-aminoacetonephenone. N-HyNA showed a maximum absorption wavelength at 465.0 nm, and fluorescence emission at 357.0 nm with the excitation wavelength of 278.0 nm. Both absorption and fluorescence signals of N-HyNA were selectively quenched in the presence of aluminium ion. Under optimal conditions for Al3+ detection, the absorption mode of N-HyNA with DMSO as a solvent had the limit of detection (LOD) of 0.005 ppm and detection range of 0.01 – 2.0 ppm, while the fluorescence mode with EtOH as a solvent had the LOD of 0.013 ppm and detection range of 0.05 – 0.40 ppm. The developed approach demonstrated good agreement in Al3+ determination with the conventional atomic absorption spectroscopic technique when using natural water samples and their standard-spiked samples with recovery ranging from 84.0 – 114.0 %. Additionally, analytical characterization was conducted to investigate the quenching mechanism between Al3+ and N-HyNA, and a computational study was performed to elucidate the binding position of Al3+ in the N-HyNA complex. This developed chemosensor offered a simple and fast, yet accurate and selective detection of Al3+ in water samples.

Oxidation of glyoxal with the Mo-oxime complex in a benzalkonium chloride interface: Raghavan and Srinivasan kinetic model

Gaining an understanding of the glucose oxidation product (glyoxal) interaction with the metal–organic complex in a biological environment is pivotal to its usage. Thus, the glyoxal (Gyx) oxidation with Mo-oxime complex (MC) is studied with the spectrophotometric method, following a pseudo-phase approach. The result highlights the inclusion of hydrolysis, ion catalysis, the neutral primary salt effect, and radical generation as the essential factors in Gyx oxidation, with the exclusion of intermediate species formation. The hydrolysis of Gxy is observed to actively engage MC without charge inhibition as charge-neutral reacting species are involved, thus, implicating neutral primary salt effect where the variation of ionic strength of the system keeps the redox rate unchanged. The involvement of charge-neutral specie at the rate controlling step encouraged electrostatic attraction when Mg2+ ion additive is incorporated into the system, leading to ion catalysis. The generation of free radical from Gxy aids the emergence of formic acid. The zero intercept of Michealis-Menten type plot and the non-appreciable shift in the maximum absorption wavelength of the reaction system and MC rule-out the presence of intermediate species. The contribution of thermodynamic enthalpy is instrumental in the redox process, leading to the formic acid product. The inclusion of benzalkonium chloride (BZC) hastens the Gxy oxidation, which is supported by Raghavan and Srinivasan’s model.

Drug molecules beyond chemical biology: fluorescence- and DFT-based investigations for fluoride ion sensing and the trace detection of chloroform.

Excessive unmonitored use of fluoride has remained a threatening issue for a long time now as its long-term use is linked to several health issues. Similarly, chloroform is a highly carcinogenic solvent that requires proper monitoring. The increasing demand for a convenient, selective and sensitive fluoride and chloroform sensor intrigued us to utilize etoricoxib (ECX) as a sensor as it is highly safe and easily available. The photophysical properties of ECX, which were previously unexplored, were now studied with increasing water fractions and a significant aggregation-induced emission enhancement (AIEE) was seen through fluorescence spectroscopy. ECX was also successfully used for the trace level detection of chloroform through a significant emission enhancement. Similarly, the ECX-based sensor successfully detected fluoride ions by showing enhancement in emission intensity with maximum emission wavelength at 373 nm. Through fluorescence titration experiments, the effects of different conditions and interfering species on the sensing efficiency of ECX were studied, and the results showed that the sensor was highly selective and sensitive towards fluoride, with a limit of detection of 20 nM. Other than fluorescence spectroscopy, the type of interaction between the sensor and analyte was also studied through UV-Vis spectroscopy, revealing a non-covalent type of interaction, which was further validated through DFT studies. Frontier molecular orbital (FMO) analysis was performed along with density of state (DOS) studies to investigate the energy levels of the orbitals. Non-covalent interaction (NCI) and natural bond orbital (NBO) analysis provided information about the types of interaction and charge transfer. ECX has the potential to be used for real-time sensing applications and could be used for sensing moisture and fluoride in real samples.

Study on the Structural Changes of Boneless Chicken Claw Collagen and Its Effect on Water Retention Performance.

The purpose of this study was to explore the water retention mechanism of chicken claws by detecting the structural changes in collagen in boneless chicken claws under different expansion rates. Firstly, boneless chicken claw collagen with different expansion rates (0%, 10%, 20%, 30%, 40%, 50%) was extracted by the acid-enzyme complex method, and the changes in collagen were determined by scanning electron microscopy (SEM), ultraviolet spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), low-field nuclear magnetic resonance LF-NMR) and surface hydrophobicity to explore the mechanism that leads to changes in the water retention performance. The results of scanning electron microscopy showed that with the increase in the expansion rate, collagen molecules showed curling, shrinking, breaking and crosslinking, forming a loose and irregular pore-like denatured collagen structure. UV analysis showed that the maximum absorption wavelength of chicken claw collagen was blue shifted under different expansion rates, and the maximum absorption peak intensity increased first and then decreased with the increase in expansion rate. The FTIR results showed that collagen had obvious characteristic absorption peaks in the amide A, B, I, II and III regions under different expansion rates, and that the intensity and position of the characteristic absorption peaks changed with the expansion rate. The results of the CD analysis showed that collagen at different expansion rates had obvious positive absorption peaks at 222 nm, and that the position of negative absorption peaks was red shifted with the increase in expansion rate. This shows that the expansion treatment makes the collagen of chicken claw partially denatured, and that the triple helix structure becomes relaxed or unwound, which provides more space for the combination of water molecules, thus enhancing the water absorption capacity of boneless chicken claw. The results of the surface hydrophobicity test showed that the surface hydrophobicity of boneless chicken claw collagen increased with the increase in expansion rate and reached the maximum at a 30% expansion rate, and then decreased with the further increase in the expansion rate. The results of LF-NMR showed that the water content of boneless chicken claws increased significantly after the expansion treatment, and that the water retention performance of chicken claws was further enhanced with the increase in the expansion rate. In this study, boneless chicken claws were used as raw materials, and the expansion process of boneless chicken claws was optimized by acid combined with a water-retaining agent, which improved the expansion rate of boneless chicken claws and the quality of boneless chicken claws. The effects of the swelling degree on the collagen structure, water absorption and water retention properties of boneless chicken claws were revealed by structural characterization. These findings explain the changes in the water retention of boneless chicken claws after expansion. By optimizing the expansion treatment process, the water retention performance and market added value of chicken feet products can be significantly improved, which is of great economic significance.

Wide range luminescence lifetime-based pH sensing with covalently immobilized multi-protonatable Ru(II) complexes

To overcome the limitations of optical pH sensors, the response of which is just ca. one pH unit around the pKa value of the indicator dye and capitalize on the advantages of red-luminescent Ru(II) complexes for optical sensing, multi-pKa members of this family are proposed. Bipyridine ligands bearing protonatable groups (amines and carboxylates) are the basis to design and prepare the indicator dyes. Their photophysical properties and response to pH changes were investigated in the pH 3.5 − 9.0 range. The complex [Ru(DCB)2DEAMB], where DCB and DEAMB stand for 2,2’-bipyridine-4,4’-dicarboxylate and 4,4’-(N,N-diethylaminomethyl)-2,2’-bipyridine, respectively, shows a reversible monotonic change of its emission wavelength maximum (648 – 634 nm), luminescence intensity (1.40x) and lifetime (335 – 429 ns) in solution with increasing pH. This complex and two similar ones were covalently tethered to commercial TentaGel® M Br polymer microbeads for luminescence phase shift fiberoptic pH measurements. The immobilized [Ru(DCB)2DEAMB] displays the widest pH sensitivity over pH 3.5 to pH 8.5. The stability of this sensor was satisfactory when cycling between pH 3.5 and 8.5 for five days as well as under a three-day cycle between each pH unit. Changes of the buffer type, buffer concentration and osmolarity did not significantly influence the sensor response; however, large variations of dissolved oxygen and, naturally, temperature would require correction by the corresponding sensors. The novel, robust luminescent pH sensor has been tested in phase-sensitive mode for cell cultures monitoring in commercial bioreactors, but its response would also be suitable for in situ monitoring of natural waters.

Isolation and identification of diosgenin and flavonoids compound from ethanol extract of Dioscorea hispida Dennst. tuber

The tuber of Dioscorea hispida Dennst. has potential for development as a synthetic pharmaceutical ingredient due to the presence of secondary metabolites such as diosgenin and flavonoids, which exhibit biological activity within the body. Further exploration of this potential requires the isolation and identification of these compounds. Diosgenin was isolated from the ethanol extract using thin-layer chromatography, while flavonoids were isolated from the ethyl acetate fraction using paper chromatography. The pure isolates of both compounds were identified using UV-Vis spectrophotometry and FT-IR spectroscopy. The UV-Vis spectrophotometric analysis of diosgenin revealed maximum absorption wavelengths at 205 and 453 nm. Flavonoid isolates exhibited maximum absorption wavelengths of 264 nm for the first isolate, 265 nm for the second, 276 nm for the third, and 272 nm for the fourth. FT-IR spectroscopic analysis of the diosgenin isolate indicated the presence of functional groups such as -OH, aromatic C=C, and aromatic C-O, while the flavonoid isolate showed the presence of O-H, aromatic C-H, aliphatic C-H, C=O, C=C, and C-O. These identification results confirm that the isolates obtained indeed contain diosgenin and flavonoids.

Conjugated polymer-boosted near-infrared electrochemiluminescence of organic dye for detecting acetamiprid

BackgroundThe near-infrared electrochemiluminescence (NIR-ECL) has excellent penetration and near zero background interference, and has shown unique advantages in clinical medicine and bioimaging. Among various types of NIR-ECL emitters, NIR organic dyes have arouse the concern of researchers due to their adjustable structure and diverse optical properties. However, the currently available NIR dyes usually have inherent self-quenching effect and poor photostability, so their ECL efficiency is low, and it is a great challenge to improve their ECL performance. ResultConjugated polymer-boosted NIR-ECL strategy was creatively developed to overcome ECL performance limitations of NIR dyes. IR 783, as one of heptamethine cyanine dyes, was performed a nanoprecipitation in the presence of poly[(9,9-dlhexyfluoren-2,7-dlyl)-co-(anthracen-9,10-dlyl)] (PFAD) to prepare IR polymer nanoparticles (IR PNPs). Due to resonance energy transfer (RET) from PFAD to IR 783 and encapsulation of IR 783 by PFAD, the resulting IR PNPs exhibited a strong and stable NIR-ECL emission with a maximum ECL wavelength of 802 nm under coreactant tripropylamine (TPrA) and H2O2 can effectively quench it. IR PNPs coupled proximity ligation assay (PLA)-induced DNA walker to achieve acetamiprid (ACE) analysis. ACE triggered PLA to form bipedal DNA walker, and further release G-rich secondary target (ST). With ST and hemin being captured on IR PNPs modified electrode, hemin/G-quadruplex was assembled to consume H2O2, thereby restoring ECL signal for ACE detection with a limit of detection of 4.74 × 10−15 M. SignificanceThis work opens up a new and simple way to boost NIR-ECL of organic dyes, and IR PNPs create a promising NIR-ECL platform for pesticide detection.

SILVER NANOPARTICLES-AQUEOUS LEAF EXTRACT OF SIDAGURI (SIDA RHOMBIFOLIA) AS REDUCING AGENTS

The Sidaguri leaf, scientifically known as Sida rhombifolia, is a plant species rich in flavonoids that have the ability to act as reducing agent in formation of silver nanoparticles. This study presented the synthesis of silver nanoparticles (AgNp-Sid) using aqueous leaf extract of sidaguri. This study utilized a concentration ratio of 2:90 mL aqueous leaf extract of Sidaguri and AgNO3 1 mM. The size and morphology of AgNp-Sid was measured using UV-Visible Spectrophotometer, PSA, FT-IR, SEM-EDS, and XRD. The investigation revealed an ordinary particle size of 63.5 nm with polydispersity index (PI) of 0.284. The maximum wavelength varies between 405.4 nm and 407.8 nm with the increasing of time. AgNp-Sid exhibited a spherical morphology and had a crystalline structure that is face-centered cubic. The results suggested that the aqueous leaf extract of sidaguri had the ability to function as a reducing agent in the synthesis of silver nanoparticles, offering a safe, cost-effective, and environmentally friendly alternative.

Two-core photonic quasicrystal fiber - surface plasmon resonance (PQF-SPR) methane sensor comprising the ZnO/Au composite film: design and FEM simulation

A photonic quasicrystal fiber - surface plasmon resonance (PQF-SPR) methane sensor made up of the eight-fold photonic quasicrystal fiber has been designed and analyzed. The PQF is used to construct the double-core D-type structure with air holes forming a hole groove on the D-type surface. The grooves are plated with ZnO and Au films successively, following the deposition of a methane-sensitive film containing Cryptophane-E. The effects of the air hole diameter, materials, and relative thickness of the composite film on the sensing properties are studied by finite element simulation. The results show that the wavelength sensitivity of the sensor with the ZnO-Au and TiO2-Au composite film with the same thickness is significantly higher than that with a single gold film coating in the methane concentration range of 0%–3.5%, confirming that the composite film enhances the SPR effect and improves the sensing properties. The ZnO-Au composite film has the best properties such as maximum and average wavelength sensitivities of 64 nm/% and 40.24 nm/%, respectively. The performance of this sensor is notably superior to that of comparable methane sensors previously documented.

Synthesis of Side-Chain Liquid Crystalline Polyacrylates with Bridged Stilbene Mesogens.

In recent years, π-conjugated liquid crystalline molecules with optoelectronic functionalities have garnered considerable attention, and integrating these molecules into side-chain liquid crystalline polymers (SCLCPs) holds potential for developing devices that are operational near room temperature. However, it is difficult to design SCLCPs with excellent processability because liquid crystalline mesogens are rigid rods, have low solubility in organic solvents, and have a high isotropization temperature. Recently, we developed near-room-temperature π-conjugated nematic liquid crystals based on "bridged stilbene". In this work, we synthesized a polyacrylate SCLCP incorporating a bridged stilbene that exhibited a nematic phase near room temperature and could maintain liquid crystallinity for more than three months. We conducted a thorough phase structure analysis and evaluated the optical properties. The birefringence values of the resulting polymers were higher than those of the corresponding monomers because of the enhanced order parameters due to the polymer effect. In addition, the synthesized polymers inherited mesogen-derived AIE properties, with high quantum yields (Φfl = 0.14-0.35) in the solid state. It is noteworthy that the maximum fluorescence wavelength exhibited a redshift of greater than 27 nm as a consequence of film formation. Thus, several unique characteristics of the SCLCPs are unattainable with small molecular systems.

Comprehensive analysis of dye adsorption and supramolecular interaction between dyes and cotton fibers in non-aqueous media/less water dyeing system

Cotton textile dyeing consumes large amounts of energy and water and discharges large amount of wastewater and pollutants. Zero or less discharge of the wastewater and contaminants from the cotton textile dyeing has been under high demands from textile industry. Recently, a novel reactive dyeing technology of using a non-aqueous medium with little water (NMLW) was developed for cotton fabrics. However, the use of high concentration of reactive dyes in the system triggers aggregation of the dyes in cotton fibers, influencing the quality of dyed cotton textiles. In this investigation, adsorption, diffusion, and aggregation behavior of reactive dyes in cotton fibers were studied. Compared to traditional water-based dyeing system, cotton fabrics demonstrated superior color depth, as long with higher rates of dye uptake and fixation for reactive dyes. At low dye concentrations, the maximum absorption wavelengths of reactive dyes were unchanged, and complied with the Lambot-Beer law. However, when the dye concentration was excessively high, reactive dyes with different molecular structures, as well as multi-layer dye aggregates with π-π stacking and hydrogen bonding interactions, showed different light absorption spectral characteristics and photophysical properties. Moreover, the dye particle size and dye ionization were influenced by the dye concentration, molecular weight, molecular configuration, etc. Analysis of the molecular dynamics of reactive dyes revealed that the maximum dye aggregation size was predominantly dimer at low dye concentration. However, the dimer ratio significantly decreased, while the trimer ratio increased, and higher-order aggregates were observed at a higher dye concentration. The strength of hydrogen bonds between dye molecules and water molecules, as well as the number of water molecules surrounding dye molecules, was influenced by dye concentration and alkali. This study provides a foundation for understanding the micro-aggregation behavior of reactive dyes and offer guidance for optimizing the dyeing process in practical production settings.

Switchable multi-wavelength pulse fiber laser with mode conversion

A switchable multi-wavelength pulse fiber laser based on dual-Sagnac comb filter, nonlinear optical loop mirror (NOLM) and a homemade mode selective coupler (MSC) is proposed and experimentally demonstrated. The dual-Sagnac comb filter and the NOLM are adopted as wavelength selective filter and saturable absorber (SA) in this work, respectively. This proposed fiber laser has a maximum output wavelength number of four. And the fiber laser can output multi-wavelength pulse lasers within a certain interval of the integer times of 1 nm and 1.9 nm. Moreover, when the pump power is 150 mW, the mode-locked fiber laser with the pulse repetition frequency of 120 MHz, a pulse duration of 4 ns and pulse interval of 8.3 ns have been realized via carefully adjusting the PC. And the fiber laser has a maximum output power of 226 μW under 300 mW pump power. In addition, the homemade MSC is utilized as mode converter to realize mode conversion up to LP31 and the mode purity is higher than 92 %. This work can find applications in wavelength division multiplexing (WDM) and the optical communication.

Innovative Photoprotection Strategy: Development of 2-(Benzoxazol-2-Yl)[(2-Hydroxynaphthyl)Diazenyl] Phenol Derivatives for Comprehensive Absorption of UVB, UVA, and Blue Light.

Overexposure to blue light due to the excessive use of electronic devices has been implicated in premature skin aging and eye damage, among other injuries to health. This study aimed to synthesize two azo derivatives of the 2-(amino-2'-hydroxyphenyl) benzoxazole and explore their potential as UV and blue light filters, proposing a new spectral profile. The synthesis of the heterocyclic compounds involved condensation reactions and diazotation. The derivatives 2-(benzoxazol-2-yl)-5-[(2-hydroxynaphthyl)diazenyl]phenol and 2-(benzoxazol-2-yl)-4-[(2-hydroxynaphthyl)diazenyl]phenol were synthesized with a yield greater than 70%. Solubility was evaluated in seven different solvents. The maximum absorption wavelengths (λmax) were determined using UV-Vis scanning spectrophotometry in the range of 200-600 nm. Photostability was assessed using a solar simulator and the Sun protection factor (SPF) was determined using invitro methodology. Cytotoxicity was evaluated using the MTT assay in V79 cells. These compounds were able to absorb UVA, UVB, and blue light, with λmax ranging from 300 to 500 nm and demonstrated photostability after 3 h of exposure to solar simulator with an SPF higher than 45. The compounds exhibited solubility in all lipophilic solvents tested. Regarding cytotoxicity, IC50 values were comparable to other filters. These findings indicate that both compounds hold promise as potential organic filters.

PHYSICOCHEMICAL AND SPECTROSCOPIC ANALYSIS OF INTERACTIONS BETWEEN ASPIRIN AND NORMAL SALINE AT DIFFERENT TEMPERATURES

The primary goal of the current investigation is to explore the molecular interactions between the aspirin (2-Acetoxybenzoic acid) and normal saline (0.9% w/v aqueous NaCl) at various concentrations (0.001–0.010) m and temperature (T= 300.15–315.15) K. To understand the various possible molecular interactions, volumetric, acoustic, conductometric and viscometric parameters were evaluated using experimental measured values of densities (ρ), ultrasonic velocities (u), specific conductance (κ), and viscosities (η). The results derived from these parameters have been examined in terms of drug–solvent and drug-drug interactions. The results of physicochemical studies indicate that aspirin exhibits strong interactional and structure–forming behaviour in normal saline. These results were well supported by UV-visible spectral studies which indicate the existence of intense aspirin–normal saline interactions in the form of modification in absorption maximum and absorption wavelength. The cyclic voltammetric studies were also performed to explore the oxidation/reduction behaviour and effect of aspirin on hemolysis. The experimental analysis of these studies provides valuable insights for better drug design, drug delivery, compatibility, potential safety, and biological relevance for the pharmaceutical and health industries.

Biosynthesis of silver nanoparticles (AgNPs) from coconut leaf extract and their antifungal activity against Ganoderma boninense mycelia

Basal stem rot disease caused by Ganoderma is a major problem in palm cultivation in Indonesia, so an appropriate solution is needed to overcome this problem. One of the solutions that can be applied is through silver nanoparticles. Synthesis of silver nanoparticles can use coconut leaves as a source of flavonoids. Flavonoids are one of the phenolic compounds that are widely used in the process of synthesizing silver nanoparticles. Flavonoid compounds have a hydroxyl group (OH), which can be reduced by donating electrons to the Ag+ ion from AgNO3 to Ag0. This research aims to synthesize silver nanoparticles (AgNPs) using coconut leaf water extract and its assessment as an antifungal for Ganoderma boninense. Silver nanoparticles were synthesized by mixing coconut leaf extract in 1 mM of AgNO3 solution with a ratio of 1:9 (v/v). The concentrations of coconut leaf water extract were 1% and 3% with a heating temperature of 60°C. Silver nanoparticles were characterized using a UV-Vis spectrophotometer, PSA, FTIR, TEM, and SEM-EDS. The AgNPs had a maximum wavelength of 430 nm, with morphologies like a ball, triangle, and square, a mass percentage of Ag of 51.77%, smallest particle size of 63.29 nm, PdI value of 0.3361, and a zeta potential of -16.98 mV. The FTIR spectra show that the functional group that plays a role in the reduction process is the –OH group. The antifungal activity assay produced the highest percentage of colony growth inhibition (68.37%) at a concentration of 4.9 ppm in the 10-day incubation.

Photoluminescence of Tetra(benzimidazole)phenylethene Derivatives and Their Carbene Metallacycles in Aggregates and Langmuir-Blodgett Films.

Molecular structure, external stimuli, and environmental factors all have a strong effect on the internal molecular rotation and vibration of aggregate-induced emission (AIE) luminogens. Here, we report the AIE effect for several newly synthesized amphiphilic tetra(benzimidazole)phenylethene (TBiPE) derivatives and their binuclear N-heterocyclic carbene silver (NHC-Ag) metallacycles in solutions, aggregates, and Langmuir-Blodgett (LB) films. Monolayer behaviors and microscopic images indicate that introducing alkyl chains and binuclear NHC-Ag metallacycles can facilitate the formation of a well-defined insoluble monomolecular layer at the air-water interface. Absorption and luminescence spectral features suggest that both the TBiPEs' cyclization structure and binuclear NHC-Ag metallacycles can provide additional driving forces to restrict the internal molecular motion of the tetraphenylethene (TPE) unit, thus enhancing the AIE effects. Further, external stimuli and environmental factors such as poor solvent addition and LB film deposition also play important roles in the photoluminescent intensity, maximum wavelength, and lifetime. These internal and external factors can result in around 30-40 nm blue-shift for the maximum luminescence wavelength and 2-3 times shorter for the luminescent lifetime. These phenomena can be attributed to the reason that the nonradiative energy transfer efficiency is weakened because of the enhanced hydrophobic interaction and metal-carbene coordination as well as the closely packed arrangement of AIEgens in the LB films; consequently, the radiation energy transfer efficiency increased.

A convenient approach for generating dimeric nucleic acid dyes via click-chemistry

Fluorescent dyes are essential tools for visualizing DNA and RNA. Dimeric dyes like GelGreen have gained popularity as safer alternatives to ethidium bromide (EB) due to their reduced mutagenicity and genotoxicity. In this study, we present a straightforward method to synthesize novel acridine orange (AO)-based dimeric dyes using click chemistry. Starting from acridine orange, these dyes can be synthesized in just two steps. Compared to GelGreen, these new dyes incorporate additional triazole groups in their linkers. They exhibit a maximum absorption wavelength of approximately 472 nm, which shifts to around 503 nm upon binding with DNA, allowing excitation by blue light. These dyes show minimal fluorescence in aqueous solutions, indicating that they adopt a closed conformation where the fluorescence of acridine orange is quenched due to intramolecular aggregation. The presence of DNA significantly enhances their fluorescence at around 526 nm, suggesting that DNA binding induces an open conformation. This “light-up” property makes them highly sensitive DNA dyes with a strong signal-to-noise ratio. We successfully applied these novel dyes in agarose gel electrophoresis, where they demonstrated excellent performance.

A novel RP-HPLC method for the simultaneous quantification of azithromycin and dexamethasone in marketed ophthalmic drops

A straightforward, precise, accurate, specific, and sensitive RP-HPLC technique has been established for the quantification of Azithromycin Dihydrate and Dexamethasone Sodium Phosphate in their commercial formulation. The wavelength maxima for Azithromycin and Dexamethasone were considered to be 215 nm for estimation. In RP-HPLC separations were carried out on a Zorbax SB C18 column (250mm X 4.6mm, 5 μm) and mobile phase consisting of Acetonitrile: Monobasic Potassium Phosphate (KH2PO4) buffer in the proportion of 75:25 v/v and pH of the buffer was adjusted to 5.5 with OPA. The estimation was carried out at 215 nm using UV detector keeping the flow rate of 1.2 ml/min and injection volume of 50 μl. The current method demonstrates good linearity over the range of 20 - 120 μg/ml and 2 - 12 μg/ml for Azithromycin and Dexamethasone respectively. No interference of excipients was found during estimation. The recommended techniques were verified and determined to be specific, accurate, and exact. The approaches were effectively used for the concurrent quantification of both medicines in pharmaceutical formulations, making them suitable for regular quality control examination.

Developing a Photoacoustic Probe for in vivo Tumor pH Detection by Gaussian calculation

pH dysregulation is a major feature of cancer, and the development of advanced photoacoustic probes capable of monitoring pH is important for both diagnosis and treatment of cancer. Previous work (done by Tijana Jokic’s group) found that aza-BODIPY molecule has better photoacoustic properties and this was investigated in depth, leading to the development of new pH probes, but the functionality of the molecule can be upgraded again if the photoacoustic properties of the molecule can be further expanded, while the maximum wavelength of the molecule can be further extended to fit the commercial range. This study optimized the previous molecule based on the Gaussian program, and the new molecule with NO2 attached to R4 showed the best properties in which the maximum excitation wavelength reached 770.85 nm.

Computational Assessment of Novel Ruthenium Phenoxazine‐Based Complexes as Photosensitizers in Photodynamic Therapy

AbstractA computational examination of two new polypyridyl ruthenium complexes, containing meldola blue (MDB) and nile blue (NB) chromophores, is here reported in order to assess the applicability of phenoxazine‐containing complexes in photodynamic therapy (PDT). The designed complexes, named Ru‐3ENB and Ru‐3EMDB, are based on a recently synthesized Ru(II)‐based complex bearing a bipyridyl‐ethynyl‐Nile Red (NR) ligand and proposed for PDT applications. DFT outcomes elucidated how the replacement of NR with MDB induces a red shift of the maximum absorption wavelength within the therapeutic window, up to 638 nm. A change in the molecular orbitals involved in the population of excited states was observed upon chromophore substitution that results in ISC kinetic significantly faster than that computed for the synthesized complex Ru‐3ENR.