Maximum Shift Research Articles

Designing Multifunctional AIEgens by Molecular Engineering of Imidazo[1,2-a]pyridine For Color Tunable Molecular Salts, Anti-counterfeit applications and Sensing of Mn²⁺, Ag⁺, and Fe³⁺.

Mechanochromic materials, known for their ability to change color in response to mechanical stimuli such as pressure, stretching, grinding, or rubbing, hold significant importance due to their diverse applications. In this study, we synthesized and characterized two novel pyridine-tethered imidazo[1,2-a]pyridine mechanoresponsive luminogens with appended tetraphenylethene, named GBY-10 and GBY-11. GBY-10 exhibited reversible mechanofluorochromism, while GBY-11 did not revert to its original color after solvent fuming. The photophysical properties of these luminogens were significantly influenced by the position of the terminal pyridine. Additionally, we created color-tunable mechanoresponsive molecular salts by co-grinding GBY-11 with various aryl acid derivatives. Co-grinding GBY-11 with pentafluorobenzoic acid resulted in a significant bathochromic shift of the emission maxima by 66 nm, compared to 37 nm and 12 nm shift for benzoic acid and para-nitrobenzoic acid, respectively. This counter-ion-dependent luminescence suggests strong electronic interactions between the counter ions. These luminogens also demonstrated reversible pH-responsive behaviour, making them suitable for anti-counterfeiting applications. Furthermore, the pyridine-functionalized luminogen, GBY-10, showed metal ion detection (Mn²⁺, Ag⁺, Fe³⁺) ability in water, with detection limits as low as 0.0043, 0.015, and 0.0029 mM, respectively. This report opens new avenues for designing promising AIE-active materials for potential applications in anti-counterfeiting, sensing, optoelectronics, and biomedicine.

Increasing the sensitivity of Love wave MSAW sensors by magnetoelastic layer thickness variation

Abstract Increasing the magnetic field sensitivity is one of the major challenges in the study of magnetic surface acoustic wave (MSAW) sensors. In this paper, Love wave MSAW sensors are investigated in a Transmissive Single Port Delay Line (TSP-DL) configuration, on ZnO (700 nm)/Y-X LiNbO3. CoFeB (100 nm) or CoFeB(100 nm)/SiO2(3 nm)/CoFeB(100 nm) sensitive magnetoelastic layers are placed in the acoustic path between two electrically connected interdigital transducers. The fundamental Love wave on ZnO(700 nm)/ Y-X LiNbO3 presents a high electromechanical coupling coefficient (K 2), resulting in a high signal amplitude, which is favorable for delay lines performances. Additionally, shear waves are highly sensitive to the magnetic field due to the large ΔG effect in the magnetoelastic layers. A maximum frequency shift of 0.36% was achieved using a CoFeB(100 nm)/SiO2(3 nm)/CoFeB(100 nm) stack as the sensitive layer, with a high maximum magnetic sensitivity of 3630 ppm mT−1 (1482 kHz mT−1 at 410 MHz). This sensitivity is among the highest reported in the literature on magnetic SAW sensors.

Synthesis of zwitterionic asymmetric and symmetric carboxy-imidazolium derivatives and their use in molecular interactions with bovine serum albumin.

For the first time asymmetric and symmetric carboxytriazoleimidazolium derivatives with different structures were synthesized. The critical micellization concentration (CMC) value was estimated using a pyrene fluorescent probe and the solubility of Orange OT. The complexation ability of carboxytriazoleimidazolium derivatives toward bovine serum albumin (BSA) has been investigated by various physico-chemical methods: fluorescence spectroscopy, electrophoretic light scattering and circular dichroism. The effect of the oxo-bridge and the presence of a hydrophobic fragment in the structure of the molecules and its influence on their aggregation properties and interaction with BSA has also been studied. According to the fluorescence data, only in the case of the asymmetric derivatives with long alkyl fragments a shift of the BSA emission maximum is observed, indicating a change in the BSA microenvironment. The secondary structure of BSA remains virtually unchanged in the presence of carboxytriazoleimidazolium derivatives, as shown by circular dichroism. No significant changes in the structure of BSA were observed in the presence of zwitterionic compounds with an oxo-bridge at concentrations where fluorescence quenching occurs, as shown by time-resolved fluorescence measurements. Electrophoretic light scattering showed a recharging of BSA from a negative to a positive zeta potential in the presence of amphiphilic derivatives.

Radiation-Induced Wavelength Shifts in Fiber Bragg Gratings Exposed to Gamma Rays and Neutrons in a Nuclear Reactor.

Fiber Bragg gratings (FBGs) inscribed by UV light and different femtosecond laser techniques (phase mask, point-by-point, and plane-by-plane) were exposed-in several irradiation cycles-to accumulated high doses of gamma rays (up to 124 MGy) and neutron fluence (8.7 × 1018/cm2) in a research-grade nuclear reactor. The FBG peak wavelengths were measured continuously in order to monitor radiation-induced shifts. Gratings inscribed on pure silica core fibers using near-IR femtosecond pulses through a phase mask showed the smallest shifts (<30 pm), indicating that these FBGs are suitable for temperature measurement even under extreme ionizing radiation. In contrast, the pointwise inscribed femtosecond gratings and a UV-inscribed grating showed maximal shifts of around 100 pm and 400 pm, respectively. Radiation-induced red shifts are believed to arise from gamma radiation damage, which may partially recover after irradiation is stopped. At the highest neutron exposures, grating peak blue shifts started to appear, apparently due to fiber compaction.

Luminescence of the Cs2ZrCl6 under High Pressure.

The photoluminescence (PL) and Raman spectra of the Cs2ZrCl6 crystal over a wide range of pressures were studied in this work for the first time. PL measurements were performed up to 10 GPa, while the Raman spectra were measured up to 20 GPa. The PL data revealed a linear blue shift of the emission maximum from about 2.5 eV at ambient pressure to 3.1 eV at 5 GPa and a strong intensity quenching. The indirect-to-direct bandgap transition at about 5 GPa, a phenomenon previously predicted only theoretically, was used to explain the strong quenching of the PL. This model was confirmed by fitting PL intensity data and analysis of the PL decay kinetics, which exhibited a shortening of the pulse decay time with the increasing pressure. Raman spectra confirmed the stability of Cs2ZrCl6 up to 20 GPa and showed no evidence of pressure-induced structural phase transitions. An energetic scheme of excitonic levels, which takes into account the indirect-to-direct bandgap transition, was proposed to explain the rapid PL quenching with increasing pressure.

Deconvoluting capping ligand influence on photophysical properties in tetrathiafulvalene-based diradicaloids.

Tetrathiafulvalene-2,3,6,7-tetrathiolate (TTFtt) complexes are synthetically tunable and emit brightly in the near-infrared II region (NIR II, 1000-1700 nm). Their emission/absorption energies respond to the identity of the capping ligands on the metal center, but a detailed understanding of how ligand bonding interactions dictate photophysical properties is key to predictive design optimization. Here we assess the relative influence of ligand pi (π) backbonding versus sigma (σ) donation in these complexes across a new series of olefin- and phosphite-capped complexes. Increasing the backbonding character of peripheral ligands results in a hypsochromic shift in the absorption maxima, while stronger σ donation results in a bathochromic shift.

Multiphysics Ensemble Framework for Representing Western Himalayan Precipitation Climatology and Extremes: An Assessment from the WRF Model

Abstract Numerical model simulations are sensitive to the choice of physical parameterizations, particularly those related to convection processes, especially over complex terrains like the western Himalayan region. This study evaluates the sensitivity of the Weather Research and Forecasting (WRF) Model to three convective parameterization schemes [Betts–Miller–Janjić (BMJ), Kain–Fritsch (KF), and Grell–Freitas (GF)] and their multiphysics ensemble mean (ENSM) through long-term (2001–16) winter (December–March) simulations. Model outputs are validated against multisource datasets [India Meteorological Department (IMD), IMERG, ERA5, and Indian Monsoon Data Assimilation and Analysis (IMDAA)], with extreme precipitation events (EPEs) identified as those exceeding the 95th-percentile threshold. Climatology analysis reveals systematic precipitation biases across all single schemes, significantly reduced in the ENSM. Improvements in skill scores observed for ENSM highlight the reliability of the ensemble approach as an alternative to account for model errors. Underestimations of low-level clouds and hydrometeors improve in ENSM. BMJ and KF (GF) schemes exhibit overestimated (underestimated) magnitudes and location-wise discrepancies for baroclinic instability and moisture transport. These issues are mitigated in ENSM, resulting in better alignment with reference datasets. Additionally, ENSM and KF’s storm tracks align well with reanalyses, while individual schemes show a minor northward placement. For EPEs, ENSM highlights Jammu and Kashmir, Himachal, and Uttarakhand as zones of maximum heavy precipitation and frequency. ENSM realistically represents the western disturbance (WD)-induced circulation characteristics, southward-displaced subtropical jet, shifts in WD-associated vorticity maxima, and potential vorticity intrusions during extremes. Consistent with reference datasets, ENSM demonstrates the crucial role of vertical advection and dynamical controls in moisture distribution during EPEs. Our analysis indicates that a suitable WRF cumulus configuration includes either the multiphysics ENSM or the KF scheme, while the GF scheme yields the poorest results. The findings underscore the importance of evaluating both precipitation characteristics and underlying physical mechanisms to identify sources of systematic biases in model simulations.

Coordination Chemistry of Mixed-Donor Pyridine-Containing Macrocyclic Ligands: From Optical to Redox Chemosensors for Heavy Metal Ions.

2,8-Dithia-5-aza-2,6-pyridinophane (L1) has been used as a receptor unit in the construction of the conjugated redox chemosensor 5-ferrocenylmethyl-2,8-dithia-5-aza-2,6-pyridinophane (L3). In order to further explore the coordination chemistry of L1, and comparatively, that of its structural analogue 2,11-dithia-5,8-diaza-2,6-pyridinophane (L2), featuring two secondary nitrogen atoms in the macrocyclic unit, the crystal structures of the new synthesised complexes [Pb(L1)(ClO4)2]·½CH3CN, [Cu(L2)](ClO4)2·CH3CN and [Cd(L2)(NO3)]NO3 were determined by X-ray diffraction analysis. The electrochemical response of L3 towards the metal ions Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+ was investigated by cyclic voltammetry (CV) in CH2Cl2/CH3CN 0.25:1 (v/v) mixture. Upon addition to L3 of increasing amounts of the aforementioned metal cations, the wave corresponding to the Fc+/Fc redox couple of the un-complexed L3 was gradually replaced by a new reversible wave at more positive potentials and corresponding to the Fc+/Fc redox couple of the complexed ligand. The maximum anodic shift of the ferrocene oxidation wave is observed in the presence of Pb2+ (230 mV), to which corresponds a reaction coupling efficiency (RCE) value as large as 7.9 × 103. The response selectivity of L3 is discussed in reference to the optical selectivity observed for conjugated chemosensors featuring L1 as receptor unit and different fluorogenic fragments as signalling units.

The Impact of Carbon on Electronic Structure of N-Doped ZnO Films: Scanning Photoelectron Microscopy Study and DFT Calculations.

A Scanning Photoelectron Microscopy (SPEM) experiment has been applied to ZnO:N films deposited by Atomic Layer Deposition (ALD) under O-rich conditions and post-growth annealed in oxygen at 800 °C. State-of-the-Art spatial resolution (130 nm) allows for probing the electronic structure of single column of growth. The samples were cleaved under ultra-high vacuum (UHV) conditions to open atomically clean cross-sectional areas for SPEM experiment. It has been shown that different columns reveal considerably different shape of the valence band (VB) photoemission spectra and that some of them are shifted towards the bandgap. The shift of the VB maximum, which is associated with hybridization with acceptor states, was found to be correlated with carbon content measured as a relative intensity of the C1s and Zn3d core levels. Generalized Gradient Approximation (GGA) supplemented by +U correction was applied to both Zn3d and O2p orbitals for calculation of the VZn migration properties by the Nudged Elastic Band (NEB) method. The results suggest that interstitial -CHx groups facilitate the formation of acceptor complexes due to additional lattice perturbation.

Phosphorus Doping Effects on the Optoelectronic Properties of K₂AgAsBr₆ Double Perovskites for Photovoltaic Applications

This work explores the modifications of optoelectronic properties in K₂AgAsBr₆ double perovskites induced by phosphorus doping. First-principles calculations using the CASTEP code with the PBE functional were carried out based on density functional theory (DFT). Our research investigates the electronic structure and optical behavior of the cubic Fm-3m phase of K₂AgAsBr₆, K₂AgAs₀.₈P₀.₂Br₆, and K₂AgAs₀.₆P₀.₄Br₆ to elucidate the impact of progressive phosphorus (P) substitution. P was chosen for its potential to modify the electronic structure due to its smaller atomic radius and different valence orbital energies compared to As. Our results reveal a systematic narrowing of the band gap with increasing P content, from 0.749 eV for the undoped compound to 0.587 eV for K₂AgAs₀.₈P₀.₂Br₆ and 0.424 eV for K₂AgAs₀.₆P₀.₄Br₆. This trend is attributed to the upward shift of the valence band maximum due to the higher energy of P 3p orbitals compared to As 4p orbitals. Analysis of the density of states confirms increased hybridization between P-p and As-p states at the valence band edge. Optical properties, including absorption coefficient, dielectric function, refractive index, and extinction coefficient, demonstrate a consistent red-shift and broadening of spectral features with P doping. Notably, P-substituted compounds exhibit enhanced absorption in the visible light region, with up to a 20% increase in the absorption coefficient at 550 nm for K₂AgAs₀.₆P₀.₄Br₆ compared to the undoped compound. This study reveals that elemental substitution offers a viable route to tailor optical and electronic properties of double perovskites, paving the way for the design of novel materials for next-generation photovoltaic and photoelectric devices.

Impact of gate bias on TID responses of BCD MOSFETs

The total ionizing dose (TID) effect on MOSFETs, which use the Bipolar-CMOS-DMOS (BCD) technology, is investigated under different gate biases utilizing X-rays. The threshold voltage, maximum transconductance and subthreshold swing of the device before and after irradiation were obtained. The results indicate that the TID effect is significantly influenced by gate bias. For NMOSFET, the maximum threshold voltage shift occurs at a positive gate bias of 3 V. For PMOSFET, the minimum threshold voltage shift occurs at a negative gate bias of −3 V. The mechanism was revealed to be the result of the combined effects of initial recombination, hole capture, and electron tunneling processes. However, the case of PMOSFET differs from NMOSFET due to the disappearance of electron tunneling and the change in the direction of hole movement under negative gate bias.

Towards Novel Antiplasmodial Agents-Design, Synthesis and Antimalarial Activity of Second-Generation β-Carboline/Chloroquine Hybrids.

As the resistance of Plasmodium to the existing antimalarials increases, there is a crucial need to expand the antimalarial drug pipeline. We recently identified potent antimalarial compounds, namely harmiquins, hybrids derived from the β-carboline alkaloid harmine and 4-amino-7-chloroquinoline, a key structural motif of chloroquine (CQ). To further explore the structure-activity relationship, we synthesised 13 novel hybrid compounds at the position N-9 of the β-carboline ring and evaluated their efficacy in vitro against Plasmodium falciparum 3D7 and Dd2 strains (CQ sensitive and multi-drug resistant, respectively). All compounds exhibit persistent antimalarial activity against both strains of P. falciparum. The most interesting derivatives had low nanomolar activity against both strains (IC50 (33) = 4.7 ± 1.3 nM against Pf3D7 and 6.5 ± 2.5 nM against PfDd2; IC50 (37) = 4.6 ± 0.6 nM against 3D7 and 10.5 ± 0.4 nM against Dd2). Resistance indices (RIs) ranged from 0.9 to 5.3 compared to CQ (RI = 14.4), highlighting their superior consistency in activity against both strains. The cytotoxicity screening performed on HepG2 revealed over 3 orders of magnitude higher IC50 for most of the compounds, with SIs from 711.0 to 8081.8. Spectroscopic studies explored the affinities of newly synthesised compounds for DNA, RNA, and HSA. Both tested hybrids, 34 and 39, were intrinsically fluorescent in an aqueous medium, characterised by remarkable Stokes shifts of emission maxima (Δλ = +103 and +93 nm for 34 and 39, respectively). Fluorimetric experiments revealed that compound 34, with its shorter and more flexible linker, exhibited at least an order of magnitude higher affinity toward ds-DNAs versus ds-RNA and two orders of magnitude higher affinity toward GC-DNAs compared to 39. The behaviour of the investigated compounds upon binding to HSA is very similar, showing a strong hypsochromic shift of the emission maximum (almost Δλ = -70 nm) and demonstrating their effectiveness as fluorimetric probes for distinguishing between DNA/RNA and proteins.

Assessing intra- and interfraction motion and its dosimetric impacts on cervical cancer adaptive radiotherapy based on 1.5T MR-Linac

PurposeThe purpose of this study was to quantify the intra- and interfraction motion of the target volume and organs at risk (OARs) during adaptive radiotherapy (ART) for uterine cervical cancer (UCC) using MR-Linac and to identify appropriate UCC target volume margins for adapt-to-shape (ATS) and adapt-to-position (ATP) workflows. Then, the dosimetric differences caused by motion were analyzed.MethodsThirty-two UCC patients were included. Magnetic resonance (MR) images were obtained before and after each treatment. The maximum and average shifts in the centroid of the target volume and OARs along the anterior/posterior (A/P: Y axes), cranial/caudal (Cr/C: Z axes), and right/left (R/L: X axes) directions were analyzed through image contours. The bladder wall deformation in six directions and the differences in the volume of the organs were also analyzed. Additionally, the motion of the upper, middle and lower rectum was quantified. The correlation between OAR displacement/deformation and target volume displacement was evaluated. The planning CT dose distribution was mapped to the MR image to generate a plan based on the new anatomy, and the dosimetric differences caused by motion were analyzed.ResultsFor intrafraction motion, the clinical tumor volume (CTV) range of motion along the XYZ axes was within 5 mm; for interfraction motion, the range of motion along the X axis was within 5 mm, and the maximum distances of motion along the Y axis and Z axis were 7.45 and 6.59 mm, respectively. Additionally, deformation of the superior and anterior walls of the bladder was most noticeable. The largest magnitude of motion was observed in the upper segment of the rectum. Posterior bladder wall displacement was correlated with rectal and CTV centroid Y-axis displacement (r = 0.63, r = 0.50, P < 0.05). Compared with the interfractional plan, a significant decrease in the planning target volume (PTV) D98 (7.5 Gy, 7.54 Gy) was observed. However, there were no significant differences within the intrafraction.ConclusionDuring ART for UCC patients using MR-Linac, we recommend an ATS workflow using isotropic PTV margins of 5 mm based on intrafraction motion. Based on interfraction motion, the recommended ATP workflow uses anisotropic PTV margins of 5 mm in the R/L direction, 8 mm in the A/P direction, and 7 mm in the Cr/C direction to compensate for dosimetric errors due to motion.

An Approach to Identifying Single-Nucleotide Mutations Using Noncovalent Associates of Gold Nanoparticles with Fluorescently Labeled Oligonucleotides.

Globally, widespread tuberculosis is one of the acute problems of healthcare. Drug-resistant forms of tuberculosis require a personalized approach to treatment. Currently, rapid methods for detecting drug resistance of Mycobacterium tuberculosis (MTB) to some antituberculosis drugs are often used and involve optical, electrochemical, or PCR-based assays. Despite the large number of these assays, it is necessary to develop new tests (for drug-resistant MTB strains) that are structurally simple and do not require specialized equipment. Colorimetric assays involving a colloidal solution of gold nanoparticles (AuNPs) have good potential for the development of the needed diagnostic tools. Here, conditions were found for the formation of tandem duplexes between DNA probes and DNA targets, representing a part of MTB gene gyrA, either wildtype or containing a single-nucleotide polymorphism associated with fluoroquinolone resistance of MTB. Adsorption of the duplexes on AuNPs allowed to distinguish the two targets owing to the formation of nano-constructs of different structures. Interaction of DNA with AuNPs was analyzed by optical spectroscopy, dynamic light scattering, and transmission electron microscopy. A scheme is proposed for direct colorimetric detection of the fluoroquinolone-resistance-associated single-nucleotide polymorphism at a 2 nM concentration in a liquid system based on a shift of AuNPs' optical absorption maximum.

Triskelion-Shaped Hexabenzocoronenes: Synthesis and Characterization of Tris-Substituted HBC Derivatives.

The synthesis of unprecedented triskelion-shaped hexa-peri-hexabenzocoronenes with C3, C3h or D3h symmertry is reported. We present a new, five step synthetic access to tris-iodinated HBC derivatives carrying different solubilizing moieties (tert-butyl and mesityl), which serve as suitable building blocks for further functionalization. These molecules can undergo Sonogashira cross coupling reactions to obtain a series of seven ethynyl tris-substituted HBCs. The coupling partners range from carbon-based aromatic scaffolds (tBu-benzene, naphthalene, phenanthrene) to ligands for metal complexes (bipyridine, phenanthroline, terpyridine, acetylacetone). The optoelectronic properties were investigated by UV/vis absorption spectroscopy resulting in a significant bathochromic shift of the absorption maximum compared to the iodinated starting material. Semiempirical calculations were used to determine the conformation and symmetry of the compounds.

Synthesis and Spectral Properties of Iodine-Substituted Dyes Based on Benzothiazolium Salts

Two series of new thiacarbocyanines with iodine atoms in the donor and/or acceptor block have been synthesized. The absorption spectra of the iodinated dyes in the region of singlet-singlet S0-S1 and singlet-triplet S0-T1 transitions are investigated. The introduction of iodine atoms into the dye structures leads to a red shift of the absorption maximum, regardless of the position of iodine in the molecule. For dyes with two or more iodine atoms, a low-intensity long-wave absorption shoulder in the region from 650 to 1000 nm is detected, which corresponds to singlet-triplet absorption.

A Facile and Efficient Synthesis of BODIPY-Based Fluorescent Probes for Selective Detection of Hydrazine.

A facile and ratiometric BODIPY-based fluorescent probe 4 was developed for the selective detection of hydrazine in solution phase. The BODIPY-based fluorophores 3 and 4 were easily prepared in high yields from the L-proline catalyzed reaction between α/β-formyl BODIPY 1 a/1 b and 3-cyanoacetylindole 2. Use of easily accessible substrates, benign solvent, catalytic amount of L-proline and high product yields are the advantageous features of the developed protocol. Prepared BODIPYs 3 (536 nm) and 4 (567 nm) showed bathochromic shifts (36-67 nm) in UV-Visible absorption maxima when compared to parent BODIPY (500 nm) in dichloromethane (DCM). The stable and economical BODIPY-based probe 4 exhibited rapid response and remarkable selectivity towards hydrazine when compared to other commonly occurring analytes. At low concentration, the BODIPY probe 4 (10 μΜ) is non-fluorescent, however, a significant enhancement in fluorescent (turn-on) was observed with the increasing concentration of hydrazine (0-100 μΜ). This change in fluorescent behaviour may be ascribed to intramolecular charge transfer (ICT) effect as supported by density functional theory (DFT) calculations. With a 4.3 μM detection limit, the BODIPY probe 4 was also found to be useful in detecting hydrazine in real environmental samples.

Impact of Process and Machine Parameters in the Charging Section on the Triboelectric Separation of Wheat Flour in a Vertical Separator

Triboelectric separation has recently been investigated as a novel process for dry enrichment and separation of protein of various crops like wheat flour. The triboelectric effect allows for the separation of starch and protein particles in an electric field based on their different charging behavior despite having a similar density and size distribution. Particles are triboelectrically charged in a charging section before being separated in an electric field based on their polarity. While the charging section is crucial, the influence of process parameters remains largely unexplored. Thus, the influence of the charging sections’ dimensions and the particle concentration as process key parameters was investigated experimentally. Varying the length (0, 105, and 210 mm) showed that the protein shift increases with the length (max. 0.53%) during separation. Varying the diameter (6, 8, and 10 mm) influenced the charging behavior, resulting in an increase in protein accumulation on the negative electrode as the diameter decreased. Varying the mass flow of flour (40, 80, 160, and 320 g·h−1) also affected the separability, leading to a maximum protein shift of 0.61%. Based on the observed results, it is hypothesized that the electrostatic agglomeration behavior of oppositely charged particles is directly affected by alterations in machine parameters. These agglomerates have a charge-to-mass ratio that is too low for separation in the electric field.

Estimation of Link Margin and Doppler Shift of Ground Sensor Terminal for Nanosatellite Payload

Abstract The primary objective of this study is to develop and validate a method for estimating Link Margin and Doppler Shift to enhance the performance of the Ground Sensor Terminal (GST) for nanosatellite communication systems. The Link Margin estimation considers key factors such as Antenna Gain and losses, Atmospheric Effect, System Noise Temperature (Tsys), Margin (M), and Received Signal Strength (Pr). The methodology includes calculating the uplink budget using both the EB/No and SNR methods, with parameters extracted from the AMSAT IARU Link Model. Additionally, Doppler Shift is analysed as the change in frequency of the signal due to the relative motion between the satellite and the ground station. Mitigation strategies, including frequency management, adaptive modulation and coding, predictive tracking algorithms, and real-time feedback control systems, were explored as effective means to counteract the Doppler effect’s influence on signal integrity. The results indicate that for a satellite positioned at an altitude of 400 km, with a frequency of 145.825 MHz, the maximum Doppler shift at 0 degrees elevation is observed to be 4 kHz. Communication can be established with a link margin of 11.3 dB, starting from an elevation of 0 degrees, using the EB/No method, significantly improving the reliability and efficiency of data transmission in nanosatellite missions.

CdS-Titania nanocomposite: An improved visible active photocatalyst for dye degradation

Abstract Photocatalysis is emerged as a feasible solution for addressing the issues related to green energy production and sustainable environment. Among various reported photocatalysts, Titania is one of the widely used one due to its high stability, and low cost. However, its wide band gap and poor charge separation limits its photocatalytic performance in the UV region only. Coupling of Titania with suitable visible active semiconductor is a proven strategy to improve the performance. In this context, CdS-Titania (Anatase) nanocomposite has been synthesized via facile hydrothermal route and its impact on photon absorption and carrier separation efficiency were studied. The synthesized samples were characterized through various structural, optical and electrochemical analysis. X-ray diffraction pattern confirms the formation of CdS-Titania (Anatase) composite and its physicochemical properties. FE-SEM confirms the disintegration of CdS microspheres into smaller agglomerated particulates. The absorption spectroscopy confirms that induction of CdS improves the visible light absorption capacity. The composite consisting CdS-Titania (Anatase) (CdSA) shows the maximum red shift in the visible range. The low charge transfer resistance of composite observed in EIS analyses further confirms the proper separation of charge carriers at junction. The photocatalytic degradation performance under visible light irradiation was performed and found that the nanocomposite performs better than the pristine Anatase and CdS. CdSA has been found to have superior photocatalytic ability. It shows 43 times and 1.52 times better performance than pristine Titania and CdS respectively. This can be attributed to the enhanced visible photon absorption achieved through the successful formation of heterojunction. This opens up a new area of research for improving the performance of pristine Titania.