Efficiency Drop Research Articles

Novel spacer geometries for membrane distillation mixing enhancement

Membrane distillation is an emerging promising desalination method that requires further improvement in order to become industrially viable. Due to the fact that evaporation is the primary process in membrane distillation, one strategy to boost membrane permeate flux is to optimize the energy supply to the water interface by increasing mixing in the hot channel via the use of optimized spacers. Contemporary spacer designs predominantly induce turbulence, resulting in elevated pumping energy requirements. This study introduces novel spacer geometries, inspired by industrial mixer designs, to surmount the limitations of conventional spacer configurations. The mixing efficiency, thermal performance, and pressure drop induced by the two novel geometries are studied and compared to those of commonly utilized spacer designs. It is confirmed, that the first of these novel geometries significantly enhances mixing, whereas the other causes a lower pressure drop and appears to be a viable solution when a spacer is a necessary structural component. In the course of the analysis, it is also shown that the coefficient of variation coupled with the Nusselt number at the membrane can be used to assess spacers' performance.

Microstructures, Optical, magnetic Properties, and photocatalytic activity of magnetically separable and reusable ZnO-Doped Fe3O4/rGO nanocomposite synthesized via green route

We report magnetically-separable, reusable, green-synthesized Fe3O4/rGO/ZnO, as heterogeneous catalyst for photo-Fenton degradation of organic pollutants in aqueous solution under certain treatments. Fe3O4 nanoparticles was green-synthesized using Moringa oleifera leaf extract, while rGO was synthesized utilizing Amaranthus viridis leaf extract. Fe3O4/rGO was composited under sonication treatment. Afterwards, Fe3O4/rGO was doped with ZnO with various concentration of ZnO. X-ray diffraction and selected area electron diffraction showed that Fe3O4 and ZnO had spinel cubic and hexagonal structure, respectively; another phase appeared as Fe2O3 spinel cubic structure. Crystallite size was decreased as the ZnO concentration increased. Morphology image showed almost spherical, non-uniform, and slightly dispersed particle under agglomerated condition, attaching to rGO sheets. The particle size of Fe3O4, Fe3O4/rGO, and Fe3O4/rGO/ZnO is 14.3; 14.1; and 10.4 nm, respectively. Fourier-transform infrared spectra showed metallic functional groups, such as Fe-O and Zn–O at 562–589 and 462–478 cm−1 also suggests nanocomposite formation. However, blue-shift absorption and band gap widening were observed with ZnO addition. Raman spectroscopy revealed the formation as-synthesized GO and rGO. Vibrating sample magnetometer showed that green-synthesized Fe3O4/rGO/ZnO exhibited superparamagnetic properties. Removal efficiency of photodegradation methylene blue was optimal for green-synthesized Fe3O4/rGO/ZnO under sonication treatment, reached 100 % degradation within 180 min for uptake every 30 min. Photodegradation was also analyzed using Langmuir-Hinshelwood kinetic model, resulting rate constant of 24.7 × 10−3 min−1 and half-life time of 28.1 min at optimum treatment. Reusability of photocatalytic activity after 3 cycles showed only a tiny drop in catalytic efficiency. Meanwhile, it possesses high stability in catalytic activity and structure. The green-synthesized Fe3O4/rGO/ZnO potential as an environmentally friendly reusable photocatalyst for wastewater degradation.

Advanced hemodynamics for prognostication in heart failure: the pursuit of the patient-specific tipping point.

Objective tools to define the optimal time for referral for advanced therapies and to help guide escalation and de-escalation of support can improve management decisions and outcomes for patients with advanced heart failure. The current parameters have variable prognostic potential depending on the patient population being studied and often have arbitrary thresholds. Here, a mathematical and physiological framework to define the patient-specific tipping point of myocardial energetics is defined. A novel hemodynamic parameter known as the myocardial performance score (MPS), a marker of power and efficiency, is introduced that allows for the objective assessment of the physiological tipping point. The performance of the MPS and other advanced hemodynamic parameters including aortic pulsatility index (API) and cardiac power output (CPO) in predicting myocardial energetics and the overall myocardial performance was evaluated using a validated computer simulation model of heart failure (Harvi) as well as a proof-of-concept clinical validation using a cohort of the Society for Cardiovascular Angiography and Interventions (SCAI) Stage C cardiogenic shock patients. Approximately 1010 discrete heart failure scenarios were modeled. API strongly correlated with the left ventricular coupling ratio (R2 = 0.81) and the strength of association became even stronger under loaded conditions where pulmonary capillary wedge pressure (PCWP) was >20 mmHg (R2 = 0.94). Under loaded conditions, there is a strong logarithmic relationship between MPS and mechanical efficiency (R2 = 0.93) with a precipitous rise in potential energy (PE) and drop in mechanical efficiency with an MPS <0.5. An MPS <0.5 was able to predict a CPO <0.6 W and coupling ratio of <0.7 with sensitivity (Sn) of 87%, specificity (Sp) of 91%, positive predictive value of 81%, and negative predictive value of 94%. In a cohort of 224 patients with SCAI Stage C shock requiring milrinone initiation, a baseline MPS score of <0.5 was associated with a 35% event rate of the composite endpoint of death, left ventricular assist device, or transplant at 30 days compared with 3% for those with an MPS >1 (p < 0.001). Patients who were able to augment their MPS to >1 after milrinone infusion had a lower event rate than those with insufficient reserve (40% vs. 16%, p = 0.01). The MPS, which defines the patient-specific power-to-efficiency ratio and is inversely proportional to PE, represents an objective assessment of the myocardial energetic state of a patient and can be used to define the physiological tipping point for patients with advanced heart failure.

Significant reduction in sidewall damage related external quantum efficiency (EQE) drop in red InGaN microLEDs (∼625 nm at 1 A cm−2) with device sizes down to 3 μm

Ultra-small (10 μm) InGaN-based red microLEDs (625 nm at 1 A cm−2) are necessary for modern displays. However, an increase in surface-area-to-volume ratio with a decrease in the micro-LED size resulting in higher surface recombination causes a drop in efficiency with device size. In this letter, we demonstrate microLEDs from 60 μm down to 3 μm with significantly reduced sidewall-related efficiency reduction using a two-step passivation technique using Al2O3 and Si3N4. The peak on-wafer EQE changes from 0.21% to 0.35% as the device size reduces from 60 to 3 μm, possibly due to improved light extraction efficiency for smaller mesa-widths.

Unveiling the relationship between structural evaluation and catalytic performance of InOOH during electroreduction of CO2 to formate

The electrochemical CO2 reduction reaction (ECO2RR) to formate is perceived as a technoeconomic pathway for transforming renewable electricity into fuels. However, the indeterminate mechanism underlying structural self-reconstruction obstructs the strategic design of a high-performance In catalyst for the ECO2RR. In this study, we chose InOOH as the model catalyst to illustrate the dynamic structure of In-based catalysts during reconstruction in the ECO2RR. The findings of the current study indicate that the in situ electrochemical reconstruction of crystalline InOOH results in the creation of crystalline In clusters/InOOH, followed by In/InOOH heterostructures, and finally, metallic In over time. The efficiencies of the different phases conformed to the sequence: In clusters/InOOH > In/InOOH heterostructures > metallic In. This progression leads to a continuous drop in maximum current density and Faradaic efficiency from 29.6 mA/cm2 and 87% to 6.3 mA/cm2 and 75%, respectively with time extending to 7200 s, at –1.0 V relative to the reversible hydrogen electrode. Our in situ characterization and theoretical studies highlighted the crucial role of the In-cluster/InOOH interface in CO2 activation and conversion.

Numerical study on performance optimization and flow mechanism of a new cyclone separator

This study proposed a new cyclone separator, using a designed nozzle inside the traditional cyclone separator, which significantly improved the efficiency of separating fine particles while maintaining an essentially unchanged pressure drop. Firstly, computational fluid dynamics (CFD) was used to compare the flow characteristics of the new cyclone separator with those of the traditional cyclone separator. On this basis, this study comprehensively investigated the pressure drop and separation efficiency of two separators under varying working conditions. The new separator achieved a separation efficiency for particles with a particle size of 1 μm that was approximately 45% higher than that of the traditional separator when the inlet velocity was 2–10 m/s. Besides, the pressure drop of the cyclone separator remained unchanged while the separation efficiency increased by 46% at an inlet flow rate of 2 m/s. The influence of the outlet area of the nozzle inside the new cyclone separator on the separation efficiency and pressure drop was analyzed, and the outlet area of the nozzle with the best overall performance was determined. It was found that the overall performance of the new cyclone separator is optimal when the nozzle outlet area is S/f = 2 cm. Finally, an energy-saving cyclone separator with high separation efficiency was developed through an in-depth study of the variation of particle motion configuration with time. It is worth noting that this study provides a guidance for the flow field analysis and geometry optimization of new gas-solid separators, not limited to cyclone separators.

Contextual existence of an optimum through-plane orientation and aspect ratio of a fiber-segment in fibrous air filters

Fibrous air filters have emerged extensively as a remedial indoor solution to address severe air pollution. To understand the complexities involved in variation of their performance with respect to their fiber anisotropy, a fundamental numerical study is undertaken to investigate the capture of inertia-dominated airborne particles by a fiber-segment at different through-plane orientations with respect to airflow direction. An in-house MATLAB code has been developed using the lattice Boltzmann method to model the airflow across fiber-segment, coupled with the Lagrangian approach to model the motion of particles as well as their interactions with the fiber-segment. The filtration performance parameters, viz., capture efficiency, pressure drop, and quality factor, have been evaluated at different through-plane orientations of the fiber-segment for its various segmental aspect ratios and different Stokes numbers. It is found that as the fiber-segment is turned from a parallel to orthogonal orientation with respect to airflow direction, the capture efficiency and pressure drop exhibit either a monotonic rise or broadly an increasing–decreasing kind of trend with an intermediate maximum, depending on the segmental aspect ratio of fiber and the Stokes number. Also, both these parameters are observed to decrease as the segmental aspect ratio of fiber is increased. Furthermore, an optimum through-plane orientation as well as an optimum segmental aspect ratio of the fiber-segment are found to exist for which the overall filtration performance is highest. The indicative optimum through-plane orientation of the fiber-segment is found to be a function of its segmental aspect ratio but not the Stokes number.

A Coordinate Positioning Technique Based on Region Partitioning for EV Wireless Charging System

The performance of wireless charging systems is very sensitive to the relative position of couplers. A small displacement between the transmitting and the receiving coils may lead to severe efficiency drop and degradation in system performance. Therefore, it is necessary to include a positioning-technique-based parking guiding program in EV wireless charging systems. To offer fast and clear location information of the couplers to the driver or automatic parking program, a coordinate positioning technique based on region partitioning for determining the relative position between the transmitting and receiving coils as well as the correct moving direction of the receiving coil is proposed in this paper. Meanwhile, a simple exciting circuit is also proposed to energize the source coil. Therefore, the proposed positioning system consists of the transmitting coil, receiving coil, two auxiliary coils and the corresponding low power converters. With the proposed technique, an EV can move to the near-perfect-coupling zone. Theoretical analysis and experimental verifications are provided.

All-fluorescent white organic light-emitting diodes employing a deep-blue HLCT material simultaneously as emitter and host achieving excellent electroluminescence performance with efficiency roll-off

Simultaneously achieving high efficiency and small efficiency roll-off remains a huge challenge for white organic light-emitting diodes (OLEDs), which greatly restricts their industrial application in the lighting field. Recently developed hybridized local and charge transfer (HLCT) materials have a “hot exciton” channel, which can maximize the utilization rate of excitons and suppress efficiency roll-off via rapid reverse intersystem crossing (RISC) from high-lying triplet state (Tn, n ≥ 2) to singlet state (S1). In this work, employing blue HLCT material pCzAnN as the sensitizing host, by precise concentration management, the traditional fluorescent C545T- and DCJTB-based green and orange-red OLEDs are first fabricated, which achieve the maximum external quantum efficiency (EQE) exceeding the theoretical limit of 5 %, reaching 8.51 % and 6.64 %, respectively. On this basis, by strategic device structure design, all-fluorescent two- and three-color white OLEDs are demonstrated having pCzAnN simultaneously as blue emitter and sensitizing host of C545T and DCJTB. The resulting two- and three-color white devices obtain maximum EQE beyond 5 %. What's more, all three-color white devices exhibit extremely small efficiency roll-off, where the efficiency drops are less than 1 % at a practical luminance of 1000 cd/m2, which is comparable to the best works reported in the literatures. At the same time, the optimized three-color white device realizes ideal white emission, in which the electroluminescence (EL) spectra contain three almost equal intensity emission wavebands accompanied by a high color rendering index of 87. Stable EL spectra under a wide luminance range (3863 ∼ 27710 cd/m2) indicate a huge potential application. We believe this work can provide new idea for developing high-efficiency and low roll-off white OLEDs in the future.

Enhanced particulate filter with electrostatic charger: Insights for low-resistance and high-efficiency ship-based nanoscale black carbon capture

Black carbon emission from ships has attracted great concern due to its significant impact on the environment, climate, and human health. This study presents a comprehensive approach to address black carbon emissions from ships with simulated nanoparticles (SP-BC) by integrating a particulate filter with an electrostatic charger (EC-PF). Low filtration velocity (1.5 cm/s) is beneficial for the high-efficiency and low pressure drop collection of SP-BC by PF, while the optimum filtration temperature should be within 673 K to prevent decomposition and fragmentation of SP-BC. The electrostatic charger can significantly improve the PF collection efficiency by 10% while reducing the PF pressure drop variation by nearly 50%, based on the looser DPM layer formation and electrostatic attraction. Varying applied voltage in EC-PF systems have different effects on the efficiency and pressure drop, and 80% of the maximum applied voltage (i.e. 21 kV at 573 K)is considered the optimal operating mode of EC-PF, with a reduction in the median diameter of more than 20 nm compared to the PF. For long-term operation, the operating voltage should be reduced to mitigate the occurrence of breakdown and prevent a significant increase in pressure drop. At higher filtration velocities of up to 9 cm/s, the efficiency enhancement of the EC-PF becomes more apparent, with collection efficiencies exceeding 90%. In addition, pulse-jet cleaning is shown to be a feasible assisted regeneration method for EC-PF with a low pressure drop after regeneration. Consequently, this study has significant implications for low-resistance and high-efficiency ship-based black carbon capture, contributing to the mitigation of Arctic glacier melting and global warming.

Highly Stretchable Photovoltaic Module with Improved Mechanical Robustness through Elastomeric Interconnections

Stretchable photovoltaics have garnered increasing attention due to their adaptability to various surfaces and applications, meeting the rising demands for portable and flexible power sources. Herein, stretchable solar modules are demonstrated by sandwiching electrically connected rigid solar cells between top and bottom polydimethylsiloxane (PDMS) layers, which are then attached onto an elastomer with an island and trench structure. The electrical connection of solar cells is achieved by dispenser printing of electrically conductive adhesive (ECA). The fabricated stretchable solar modules have a maximum biaxial elongation of 75%, and the electrical connection of the solar cells using ECA results in a negligible efficiency loss of 1.6%. In particular, embedding of solar cells and interconnects between PDMS layers enhances mechanical stability by placing these key components at the mechanical neutral plane and the long‐term stability against humidity due to the encapsulation role of the PDMS layer. The module demonstrates only a 5% of efficiency drop after 1000 hours in the dump‐heat test (85°C/85%). The results in this study are not limited to solar cells but can be applied to various types of rigid devices, paving the way for the commercialization of stretchable electronics.

ASSESSING AND OPTIMIZING THE PERFORMANCE OF A SHELL AND TUBE HEAT EXCHANGER (E-2502) IN PHOSPHORIC ACID PRODUCTION: A CASE STUDY AT PT. PETROKIMIA GRESIK

PT. Petrokimia Gresik, established with a construction contract on August 10, 1964, stands as Indonesia's most comprehensive fertilizer factory. The company comprises various departments, including the Production Department IIIA, specializing in Phosphoric Acid Production. The objective of assessing the efficiency of a shell and tube cooler-type heat exchanger is to evaluate its performance, determining compliance with design specifications and identifying the need for cleaning and maintenance. The utilized heat exchanger, of the shell and tube type, employs water as its cooling source. According to design calculations conducted between September 13 and September 18, 2023, the expected efficiency of the cooler-type heat exchanger is 91.44%. However, actual data analysis over six days reveals a significant drop in efficiency, registering below 50%. A comparison between design and actual data suggests a decline in efficiency for the E-2502 cooler type. The decrease is attributed to substantial scaling in the E-2502 Heat Exchanger, stemming from the cooled P2O5 Acid solution and resulting in deposition during the heat transfer process. Consequently, it is imperative to initiate a cleaning process for the cooler-type heat exchanger to optimize the heat transfer mechanism.

Investigation of entropy generation in the existence of heat generation and nanoparticle clustering on porous Riga plate during nanofluid flow

The objective of this research is to examine the impact of many parameters, including entropy production resulting from nanoparticle aggregation, viscous dissipation, heat source, and buoyancy, on the flow behavior of nanoliquids through a vertical Riga plate made of porous media at the two-dimensional stagnation point. By combining elements of the original Krieger-Dougherty model with the Maxwell-Bruggeman model, a new correlation for the aggregation process may be reached. The PDEs that control the boundary layer area of this problem are changed into a group of nonlinear PDEs using the right non-similarity transformations. The issue may be solved by using the BVP4c MATLAB program, which implements the local non-similarity approach and includes an extra degree of truncation. It was also found that the skin friction coefficient increased by 3.35% to 7.18% for both the aiding and opposing flow zones with the incorporation of a 1% nanoparticle volume fraction. Incorporating the Eckert number resulted in a consistent drop in heat transfer efficiency, from 7.27% to 10.24%. Aggregation of nanoparticles increases the magnitude of velocity and the temperature distribution, as shown by the model of aggregation. The augmentation of the A values is widely acknowledged as a strategy to prolong the initiation of entropy; however, on the contrary, the elevation of the Bejan number helps to expedite it. It has been empirically shown that increasing the ϕ value has a beneficial effect on both the entropy inception field and the Bejan number. An increase in the Brinkman number leads to an acceleration in the rate of entropy generation, concomitantly resulting in a decrease in the Bejan number. The suggested numerical model is validated by comparing it to existing findings that have been made public.

Efficiency Roll-Off in Light-Emitting Electrochemical Cells.

Understanding "efficiency roll-off" (i.e., the drop in emission efficiency with increasing current) is critical if efficient and bright emissive technologies are to be rationally designed. Emerging light-emitting electrochemical cells (LECs) can be cost- and energy-efficiently fabricated by ambient-air printing by virtue of the in situ formation of a p-n junction doping structure. However, this in situ doping transformation renders a meaningful efficiency analysis challenging. Herein, a method for separation and quantification of major LEC loss factors, notably the outcoupling efficiency and exciton quenching, is presented. Specifically, the position of the emissive p-n junction in common singlet-exciton emitting LECs is measured to shift markedly with increasing current, and the influence of this shift on the outcoupling efficiency is quantified. It is further verified that the LEC-characteristic high electrochemical-doping concentration renders singlet-polaron quenching (SPQ) significant already at low drive current density, but also that SPQ increases super-linearly with increasing current, because of increasing polaron density in the p-n junction region. This results in that SPQ dominates singlet-singlet quenching for relevant current densities, and significantly contributes to the efficiency roll-off. This method for deciphering the LEC efficiency roll-off can contribute to a rational realization of all-printed LEC devices that are efficient at highluminance.

Evaluation and risk communication of the effects of alcohol exposure on disposable procedure masks and portable air purifiers in hospital environments.

Electret technology was widely used to prevent the airborne transmission of bioaerosols during the COVID-19 pandemic and improve the filtration efficiency of masks and high-efficiency particulate air (HEPA) filters. As alcohol disinfectants are widely used in medical and welfare institutions, concerns about alcohol exposure inactivating electret exist. However, comprehensive alcohol exposure tests have not been conducted on masks and HEPA filters distributed in Japan. Twenty-five types of masks and five types of HEPA filters were subjected to a discharging process according to ISO 16890 to quantitatively elucidate the resistance to alcohol exposure. Measurements of changes in filtration efficiency and pressure drop before and after discharge show that 17 masks (68%) and four HEPA filters (80%) exhibited a significant decrease in filtration efficiency, confirming their vulnerability to alcohol. In addition, a survey (n = 500 Japanese adults, including 30 healthcare professionals) revealed that ∼90% of the general public were unaware that alcohol exposure could degrade masks and air purifiers. Furthermore, 36% of the surveyed healthcare professionals had sprayed alcohol directly onto their masks. The effectiveness of user warnings through product labels and instructions was investigated from the perspective of ensuring the safety of patients and healthcare professionals. Results revealed that the best approach was to describe the extent and duration of the adverse effects caused by disregarding precautions. Increase in awareness of healthcare professionals and general public by authorities and manufacturers through guidelines and warning labels would reduce the risk of inhaling bioaerosols caused by unintentional electret inactivation.

Intense field dielectric purification of oil droplets in machining buildings

Intense field dielectric (IFD) exhibits environmental friendliness and high efficiency in particle purification, with varying efficiencies based on the physical properties of the particles. However, limited research has been conducted on the application of IFD for purifying indoor air polluted by oil droplets. This study experimentally investigated the efficacy of IFD in purifying machining-generated oil droplets. The primary objectives were to clarify the advantages, applicability, and recommended parameters for the purification of oil droplets using IFDs. The results indicate that the efficiency and pressure drop of using IFD for oil droplet purification can reach three times and half, respectively, compared to the conventional low-resistance filter (G4 filter). Furthermore, a formula was derived through fitting to describe the efficiency and pressure drop of IFD for oil droplet purification. IFD achieved a purification efficiency of over 90 % with a deviation of less than 8 % for oil droplet diameters greater than 5.0 μm or airflow velocities below 0.5 m/s. IFD exhibited over 4 % and 2 % higher purification efficiency for atomized and soluble oil droplets, respectively, in comparison to evaporated-condensed and straight oil droplets. At airflow velocities below 1.0 m/s, IFD demonstrated purification efficiencies exceeding 80 % for oil droplets generated by evaporation-condensation and over 90 % for those generated by atomization. Increasing the atomized oil flow rate from 20 to 60 ml/h resulted in corresponding 15 % improvement in purification efficiency, attributed to the larger droplet diameters. This study laid the groundwork for effective utilization of IFDs in the context of machining-generated oil droplet purification.

Highway usage efficiency and debt burden: Evidence from China

China’s highway network experienced rapid expansion during the 2010s, accompanied by a surge in debt borrowed for construction. Are these newly-constructed highways being fully utilized? To examine the impact of usage efficiency on the debt burden, we construct a unique dataset that includes transportation densities and financial indicators of toll highways. Our findings indicate that declining usage efficiency significantly increases the debt burden. Specifically, for every additional 100 million yuan invested in toll road construction, the average freight density on the highway network decreases by 3,630 tons, and passenger density decreases by 1,340 individuals. The decline in usage efficiency escalates debt service payments and expands budget deficits. Heterogeneity analysis reveals that the drop in usage efficiency notably increases toll road debt burdens in economically less-developed regions and in government-repaid toll road projects.

Tetracycline removal from wastewater via g-C3N4 loaded RSM-CCD-optimised hybrid photocatalytic membrane reactor

In this study, a split-type photocatalytic membrane reactor (PMR), incorporating suspended graphitic carbon nitride (g-C3N4) as photocatalyst and a layered polymeric composite (using polyamide, polyethersulfone and polysulfone polymers) as a membrane was fabricated to remove tetracycline (TC) from aqueous solutions as the world's second most used and discharged antibiotic in wastewater. The photocatalyst was synthesised from melamine by ultrasonic-assisted thermal polymerisation method and, along with the membrane, was characterised using various methods, including Brunauer–Emmett–Teller analysis (BET), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Field emission scanning electron microscopy (FESEM), and Ultraviolet–visible spectroscopy (UV–Vis). The PMR process was optimised, using Design-Expert software for tetracycline removal in terms of UV irradiation time, pH, photocatalyst loading, tetracycline concentration, and membrane separation iteration. It was revealed that a membrane-integrated reactor as a sustainable system could effectively produce clean water by simultaneous removal of tetracycline and photocatalyst from aqueous solution. The maximum removal of 94.8% was obtained at the tetracycline concentration of 22.16 ppm, pH of 9.78 with 0.56 g/L of photocatalyst in the irradiation time of 113.77 min after six times of passing membrane. The PMR system showed reasonable reusability by about a 25.8% drop in TC removal efficiency after seven cycles at optimal conditions. The outcomes demonstrate the promising performance of the proposed PMR system in tetracycline removal from water and suggest that it can be scaled as an effective approach for a sustainable supply of antibiotic-free clean water.

Sol-gel combustion synthesis and near-infrared luminescence of Ni2+-doped MgAl2O4 spinel phosphor

Near-infrared phosphor converted light-emitting diode (NIR pc-LED) has many advantages over traditional NIR light sources, and has broad application prospects in night vision surveillance, non-destructive testing, bioimaging, and other fields. Phosphors are typically synthesized by the high-temperature solid-phase method as chunks or large granules, which need to be ground to small particles for practical application. This process introduces surface defects and reduces the luminous efficiency of phosphors. In this work, near-infrared phosphors composed of spinel MgAl2O4:Ni2+ with particle size less than 100 nm was synthesized in high-purity by sol-gel combustion method using nitrate salts with citric acid were used as raw materials. Under 365 nm excitation, MgAl2O4:Ni2+ phosphors emit broadband near-infrared luminescence of 1000–1600 nm with a width at half maximum of 237 nm. The optimal Ni2+ doping concentration was determined to be 1.5 mol% and the optimal sintering temperature was 1200 °C. The thermal activation energy of this phosphor was found to be 0.409 eV and the phosphor had good luminescence thermal stability. An NIR pc-LED device was assembled from the phosphor and commercially available near-ultraviolet LED, which showed a current-dependent increased of NIR luminescence up to 160 mA and an efficiency drop appeared with further increase of the current, suggesting a thermal dependent quenching may have occurred. On the other hand, the output of NIR luminescence increased nearly linearly with the increased of current when a 360 nm laser diode was used as the excitation light source, indicating the NIR phosphor has a very high fluorescence saturation threshold. Our study provides the utility for the sol-gel method in the preparation and the potential application of the nanoscale NIR-II phosphor materials.

In2S3/HAp nanocomposite: a comprehensive study on synthesis, structural insights, and high-performance adsorption of Methyl Red dye in water treatment applications

ABSTRACT This research aims to show the synthesis, characterisation, and adsorptive performance of a novel In2S3/HAp nanocomposite, in which In2S3 nanoparticles are anchored onto hydroxyapatite (HAp) produced from fish scales. The nanocomposite adsorbs Methyl Red (MR) dye from aqueous solutions with surprising efficiency. The structural and chemical properties of the In2S3/HAp nanocomposite were determined using a variety of analytical techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Comprehensive isotherm and thermodynamic analyses demonstrated a significant adsorption capacity of 331.91 mg g−1, yielding a superior removal efficiency of 91.78% for 20 mg L−1 MR dye utilising just 10 mg (0.2 g L−1). Statistical physics modelling (SPM) gave quantitative insights into adsorption, revealing critical parameters such as adsorption site density, saturation adsorption capacity, and adsorption energies. The study found that MR dye adsorption happened in both parallel and non-parallel processes, highlighting the complex nature of the interaction between dye molecules and the nanocomposite surface. The adsorption process was discovered to be exothermic. Furthermore, reusability studies revealed that the nanocomposite may be reused up to 5 times with just a 13% drop in efficiency, confirming its promise for practical applications. The nanocomposite functioned consistently across several water matrices, demonstrating versatility in various water treatment applications. Finally, the In2S3/HAp nanocomposite appears as a viable and long-lasting option for MR dye removal, as evidenced by extensive characterisation, statistical modelling, and exceptional performance. These findings highlight its potential for larger environmental remediation applications in treating dye contamination in bodies of water.