Filtering Effect Research Articles

Effectiveness of Air Filtration in Reducing PM2.5 Exposures at a School in a Community Heavily Impacted by Air Pollution

Reducing children’s exposure to air pollution is a priority among California communities heavily impacted by air pollution exposures. We conducted an observational air quality study at a school to investigate the effectiveness of improved Heating, Ventilation, and Cooling (HVAC) system filters and portable air cleaners (PACs) in reducing children’s exposure to fine particulate matter (PM2.5) under real-world classroom conditions. This study included five classrooms, three of which had PACs. Halfway through the study period, high-efficiency HVAC filters were installed in all five classrooms. Continuous measurements of outdoor and in-classroom PM2.5 concentrations were used to evaluate filtration effectiveness. The air filtration strategies, alone and in combination, demonstrated 14–56% reductions in indoor PM2.5 concentrations compared to outdoor levels. There were significant improvements in filtration resulting from HVAC filter upgrades in the two classrooms without PACs (11% and 22% improvement, p < 0.001). Upgrading HVAC filters in classrooms with PACs did not significantly improve filtration effectiveness, suggesting that utilizing both strategies simultaneously may not meaningfully improve air quality under these circumstances. CO2 data, as a proxy for ventilation, helped demonstrate that the observed filtration effectiveness was likely impacted by the variable HVAC system use and open doors.

Novel fluorescent nanoplatform for all-in-one sensing and removal of acrolein: An ultrasensitive probe to evaluate its removal efficiency

As a highly toxic aldehyde, acrolein is widely found in diet and environment, and can be produced endogenously, posing a serious threat to human health. Herein, we designed a novel fluorescent nanoplatform integrating carbon dots‑manganese dioxide (CDs-MnO2) and glutathione (GSH) for all-in-one sensing and removal of acrolein. By converting Mn4+ to free Mn2+, GSH inhibited the inner filter effect (IFE) of MnO2 nanosheets, and the Michael addition of acrolein with GSH inhibited the GSH-induced Mn4+ conversion, forming an “off-on-off” fluorescence response of CDs. The developed fluorescent nanoplatform exhibited high sensitivity (LOD was 0.067 μM) and selectivity for the simultaneous detection and removal of acrolein. The combination of CDs-MnO2 hydrogels with smartphones realized the point-of-care detection of acrolein, yielding satisfactory results (recovery rates varied between 97.01–104.65%, and RSD ranged from 1.42 to 4.16%). Moreover, the capability of the nanoplatform was investigated for on-site evaluating acrolein scavengers' efficacy, demonstrating excellent potential for practical application.

A dual-channel sensing platform for the cross-interference-free detection of tetracycline and copper ion

Tetracycline (TC) and copper ion (Cu2+), as important additives in animal feed, play a crucial role in disease prevention and growth regulation. However, the abuse leads to concentration accumulation, which seriously threatens human health and the ecological environment. There is an urgent need to develop a detection method to achieve fast and synchronous detection of these pollutants without cross-interference. Here, a carbon dots-doped lanthanide-based fluorescent nanosensor (CDs@Tb-MOFs@SiO2–NH2-Eu) was synthesized, which can detect TC in the 380 nm channel by “antenna effect” and internal filtering effects (IFE), and identify Cu2+ in the 320 nm channel. The sensor was highly sensitive to TC within 0–4 μM with a detection limit as low as 3.64 nM, and Cu2+ could be detected within 0–40 μM with a detection limit of 38 nM. A portable dual-channel visual fluorescence sensor was obtained by loading the probes onto test paper and cotton swabs in food samples, which indicates the practicability of this sensing strategy.

Green method for quantification of lavender and sweet orange essential oils in blends by synchronous fluorescence first derivative

A simple green method for the quantification of sweet orange and lavender essential oils (EOs) content in blends was developed using synchronous fluorescence of the first derivative spectra and sample preparation by surfactant-free microemulsions (SFMEs). Excitation and emission wavelengths pairs (λex/λem) were determined for both EOs (at 336/436 nm for sweet orange and at 330/388 nm for lavender). Optimization was conducted to establish the condition to prepare the SFMEs systems: 50 μL of oily phase containing EO diluted in octan-1-ol (1:4, v/v), 2.0 mL of water and propan-1-ol up to 5.0 mL final volume. Different proportions of EO in the oily phase were evaluated for analytical curves construction. Synchronous fluorescence measurements were performed and the acquired data were corrected by inner filter effect. Considering the first derivative of the synchronous scanning, data were extracted at 316.8 nm (Δλ = 100 nm) and 352.0 nm (Δλ = 58 nm) for sweet orange and lavender EOs, respectively, with correlation coefficients above 0.99. Limits of quantification of 7.97 μg mL−1 and 65.80 μg mL−1 were obtained indicating that 0.46% of sweet orange and 3.69% of lavender EOs can be quantified in mixtures. Simulated blends (25:75%, 50:50% and 75:25%, volume proportions) were also evaluated with recoveries of 71.5 – 128.9% and coefficient of variation between 3.1% – 11.6%. Additionally, the method's greenness was evaluated through three green metrics (Analytical Eco-Scale, GAPI, and AGREE) with consistent results.

Non-pyrolytic synthesis of laccase-like iron based single-atom nanozymes for highly efficient dual-mode colorimetric and fluorescence detection of epinephrine

Single-atom nanozymes have garnered significant attention due to their exceptional atom utilization and ability to establish well-defined structure-activity relationships. However, conventional pyrolytic synthesis methods pose challenges such as high energy consumption and random local environments at the active sites, while achieving non-pyrolytic synthesis of single-atom nanozymes remains a formidable technical hurdle. The present study focuses on the synthesis of laccase-like iron-based single-atom nanozymes (Fe-SAzymes) using a non-pyrolysis method facilitated by microwave irradiation. Under low iron loading conditions, Fe-SAzymes exhibited significantly enhanced laccase activity (12.1 U/mg), surpassing that of laccase by 24-fold. Moreover, Fe-SAzymes demonstrated efficient catalytic oxidation of epinephrine (EP), enabling its colorimetric detection. Owing to the remarkable laccase activity of Fe-SAzymes, the conventional nanozymes EP detection time was reduced from 60 min to 20 min, with an impressive low detection limit as low as 2.95 μM. In addition, an ultra-sensitive fluorescence method for EP detection was developed using the internal filter effect of EP oxidation products and CDs combined with carbon dots probe. The detection limit of fluorescence method was only 0.39 μM. Therefore, an visual, fast, and highly sensitive dual-mode EP detection strategy has great potential in the clinical diagnostic industry.

Advances in 4-Nitrophenol Detection and Reduction Methods and Mechanisms: An Updated Review.

This review emphasizes the progress in identifying and eliminating para-nitrophenol (4-NP), a toxic organic compound. It covers various strategical methods and materials, including organic and inorganic nanomaterials, for detecting and reducing 4-NP. Detection techniques such as electrochemical methods. Optical fiber-based surface plasmon resonance and photoluminescence, as well as the mechanisms of Förster Resonance Energy Transfer (FRET) and Inner Filter Effect (IFE) in fluorescence detection, are presented. Removal techniques for this contaminant include homogeneous catalysis, electrocatalysis, photocatalysis, and thermocatalysis, and their reaction mechanisms are also discussed. Further, the theoretical perspectives of 4-NP detection and reduction, parameters influencing the activities, and future perspectives are also reviewed in detail.

Effect of post-storage filters vs. pre-storage filters for leukoreduction of blood components on clinical outcomes: a systematic review and meta-analysis

BackgroundLeukoreduction has been used to limit the risk of adverse events. The most commonly used methodology is filtration (pre- or post-storage). However, whether pre-storage filtration is better than post-storage filtration needs to be clearly defined, particularly for countries that still use post-storage filtration. This study aimed to synthesize the best available evidence on the effectiveness of pre-storage filters compared with post-storage filters for transfusion reactions, for the occurrence of infections, for the length of hospital stay, and for the death of patients undergoing leukoreduced transfusion.MethodsWe searched the MEDLINE (PubMed), CINAHL (EBSCO), PsycINFO (APA), Scopus (Elsevier), The Cochrane Library (J. Wiley), Web of Science Core Collection (Clarivate Analytics), Embase (Elsevier), and LILACS (VHL) databases and gray literature for eligible studies in August 2020 and updated the search in October 2023. The Joanna Briggs Institute critical assessment tools were applied to analyze the quality appraisal of the studies. GRADE was used to determine the certainty of the evidence.ResultsThe meta-analysis showed that pre-storage filtration was a protective factor for the occurrence of febrile non-hemolytic transfusion reaction in red blood cells (RR 0.49, 95% CI 0.41–0.59) and platelet concentrate transfusions (RR 0.16, 95% CI 0.12–0.22). The same did not occur for post-surgical infection after platelet concentrate transfusions (RR 0.82, 95% CI 0.65–1.04). Only one study analyzed the length of hospital stay and showed no significant difference between patients who received leukoreduced transfusions according to the type of filter used. According to the GRADE criteria, the certainty of the evidence for febrile non-hemolytic transfusion reactions was low for red blood cells and very low for platelet concentrate due to the high risk of bias. Infection was a low risk due to imprecision.ConclusionsThe results of this review showed that the certainty of recommending the best type of filter (pre- or post-storage) for the benefit of the outcomes analyzed is still fragile; therefore, more robust evidence is needed.Systematic review registrationPROSPERO CRD42020192202.

Aptamer-controlled gold nanozyme sensor for fluorescent and colorimetric dual-channel detection of methamphetamine

Methamphetamine (METH) is the second abused drug which affects abusers’ health and induces social crimes, developing novel methods with high sensitivity and selectivity for METH detecting is still challenging. In this paper, a colorimetric and fluorescent dual-channel sensor for METH has been constructed. We combine the enzyme-mimic catalytic activity of gold nanoparticles (GNPs) with high target specificity of METH aptamer to create a nanosensor (Apt-GNP), in the presence of METH, the absorption of 3,3′,5,5′-tetramethylbenzidine (OxTMB) at 650 nm enhanced with METH concentration increasing, while the absorption characteristic peak of GNPs at 530 nm remained almost unchanged. The ratio of A650nm/A530nm and METH concentration had a good linear relationship when METH concentration was in the range of 5–50 μM, and the corresponding linear equation is A650nm/A530nm = 0.00727CMETH (μM) + 0.783 with R2 = 0.997 and LOD = 0.40 μM (LOD = 3σ/s, n = 11). Interestingly, the fluorescence emission of Rhodamine B (RB) overlaps with the absorption spectrum of OxTMB which represents the content of METH and the fluorescence signal of RB can be quenched through internal filtering effect (IEF). Hence, when RB was doped to the detection system, the decay of RB fluorescence can reflect the concentrations change of METH. Accordingly, the linear equation is F/FR = –0.00751CMETH (μM) + 0.895 with R2 = 0.993 and LOD = 0.40 μM, where F was the fluorescence of the analytical solution at 580 nm with METH and FR was fluorescence of RB control solution. The dual-channel sensor can measure METH in serum and artificial urine successfully which is potential to be applied in drug-using crime sites and provide direct evidence to law enforcement officials.

A longitudinal meta-analysis of range restriction estimates and general mental ability validity coefficients: Better addressing overcorrection amid decline effects.

Psychometric corrections can be crucial for obtaining valid operational results, but concerns are rising about potential overcorrections for general mental ability (GMA) validity coefficients. Our two-part study identifies a source of overprediction: using national norms rather than recent local applicant pool variance for range restriction corrections. Study 1 demonstrates increasing homogeneity in Wonderlic occupational applicant pool variance across four data time waves, suggesting they are no longer interchangeable with the general working population, a divergence attributable to a rise in education. Study 2 employs the Morris meta-analytic approach to gauge the impact of using national norms over occupational ones in range restriction. An analysis of 649 GMA validity coefficients from four time waves of General Aptitude Test Battery and Wonderlic data shows a radical drop in corrected and uncorrected correlations, indicating that historical corrected GMA validity coefficients differ from contemporary ones by up to 16-fold (i.e., an R² of 42.3% vs. 2.6%), and range restriction corrections are now minimal in about 75% of cases. This drop in correlations appears due to the filtering effects of increased education, both due to the demands of the knowledge economy and credentialism, where organizations are using college or university degrees as a proxy for GMA. Credentialism is an incredibly inefficient form of GMA assessment, suggesting an urgent societal need to incorporate selection fundamentals more broadly. Altogether, these results indicate that labor market dynamics have a deeper impact on personnel selection than typically appreciated, meaning that many of our estimates have and will eventually age out. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Integrating carbon dots and gold/silver core-shell nanoparticles to achieve sensitive detection of dopamine with fluorometric/colorimetric dual signal.

Dopamine (DA) is a potent neuromodulator in the brain that affects a wide range of motivated behaviors. Abnormal concentration of DA is related to a variety of diseases. Hence, it is imperative to establish a rapid and precise method for quantifying DA. In this work, we integrate orange-yellow emissive carbon dots (CDs) with target-induced silver deposition on gold nanoparticles (Au NPs), forming gold/silver core-shell nanoparticles (Au@Ag NPs), to construct a fluorometric and colorimetric dual-signal sensor for sensitive detection of DA. Au NPs and silver ions (Ag+) have minimal effect on the fluorescence of CDs. DA can reduce the silver ions to Ag(0) on the surface of the Au NPs to form a silver shell, resulting in the blue-shift of theabsorbance peak from 520 to 416nm, which overlaps with the excitation spectrum of CDs. As a result, the system color turns from pink to orange-yellow, and the fluorescence of CDs is quenched due to the strong inner filter effect. The linear range of the colorimetry is 0.5-18μM with a limit of detection (LOD) of 0.41μM, while the linear range for the fluorometry method is 0.5-14μM with a LOD of 0.021μM. This method demonstrates notable advantages including a low detection limit, rapid response time, and straightforward operation in practical samples, showing great potential in biomedical analysis.

Green synthesis of fluorescent carbon dots from waste chicken feathers for chlortetracycline sensing

Herein, we present a novel, straightforward, eco-friendly and cost-effective method for synthesizing fluorescent carbon dots. A simple one-pot hydrothermal method was used to create blue-emitting nitrogen-doped carbon dots (N-CDs) from waste chicken feathers and ammonium chloride (NH4Cl) as precursors. The research demonstrates that N-CDs not only exhibit excellent photostability, but also serve as a versatile nanoscale fluorescence sensor for the efficient qualitative and quantitative detection of chlortetracycline (CTC) in samples. The mechanism of fluorescence quenching is attributed to the specific and rapid quenching of N-CDs fluorescence by chlortetracycline through the static quenching and inner filter effect (IFE). The concentration of CTC within the range of 0.05–0.35 mM exhibits a significant linear relationship with the fluorescence quenching of NCDs, as indicated by the formula (I0-I)/I = 4.74248c(CTC)-0.09041. Subsequent spiked recovery experiment confirms the feasibility of this method for the detection of CTC in samples. Therefore, leveraging the concept of turning waste into treasure, this study successfully developed a green and cost-effective method for synthesizing NCDs from natural biomass, offering a novel perspective for further development of multifunctional sensors.

Determination of acetaldehyde in Chinese Baijiu based on the light-activated oxidase-mimic activity of fluorine-containing carbon dots (dF-CDs)

Acetaldehyde (AH) is defined as a carcinogen, the widely existence in alcoholic beverages has led its determination an essential aspect related to human health. Fluorine doped carbon dots (dF-CDs) is developed, which process light-activated oxidase-mimic property and high stability at acidic condition. Under the UV irradiation, dF-CDs generate reactive oxygen species (ROS) to oxidize o-phenylenediamine (OPD) into 2,3-diaminophenazine (DAP), showing absorption peak at 450 nm and strong emission at 577 nm, meanwhile, the produced DAP quenches the original emission of dF-CDs at 455 nm via an inner filter effect (IFE). However, the introduction of AH inhibits such processes efficiently, thereby establishing a colorimetry and ratiometric fluorescence method for AH determination. Of note, this dual-responsive method has been used for the accurate AH determination in Chinese Baijiu. Therefore, the developed method not only provide a dual-sensing platform to determine AH, but also extends the applications of CDs in food analysis.

Lignin/carbon dots-embedded cellulose nanofibrils hydrogel: An effective, inexpensive and versatile platform for doxycycline adsorption and determination

Herein, a novel hydrogel, lignin/carbon dots-embedded cellulose nanofibrils hydrogel (LCCH), was fabricated for doxycycline (DOX) adsorption and determination. The adsorption characteristics of LCCH under various conditions were investigated. According to the Langmuir model fitting results, the maximum capacity of LCCH reached 1686 mg/g. Moreover, it exhibited excellent reusability, with an adsorption capacity maintained above 80.4 % after 5 cycles. Additionally, the LCCH demonstrated stable fluorescence properties, with DOX causing significant quenching of fluorescence attributed to both the internal filtration effect and static quenching. Within the ranges of 10–120 mg/L and 0.2–1.0 μg/L, the fluorescence of LCCH gradually decreased with the increasing concentration of DOX, reaching a limit of detection as low as 0.08 μg/L. Lastly, a cost analysis considering energy consumption and reagent prices demonstrated LCCH's cost-effectiveness as an adsorbent. Overall, this study presents a novel approach for designing and preparing an effective, inexpensive, and versatile hydrogel for the removal of antibiotics.

A label-free fluorescence sensing strategy based on gold nanoparticles assisted copper nanoclusters for the detection of aflatoxin B1 in cereals and peanuts

To effectively monitor the degree of aflatoxin B1 (AFB1) contamination in food and mitigate potential health risks to consumers eating food contaminated with AFB1, a label-free fluorescence aptamer-sensing strategy utilizing gold nanoparticles (AuNPs) was developed. Polyvinylpyrrolidone-copper nanoclusters (PVP-CuNCs) and AuNPs were selected as donor/acceptor pairs to convert the color signal change of AuNPs into fluorescence signal changes in PVP-CuNCs via the inner filter effect (IFE). In the presence of AFB1, the aptamer preferentially adsorbed with AFB1, and the AuNPs without aptamer protection changed color from red to blue under NaCl-induced aggregation. The green fluorescence of PVP-CuNCs recovered gradually. The developed strategy offers high sensitivity for the detection of AFB1, with a linear range of 0.02–20 μg L−1, and a low detection limit of 0.69 μg L−1. In addition, the strategy was successfully applied to real samples such as corn, rice, oats and peanuts, and the recovery rate was 93.4–106.2 %, which verified the reliability and applicability of this strategy. This strategy has the advantages of cost-effectiveness, high sensitivity, low detection limit and easy operation, providing a reference for sensitive and selective detection of mycotoxins contamination in food.

Performance evaluation of coloured filters on PV panels in an outdoor environment

AbstractThis study aims to investigate the effects of colour filters and tilt angles on the electrical output characteristics of solar photovoltaic modules. The experimental set‐up allowed for the evaluation of various combinations of colour filters and tilt angles by using a realistic simulation of solar panel installations. The various light spectrum wavelengths and energy levels were taken into account, keeping in mind any potential impacts on the solar cells' conversion efficiency. The results showed that compared to other filter combinations, the use of red colour filters with a 10% blockage rate and an optimal tilt angle led to a noticeable increase in electrical output. This result emphasises the value of colour filtering and tilt angle selection in raising solar photovoltaic systems' overall performance. When compared to the other filters, the red, orange, and yellow filters stand out due to their outstanding efficiency of around 84.98%, 84.08%, and 83.69%. However, the teal, green, and blue filters exhibit relatively low levels of efficiency of about 69.62%, 67.06%, and 58.52%, respectively. The distinct reaction shown by purple and pink filters, when subjected to tilt angle of 30 degrees, offers a potentially productive direction of enhancing the efficiency of PV panel.

Quantum confinement and energy filtering effect enhancing the thermoelectric power factor of InGaAs with buried ErAs nanoparticles

Quantum confinement and energy filtering effect enhancing the thermoelectric power factor of InGaAs with buried ErAs nanoparticles

Unipolar spin diodes and unipolar spin switches by Spin-Transfer torque in doped graphether

Spin switches are a fundamental component in the majority of spintronic devices, and have found extensive application in data storage, logical data manipulation, and signal processing. An essential aspect of constructing a spin switch is determining a stable two-dimensional material, which is easy to control and produce. Theoretical studies have shown that graphether is particularly promising due to its exceptionally high melting point and outstanding air stability. The band structure can be modified by doping, making it an important material for spin switch applications. In this paper, we have calculated the electromagnetic properties of doped graphether by first principles. Then we select a modified graphether with P-type and N-type doping configurations to construct magnetic tunnel junctions (MTJ). The results show that the MTJ exhibits perfect highly efficient spin switch as a result of spin reversal induced by spin-transfer torque (STT). In addition, our designed MTJ shows a remarkable rectification effect and spin filtering effect (SFE). According to our calculations, the modified graphether materials also show promise as two-dimensional spintronics materials.

Synthesis of four coordination polymers with Zn(II), Cd(II), Mn(II), or Co(II) ions and their application for fluorescence sensing toward nitenpyram, imidacloprid, and vitamin B2

Four new Zn(II)-, Cd(II)-, Mn(II)-, and Co(II)-based 1D to 2D coordination polymers (CPs) were synthesized from metal salts and 1,4-di(1-imidazol-1-yl)naphthalene (DIN) ligand via the coordination reaction under hydrothermal conditions with quantitative yields, namely, [Zn(SO4)(DIN)(H2O)] (CP-1), [Cd(NO3)2(DIN)] (CP-2), [Mn(SO4)(DIN)(H2O)3] (CP-3), and [Co(NO3)2(DIN)2(H2O)4] (CP-4). The CPs were analyzed and characterized using FT-IR, Elemental Analysis, TGA, SC-XRD, and PXRD. CP-1 was selected as a model sensor for fluorescence detection, and the sensor exhibited high quenching rates at two excitation wavelengths of λex = 230 and 290 nm, and at a single emission wavelength of λem = 350 nm. At these two different excitation wavelengths, CP-1 behaved differently during the sensing of pesticides, and the highest quenching rate was achieved by the sensor for nitenpyram (λex = 230 nm) and imidacloprid (λex = 290 nm). Furthermore, during the sensing of vitamins, CP-1 encountered a strong quenching effect toward vitamin B2. During the sensing processes, the inner filter effect (for nitenpyram, imidacloprid, and vitamin B2), fluorescence resonance energy transfer (for nitenpyram, imidacloprid, and vitamin B2), and photo-induced electron transfer (for vitamin B2) were the mechanisms responsible for fluorescence quenching.

Lateral flow assay with dual-emission nitrogen-doped carbon dots for ratiometric fluorescent determination of nitrite in food

Nitrite ion (NO2–), renowned for its potent antiseptic properties and color-preserving abilities, potentially leads to carcinogenesis and hypertension if consumed excessively. Herein, a ratiometric fluorescent probe exhibits specific response to NO2– using nitrogen-doped carbon dots (N-CDs) with a low detection limit (LOD) as low as 52 nM and a low quantification limit (LOQ) of 173 nM. Initially, the emission peaks at 495 nm and 415 nm decrease as result of the internal filtration effect (IFE). With further increasing NO2– concentration, the reaction between NO2– and N-CDs forms an azoic compound (N-CDs@NO2–), which promotes the instant quenching of the emission peak at 415 nm through fluorescence resonance energy transfer (FRET). Moreover, portable N-CDs/LFASs devices with smartphone are successfully applied to visually identify NO2– with the exceptional LOD, achieving excellent recoveries and high precision in real sample. Therefore, this newly N-CDs/LFASs offers a reliable means for the NO2– detection, showcasing potential applications.

Tunable and switchable multi-wavelength mode-locked fiber lasers induced by an optimized hybrid mode-locked composite filtering effect.

A multi-wavelength mode-locked fiber laser can generate different wavelengths from a single laser cavity, offering potential as a dual-frequency comb and serving as an ideal light source for terahertz wave generation. We present an optimized hybrid mode-locked Er-doped fiber laser with flexible outputs: switchable and tunable dual-wavelength mode-locking, along with stable tri-wavelength mode-locking, which is achieved by introducing 0.69 m polarization-maintaining fiber and bent 200 m single-mode fiber to enhance intra-cavity birefringence and nonlinear effect to optimize the hybrid mode-locking effect, that is, build the composite filter effect. The dual-wavelength mode-locking not only covers a tunable wavelength range of 5 nm but also provides tunable wavelength intervals of 4-26 nm due to the composite filter effect. The formation dynamics of the tri-wavelength mode-locking can be switched either pair-by-pair or one-by-one. This approach enables the realization of wavelength interval tunable dual-wavelength mode-locking in mode-locked fiber lasers simply by introducing fiber without additional actions. Such a simple, compact fiber laser with tunable wavelength capabilities holds significant potential for diverse applications.