Relative Concentration Ratio Research Articles

Influence of trap centers on persistent luminescence of Cr3+ or Yb3+ Co‐doped Y3Al2Ga3O12:Pr3+ ceramic phosphors

AbstractLanthanide ion doped garnet is one of the representative persistent luminescence (PersL) phosphors that have been widely investigated. However, the role of the trap centers, either intentionally added co‐dopants or intrinsic defects arising during the sintering process, and their effect on the performance of PersL has not been completely elucidated, especially when they coexist. In pursuit of clarifying the relationship among different trap centers and their impact on the afterglow, herein, low‐concentration Pr3+ and Cr3+/Yb3+ (electron trap) co‐doped Y3Al2Ga3O12 ceramic phosphors are synthesized using a solid‐state reaction method under a vacuum atmosphere and some of them are further subjected to annealing condition. The observed thermoluminescence glow curves are composed of two strong peaks related to oxygen vacancies and a weak peak formed by each Cr and Yb trap based on the relative concentration ratio. On the other hand, it is found that the Cr3+ and Yb3+ions act as prominent near‐infrared (NIR) PersL centers in the NIR‐I and NIR‐II region, respectively, matching with the first and the second biological window. This work allowed for an exploration of the properties of distinct trap centers and how they influence the PersL and are likely to hasten the development of new PersL materials.

The synergetic effect of He and Kr irradiation on helium bubble evolution in SiC/SiC composite: Combining in-situ TEM observation with MD simulation

SiC fiber reinforced SiC matrix composites (SiC/SiC composites) are considered as one of the promising structural materials for liquid type breeding blanket in the fusion energy system. The transmutation gas production rate in fusion reactor is significantly higher compared with fission reactors. An innovative method combining in-situ irradiation and TEM observation and MD simulation was utilized to evaluate the synergetic effects of helium and irradiation on SiC/SiC composites. A comprehensive experiment matrix including Kr irradiation, He pre-implantation with sequential Kr irradiation as well as simultaneous dual beam at 1073 K to 16 dpa and 2400 appm He (150 appm/dpa) was performed using 800 keV Kr and 50 keV He ions. With the support of MD results, the impact of relative concentration ratio of vacancies and helium atoms on the bubble evolution was systematically investigated and the corresponding mechanism was further unraveled, which provides the basis of limiting the bubble density in SiC/SiC composites. Additionally, the direct evidence for the competition of irradiation-assisted bubble growth and re-dissolution was in-situ observed in SiC matrix for the first time.

Preparation, optical properties and energy transfer of SrLaAlO4: Dy3+, Eu3+

A series of Dy3+/Eu3+ single doped and co-doped SrLaAlO4 phosphors was synthesized by the traditional high-temperature solid-state method, and their structure, morphology and optical properties were characterized. The X-ray diffraction (XRD) shows a small amount of doping with Dy3+ and Eu3+ does not change the crystal structure of the matrix SrLaAlO4 and the best synthesis temperature is 1450 °C. The scanning electron microscopy (SEM) indicates the particle size directly ranges from 1 to 5 μm roughly and the energy dispersive spectroscopy (EDS) patterns show that SrLaAlO4: Dy3+ phosphor and SrLaAlO4: Dy3+, Eu3+ phosphor were successfully synthesized. SrLaAlO4: Dy3+ phosphor can be effectively excited by near-ultraviolet light, producing two strong emission lights at 483 nm (blue light) and 579 nm (yellow light), presenting a cold white light; SrLaAlO4: Eu3+ phosphor can be effectively excited by near-ultraviolet light, producing red lights at 622 nm; the characteristic emission peaks of Dy3+ and Eu3+ can be shown simultaneously under the same excitation wavelength in SrLaAlO4: Dy3+, Eu3+ phosphor. By changing the relative doping concentration ratio of Dy3+ and Eu3+, the modulation of SrLaAlO4: Dy3+, Eu3+ phosphor from cold white to warm white light can be achieved. In addition, the study of the luminescent mechanism and lifetime shows that there is energy transfer between Dy3+ and Eu3+ in SrLaAlO4: Dy3+, Eu3+ phosphor.

Heterogeneous Hierarchical Self-Assembly Forming Crystalline Nanocellulose–CaCO3 Hybrid Nanoparticle Biocomposites

Nanocellulose is increasingly proposed as a sustainable raw material having strong interparticle bonding. However, cellulose alone has limited bending and impact resistance. We newly observe self-assembly between crystalline nanocellulose (CNC) and ultrafine ground chemical-free calcium carbonate nanoparticles (UGCC). The suspension displays an intrinsic gel-like state, and heterogeneous adsorption occurs under the specific conditions where Brownian motion of both species is arrested by application of ultralow shear (0.01 s−1). In contrast, simple static aging of the mixture leads to autoflocculation of each species independently. The heterogeneous adsorption results in compound particle self-assembly leading to multi-level hierarchical structures depending on relative species size and concentration ratio. Fine particles from species 1 adsorb onto the coarser complementary particles of species 2 and vice versa. Depending also on whether CNC or UGCC particles are in excess, the structural assembly occurs primarily through either CNC–CNC hydrogen bonding or CaCO3–CaCO3 autogenous flocculation, respectively. Controlling the hierarchical composite structure bonding in this way, the resulting morphology can express dual or predominantly single either mineralic or cellulosic surface properties. Novel complex hybrid biocomposite materials can therefore be produced having designable compatibility across a broad range of both natural and oil-based polymeric materials. Both CNC and UGCC are exemplified here via commercial products.

Design of a line-of-sight fluorescence-based imaging diagnostic for classification of microbe species

Fluorescence imaging of certain biochemicals, including flavins and pyridine nucleotides, has utility in characterizing the metabolic state of tissue and in discriminating between microbial species. There is significant clinical utility in this class of imaging techniques but most measurements reported to date require specialized training and equipment rendering most implementations unsuitable for routine medical imaging. Here, a low-cost and robust imaging technique is designed using ultraviolet-induced fluorescence of pyridine nucleotides (primarily NADH) and flavins (primarily FAD) in microbial samples. The diagnostic is optimized to distinguish between different microbial species based on previously reported spectral data using a ratiometric imaging approach. A detailed performance analysis is provided that relates the measured fluorescence intensity ratio (FIR) to the relative concentration ratio of NADH to FAD using a simplified spectroscopic model. Analysis suggests the technique is sensitive to changes in the NADH/FAD concentration ratio over several orders of magnitude, with better than 10% FIR precision on a per-pixel basis for microbial smears as thin as 10 s of microns at a resolution of 30 mm−1 and exposures of 20 ms. Representative microbe samples from eight species were imaged to demonstrate the proposed technique. Results show that the FIR varies by an order of magnitude across different species but the intra-species variation is only ∼5% for the conditions used here. An additional imaging band may be necessary to classify species that contain red pigments or bacteriochlorophyll. Radiative trapping was discussed as a possible limitation of the technique, but no clear evidence for radiative trapping was observed here. Overall, the results suggest that the proposed approach is feasible for rapid, low-cost, and robust characterization of microbial samples.

Methodological aspects of assessment the level of industry markets concentration

The theoretical and methodological aspects of the assessment of industrial markets concentration level have been investigated. Features of identification of industrial markets and establishment of product, geographical and time boundaries have been considered. It has been concluded that it’s appropriate to determine the product boundaries of the industrial market based on the characteristics of the product, which the consumer perceives as useful properties for satisfaction of his personal needs. It is recommended to implement the methods that allow you to evaluate the degree of goods interchangeability for the consumer (cross elasticity of demand, the small but significant non-transitory increase in price test (the SSNIP test), and correlation of prices of goods over time) and the possibility of interchangeability on the supply side. Geographical boundaries of the industrial market are usually established on the basis of the minimum territory within which the consumer can easily satisfy his demand for a certain product in normal conditions. Time limits of the market cover the period during which the structure of the market, the ratio of demand and supply on it does not change significantly. It has been noted that the analysis of the industrial market with the help of concentration indicators makes it possible to assess the strength of competition and the monopolization level. It also has been mentioned about the impact of the industrial market structure on the concentration level which depends on the number of operating enterprises and their size. It has been emphasized that the very sales volumes are taken into account in the investigation of the industrial market structure but not the amount of goods production as it is done during the industry analysis. It has been recommended to calculate the following indicators of the industrial market concentration level: concentration ratio, four-firm concentration ratio, Herfindahl-Hirschman index, relative concentration ratio, Hall-Tideman index (Rosenbluth index), etc. The need for calculation the relative and absolute indicators of concentration in the process of industrial markets analysis has been mentioned. It has been found out that some difficulties with access to information on the sales volume of goods by all business entities operating in the industrial market may arise during data collection for the calculation of the mentioned indicators. It has been recommended to calculate several concentration indicators at the same time in order to obtain the most accurate and objective results of the analysis

Application of Remote Sensing Methodology for Vehicle Emission Inspection

Remote sensing detection of vehicle emissions is an effective supplement to the statutory periodic inspection of in-use vehicle emissions and it is a convenient technical method for real-time screening of high-emission vehicles. The principle of remote sensing detection is to inversely calculate the absolute concentrations of gaseous pollutants in vehicle exhaust according to the relative volume concentration ratio of each exhaust component to carbon dioxide (CO2) in the vehicle exhaust plume. Because the combustion mechanisms of gasoline engines and diesel engines are different, different inversion calculation methods of remote sensing data must be applied. The absolute concentrations of gasoline vehicle gaseous emissions measured by remote sensing can be calculated by the inversion calculation method based on the theoretical air–fuel ratio combustion mechanism. However, the absolute concentrations of diesel vehicle nitrogen oxide (NOx) measured by remote sensing must be calculated by the inversion calculation method based on the correction of the excess air coefficient. For the integrated remote sensing test system of gasoline and diesel vehicles, it is necessary to determine the vehicle category according to the vehicle type and license plate and adopt different inversion calculation methods to obtain the correct remote sensing results of vehicle emissions. The big data statistical analysis method for vehicle emission remote sensing results can quickly screen high-emission vehicles and dynamically determine the remote sensing emission screening threshold of high-emission vehicles as the composition of in-use vehicles changes and the overall emission of vehicles declines, so as to achieve dynamic and accurate screening of high-emission vehicles.

Enhanced photocatalytic overall water splitting by tuning the relative concentration ratio of bulk defects to surface defects in SrTiO3

Defects such as oxygen vacancies play an important role in the photoactivation processes. However, the roles of surface and bulk defects in photocatalytic water splitting are still ambiguous. This paper would report a new method to introduce surface and bulk defects in SrTiO3 nanocrystals. Melamine was used as a reducing agent which would be carbonized under the N2 atmosphere. During thermal decomposition of melamine, reductive NH3 and C would generate in succession to reduce the SrTiO3 nanocrystals. The relative concentration ratio of bulk defects to surface defects in SrTiO3 nanocrystals would be tuned from 0.78 to 2.55 after reduction treatment. Furthermore, the band structures of surface and bulk defects in SrTiO3 were studied by DFT. The surface oxygen defects would make the band structure shift to a high energy level, while the bulk oxygen defects of SrTiO3 would restore the energy levels of the band structure. Thus, photocatalytic overall water splitting activity would improve significantly by rational relative concentration ratio of bulk defects to surface defects in SrTiO3.

Hierarchically nanostructured Ag/ZnO/nBC for VOC photocatalytic degradation: Dynamic adsorption and enhanced charge transfer

The adsorption-photodegradation strategy can achieve continuous enrichment and efficient oxidation of volatile organic compounds (VOCs), but it requires a trade-off among adsorption, mass transfer, and charge transfer in this dynamic process. Therefore, the construction of an effective and stable catalytic system remains an immense challenge. Here, we report a strategy for constructing a hierarchically structured photocatalyst for efficiently degrading VOCs by assembling nanobiochar (nBC, ∼ 6.25 µm), the active center of ZnO (∼ 460 nm), and plasmonic-Ag nanoparticles (Ag NPs, ∼ 10 nm). Benefiting from its abundant surface functional groups (–OH, –CO, and –CO) and hierarchical structure-induced mesopores and macropores, VOCs can be quickly captured and dynamically diffused. Furthermore, Ag NPs build a charge transfer bridge and accumulate electrons to nBC from both the photogenerated electrons that are induced by ZnO and hot electrons from the local surface plasmon resonance (LSPR) effect of Ag NPs. Afterward, a desirable spatial separation of charge carriers and visible-light response can be achieved. Therefore, Ag/ZnO/nBC maximizes the reactive oxygen species (e.g., ·OH and ·O2−) and shows a 7.8 times higher degradation rate of formaldehyde than ZnO, and it also displays universality and stability with high photocatalytic efficiency. The photocatalytic performance was comprehensively determined based on the relative humidity, initial concentration, catalyst dose, and mass ratio of Ag NPs. This facile and universal strategy for architecting hierarchically structured photocatalysts provides an approach for enhancing photocatalytic performance for VOC degradation and environmental pollution treatment.

Enhanced contaminant retardation by novel modified calcium bentonite backfill in slurry trench cutoff walls

This study aimed at assessing containment properties of slurry wall backfill containing sodium hexametaphosphate (SHMP) modified calcium bentonite to contaminated groundwater. Free swell index and flexible-wall hydraulic conductivity (k) tests were conducted to investigate swelling and hydraulic performances of this novel backfill. The relative concentration (RC) and cumulative mass ratio (CMR) methods were adopted to assess transport parameters including hydrodynamic dispersion coefficient (D) and the retardation factor (Rd) of calcium ion (Ca2+) through the backfills. The results showed negligible to moderate decrease in the swell index of the modified bentonite and the modified backfill when exposed to 5 mM and 1 M calcium chloride (CaCl2) solution. Permeation with CaCl2 solutions increased the short-term k of the backfill by a factor of 0.9 to 1.1 as compared to the tap water permeation. The D values varied from 1.44 × 10–10 m2/s to 2.89 × 10–10 m2/s regardless of the CaCl2 concentration, whereas Rd was vulnerable to CaCl2 concentration. The CMR method yielded a higher coefficient of determination than the RC method, but it showed no particular advantage in evaluating the transport parameters. The SHMP-modification delayed the breakthrough time of Ca2+ by a factor of 15 to 199 in a model slurry trench wall.

Assessment of the State of Competition in the Tourist Market of Ukraine

The article evaluates the intensity of competition and the level of monopolization in the tourism market of Ukraine. It is noted that the most important feature of the tourist market of Ukraine is the intensity of competition – the struggle between tourist organizations for the most favorable conditions of production and sale in order to achieve better business results and business development. In such conditions, the assessment of the intensity of competition and the level of monopolization of the tourism market will allow companies to develop their pricing, product, sales and communication policies, to shape their strategy and tactics of behavior in the market. It is noted that among the indicators most often used to assess the intensity of competition in the industry: market concentration index, Rosenbluth index (Hall-Tydman), Herfindahl-Hirschman index and the relative concentration ratio. It is possible to assess the efficiency of a tourist enterprise, as well as to predict the prospects of its development with the help of a traditional tool – market share. It demonstrates the place of a travel company in the relevant market segment among competitors. It is proved that the information base for the analysis of competition in the market of tourist services of Ukraine is statistical and accounting of enterprises of various types for which tourism is the main, statistics of the Main Department of Statistics of Ukraine, State Agency for Tourism Development of Ukraine, State Statistics Service of Ukraine. The rating of tour operators of Ukraine by the number of served tourists was assessed. It is determined that the leaders in the tourist market and the largest share in the number of tourists served are tour operators “Join UP!”, Travel Company “Anex Tour”, “TEZ Tour”, “Coral Travel”. Indicators of intensity of competition in the tourist market of Ukraine for 2018-2019 are calculated. According to the indicators for assessing the intensity of competition in the market, it was noted that the market is non-monopolized, low-concentrated (moderately concentrated) and high-intensity competition. The results of the assessment of the intensity of competition can be used in the formation of competitive strategies of tour operators in Ukraine, in deciding on the entry of new enterprises in the industry or on the feasibility of continuing to operate effectively in existing firms. Keywords estimation, tourist market, competition, intensity, monopolization, indicators, index, coefficient.

Self-assembly of superstructures at all scales

Summary Controllable assembly of molecular and nanoscale building blocks into uniform superstructures up to bulk dimensions remains a key challenge in the next phase of nanotechnology development. Here, we report the self-assembly of superstructures at all scales by taking advantage of the partial miscibility of water and 1-butanol to generate transient aqueous emulsion droplets that can encapsulate the target materials and introduce them into template holes. Further diffusion of water into 1-butanol depletes the emulsion droplets, assembling the building blocks into one well-defined superstructure in each hole. Superstructuring of various types and shapes of nanoparticles, biomolecules, and inorganic compounds could be achieved without the need for surfactants and chemical modifications. The versatility, scalability, low-cost, and accurate positioning are crucial advantages for the future development of advanced precision manufacturing.

The economics of recycling rate: New insights from waste electrical and electronic equipment

This paper addresses the determinants of metal recycling rates. The literature on recycling flows is scarce and does not directly address the issue of achieving a high recycling rate. In addition, extant literature has not quantified the recycling rate response to metal prices. Therefore, this paper explores factors that affect the recycling rate of different metals embodied in computers. We examine the effects of metal price, metal concentration in products, relative concentration ratio (i.e., primary vs. secondary supply), and embodied metal value on the recycling rate. Although the results reveal a significant effect of metal price on the recycling rate, the marginal response is low across different models (ordinary least squares, generalized linear model, fractional response model with endogenous regressor, and left-censored Tobit). This effect is not surprising and is in line with extant literature on recycling flows. Unfortunately, for most unrecycled metals, achieving a minimum embodied value is unlikely, as it would require a median price increase by one or two order of magnitude. In addition, it seems that the recycling rate is more elastic to other technical factors, such as the metal concentration in products or the relative concentration ratio. While the findings suggest important public policy implications, more data and interdisciplinary research are required to support these preliminary results.

Effects of nutrient deficiency on the CH2I2, CH2ClI, and CH2BrI production in cultures of the temperate marine phytoplankton Bigelowiella natans

Volatile organic iodine compounds (VOICs) such as di-iodomethane (CH2I2) released from the ocean are important vectors of iodine in the atmosphere and play an important role in atmospheric chemistry. In temperate ocean waters, several studies observed or presumed CH2I2 production. Here, we investigated the ability of temperate marine phytoplankton to produce VOICs in a culture experiment. To evaluate the decrease of 13CH2I2 by photolysis and release during sampling, we also performed an incubation experiment involving the addition of 13CH2I2 to the f/2-Si medium. Axenic cultures of B. natans in f/2-Si medium showed no production of CH2I2, but axenic cultures of B. natans in phosphorus-deficient cultures and nitrogen-deficient cultures exhibited remarkable rates of CH2I2 production: 5.3–5.9 pmol (μg chlorophyll a)−1 d−1 and 0.8–1.3 pmol (μg chlorophyll a)−1 d−1, respectively. Similarly, the production of chloroiodomethane (CH2ClI) and bromoiodomethane (CH2BrI) was observed in phosphorus- or nitrogen-deficient cultures, but not in f/2-Si culture. Higher production rates of CH2I2, CH2ClI, and CH2BrI were observed during the early exponential phase of B. natans cultures. The relative concentration ratio of CH2I2, CH2ClI, and CH2BrI in the B. natans cultures were approximately 70:8:1 and 15:10:1 in the phosphorus-deficient and nitrogen-deficient cultures, respectively. Based on the results of the addition of 13CH2I2 in a culture experiment, we estimated that CH2I2 was decreased by approximately 8.6% due to photolysis and volatilization during the fifth and tenth day, during which time CH2I2 production was observed in B. natans cultures in f/2-Si with a half-concentration of phosphorus. These results suggested that a nutrient deficiency could induce the production of VOICs derived from temperate marine phytoplankton such as B. natans and that nutritional conditions are one of the important factors for the estimation of VOIC emissions from temperate open ocean.

Insights for optimum cation defects in photocatalysis: A case study of hematite nanostructures

The effect of defects on photoinduced electron–hole (e–h) separation is remaining unclear; especially the role of cation defects is poorly understood. In this work, a series of α−Fe2O3 nanostructures with tunable cation defects were synthesized and characterized with positron annihilation. We discover that increasing the relative concentration ratio of large size surface cation defects (LSCD) to smaller size bulk cation defects (SBCD) in α−Fe2O3 facilitates the improvement of separation efficiency for photogenerated e–h pairs. Both theory and experiment data demonstrate that when the relative concentration ratio of LSCD to SBCD increases, oxygen molecules are more likely adsorbed on the surface of the α−Fe2O3 nanostructure and are prone to transfer electron, thereby forming more reactive oxygen species (ROS). This work provides insight into finding the optimum cation defect that contributes to the photocatalytic process, and provides a new idea for designing high efficiency photocatalysts based on defect engineering.

Digital image-based quantification of chlorpyrifos in water samples using a lipase embedded paper based device

A paper-based device (PBD) for the detection of chlorpyrifos pesticide at field application was fabricated based on the principles of enzyme inhibition and image processing. Rhizopus niveus lipase, p-nitrophenol palmitate and Whatman No.1 paper were used as an enzyme, substrate and support matrix, respectively. The performance of functionalized PBD was tested for lateral flow assay reaction in pure water (negative control), artificial pesticide water (positive control) and selected fruits and vegetables wash water (test). The digital image of the PBD after the test was captured using an android smartphone and analyzed in MATLAB software. Different colour space models such as, grey, RGB, HSV and YCbCr were studied and the Cb coordinate was chosen for its higher linearity (R2 = 0.988) with pesticide concentration. Experimental variations such as paper length, relative concentration ratio of the substrate and enzyme were investigated to minimize the product cost and analysis time. The developed PBD showed a significant response over wide range of sample solution's pH and operational temperature. Further, a long-term storage stability was measured for developed PBD. The LOD and LOQ were found to be 0.065 mgL−1 and 0.198 mgL−1. The results obtained from newly developed image processing method showed 92.8% accuracy with microtiter plate assay. Higher MRL was determined in the wash water of cauliflower, grapes, coriander leaves, brinjal and bitter guard. Overall, the developed paper biosensor was precise, cost effective and most suitable for field applications.

Monodisperse Na0.39Y0.61F2.35:Ln3+ (Ln=Dy, Tb, Eu) and NaYF4 nano-/micromaterials: Controllable morphology, porous structure, tunable multicolor and energy transfer

In this paper, monodisperse and uniform Na0.39Y0.61F2.35 (denoted as NYF hereafter) and NaYF4 nano-/micromaterials were synthesized by trisodium citrate (labeled as Cit3-) assisted one-step hydrothermal method. Various morphologies and sizes could be easily modulated by changing the ratio of reactants under the alkaline conditions, including porous nanoparticles, microrods stacked by nanospheres, turtle shell-like and hexagonal microprisms. XRD, SEM, photoluminescence (PL) and nitrogen adsorption desorption were used to characterize the prepared samples. Additionally, by co-doping the Tb3+, Eu3+ and tri-doping Dy3+, Tb3+, Eu3+ ions into the NYF host and tuning their relative concentration ratio, multicolor tunable emissions were obtained. The energy transfer process from Tb3+ to Eu3+ was studied in co-doped and tri-doped systems and demonstrated to be an exchange interaction mechanism. These results show that the NYF porous nanomaterials may have potential applications in the field of luminescence.

Heterogeneity of material structure determines the stationary surface topography and friction

The character of surface roughness and the force of friction in the stationary state after a sufficiently long run-in process are of key importance for numerous applications, e.g. for friction between road and tire. In the present paper, we study theoretically and experimentally the asymptotic worn state of a bi-phasic material that is arbitrarily heterogeneous in the contact plane, but homogeneous in the direction of the surface normal. Under the assumption of Archard’s wear law in its local formulation, the asymptotic shape is found in the closed integral form. Given the surface profile, the coefficient of friction can be estimated, since the coefficient of friction is known to be strongly correlated with the mean square root value of the surface slope. The limiting surface profiles and the corresponding coefficient of friction are determined as functions of size, relative concentration and wear ratio of the phases. The results of numerical calculations are compared to and validated by experiments carried out on simplified model systems. The main conclusion is that the rms value of the surface slope is not influenced by the characteristic linear size of inclusions and depends solely on the relative concentration of phases, as well as the ratio of their wear coefficients.

Effects of Angular Dependency of Particulate Light Scattering Intensity on Determination of Samples with Bimodal Size Distributions Using Dynamic Light Scattering Methods.

The angular dependency of light scattering intensity from differently sized particles strongly influences the apparent particle size distribution, as determined by dynamic light scattering (DLS) methods. Manufactured nanomaterials have size distributions more or less; therefore, the effect of detecting the angular dependency of the apparent size distribution by DLS is crucial. Commercial DLS instruments typically have two different types of detector angular position. The first is a detector angled at 90°, and the other is a backscattering angle detector. We therefore investigated the coverage and angular dependency when determining the relative concentrations of nanoparticles in polystyrene latex samples with a bimodal size distribution, using DLS methods both experimentally and theoretically. We used five differently sized polystyrene latex particles (one was a 70-nm nanoparticle and the others were various submicron-sized particles) in a variety of mixtures (the ratio of the difference of particle sizes ranged from approximately 2 to 7) to investigate the coverage and angular dependency of the recognition of the relative concentration ratio. In the case of size difference of approximately a factor of 2 or 3 between the two mixed particles (one was fixed at 70 nm), for DLS measurements at light scattering detector angles ranging from 60° to 150°, the homodyne photon correlation functions were approximately straight lines for mixtures of two differently sized polystyrene latex particles. The straight homodyne photon correlation functions were caused by the relatively strong light scattering from larger submicron particles masking the weaker light scattering from the smaller nanoparticles. As a result, DLS analysis could not recognize the relative concentration of nanoparticles in the mixture. In contrast to these samples, for mixtures of two differently sized polystyrene latex particles (one was 70 nm in size) with a size difference of a factor of 5, the homodyne correlation functions displayed an obvious curve for angles larger than 120°. This curve reflected an appropriate relative concentration ratio for the two differently sized polystyrene latex particles. Furthermore, for a mixture of two differently sized particles (one was again 70 nm) with size differences of a factor of 7, the homodyne correlation functions showed a clearly curved shape for detector angles larger than 90°, and yielded appropriate relative concentration ratios for the two different sizes of polystyrene latex particles. These observations were supported by theoretical investigation using Mie theory and asymmetric flow field-flow fractionation measurements with a multi-angle light scattering detector. Our investigation is crucial for achieving some degree of concordance on the determination of the size distribution of particles using DLS methods in industrial and academic fields.

Effects of divalent anionic catalysts on cross-linking of cellulose with 1,2,3,4-butanetetracarboxylic acid

1,2,3,4-Butanetetracarboxylic acid (BTCA) can efficiently esterify cellulose with pyrophosphoric acid (PPA) as a catalyst to remove protons of reaction intermediates. However, valence and relative concentration ratio (RCR) of catalyst anions correlating to pH of finishing bath played a critical role in the reactions. Results here indicated that wrinkle recovery angle, tensile strength retention and ester absorbance of fabrics treated at pH of 2.8 showed higher values. It was a competing reaction for BTCA molecules to esterify or depolymerize cellulose. Importantly, divalent PPA anions were more efficient than monovalent ones in catalyzing the esterification between anhydrides and cellulose, which was confirmed by FTIR results and two-dimensional correlation spectroscopy analyses and by the RCRs of PPA anions and their changing rates versus pH. Furthermore, the higher catalytic efficiency of divalent anions was proved by the selected model catalysts. Meaningfully, the fabrics treated at pH≤3.2 presented good durability.