Dion-Jacobson Type Lead-Free Double Perovskite with Ultra-Narrow Aromatic Interlayer Spacing for Highly Sensitive and Stable X-ray Detection.

The low-toxic and environmentally friendly 2D lead-free perovskite has made significant progress in the exploration of "green" X-ray detectors. However, the gap in detection performance between them and their lead-based analogues remains a matter of concern that cannot be ignored. To reduce this gap, shortening the interlayer spacing to accelerate the migration and collection of X-ray carriers is a promising strategy. Herein, a Dion-Jacobson (DJ) lead-free double perovskite (4-AP)2AgBiBr8 (1, 4-AP = 4-amidinopyridine) with an ultra-narrow interlayer spacing of 3.0 Å, is constructed by utilizing π-conjugated aromatic spacers. Strikingly, the subsequent enhanced carrier transport and increased crystal density lead to X-ray detectors based on bulk single crystals of 1 with a high sensitivity of 1117.3 µC Gy-1 cm-2, superior to the vast majority of similar double perovskites. In particular, the tight connection of the inorganic layers by the divalent cations enhances structural rigidity and stability, further endowing 1 detector with ultralow dark current drift (3.06 × 10-8 nA cm-1 s-1 V-1, 80 V), excellent multiple cycles switching X-ray irradiation stability, as well as long-term environmental stability (maintains over 94% photoresponse after 90 days). This work brings lead-free double perovskites one step closer to realizing efficient practical green applications.

Chemical and Structural Engineering of Gelatin-Based Delivery Systems for Therapeutic Applications: A Review.

As a biodegradable and biocompatible protein derived from collagen, gelatin has been extensively exploited as a fundamental component of biological scaffolds and drug delivery systems for precise medicine. The easily engineered gelatin holds great promise in formulating various delivery systems to protect and enhance the efficacy of drugs for improving the safety and effectiveness of numerous pharmaceuticals. The remarkable biocompatibility and adjustable mechanical properties of gelatin permit the construction of active 3D scaffolds to accelerate the regeneration of injured tissues and organs. In this Review, we delve into diverse strategies for fabricating and functionalizing gelatin-based structures, which are applicable to gene and drug delivery as well as tissue engineering. We emphasized the advantages of various gelatin derivatives, including methacryloyl gelatin, polyethylene glycol-modified gelatin, thiolated gelatin, and alendronate-modified gelatin. These derivatives exhibit excellent physicochemical and biological properties, allowing the fabrication of tailor-made structures for biomedical applications. Additionally, we explored the latest developments in the modulation of their physicochemical properties by combining additive materials and manufacturing platforms, outlining the design of multifunctional gelatin-based micro-, nano-, and macrostructures. While discussing the current limitations, we also addressed the challenges that need to be overcome for clinical translation, including high manufacturing costs, limited application scenarios, and potential immunogenicity. This Review provides insight into how the structural and chemical engineering of gelatin can be leveraged to pave the way for significant advancements in biomedical applications and the improvement of patient outcomes.

Psychometric properties of anxiety sensitivity Index-3 among Chinese college students and its preliminary application among this population experiencing campus lockdown.

PURPOSE: Anxiety sensitivity (AS) refers to fear of anxiety-related sensory arousal and has been revealed to be associated with increased psychological distress and mental problems. Although Anxiety Sensitivity Index-3 (ASI-3) has been confirmed to be effective in evaluating this construct, whether it is consistently applicable in college students is still elusive. The present study aimed to examine the psychometric properties and measurement invariance of Chinese version of ASI-3 (C-ASI-3) among college students experiencing campus lockdown due to novel coronavirus disease 2019 (COVID-19) pandemic. METHODS: A total of 1532 Chinese college students (397, 25.9% males) aged between 16 and 25 were included in this study. Confirmatory factor analysis (CFA) was used to verify the factor structure of C-ASI-3. Multi-group CFA was conducted for analysis of measurement invariance with regard to gender. McDonald's omega values were computed for examination of scale reliability. For criterion, convergent, and divergent validity, average variance extracted (AVE) values for C-ASI-3 subscales, difference between square root of AVE for each factor and inter-factor correlation, as well as pearson correlation and partial correlation between the C-ASI-3 and other three scales, including the Depression, Anxiety, and Stress Scale-21 (DASS-21), the State-Trait Anxiety Inventory (STAI), and the Fear of COVID-19 scale (FCV-19 S) were evaluated. RESULTS: The C-ASI-3 presented a three-factor scale structure with fit indices being as follows: χ2/df = 11.590, CFI = 0.938, RMSEA = 0.083, SRMR = 0.042. Strict measurement invariance was reached across gender. Regarding convergent validity, the C-ASI-3 had a high correlation with the DASS-21 (r = 0.597, p < 0.01) and the STAI (r = 0.504, p < 0.01). All AVE values for C-ASI-3 subscales were above 0.5. In terms of divergent validity, the C-ASI-3 had medium correlation with the FCV-19 S (r = 0.360, p < 0.01). Square of root of AVE for each factor was higher that inter-factor correlation. McDonald's omega values of the three dimensions ranged from 0.898 ~ 0.958. CONCLUSION: The C-ASI-3 has acceptable psychometric properties among college students. College students with different gender have consistent understanding on the scale construct.

Effluent quality prediction of the sewage treatment based on a hybrid neural network model: Comparison and application.

The accurate prediction and assessment of effluent quality in wastewater treatment plants (WWTPs) are paramount for the efficacy of sewage treatment processes. Neural network models have exhibited promise in enhancing prediction accuracy by simulating and analyzing diverse influent parameters. In this study, a back propagation neural network hybrid model based on a tent chaotic map and sparrow search algorithm (Tent_BP_SSA) was developed to predict the effluent quality of sewage treatment processes. The prediction performance of the propose hybrid model was compared with traditional neural network models using five performance indicators (MAE, RMSE, SSE, MAPE and R2). Specifically, in comparison with the prior Tent_BP_SSA, Tent_BP_SSA2 demonstrated notable enhancements, with the R2 increasing from 0.9512 to 0.9672, while MAE, RMSE, SSE, and MAPE decreased by 9.62%, 18.84%, 24.80%, and 47.10%, respectively. These indicators collectively affirm that the utilization of higher-order input parameters ensures improved accuracy of the Tent_BP_SSA2 hybrid model in predicting effluent quality. Moreover, the Tent_BP_SSA2 model exhibited robust prediction ability (R2 of 0.9246) when applied to assess the effluent quality of an actual sewage treatment plant. The incorporation of integrated models comprising the sparrow search optimizing algorithm, tent chaotic mapping, and higher-order magnitude decomposition of input parameters has demonstrated the capacity to enhance the accuracy of effluent quality prediction. This study illuminates novel perspectives on the prediction of effluent quality and the assessment of effluent warnings in WWTPs.

Multi-axial Self-driven X-ray Detection by a Two-dimensional Biaxial Hybrid Organic-Inorganic Perovskite Ferroelectric.

Metal halide perovskite ferroelectrics combining spontaneous polarization and excellent semiconducting properties is an ideal platform for enabling self-driven X-ray detection, however, achievements to date have been only based on uniaxiality, which increases the complexity of device fabrication. Multi-axial ferroelectric materials have multiple equivalent polarization directions, making them potentially amenable to multi-axial self-driven X-ray detection, but the report on these types of materials is still a huge blank. Herein, a high-quality (BA)2(EA)2Pb3I10 (1) biaxial ferroelectric single crystal was successfully grown, which exhibited significant spontaneous polarization along the c-axis and b-axis. Under X-ray irradiation, bulk photovoltaic effect (BPVE) was exhibited along both the c-axis and b-axis, with open circuit voltages (Voc) of 0.23 V and 0.22 V, respectively. Then, the BPVE revealed along the inversion of polarized direction with the polarized electric fields. Intriguingly, due to the BPVE of 1, 1 achieved multi-axial self-driven X-ray detection for the first time (c-axis and b-axis) with relatively high sensitivities and ultralow detection limits (17.2 nGyair s-1 and 19.4 nGyair s-1, respectively). This work provides a reference for the subsequent use of multi-axial ferroelectricity for multi-axial self-driven optoelectronic detection.

Dion-Jacobson to Alternating-Cations-Interaction Reconstruction toward Narrow Bandgap 2D Aromatic Hybrid Perovskite.

The 2D aromatic Dion-Jacobson (DJ) hybrid perovskites combining advantages of high stability, enhanced light absorption, and favorable charge transport, are regarded as a kind of very promising materials for high-performance optoelectronic applications. However, due to the rigidity and large size of the aromatic ring, how to further reduce the interlayer distance to achieve better carrier transport and wider light response window still remain extremely challenging. Here, an interesting DJ-to-ACI (alternating-cations-interaction) reconstruction in 2D aromatic perovskite is first realized by inserting MA+ cations into (4-AP)PbI4 (1, 4-AP = 4-amidinopyridinium), successfully constructing an unprecedented ACI perovskite of (4-AP)(MA)2 Pb2 I8 (2, MA = methylamine). Remarkably, such a DJ-to-ACI reconstruction not only effectively reduces the interlayer spacing from 3.89 to 3.15 Å but also alleviates the structural distortion, which jointly causes a significant bandgap narrowing from 2.22 to 1.95 eV (smaller than all current 2D monolayered DJ perovskites), hence achieving a broad photodetection window over 660 nm. This work reports a novel narrow bandgap 2D ACI perovskite derived from the aromatic DJ motif, which sheds light on future regulations on the structure and properties of hybrid perovskites.

Noble Metal Nanoparticle Biosensors: From Fundamental Studies toward Point-of-Care Diagnostics.

Noble metal nanoparticles (NMNPs) have become firmly established as effective agents to detect various biomolecules with extremely high sensitivity. This ability stems from the collective oscillation of free electrons and extremely large electric field enhancement under exposure to light, leading to various light-matter interactions such as localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering. A remarkable feature of NMNPs is their customizability by mechanisms such as particle etching, growth, and aggregation/dispersion, yielding distinct color changes and excellent opportunities for colorimetric biosensing in user-friendly assays and devices. They are readily functionalized with a large variety of capping agents and biomolecules, with resultant bioconjugates often possessing excellent biocompatibility, which can be used to quantitatively detect analytes from physiological fluids. Furthermore, they can possess excellent catalytic properties that can achieve significant signal amplification through mechanisms such as the catalytic transformation of colorless substrates to colored reporters. The various excellent attributes of NMNP biosensors have put them in the spotlight for developing high-performance in vitro diagnostic (IVD) devices that are particularly well-suited to mitigate the societal threat that infectious diseases pose. This threat continues to dominate the global health care landscape, claiming millions of lives annually. NMNP IVDs possess the potential to sensitively detect infections even at very early stages with affordable and field-deployable devices, which will be key to strengthening infectious disease management. This has been the major focal point of current research, with a view to new avenues for early multiplexed detection of infectious diseases with portable devices such as smartphones, especially in resource-limited settings.In this Account, we provide an overview of our original inspiration and efforts in NMNP-based assay development, together with some more sophisticated IVD assays by ourselves and many others. Our work in the area has led to our recent efforts in developing IVDs for high-profile infectious diseases, including Ebola and HIV. We emphasize that integration with digital platforms represents an opportunity to establish and efficiently manage widespread testing, tracking, epidemiological intelligence, and data sharing backed by community participation. We highlight how digital technologies can address the limitations of conventional diagnostic technologies at the point of care (POC) and how they may be used to abate and contain the spread of infectious diseases. Finally, we focus on more recent integrations of noble metal nanoparticles with Raman spectroscopy for accurate, noninvasive POC diagnostics with improved sensitivity and specificity.

Accuracy and modification of the STOP-bang questionnaire for screening patients with obstructive sleep apnea in China.

Despite the high sensitivity of the STOP-Bang questionnaire [snoring, tiredness, observed apneas, high blood pressure, body mass index, age, neck size, gender] questionnaire (SBQ), which is widely used to screen individuals at high risk of obstructive sleep apnea (OSA), few studies have evaluated the discrimination related to sex in the SBQ. Therefore, our study aimed to assess whether SBQ performance is gender-related and modified by changing body mass index (BMI) and neck circumference (NC) cut-off values. A total of 470 patients attended the sleep centres. They were divided into moderate-to-severe OSA and non-moderate-to-severe OSA groups based on the apnea-hypopnea index (AHI) and the results of the SBQ screening. The predictive performance of the SBQ screening instrument was evaluated by 2 × 2 contingency tables and discriminatory ability, which was estimated from the area under the curve (AUC) obtained from receiver operating characteristic curve. Our results suggest that when screening for moderate-to-severe OSA, the original SBQ has higher sensitivity and lower specificity for men; however, women have higher specificity and lower sensitivity. The SBQ achieved the maximum AUC of 0.783 for men and 0.634 for women when the BMI cut-off value was established at 30 kg/m2 and the NC cut-off value was established at 38 cm in men, and the BMI cut-off value was established at 25 kg/m2 and the NC cut-off value at 36 cm in women. Balancing the optimal sensitivity and specificity, the cut-off value of the optimal modified SBQ total scores for men was determined to be ≥4 and ≥3 for women.

Modeling and optimizing of an actual municipal sewage plant: A comparison of diverse multi-objective optimization methods.

The activated sludge process of an actual municipal sewage treatment plant was systematically modeled, calibrated, and verified in this study. Identified multi-objective optimization (MOO) methods were employed to optimize the process parameters of the validated model, and the optimal MOO algorithm was obtained by comparing Pareto solution sets. The optimization model consisted of three key evaluation indicators (objective functions), which are the average effluent quality (AEQ), overall cost index (OCI), and total volume (TV) of the biochemical tank, along with 12 more process parameters (decision variables). Three optimization algorithms, i.e., adaptive non-dominated sorting genetic algorithm III (ANSGA-III), non-dominated sorting genetic algorithm II (NSGA-II), and particle swarm algorithm (PSO), were adopted using MATLAB. The comparison of these algorithms demonstrated that the ANSGA-III algorithm had better Pareto solution sets under the triple objective optimization, and the effluent quality of COD, TN, NH4+-N, and TP after optimization decreased by 2.22, 0.47, 0.13, and 0.02 mg/L, respectively. Additionally, the simulated AEQ was reduced by 13% compared to the original effluent, and the OCI and TV decreased from 21,023 kWh d-1 and 17,065 m3 to 20,226 kWh d-1 and 16,530 m3, respectively. The reported ANSGA-III algorithm and the proposed multi-objective method have a promising ability for energy conservation, emission reduction, and upgrading of municipal sewage treatment plants.

Psychometric evaluation of the Chinese version of social anxiety scale for social media users and cross-sectional investigation into this disorder among college students.

BACKGROUND: Recent years have seen an increased incidence of social anxiety due to increasing intensive use of social media, especially among young adults. OBJECTIVE: The present study aimed to translate the original English version of Social Anxiety Scale for Social Media Users (SAS-SMU) into Chinese, examine its applicability among Chinese College students via reliability and validity indexes, and investigate the influencing factors contributing to SAS-SMU. METHODS: A cross-sectional study was conducted among a cohort of 1307 Chinese college students, 486 males and 821 females, aged 20.75 ± 3.13 years old. The original version of SAS-SMU was translated into Chinese using the backward and forward translation procedure. An exploratory factor analysis (EFA) and a confirmatory factor (CFA) analysis were used for construction of underlying factor structure. Criterion-related validity was assessed using Interaction anxiousness scale (IAS) and the "extraversion" domain of Eysenck Personality Short Scale (EPQ-R-S). Cronbach's alpha coefficient was computed for evaluation of internal consistency. A multivariate stepwise linear regression analysis was conducted for determining the potential correlates of SMU-related social anxiety. RESULTS: The final Chinese version of SAS-SMU had 21 items. Item analysis, exploratory factor, EFA, and CFA jointly supported a three-factor structure of the translated version, defined as social recognition anxiety, interaction anxiety, and privacy concern anxiety, respectively. The three-factor structure of this scale showed configural, metric, scalar measurement invariance across gender. Cronbach's alpha coefficient of the scale and its three subscales were 0.96, 0.93, 0.94, and 0.91, respectively. The mean SAS-SMU overall score for each college student was 51.63 ± 16.32, with 21.64 ± 7.24 (recognition anxiety), 17.10 ± 6.30 (interaction anxiety), 12.90 ± 4.61 (privacy concern anxiety) for each subscale, respectively. IAS score, mobile phone addiction index (MPAI) score, EPQ-E score, time spent on social media per week, relationship with parents, childhood life status, whether being an only child, and cyber bullying experience can explain 51.1% of the variance of SMU related social anxiety. CONCLUSION: Based on the data, the Chinese version of SAS-SMU has shown to be satisfactory in psychometric properties. Subjects prone to interaction anxiousness, addictive smartphone use, extraversion personality trait, bad relationship with parents, unfortunate childhood life, only-child status, and having cyberbullying experience tend to have a higher level of SMU related social anxiety.

Self-management behavior, associated factors and its relationship with social support and health literacy in patients with obstructive sleep apnea-hypopnea syndrome.

BACKGROUND: The proportion of patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) is increasing year by year in China, which has become a major public health problem. Self-management of OSAHS and multiple support from caregivers are key to low hospital admissions and high quality of life for patients with OSAHS. Social support and health literacy are the main promoters of self-management behavior. However, their contributions have not been adequately studied. The purpose of this study is to investigate the level of self-management among patients with OSAHS and its relationship with general demographics, social support, and health literacy. METHODS: A total of 280 patients with OSAHS treated in two Classiii Grade A hospitals in Jinzhou City, Liaoning Province from October 2020 to July 2021 were selected as the study subjects. Patients were investigated by General Characteristics Questionnaire, Social Support Rating Scale (SSRS), Health Literacy Scale for Chronic Patients (HLSCP), and OSAHS Self-management Behavior Questionnaire, and the influencing factors of self-management of patients with OSAHS were analyzed. RESULTS: The average score of OSAHS self-management was 74.49(SD = 8.06), SSRS and HLSCP scores were positively correlated with total scores of self-management behavior. Furthermore, we found that disease duration, SSRS, and HLSCP scores were the main predictors of self-management behavior (R2 = 0.390, P < 0.001). CONCLUSION: This study found that OSAHS patients with a longer duration of disease and higher SSRS or HLSCP scores also had higher levels of self-management. The factors discussed in this study may be helpful in developing individualized interventions in self-management for patients with OSAHS.

Stability, aggregation, and sedimentation behaviors of typical nano metal oxide particles in aqueous environment.

The wide use of nano metal oxide particles (NMOPs) brings about their inevitable release into the water environment, affecting the environment and human health. Therefore, the stability, aggregation, and sedimentation process of four typical NMOPs (ZnO NPs, CeO2 NPs, TiO2 NPs, and CuO NPs) were investigated in artificial water and real municipal sewage to reveal their complicated behavior. Results showed that NMOPs aggregated at the pH of zero-charge point, and their hydrodynamic diameters and aggregation rates could reach the maximum values. The hydrodynamic diameters and aggregation rates of ZnO NPs, CeO2 NPs, TiO2 NPs, and CuO NPs at the zero-charge point were 617, 1760, 870, 1502 nm, and 31.7, 1158.1, 48.3, 115.7 nm/min, respectively. In addition, the dissolution of NMOPs led to the sedimentation rates under acidic conditions being much lower than those under neutral and alkaline conditions. The aggregation and sedimentation performance of NMOPs were affected by not only pH but also ionic strength (IS) and species. The aggregation rates of NMOPs increased with the increase of IS (0-10 mM), and the maximum aggregation rate of CeO2 NPs was 470.1 nm/min (pH = 7 and CaCl2 = 10 mM). According to Coulomb's law, divalent cations (Mg2+, Ca2+) were more competitively adsorbed on the surface of NMOPs than monovalent cations (K+, Na+), which increased the zeta potential and aggregation rate of NMOPs. Furthermore, the NMOPs were easier to aggregate in municipal sewage because of the homogeneous aggregation between nanoparticles and heterogeneous aggregation with natural colloids. The total interaction energy between NMOPs was calculated by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical formula, which was consistent with the experimental results.

Mechanistic Investigation of Enhanced Photoreactivity of Dissolved Organic Matter after Chlorination.

Chlorine is commonly used in disinfection processes in wastewater treatment plants prior to discharge of the effluents into receiving waters. Effluent organic matter and humic substances constitute up to 90% of dissolved organic matter (DOM) in receiving water, which induces photogeneration of reactive species (RS) such as excited triplet state of DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radical (•OH). The RS plays an important role in the attenuation of trace pollutants. However, the effect of chlorine disinfection on the photoreactivity of the DOM has remained unclear. Here, we investigated the physicochemical properties and subsequent RS variation after chlorination of DOM. Solid-state 13C cross-polarization/magic angle-spinning NMR and Fourier transform ion cyclotron resonance mass spectrometry verified that the aromaticity, electron-donating capacity (EDC), and average molecular weight of DOM decreased markedly after chlorination. It was found for the first time that the photoproduction of 3DOM*, 1O2, and •OH increased markedly after chlorination of DOM upon irradiation of simulated sunlight. The quantum yields of 3DOM*, 1O2, and •OH were positively correlated with E2/E3 (ratio of the absorbance at 254 to 365 nm) while negatively correlated with EDC before and after chlorination. These findings highlight the synergetic effect of chlorine disinfection on the photosensitization of DOM under irradiation of sunlight, which will promote the removal of trace pollutants in surface waters.

Interactions between cerium dioxide nanoparticles and humic acid: Influence of light intensities and molecular weight fractions.

Cerium dioxide nanoparticles (CeO2 NPs) are ubiquitous in the water environment due to the extensive commercial applications. The complexity of heterogeneous humic acid (HA) plays a significant role in affecting the physicochemical properties of CeO2 NPs in aqueous environments. However, the effects of light intensities and HA fractions on the interaction mechanism between CeO2 NPs and HA are poorly understood. Here, we provided the evidence that both light intensities (>3 E L-1 s-1) and molecular weights (>10 kDa) can effectively affect the interactions between CeO2 NPs and HA. The absolute content of reactive oxygen species (ROS) and quantum yield (Φ) of 3HA* were inhibited when HA (10 mg of C L-1) interacts with CeO2 NPs. However, they were positively correlated with the increasing irradiation time and simulated sunlight intensities. High molecular weights of HA fraction (>100 kDa) restrained the ROS generation and Φ of 3HA* due to surface adsorption between HA and CeO2 NPs blocking reactive sites, competitive absorption for simulated sunlight. Fourier transform infrared and three-dimensional excitation-emission matrix fluorescence spectroscopy confirmed that the carboxylic groups of HA have high complexation capacity with CeO2 NPs. These findings are essential for us to improve the understanding of the impacts of HA on CeO2 NPs under different conditions in natural waters.

Nitrous oxide emission during denitrifying phosphorus removal process: A review on the mechanisms and influencing factors.

Excessive emissions of nitrogen (N) and phosphorus (P) pollutants are leading to increased eutrophication of water bodies. Biological N and P removal processes have become a research priority in the field of sewage treatment with the aim of improving sewage discharge standards in countries worldwide. Denitrifying P removal processes are more efficient for solving problems related to carbon source competition, sludge age conflict, and high aeration energy consumption compared to traditional biological N and P removal processes, but they are easy to produce nitrous oxide (N2O) in the process of sewage treatment. N2O is a greenhouse gas with a global warming potential approximately 190-270 times that of CO2 and 4-21 times that of CH4, which was produced and released into the environmental in denitrifying P removal systems under conditions of a low C/N ratio, high dissolved oxygen, and low activity of denitrifying phosphorus accumulating organisms (DPAOs). This paper reviews the emission characteristics and influencing factors of N2O during denitrifying P removal processes and proposes appropriate strategies for controlling the emission of N2O. This work serves as a basis for the development of new sewage treatment processes and the reduction of greenhouse gas emissions in future wastewater treatment plants.

Aggregation behavior of zinc oxide nanoparticles and their biotoxicity to Daphnia magna: Influence of humic acid and sodium alginate.

The widespread applications of zinc oxide nanoparticles (ZnO NPs) have raised increasing concerns due to their adverse environmental effects. The ubiquitous natural organic matter in natural aqueous environments can interact with ZnO NPs, thereby affecting their aggregation, sedimentation and biotoxicity. Here, we systematically investigated the effects of humic acid (HA) and sodium alginate (SA) on the aggregation behavior of ZnO NPs and their biotoxicity to Daphnia magna. High concentrations (9.0 mg/L) of HA and SA accelerated the aggregation of ZnO NPs with maximum aggregation rates (ΔD/Δt) of 22.1 and 19.2 nm/min, respectively. Both HA and SA led to 31.2% and 30.1% decrease of ZnO NPs concentration compared with the control experiment. The results calculated by Derjaguin-Landau-Verwey-Overbeek theoretical formula were consistent with these of aggregation and sedimentation of ZnO NPs. Furthermore, excitation-emission-matrix fluorescence spectroscopy verified that the carboxylic groups of HA and SA have high complexation capacity with ZnO NPs. Daphnia magna was used to evaluate the biotoxicity of ZnO NPs, and the toxicity of ZnO NPs to Daphnia magna was alleviated as the HA concentration increased from 0 to 1.2 mg/L. Toxicity mitigation experiments confirmed that photocatalytic generation of reactive oxygen species was more toxic to Daphnia magna than dissolved Zn2+ in acute and chronic toxicity tests. Moreover, the attacks of active oxygen free radical damaged the antioxidant system of Daphnia magna. The information obtained will help us to improve the understanding of the impacts of ZnO NPs on freshwater ecosystems.

Roles of pH, cation valence, and ionic strength in the stability and aggregation behavior of zinc oxide nanoparticles.

The effects of pH, cation valence, and ionic strength (IS) on the stability and aggregation behavior of zinc oxide nanoparticles (ZnO NPs) were investigated in this study. Results showed that ZnO NPs were most prone to aggregation at the isoelectric point (pH = 8.7), with an aggregation rate (ΔD/Δt) of 30.1. ZnO NPs showed a greater propensity for dissolution at lower pH (pH < 7), and Zn2+ was more rapidly released into the aqueous phase in acidic solutions than neutral or alkaline conditions. The C/C0 of ZnO NPs was about 21.56% and remained stable in acidic solution of pH 4.0. Additionally, slow sedimentation with a C/C0 ratio of 95.0% was observed due to an increase in repulsive interactions between nanoparticles under pH = 10. The effect of cations on the ΔD/Δt of ZnO NPs decreased in strength as follows: Ca2+ > Mg2+ > K+ > Na+. High-valence metal cations (Ca2+, Mg2+) were more competitively adsorbed onto the surface of ZnO NPs with a hydrogen atom due to Coulomb's law, increasing the zeta potential and stabilizing the suspension of ZnO NPs at IS < 10 mM. Furthermore, compression of the electric double layer (EDL) became stronger than electrostatic adsorption with increasing IS, reaching a maximum ΔD/Δt of 23.3 (Ca2+, pH = 7, IS = 1 M). The C/C0 ratio of ZnO NPs decreased from 100% to 56.5% (Na+), 52.2% (K+), 45.2% (Mg2+), and 40.1% (Ca2+) at pH = 7 and an IS of 0.5 M. In addition to the cation valence, the hydration forces and ionic radii of the metal cations might be other factors that affected the interactions of metal cations with ZnO NPs. Finally, the total interaction energy between ZnO NPs was calculated using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical formula, and the calculated results were in agreement with the experimental outcomes under various aquatic environmental conditions.

Performance and adsorption mechanism of a magnetic calcium silicate hydrate composite for phosphate removal and recovery.

A novel magnetic calcium silicate hydrate composite (Fe3O4@CSH) was proposed for phosphorus (P) removal and recovery from a synthetic phosphate solution, facilitated by a magnetic separation technique. The Fe3O4@CSH material was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), zeta-potential and magnetic curves. The chemical composition and structure of Fe3O4@CSH and the successful surface loading of hydroxyl functional groups were confirmed. Phosphate adsorption kinetics, isotherm, and thermodynamic experiments showed that adsorption reaches equilibrium at 24 h, with a maximum adsorption capacity of 55.84 mg P/g under optimized experimental conditions. Adsorption kinetics fitted well to the pseudo second-order model, and equilibrium data fit the Freundlich isotherm model. Thermodynamic analysis provided a positive value for ΔH° (129.84 KJ/mol) and confirmed that phosphate adsorption on these materials is endothermic. The P-laden Fe3O4@CSH materials could be rapidly separated from aqueous solution by a magnetic separation technique within 1 min. A removal rate of more than 60% was still obtained after eight adsorption/desorption cycles, demonstrating the excellent reusability of the particles. The results demonstrated that the Fe3O4@CSH materials had high P-adsorption efficiency and were reusable.

Preparation and application of modified zeolites as adsorbents in wastewater treatment.

Natural zeolite has been recognized as a useful adsorbent for wastewater treatment for removing cations. Natural zeolite is a kind of porous material with large specific surface area but limited adsorption capacity. In recent years, emphasis has been given to prepare the surface modified zeolite using various procedures to enhance the potential of zeolite for pollutants. Modification treatment for zeolite can greatly change surface chemistry and pore structure. The article describes various modification methods of zeolite, and introduces the removal mechanisms of common pollutants such as ammonium, phosphorus and heavy metals. In addition, this review paper intends to present feasibility of applying modified zeolite to constructed wetlands which will be beneficial to achieve higher removal effect.

Self-Assembly and External Modulation of a Flexible Porphyrin Derivative on Highly Oriented Pyrolytic Graphite.

With the aid of scanning tunneling microscopy, we have examined the two-dimensional hydrogen-bonded networks of carboxyl-functionalized porphyrin derivative H2TCPp molecules at the heptanoic acid/HOPG interface. Moreover, we have successfully modulated the self-assembly structure of H2TCPp by introducing 1,2-di(4-pyridyl)ethylene molecules into the assembled system. By performing density functional theory calculations, we also revealed the formation mechanisms of the different assemblies and the modulation process. Comparing the self-assembly structures at the liquid/solid interface with those in bulk crystals, we have obtained deep insight into the differences in H2TCPp assemblies between 2D and 3D networks. Furthermore, this research is expected to deepen our understanding of on-surface phenomena and to provide a feasible process toward 2D assembly regulation.