Influence of kindergarten principals' contingent rewards on teachers' creative teaching performance: Testing a moderated-mediated model.

BACKGROUND: Although research has increased the current understanding of creative teaching, evidence on the factors that influence this behavior and the underlying mechanisms remains limited. OBJECTIVE: This study, grounded in conservation of resources theory, proposed and empirically examined the relation between contingent reward leadership (CRL) among Chinese kindergarten principals and teachers' creative teaching performance (CTP). In addition, the study assessed the mediating effect of organizational innovation support (OIS), bureaucratic organizational culture (BOC), and innovative organizational culture (IOC), as well as the moderating effect of ideological psychological contracts (IPCs), to provide robust insights into how CRL can motivate kindergarten teachers' CTP. METHODS: A total of 518 kindergarten teachers aged 20-55 years participated in the study. Structural equation model analysis was conducted to examine the multiple mediating effects of OIS, BOC, and IOC, as well as the moderating effect of IPC in the relation between CRL and CTP. RESULTS: OIS served as a mediator in the relation between CRL and CTP. OIS and BOC played a chain mediating role in the relation between CRL and CTP. OIS and BOC played a chain mediating role in the relation between CRL and CTP. Additionally, IPC positively moderated the indirect relation of CRL on CTP via OIS. CONCLUSIONS: Kindergarten principals should pay attention to the positive impact of leadership style and organizational culture on teachers' innovative behavior. Moreover, prioritizing the improvement of IPCs would benefit the development of innovative behavior.

Transmission of sub-terahertz signals over a fiber-FSO-5†G NR hybrid system with an aggregate net bit rate of 227.912 Gb/s.

Transmission of sub-terahertz (sub-THz) signals over a fiber-free-space optical (FSO)-fifth-generation (5 G) new radio (NR) hybrid system is successfully realized. It is a promising system that utilizes multiple media of optical fiber, optical wireless, and 5 G NR wireless to achieve a 227.912-Gb/s record-high aggregate net bit rate. The system concurrently transmits a 59.813-Gb/s net bit rate in the 150-GHz sub-THz frequency, 74.766-Gb/s in the 250-GHz sub-THz frequency, and 93.333-Gb/s in the 325-GHz sub-THz frequency through the fiber-FSO-wireless convergence, including 25-km single-mode fiber, 100-m FSO, and 30-m/25-m/20-m sub-THz-wave transmissions. This system achieves sufficiently low bit error rates (< hard-decision forward error correction (FEC) threshold of 3.8 × 10-3 at 16 and 20 Gbaud symbol rates; < soft-decision FEC threshold of 2 × 10-2 at 28 Gbaud symbol rate) and clear and distinct constellation diagrams, meeting the demands of 5 G NR communications in the sub-THz band. The development of fiber-FSO-5 G NR hybrid system represents a substantial development in the field of advanced communications. It has the ability to enhance the way we communicate in the future.

Starch supplementation improves the reproductive performance of sows in different glucose tolerance status.

This study was to evaluate the effects of glucose tolerance status, maternal starch supplementation and soybean substitution in diets on the performance of dams and their offspring. Eighty-eight pregnant sows (Landrace × Large White) were selected from an initial total of 120 sows, based on blood glucose test values, and assigned to 4 experimental treatments in a 2 × 2 factorial design. The factors were glucose tolerance status (glucose intolerant [GIT] vs. normal glucose tolerant [NGT]) or dietary treatments (corn starch diet [CS] vs. soybean substitution diet [SS]). A higher area under the curve (AUC) for post-meal glucose was observed (P < 0.05) in the GIT group than in the NGT group on d 109 of gestation. The CS group had a lower value of homeostasis model assessment-insulin resistance than the SS group (P < 0.05) on d 109 of gestation. Corn starch supplementation for sows decreased the stillbirth rate (P < 0.05), regardless of the sows' glucose tolerance status. The villus height of the jejunum and the villus height to crypt depth ratio of the ileum were greater in normal birth weight piglets from the CS group than from the SS group (P < 0.01), and so was the activity of sucrase in the jejunum and ileum (P < 0.01). Compared with the SS group, the CS group showed a reduction in pre-weaning mortality rate, an increase in the number of high-birth-weight piglets, and a decrease in the number of low-birth-weight piglets (P < 0.05) under GIT status. In conclusion, sows fed CS decreased stillbirth rate and improved insulin resistance, as well as improving the intestinal morphology and digestive enzyme activities of their progeny, regardless of glucose tolerance status. Additionally, the CS group improved birth weight distribution and decreased pre-weaning mortality rate of piglets under GIT status.

Deciphering the effects of PYCR1 on cell function and its associated mechanism in hepatocellular carcinoma.

Overexpression of pyrroline-5-carboxylate reductase 1 (PYCR1) has been associated with the development of certain cancers; however, no studies have specifically examined the role of PYCR1 in hepatocellular carcinoma (HCC). Based on The Cancer Genome Atlas expression array and meta-analysis conducted using the Gene Expression Omnibus database, we determined that PYCR1 was upregulated in HCC compared to adjacent nontumor tissues (P < 0.05). These data were verified using quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry analysis. Additionally, patients with low PYCR1 expression showed a higher overall survival rate than patients with high PYCR1 expression. Furthermore, PYCR1 overexpression was associated with the female sex, higher levels of alpha-fetoprotein, advanced clinical stages (III and IV), and a younger age (< 45 years old). Silencing of PYCR1 inhibited cell proliferation, invasive migration, epithelial-mesenchymal transition, and metastatic properties in HCC in vitro and in vivo. Using RNA sequencing and bioinformatics tools for data-dependent network analysis, we found binary relationships among PYCR1 and its interacting proteins in defined pathway modules. These findings indicated that PYCR1 played a multifunctional role in coordinating a variety of biological pathways involved in cell communication, cell proliferation and growth, cell migration, a mitogen-activated protein kinase cascade, ion binding, etc. The structural characteristics of key pathway components and PYCR1-interacting proteins were evaluated by molecular docking, and hotspot analysis showed that better affinities between PYCR1 and its interacting molecules were associated with the presence of arginine in the binding site. Finally, a candidate regulatory microRNA, miR-2355-5p, for PYCR1 mRNA was discovered in HCC. Overall, our study suggests that PYCR1 plays a vital role in HCC pathogenesis and may potentially serve as a molecular target for HCC treatment.

Mucins and Tight Junctions are Severely Altered in Necrotizing Enterocolitis Neonates.

OBJECTIVE: This study investigates the expression levels of mucin 1 (MUC1), MUC2, occludin, and zonula occludens-1 (ZO-1) in necrotizing enterocolitis (NEC). STUDY DESIGN: Intestinal specimens of surgical patients suffering from NEC (the NEC group) and intestinal specimens of patients with congenital intestinal atresia (the control group) were collected. Immunohistochemical changes in MUC1, MUC2, occludin, and ZO-1 were compared between the two groups. RESULTS: Our study showed a significant decrease in the expression levels of MUC1 (p = 0.004), MUC2 (p = 0.001), occludin (p = 0.004), and ZO-1 (p = 0.013) in neonates suffering from NEC as compared with the control group. CONCLUSION: Mucins and tight junctions are severely altered in NEC neonates. This finding might provide clues for rupture of the intestinal barrier. Further research is needed to investigate the gene expression as well as the exact mechanisms behind these changes. This will help us better understand the role of the intestinal barrier in NEC. KEY POINTS: · Mucins and tight junctions are severely altered in NEC neonates.. · We first demonstrate that the expression levels of MUC1are obviously reduced in neonates suffering from NEC.. · Expression levels of MUC2, occludin, and ZO-1, are also significantly decreased in neonates suffering from NEC..

Predicting Long non-coding RNAs through feature ensemble learning.

BACKGROUND: Many transcripts have been generated due to the development of sequencing technologies, and lncRNA is an important type of transcript. Predicting lncRNAs from transcripts is a challenging and important task. Traditional experimental lncRNA prediction methods are time-consuming and labor-intensive. Efficient computational methods for lncRNA prediction are in demand. RESULTS: In this paper, we propose two lncRNA prediction methods based on feature ensemble learning strategies named LncPred-IEL and LncPred-ANEL. Specifically, we encode sequences into six different types of features including transcript-specified features and general sequence-derived features. Then we consider two feature ensemble strategies to utilize and integrate the information in different feature types, the iterative ensemble learning (IEL) and the attention network ensemble learning (ANEL). IEL employs a supervised iterative way to ensemble base predictors built on six different types of features. ANEL introduces an attention mechanism-based deep learning model to ensemble features by adaptively learning the weight of individual feature types. Experiments demonstrate that both LncPred-IEL and LncPred-ANEL can effectively separate lncRNAs and other transcripts in feature space. Moreover, comparison experiments demonstrate that LncPred-IEL and LncPred-ANEL outperform several state-of-the-art methods when evaluated by 5-fold cross-validation. Both methods have good performances in cross-species lncRNA prediction. CONCLUSIONS: LncPred-IEL and LncPred-ANEL are promising lncRNA prediction tools that can effectively utilize and integrate the information in different types of features.

Diagnostic and prognostic value of MCM3 and its interacting proteins in hepatocellular carcinoma.

Aberrant DNA replication is one of the driving forces behind oncogenesis. Furthermore, minichromosome maintenance complex component 3 (MCM3) serves an essential role in DNA replication. Therefore, in the present study, the diagnostic and prognostic value of MCM3 and its interacting proteins in hepatocellular carcinoma (HCC) were investigated. By utilizing The Cancer Genome Atlas (TCGA) database, global MCM3 mRNA levels were assessed in HCC and normal liver tissues. Its effects were further analyzed by reverse transcription-quantitative PCR (RT-qPCR), western blotting and immunohistochemistry in 78 paired HCC and adjacent tissues. Functional and pathway enrichment analyses were performed using the Search Tool for the Retrieval of Interacting Genes database. The expression levels of proteins that interact with MCM3 were also analyzed using the TCGA database and RT-qPCR. Finally, algorithms combining receiver operating characteristic (ROC) curves were constructed using binary logistic regression using the TCGA results. Increased MCM3 mRNA expression with high α-fetoprotein levels and advanced Edmondson-Steiner grade were found to be characteristic of HCC. Survival analysis revealed that high MCM3 expression was associated with poor outcomes in patients with HCC. In addition, MCM3 protein expression was associated with increased tumor invasion in HCC tissues. MCM3 and its interacting proteins were found to be primarily involved in DNA replication, cell cycle and a number of binding processes. Algorithms combining ROCs of MCM3 and its interacting proteins were found to have improved HCC diagnosis ability compared with MCM3 and other individual diagnostic markers. In conclusion, MCM3 appears to be a promising diagnostic biomarker for HCC. Additionally, the present study provides a basis for the multi-gene diagnosis of HCC using MCM3.

IVS8-5T Allele of CFTR is the Risk Factor in Chronic Pancreatitis, Especially in Idiopathic Chronic Pancreatitis.

BACKGROUND: Cystic fibrosis transmembrane conductance regulator IVS8-5T gene variation appears to be associated with a higher risk of chronic pancreatitis (CP); however, there is inconsistency between previous reported studies. Here, we performed a meta-analysis to investigate this relationship. MATERIALS AND METHODS: PubMed and WANFANG databases were searched for the case-control studies that contained Patients with CP with IVS8-5T variation. Odd ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relevance of IVS8-5T gene variation and CP. RESULTS: Analysis showed that the frequency of the 5T allele was significantly higher in CP subjects than that in control subjects (OR = 1.43, 95% CI: 1.13-1.81, I2 = 1.2%). Based on the subgroup analysis stratified by etiology, the 5T allele was associated with a higher risk of idiopathic chronic pancreatitis (ICP) (OR = 1.80, 95% CI: 1.18-2.76, I2 = 0.0%) and not alcoholic CP (OR = 2.14, 95% CI: 0.98-4.66, I2 = 0.0%). Further study indicated that the 5T allele was related to higher ICP prevalence in the European population (OR = 1.79, 95% CI: 1.06-3.03, I2 = 0.0%). In contrast, there was no significant difference between ICP subjects and healthy controls within the Asian population (OR = 1.84, 95% CI: 0.91-3.72, I2 = 38.0%). CONCLUSIONS: Cystic fibrosis transmembrane conductance regulator IVS8-5T is a risk factor in patients with CP. IVS8-5T variation may play a significant role in the occurrence of ICP, especially in the European population.

Evaluating the role of RAD52 and its interactors as novel potential molecular targets for hepatocellular carcinoma.

BACKGROUND: Radiation sensitive 52 (RAD52) is an important protein that mediates DNA repair in tumors. However, little is known about the impact of RAD52 on hepatocellular carcinoma (HCC). We investigated the expression of RAD52 and its values in HCC. Some proteins that might be coordinated with RAD52 in HCC were also analyzed. METHODS: Global RAD52 mRNA levels in HCC were assessed using The Cancer Genome Atlas (TCGA) database. RAD52 expression was analyzed in 70 HCC tissues and adjacent tissues by quantitative real-time PCR (qRT-PCR), Western blotting and immunohistochemistry. The effect of over-expressed RAD52 in Huh7 HCC cells was investigated. The String database was then used to perform enrichment and functional analysis of RAD52 and its interactome. Cytoscape software was used to create a protein-protein interaction network. Molecular interaction studies with RAD52 and its interactome were performed using the molecular docking tools in Hex8.0.0. Finally, these DNA repair proteins, which interact with RAD52, were also analyzed using the TCGA dataset and were detected by qRT-PCR. Based on the TCGA database, algorithms combining ROC between RAD52 and RAD52 interactors were used to diagnose HCC by binary logistic regression. RESULTS: In TCGA, upregulated RAD52 related to gender was obtained in HCC. The area under the receiver operating characteristic curve (AUC) of RAD52 was 0.704. The results of overall survival (OS) and recurrence-free survival (RFS) indicated no difference in the prognosis between patients with high and low RAD52 gene expression. We validated that RAD52 expression was increased at the mRNA and protein levels in Chinese HCC tissues compared with adjacent tissues. Higher RAD52 was associated with older age, without correlation with other clinicopathological factors. In vitro, over-expressed RAD52 significantly promoted the proliferation and migration of Huh7 cells. Furthermore, RAD52 interactors (radiation sensitive 51, RAD51; X-ray repair cross complementing 6, XRCC6; Cofilin, CFL1) were also increased in HCC and participated in some biological processes with RAD52. Protein structure analysis showed that RAD52-RAD51 had the firmest binding structure with the lowest E-total energy (- 1120.5 kcal/mol) among the RAD52-RAD51, RAD52-CFL1, and RAD52-XRCC6 complexes. An algorithm combining ROC between RAD52 and its interactome indicated a greater specificity and sensitivity for HCC screening. CONCLUSIONS: Overall, our study suggested that RAD52 plays a vital role in HCC pathogenesis and serves as a potential molecular target for HCC diagnosis and treatment. This study's findings regarding the multigene prediction and diagnosis of HCC are valuable.

Success rates of in vitro fertilization versus intracytoplasmic sperm injection in men with serum anti-sperm antibodies: a consecutive cohort study.

Antisperm antibodies (ASAs) are assumed to be a possible causative factor for male infertility, with ASAs detected in 5%-15% of infertile men but in only 1%-2% of fertile ones. It remains unclear whether ASAs have an adverse effect on the outcome of in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). This study investigated differences in the rates of fertilization, pregnancy, and live births associated with serum ASA-positive and ASA-negative men following IVF or ICSI. Five hundred and fifty-four consecutive infertile couples undergoing IVF (n = 399) or ICSI (n = 155) were included. The two-sample two-sided t-test and Chi-square or Fisher's exact test was used for statistical analysis. Lower rates of fertilization (41.7% vs 54.8%, P = 0.03), good embryos (18.9% vs 35.2%, P = 0.00), pregnancy (38.5% vs 59.4%, P = 0.00), and live births (25.8% vs 42.5%, P = 0.00) were observed in men of the IVF group with a positive serum ASA than in those with a negative ASA. ASA positivity/negativity correlated with pregnancy rates (P = 0.021, odds ratio [OR]: 0.630, 95% confidence interval [CI]: 0.425-0.932) and live birth rates (P = 0.010, OR: 1.409, 95% CI: 1.084-1.831) after controlling for the female serum follicle-stimulating hormone level and the couple's ages at IVF. Women coupled with ASA-positive men had lower live birth rates with IVF than with ICSI (25.8% and 47.4%, respectively; P = 0.07). Women coupled with ASA-positive men had lower rates of pregnancy and live births following IVF than those coupled with ASA-negative men but had a similar outcome with ICSI.

Human leukocyte antigen (HLA)-DRB1 allele polymorphisms and systemic sclerosis.

Objectives: Human leukocyteantigen (HLA) is the most important gene for immune system regulation. Although studies have evaluated the association between HLA-DRB1 allele polymorphisms and systemic sclerosis (SSc), their results are still controversial. We performed a meta-analysis to assess the association of HLA-DRB1 alleles with risk of SSc.Methods: Electronic database were systematically searched for articles, a total of 11 case-control studies including 3268 cases and 5548 controls were analyzed. Odds ratio (ORs) and 95% confidence intervals were used to assess the association of HLA-DRB1 alleles with SSc. The relationship between SSc-related autoantibodies and DRB1 alleles was also analyzed.Results: In the overall analysis, four alleles (DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04) increased the risk of SSc; however, five alleles (DRB1*07, DRB1*11:01, DRB1*13, DRB1*13:01, and DRB1*14) had the opposite effect. Analysis of subgroups by ethnicity indicate that DRB1*11:01 and DRB1*13:01 confer a protective effect in Caucasians, while DRB1*11:04 was associated with a higher risk of SSc. For Asian, DRB1*13:02 was found to be a protective factor. In addition, the frequency of DRB1*11:04 alleles was significantly increased in ATA+ SSc patients compared with ATA- SSc patients.Conclusion: DRB1*04:03, DRB1*08, DRB1*11, and DRB1*11:04 were associated with the risk of SSc. Additionally, DRB1*11 and DRB1*11:04 were association with ATAs.

Insulin-like factor-2 receptor rs9456497 G genotype overrepresents in males of average population and its correlation with cardiovascular risks.

OBJECTIVES: To look at the possible effect of IGF2R rs9456497 on cardiovascular risks in a long-lived population. METHODS: IGF-2R rs9456497 was genotyped by iMLDR for 496 long-lived Zhuang Chinese (90-107 y/o) and their offspring (n = 723, 60-75 y/o) and healthy controls (n = 611, 60-75 y/o). Association analyses were then conducted among genotypes and cardiovascular risks. RESULTS: The G genotype (GA/GG) was found to represent more frequently in males of general population. No significantly difference was detected among genotypes in each group except that G genotype tended to reduce the systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels in longevity group. However, after sex stratification, total cholesterol (TC) of each genotype in offspring males was elevated versus relevant genotype in longevity and control group; the triglyceride (TG), fasting plasma glucose (FPG) and BMI of each genotype in longevity group were lower while SBP and DBP were higher than that of the relevant genotype in offspring and controls. After stratified by lipid status, the frequency of G allele was markedly increased in the dyslipidemic subgroup in the combined population and controls. Linear regressive analyses showed that HDL was positively correlated to rs9456497 GA genotype while BMI was negatively correlated to AA genotype in offspring group, whereas TC and TG were reversely while BMI was positively associated with AA genotype in CG. CONCLUSIONS: IGF-2R rs9456497 G genotype correlates to detrimental cardiovascular risks in ordinary population which might partially interpret their less preservation of health as compared to long-lived cohort.

Association Between the Asp312Asn, Lys751Gln, and Arg156Arg Polymorphisms in XPD and the Risk of Prostate Cancer.

Prostate cancer is the most common solid cancer and genetic factors play important roles in its pathogenesis. XPD is one of the 8 core genes involved in the nucleotide excision repair pathway. The relationship between Asp312Asn, Lys751Gln, and Arg156Arg polymorphisms in XPD and prostate cancer risk is a controversial topic. Therefore, we conducted a meta-analysis to explore the relationship between these 3 polymorphisms and the risk of developing prostate cancer. We searched the electronic literature in PubMed and Google Scholar for all relevant studies (last updated January 1, 2017). The pooled odds ratios and 95% confidence intervals for the associations between the Asp312Asn, Lys751Gln, or Arg156Arg polymorphisms in XPD and prostate cancer risk were calculated. To evaluate the effects of specific study characteristics on the association of these 3 polymorphisms and prostate cancer risk, we performed subgroup analysis if 2 or more studies were available. After an extensive literature review, 7 publications regarding Asp312Asn genotype distribution with 8 case-controls, 9 publications regarding Lys751Gln genotype distribution with 10 case-controls, and 3 publications regarding Arg156Arg genotype distribution with 4 case-controls were selected. The results showed that Asp312Asn (odds ratio = 1.34, 95% confidence interval: 0.96-1.87, P = .000), Lys751Gln (odds ratio = 0.98, 95% confidence interval: 0.89-1.08, P = .986), and Arg156Arg (odds ratio = 1.05, 95% confidence interval: 0.91-1.22, P = .57) polymorphisms do not increase the risk of prostate cancer in the dominant model. Further, in the subgroup analysis by ethnicity, no relationships were observed between Lys751Gln and Arg156Arg polymorphisms and prostate cancer risk. However, stratified analysis by ethnicity revealed that Asp312Asn affects African (odds ratio = 1.57, 95% confidence interval: 1.06-2.33, P = .382) and Asian populations (odds ratio = 2.09, 95% confidence interval: 1.39-3.14, P = .396) in homozygote comparison. In conclusion, this meta-analysis suggests that there is no general association between the Asp312Asn, Lys751Gln, and Arg156Arg polymorphisms in XPD and prostate cancer susceptibility.

Association between F508 deletion in CFTR and chronic pancreatitis risk.

BACKGROUND: The cystic fibrosis transmembrane conductance regulator (CFTR) has been reported to influence individual susceptibility to chronic pancreatitis (CP), but the results of previous studies are controversial. AIMS: We performed a study to demonstrate the relationship between CFTR and CP. METHODS: We searched PubMed, Scopus, and Embase for studies of patients with CP. Seven studies from 1995 to 2016 were identified, and included 64,832 patients. Pooled prevalence and 95% confidence intervals (CIs) were calculated. RESULTS: F508 deletion in CFTR was significantly positively associated with CP risk in the overall analysis (odds ratio [OR]=3.20, 95% CI: 2.30-4.44, I2=31.7%). In subgroup analysis stratified by ethnicity, F508 deletion was significantly associated with CP risk in Indian populations, using a fixed effects model (ORs=5.45, 95% CI: 2.52-11.79, I2=0.0%), and in non-Indian populations, using a random effects model (ORs=3.59, 95% CI: 1.73-7.48, I2=60.9%). At the same time, we found that Indians with F508 deletion had much higher CP prevalence than non-Indians. Interestingly, F508 deletion was also associated with CP and idiopathic CP risk in subgroup analysis stratified by aeitiology, using the fixed effects model. CONCLUSIONS: Based on current evidence, F508 deletion is a risk factor for CP, and Indians with F508 deletion have much higher CP morbidity.

PARP-1 serves as a novel molecular marker for hepatocellular carcinoma in a Southern Chinese Zhuang population.

PARP-1 (poly(ADP-ribose) polymerase-1) plays an important role in tumorigenesis. Since its effects on different populations are varied, this study investigated the impact of PARP-1 on primary hepatocellular carcinoma in a Southern Chinese Zhuang population. We assessed the global PARP-1 messenger RNA expression in patients with hepatocellular carcinoma using The Cancer Genome Atlas dataset. Increased PARP-1 expression, related to alpha-fetoprotein level, was observed. The area under the receiver operating characteristic curve value was 0.833. Kaplan-Meier survival curves indicated that higher PARP-1 expression was not correlated with poorer overall survival and recurrence-free survival. In a Zhuang population, PARP-1 messenger RNA and protein levels were increased in the hepatocellular carcinoma tissue and its adjacent liver tissues as assessed by quantitative polymerase chain reaction, immunohistochemistry, and western blotting. Higher PARP-1 level was associated with a higher tumor stage (p < 0.05), without correlation with age, gender, smoking, drinking, tumor size, serum alpha-fetoprotein level, hepatitis B virus infection, metastasis, and invasion (p > 0.05). Further analysis suggested that H2AX, a PARP-1 protein interaction partner, was coordinated with PARP-1 in hepatocellular carcinoma tumorigenesis. Overall, some new characteristics of PARP-1 expression were noted in the Zhuang population. PARP-1 is a novel promising diagnostic marker for hepatocellular carcinoma in the Southern Chinese Zhuang population.

A novel strategy to assemble colloidal gold nanoparticles at the water-air interface by the vapor of formic acid.

We report a novel strategy on the controlled assembly of gold nanoparticles (NPs) at the air-water interface by designing a concentration gradient of electrolytes utilizing volatile weak acidic electrolytes. Films of close-packed Au NPs can be facilely obtained by exposing citrate-protected gold colloids to the vapor of formic acid for several hours in an airtight desiccator at room temperature. Both the higher interfacial concentration of formic acid and the buffer effect of citrate solution play the key roles in the assembly. They engender a gradient distribution of hydrogen ions such that to trigger the interfacial assembly of gold NPs while preventing the bulk colloid from aggregation and coagulation. Comparative investigations have also been performed either using other volatile electrolytes like weaker acetic acid and stronger hydrochloric acid or adding an electrolyte directly into the colloids. The as-prepared films of gold NPs can serve as good substrates for surface-enhanced Raman scattering (SERS). This strategy has also been applied to the assembly of some other NPs like colloidal Pt at the air-water interface.