Impact of large scale, multicomponent intervention to reduce proton pump inhibitor overuse in integrated healthcare system: difference-in-difference study.

OBJECTIVE: To determine how a large scale, multicomponent, pharmacy based intervention to reduce proton pump inhibitor (PPI) overuse affected prescribing patterns, healthcare utilization, and clinical outcomes. DESIGN: Difference-in-difference study. SETTING: US Veterans Affairs Healthcare System, in which one regional network implemented the overuse intervention and all 17 others served as controls. PARTICIPANTS: All individuals receiving primary care from 2009 to 2019. INTERVENTION: Limits on PPI refills for patients without a documented indication for long term use, voiding of PPI prescriptions not recently filled, facilitated electronic prescribing of H2 receptor antagonists, and education for patients and clinicians. MAIN OUTCOME MEASURES: The primary outcome was the percentage of patients who filled a PPI prescription per 6 months. Secondary outcomes included percentage of days PPI gastroprotection was prescribed in patients at high risk for upper gastrointestinal bleeding, percentage of patients who filled either a PPI or H2 receptor antagonist prescription, hospital admission for acid peptic disease in older adults appropriate for PPI gastroprotection, primary care visits for an upper gastrointestinal diagnosis, upper endoscopies, and PPI associated clinical conditions. RESULTS: The number of patients analyzed per interval ranged from 192 607 to 250 349 in intervention sites and from 3 775 953 to 4 360 868 in control sites, with 26% of patients receiving PPIs before the intervention. The intervention was associated with an absolute reduction of 7.3% (95% confidence interval -7.6% to -7.0%) in patients who filled PPI prescriptions, an absolute reduction of 11.3% (-12.0% to -10.5%) in PPI use among patients appropriate for gastroprotection, and an absolute reduction of 5.72% (-6.08% to -5.36%) in patients who filled a PPI or H2 receptor antagonist prescription. No increases were seen in primary care visits for upper gastrointestinal diagnoses, upper endoscopies, or hospital admissions for acid peptic disease in older patients appropriate for gastroprotection. No clinically significant changes were seen in any PPI associated clinical conditions. CONCLUSIONS: The multicomponent intervention was associated with reduced PPI use overall but also in patients appropriate for gastroprotection, with minimal evidence of either clinical benefits or harms.

Intravenous dantrolene in hypermetabolic syndromes: a survey of the U.S. Veterans Health Administration database.

BACKGROUND: Intravenous dantrolene is often prescribed for hypermetabolic syndromes other than the approved indication of malignant hyperthermia (MH). To clarify the extent of and indications for dantrolene use in conditions other than MH, we sought to document current practices in the frequency, diagnoses, clinical characteristics and outcomes associated with dantrolene treatment in critical care settings. METHODS: Inpatients receiving intravenous dantrolene from October 1, 2004 to September 30, 2014 were identified retrospectively in the U.S. Veterans Health Administration national database. Extracted data included; diagnoses of hypermetabolic syndromes; triggering drugs; dantrolene dosages; demographics; vital signs; laboratory values; in-hospital mortality; complications; and lengths of stay. Frequency and mortality of patients who did not receive dantrolene were obtained in selected diagnoses for exploratory comparisons. RESULTS: Dantrolene was administered to 304 inpatients. The most frequent diagnoses associated with dantrolene treatment were neuroleptic malignant syndrome (NMS; N = 108, 35.53%) and sepsis (N = 47, 15.46%), with MH accounting for only 13 (4.28%) cases. Over half the patients had psychiatric comorbidities and received psychotropic drugs before dantrolene treatment. Common clinical findings in patients receiving dantrolene included elevated temperature (mean ± SD; 38.7 ± 1.3 °C), pulse (116.33 ± 22.80/bpm), respirations (27.75 ± 9.58/min), creatine kinase levels (2,859.37 ± 6,646.88 IU/L) and low pO2 (74.93 ± 40.16 mmHg). Respiratory, renal or cardiac failure were common complications. Mortality rates in-hospital were 24.01% overall, 7.69% in MH, 20.37% in NMS and 42.55% in sepsis, compared with mortality rates in larger and possibly less severe groups of unmatched patients with MH (5.26%), NMS (6.66%), or sepsis (41.91%) who did not receive dantrolene. CONCLUSIONS: In over 95% of cases, dantrolene administration was associated with diagnoses other than MH in critically-ill patients with hypermetabolic symptoms and medical and psychiatric comorbidities. Exploratory survey data suggested that the efficacy and safety of dantrolene in preventing mortality in hypermetabolic syndromes other than MH remain uncertain. However, randomized and controlled studies using standardized criteria between groups matched for severity are essential to guide practice in using dantrolene.

Correlates of the Abnormal Involuntary Movement Scale in Veterans With Tardive Dyskinesia.

PURPOSE/BACKGROUND: To add to limited evidence on the Abnormal Involuntary Movement Scale (AIMS) as a measure of tardive dyskinesia (TD) in clinical practice settings, the characteristics and correlates of AIMS scores were assessed. METHODS/PROCEDURES: Veterans with schizophrenia/schizoaffective, bipolar, or major depressive disorders receiving antipsychotics and at least 1 AIMS score during October 1, 2014, to September 30, 2015, were identified. Tardive dyskinesia was determined by the International Classification of Diseases, Ninth Revision, Clinical Modification, codes. Correlates of AIMS scores were examined using χ or t tests. Odds ratios and ß parameters with 95% confidence intervals for categorical and continuous variables associated with AIMS scores were derived from a multivariate logistic and linear regression, respectively. FINDINGS/RESULTS: Among 7985 veterans receiving antipsychotics, only 4706 (58.9%) had at least 1 AIMS examination. Of these, 229 (4.9%) were diagnosed with possible TD. The mean total AIMS scores and AIMS awareness/incapacitation scores were significantly higher for patients with TD (both P < 0.0001). Comparing diagnostic threshold criteria of AIMS ratings, only 17.5% to 37.1% of veterans with TD were successfully identified. Among TD patients, 21.4% had a total score of moderate-severe and 15.3% had ratings of at least mild movements in 2 or more body regions. In the regression analyses, being older, African-American, having schizophrenia/schizoaffective disorder, and receiving antipsychotics or benztropine significantly increased the severity of AIMS scores. Higher AIMS scores were not predictive of outcomes other than marital status in socioeconomic or healthcare domains. IMPLICATIONS/CONCLUSIONS: Although the AIMS is essential for TD research, its value in clinical practice without training and oversight remains unclear. Efforts to adapt screening procedures to clinical needs may be worthwhile.

Suicidal ideation and behaviors among women veterans with recent exposure to intimate partner violence.

OBJECTIVE: Women veterans have disproportionately high risk for both suicide and intimate partner violence compared to women non-veterans. The objective of this study was to assess the relationship between intimate partner violence (IPV) and suicidal ideation and suicidal or self-harm behaviors among women veterans. METHOD: Veterans Health Administration (VHA) electronic medical records were extracted for 8427 women veterans who completed screening for past-year IPV between April 2014 and 2016. Risk for suicidal ideation and self-harm behaviors were estimated as function of screening results using logistic regression. RESULTS: Overall, 8.4% screened positive for IPV. Suicidal ideation or self-harm behaviors were recorded for 3.2%. Positive IPV screen was associated with double the odds for suicidal ideation (AOR = 2.04; 95% CI = 1.47-2.86) and self-harm behaviors (AOR = 2.05, 95% CI = 1.10-3.83). Risks did not significantly differ by IPV type. Suicide-related ICD codes were most often recorded prior to IPV screening. CONCLUSIONS: There is a strong association between positive IPV screen and suicidal ideation and self-harm behaviors among VHA-engaged women veterans. Documentation of either event is an important marker for the other. Integration of suicide prevention with IPV services may enhance identification of women at risk and speed service uptake. Suicidal ideation and behaviors should be assessed among women with positive IPV screens, and identification of suicide risk should trigger IPV assessment.

Women's Healthcare Utilization Following Routine Screening for Past-Year Intimate Partner Violence in the Veterans Health Administration.

BACKGROUND: Experience of intimate partner violence (IPV) can have adverse health impacts and has been associated with elevated rates of healthcare service utilization. Healthcare encounters present opportunities to identify IPV-related concerns and connect patients with services. The Veterans Health Administration (VHA) conducts IPV screening within an integrated healthcare system. OBJECTIVE: The objectives of this study were to compare service utilization in the 6 months following IPV screening between those screening positive and negative for past-year IPV (IPV+, IPV-) and to examine the timing and types of healthcare services accessed among women screening IPV+. DESIGN: A retrospective chart review was conducted for 8888 female VHA patients across 13 VHA facilities who were screened for past-year IPV between April 2014 and April 2016. MAIN MEASURES: Demographic characteristics (age, race, ethnicity, marital status, veteran status), IPV screening response, and healthcare encounters (based on visit identification codes). KEY RESULTS: In the 6 months following routine screening for past-year IPV, patients screening IPV+ were more likely to utilize outpatient care (aOR = 1.85 [CI 1.26, 2.70]), including primary care or psychosocial care, and to have an inpatient stay (aOR = 2.09 [CI 1.23, 3.57]), compared with patients screening IPV-. Among those with any utilization, frequency of outpatient encounters within the 6-month period following screening was higher among those screening IPV+ compared with those screening IPV-. The majority of patients screening positive for past-year IPV returned for an outpatient visit within a brief time frame following the screening visit (> 70% within 14 days, >95% within 6 months). More than one in four patients screening IPV+ had an emergency department visit within the 6 months following screening. CONCLUSIONS: Women who screen positive for past-year IPV have high rates of return to outpatient visits following screening, presenting opportunities for follow-up support. Higher rates of emergency department utilization and inpatient stays among women screening IPV+ may indicate adverse health outcomes related to IPV experience.

Recent Intimate Partner Violence and Housing Instability Among Women Veterans.

INTRODUCTION: Women Veterans are at increased risk of both housing instability and intimate partner violence compared with their non-Veteran counterparts. The objectives of the present study were (1) to assess the relationship between women Veterans' experience of intimate partner violence and various indicators of housing instability, and (2) to assess what correlates help to explain experiences of housing instability among women Veterans who experienced past-year intimate partner violence. METHODS: Data were collected from U.S. Department of Veterans Affairs electronic medical records for 8,427 women Veterans who were screened for past-year intimate partner violence between April 2014 and April 2016 at 13 Veterans Affairs' facilities. Logistic regressions performed during 2017 assessed the relationship between past-year intimate partner violence and housing instability. RESULTS: A total of 8.4% of the sample screened positive for intimate partner violence and 11.3% for housing instability. Controlling for age and race, a positive intimate partner violence screen increased odds of housing instability by a factor of 3. Women Veterans with past-year intimate partner violence were more likely to have an indicator of housing instability if they identified as African American, had screened positive for military sexual trauma, or had a substance use disorder; receiving compensation for a disability incurred during military service and being married were protective. CONCLUSIONS: For women Veterans, intimate partner violence interventions should assess for both physical and psychological housing needs, and housing interventions should coordinate with intimate partner violence programs to address common barriers to resources.

Adoption, penetration, and effectiveness of a secondary risk screener for intimate partner violence: Evidence to inform screening practices in integrated care settings.

OBJECTIVE: Veterans Health Administration (VHA) has implemented screening for past-year intimate partner violence (IPV) in some healthcare facilities along with secondary screening of risk for severe violence among those screening positive in order to facilitate follow-up care for high-risk patients. We evaluated the adoption, penetration, and effectiveness of secondary screening as a tool to facilitate timely follow-up services. METHODS: Retrospective review of medical records (screening and healthcare use) of 774 women screening positive for past-year IPV (IPV+) at 11 facilities nationwide from April 2014-April 2016. Chi-square and t-tests examined factors related to secondary screening. RESULTS: Three of eleven (27.3%) facilities that implemented primary IPV screening adopted secondary screening. At adopting sites, 56.4% eligible (i.e., IPV+) women received secondary screening. Among 185 IPV+ women who completed secondary screening, 33.0% screened positive for severe IPV. Screening positive during secondary screening was associated with higher rate of psychosocial care within 60 days (73.8% vs. 54.0% of IPV+ patients screening negative; p < .05), posttraumatic stress disorder diagnosis (31.1% vs. 15.3%; p < .05), and being physically threatened or harmed (>50% vs. <15%; p < .001). CONCLUSIONS: Secondary risk assessment following IPV screening may expedite access to psychosocial follow-up care in integrated healthcare settings. However, program uptake needs to be enhanced.

Disproportionate Mental Health Burden Associated With Past-Year Intimate Partner Violence Among Women Receiving Care in the Veterans Health Administration.

Experience of intimate partner violence (IPV) can lead to mental health conditions, including anxiety, depression, and unhealthy substance use. Women seen in the Veterans Health Administration (VHA) face high rates of both IPV and mental health morbidity. This study aimed to identify associations between recent IPV experience and mental health diagnoses among women VHA patients. We examined medical records data for 8,888 female veteran and nonveteran VHA patients across 13 VHA facilities who were screened for past-year IPV between April, 2014 and April, 2016. Compared with women who screened negative for past-year IPV (IPV-), those who screened positive (IPV+; 8.7%) were more than twice as likely to have a mental health diagnosis, adjusted odds ratio (AOR) = 2.27, 95% confidence interval (CI) [1.95, 2.64]; or more than two mental health diagnoses, AOR = 2.29, 95% CI [1.93, 2.72]). Screening IPV+ was also associated with significantly higher odds of each type of mental health morbidity (AOR range = 1.85-3.19) except psychoses. Over half (53.5%) of the women who screened IPV+ had a mental health diagnosis, compared with fewer than one-third (32.6%) of those who screened IPV-. Each subtype of IPV (psychological, physical, and sexual violence) was significantly associated with having a mental health diagnosis (AOR range = 2.25-2.37) or comorbidity (AOR range = 2.17-2.78). Associations remained when adjusting for military sexual trauma and combat trauma among the veteran subsample. These findings highlight the mental health burden associated with past-year IPV among female VHA patients and underscore the need to address psychological and sexual IPV, in addition to physical violence.

Screening for Food Insecurity in Six Veterans Administration Clinics for the Homeless, June-December 2015.

OBJECTIVE: We assessed findings from a food-insecurity screening of a national sample of Veterans Administration clinics for homeless and formerly homeless veterans. METHODS: We reviewed results from initial screenings administered at 6 Veterans Administration primary care clinics for the homeless and responses from clinic staff members interviewed about the screening program. RESULTS: A total of 270 patients were screened. The average age was 53 years, and most were male (93.1%). Screening showed a high prevalence of food insecurity. Of the 270, 48.5% reported they experienced food insecurity in the previous 3 months, 55.0% reported averaging 2 meals a day, and 27.3% averaged 1 meal a day. Eighty-seven percent prepared their own meals, relying on food they bought (54.2%), help from friends and family (19.1%), and soup kitchens and food pantries (22%); 47.3% received Supplemental Nutrition Assistance Program benefits (food stamps). Additionally, of those who screened positive for food insecurity 19.8% had diabetes or prediabetes, and 43.5% reported hypoglycemia symptoms when without food. Clinic staff members responded positively to the screening program and described it as a good rapport builder with patients. CONCLUSIONS: Integrating screening for food insecurity among patients in clinical settings was well received by both patients and health care providers. Addressing these positive findings of food insecurity requires a multidisciplinary health care approach.

Services Receipt Following Veteran Outpatients' Positive Screen for Homelessness.

INTRODUCTION: The Veterans Health Administration seeks to reduce homelessness among Veterans by identifying, and providing prevention and supportive services to, patients with housing concerns. The objectives of this study were to assess the proportion of Veterans Health Administration patients who received homeless or social work services within 6 months of a positive screen for homelessness or risk in the Veterans Health Administration and the demographic and clinical characteristics that predicted services utilization. METHODS: Data were from a cohort of 27,403 Veteran outpatients who screened positive for homelessness or risk between November 1, 2012 and January 31, 2013. During 2013, AORs were calculated using a mixed-effects logistic regression to estimate the likelihood of patients' receipt of VHA homeless or social work services based on demographic and clinical characteristics. RESULTS: The majority of patients received services within 6 months post-screening; predictors of services utilization varied by gender. Among women, diagnosis of drug abuse and psychosis predicted receipt of services, being unmarried increased the odds of using services among those screening positive for homelessness, and a diagnosis of post-traumatic stress disorder increased the odds of receiving services for at-risk women. Among men, being younger, unmarried, not service-connected/Medicaid-eligible, and having a medical or behavioral health condition predicted receipt of services. CONCLUSIONS: Receipt of housing support services among Veterans post-homelessness screening differs by patient demographic and clinical characteristics. Future research should investigate the role that primary and secondary prevention interventions play in Veterans' resolution of risk for homelessness and experience of homelessness.

Screening for Homelessness in the Veterans Health Administration: Monitoring Housing Stability through Repeat Screening.

OBJECTIVE: This study examined veterans' responses to the Veterans Health Administration's (VHA's) universal screen for homelessness and risk of homelessness during the first 12 months of implementation. METHODS: We calculated the baseline annual frequency of homelessness and risk of homelessness among all veterans who completed an initial screen during the study period. We measured changes in housing status among veterans who initially screened positive and then completed a follow-up screen, assessed factors associated with such changes, and identified distinct risk profiles of veterans who completed a follow-up screen. RESULTS: More than 4 million veterans completed an initial screen; 1.8% (n=77,621) screened positive for homelessness or risk of homelessness. Of those who initially screened positive for either homelessness or risk of homelessness and who completed a second screen during the study period, 85.0% (n=15,060) resolved their housing instability prior to their second screen. Age, sex, race, VHA eligibility, and screening location were all associated with changes in housing stability. We identified four distinct risk profiles for veterans with ongoing housing instability. CONCLUSION: To address homelessness among veterans, efforts should include increased and targeted engagement of veterans experiencing persistent housing instability.

Comparative effectiveness of high-dose versus standard-dose influenza vaccination in community-dwelling veterans.

BACKGROUND: Influenza is a significant cause of morbidity and mortality in older adults. High-dose (HD) trivalent inactivated vaccine has increased immunogenicity in older adults compared with standard-dose (SD) vaccine. We assessed the relative effectiveness of HD influenza vaccination (vs SD influenza vaccination). METHODS: We conducted a retrospective cohort study among patients who receive primary care at Veteran Health Administration (VHA) medical centers, and who received influenza vaccine in the 2010-2011 influenza season. The primary outcome was hospitalization for influenza or pneumonia. We also conducted an analysis in subgroups defined by age. RESULTS: We evaluated 25 714 patients who received HD vaccine and 139 511 who received SD vaccine in 23 VHA medical centers. The rate of hospitalization for influenza or pneumonia was 0.3% in both groups in the influenza season. After accounting for patient characteristics in propensity-adjusted analyses, the risk of hospitalization for influenza or pneumonia was not significantly lower among patients receiving HD vaccine vs those receiving SD vaccine (risk ratio, 0.98; 95% confidence interval, .68-1.40). In the subgroup of patients ≥85 years of age, receiving HD (compared with SD) vaccine was associated with lower rates of hospitalization for influenza or pneumonia. CONCLUSIONS: HD vaccine was not found to be more effective than SD vaccine in protecting against hospitalization for influenza or pneumonia; however, we found a protective effect in the oldest subgroup of patients. Additional studies are needed to evaluate the effectiveness of HD vaccine.

Demographic characteristics associated with homelessness and risk among female and male veterans accessing VHA outpatient care.

BACKGROUND: This study explored demographic influences on veterans' reports of homelessness or imminent risk of homelessness with a particular focus on gender. METHODS: We analyzed data for a cohort of veterans who responded to the U.S. Department of Veterans Affairs (VA), Veterans Health Administration (VHA) universal screener for homelessness and risk during a 3-month period. Multinomial mixed effects models-stratified by gender-predicted veterans' reports of homelessness or risk based on age, race, marital status, and receipt of VA compensation. FINDINGS: The proportion of positive screens-homelessness or risk-was 2.7% for females and 1.7% for males. Women more likely to report being at risk of homelessness were aged 35 to 54 years, Black, and unmarried; those more likely to experience homelessness were Black and unmarried. Among male veterans, the greatest predictors of both homelessness and risk were Black race and unmarried status. Among both genders, receiving VA disability compensation was associated with lesser odds of being homeless or at risk. CONCLUSIONS: The findings describe the current population of veterans using VHA health care services who may benefit from homelessness prevention or intervention services, identify racial differences in housing stability, and distinguish subpopulations who may be in particular need of intervention. Interventions to address these needs are described.

Screening for homelessness among individuals initiating medication-assisted treatment for opioid use disorder in the Veterans Health Administration.

OBJECTIVE: To determine the prevalence of homelessness and risk for homelessness among veterans with opioid use disorder initiating treatment. SETTING: Addiction treatment programs operated by the US Department of Veterans Affairs (VA). PARTICIPANTS: All veterans initiating treatment with methadone or buprenorphine for opioid use disorder between October 1, 2013 and September 30, 2014 (n = 2,699) who were administered the VA's national homelessness screener. MAIN OUTCOME MEASURES: Self-reported homelessness or imminent risk of homelessness. RESULTS: The prevalence of homelessness was 10.2 percent and 5.3 percent were at risk for homelessness. Compared to male veterans, women veterans were less likely to report homelessness (8.9 percent vs 10.3 percent) but more likely to be at risk (11.8 percent vs 4.9 percent). By age group, veterans aged 18-34 and 45-54 years most frequently reported homelessness (12.0 and 11.7 percent, respectively) and veterans aged 45-54 and 55-64 years most frequently reported risk for homelessness (6.5 and 6.8 percent, respectively). CONCLUSIONS: The prevalence of homelessness in this population is approximately 10 times that of the general veteran population accessing care at VA. Screening identified a substantial number of veterans who could benefit from VA housing assistance and had not received it recently. Programs to address veteran homelessness should engage with veterans seeking addiction treatment. Integration of homelessness services into addiction treatment settings may, in turn, improve outcomes.

Catalytic hydrodechlorination of trichloroethylene in water with supported CMC-stabilized palladium nanoparticles.

In this work, we developed and tested a new class of supported Pd catalysts by immobilizing CMC (carboxymethyl cellulose) stabilized Pd nanoparticles onto alumina support. The alumina supported Pd nanoparticles were able to facilitate rapid and complete hydrodechlorination of TCE (trichloroethylene) without intermediate by-products detected. With a Pd mass loading of 0.33 wt% of the alumina mass, the observed pseudo first order reaction rate constant, k(obs), for the catalyst was increased from 28 to 109 L/min/g when CMC concentration was raised from 0.005 to 0.15 wt%. The activity increase was in accord with an increase of the Pd dispersion (measured via CO chemisorption) from 30.4% to 45.1%. Compared to the commercial alumina supported Pd, which has a lower Pd dispersion of 21%, our CMC-stabilized Pd nanoparticles offered more than 7 times greater activity. Pre-calcination treatment of the supported catalyst resulted in minor drop in activity, yet greatly reduced bleeding (<6%) of the Pd nanoparticles from the support during multiple cycles of applications. The presence of DOM (dissolved organic matter) at up to 10 mg/L as TOC had negligible effect on the catalytic activity. The alumina supported CMC-stabilized Pd nanoparticles may serve as a class of more effective catalysts for water treatment uses.

Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene.

Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsupported and supported (both calcined and uncalcined) Pd nanoparticle catalysts were characterized using transmission electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction, and Brunauer-Emmett-Teller surface area measurement and their catalytic activity toward the hydrodechlorination of trichloroethylene (TCE) in aqueous media was examined using homogeneous and heterogeneous catalyst systems, respectively. The unsupported Pd nanoparticles showed considerable activity toward the degradation of TCE, as demonstrated by the reaction kinetics. Although the supported Pd nanoparticle catalysts had a lower catalytic activity than the unsupported particles that were homogeneously dispersed in the aqueous solutions, the supported catalysts retained sufficient activity toward the degradation of TCE. In addition, the use of the hydrophilic Al(2)O(3) support material induced a mass transfer resistance to TCE that affected the initial hydrodechlorination rate. This paper demonstrates that supported Pd catalysts can be applied to the heterogeneous catalytic hydrodechlorination of TCE.

Characterization of gas-expanded liquid-deposited gold nanoparticle films on substrates of varying surface energy.

Dodecanethiol-stabilized gold nanoparticles (AuNPs) were deposited via a gas-expanded liquid (GXL) technique utilizing CO(2)-expanded hexane onto substrates of different surface energy. The different surface energies were achieved by coating silicon (100) substrates with various organic self-assembled monolayers (SAMs). Following the deposition of AuNP films, the films were characterized to determine the effect of substrate surface energy on nanoparticle film deposition and growth. Interestingly, the critical surface tension of a given substrate does not directly describe nanoparticle film morphology. However, the results in this study indicate a shift between layer-by-layer and island film growth based on the critical surface tension of the capping ligand. Additionally, the fraction of surface area covered by the AuNP film decreases as the oleophobic nature of the surfaces increases. On the basis of this information, the potential exists to engineer nanoparticle films with desired morphologies and characteristics.

Precise seed-mediated growth and size-controlled synthesis of palladium nanoparticles using a green chemistry approach.

In this paper, we present a "green" and size-controlled seed-mediated growth method by which differently sized palladium (Pd) nanoparticles, spanning from 3.4 to 7.6 nm, with an increment of 1.4 nm, were synthesized. Monodisperse Pd nanoparticles (ca. 3.4 nm, standard deviation = 0.7 nm) were first synthesized and stabilized in an aqueous solution at 95 degrees C using nontoxic ascorbic acid and sodium carboxymethyl cellulose (CMC) as reducing agent and capping agent, respectively. These Pd nanoparticles were subsequently employed as seeds on the surface of which fresh Pd (2+) ions were reduced by the weak reducing agent ascorbic acid. Optimal conditions were determined that favored the homogeneous and sequential accumulation of Pd atoms on the surface of the Pd seeds, rather than the formation of new nucleation sites in the bulk growth solution, thereby achieving atomic-level control over particle sizes. The adsorbed CMC molecules did not inhibit the addition of Pd atoms onto the seeds during the growth but provided stabilization of the Pd nanoparticles in aqueous solution after the growth. Potential mechanisms that underpin this seed-mediated growth process are provided and discussed. One advantage of this seed growth process is that it provides stoichiometric control over the size of the Pd nanoparticles by simply varying Pd(2+) added during the growth stage. Furthermore, the use of ecologically friendly reagents, such as water (solvent), CMC (capping agent), and ascorbic acid (reducing agent), in both the seed synthesis and subsequent seed-mediated growth provides both "green" and economic attributes to this process.

Polysugar-stabilized Pd nanoparticles exhibiting high catalytic activities for hydrodechlorination of environmentally deleterious trichloroethylene.

In this paper, we present a straightforward and environmentally friendly aqueous-phase synthesis of small Pd nanoparticles (approximately 2.4 nm under the best stabilization) by employing a "green", inexpensive, and biodegradable/biocompatible polysugar, sodium carboxymethylcellulose (CMC), as a capping agent. The Pd nanoparticles exhibited rather high catalytic activity (observed pseudo-first-order reaction kinetic rate constant, k(obs), is up to 828 L g(-1) min(-1)) for the hydrodechlorination of environmentally deleterious trichloroethene (TCE) in water. Fourier transform IR (FT-IR) spectra indicate that CMC molecules interact with the Pd nanoparticles via both carboxyl (-COO-) and hydroxyl (-OH) groups, thereby functioning to passivate the surface and suppress the growth of the Pd nanoparticles. Hydrodechlorination of TCE using differently sized CMC-capped Pd nanoparticles as catalyst was systematically investigated in this work. Both the catalytic activity (k(obs)) and the surface catalytic activity (turnover frequency, TOF) of these CMC-capped Pd nanoparticles for TCE degradation are highly size-dependent. This point was further verified by a comparison of the catalytic activities and surface catalytic activities of CMC-capped Pd nanoparticles with those of beta-D-glucose-capped Pd and neat Pd nanoparticles for TCE degradation.