Search All-EnPress Publisher LLC.

Jan 8, 2022

Preparation of MOF/Au composite nanoparticles and their SERS properties

Surface-enhanced Raman scattering (SERS) spectrum has the characteristics of fast-detection, high-sensitivity and low-requirements for sample pretreatment. It plays a more and more important role in the detection of organic pollutants. In this study, MIL-101 and Au nanoparticles were prepared by hydrothermal method and aqueous solution reduction method respectively, and MIL-101/Au composite nanoparticles were prepared by electrostatic interaction. The SERS properties of the composite substrate were optimized by adjusting the size of Au nanoparticles and the surface distribution density of MIL-101 nanoparticles. The detection limit of Rhodamine 6G (R6G) for the composite substrate with the optimal ratio was investigated, which was as low as 10^–11 M. It is proved that MIL-101/Au composite nanoparticles have high sensitivity to probe molecules. When they are applied to the detection of persistent organic pollutants, the detection limit for fluoranthene can reach 10^–9 M and for 3,3’,4,4’-tetrachlorobiphenyl (PCB-77) can reach 10^–5 M.

Abstract

Download PDF(1.27M)

XML

1

126

Dec 6, 2021

Benchmarking ride-hailing regulation in global cities using mixed-method approach and social practice theory

Ride-hailing or private hire has been around the globe for a decade now but even less in Asia. Singapore has had more than three revisions to its ride-hailing regulation in the six years since the arrival of the disruptive technology, the most for an Asian city. Often quoted in the list of cities with a commendable public transport policy, Singapore still manages to find a viable and significant position for ride-hailing. Singapore, to a large extent, has formulated a successful model based on current market parameters and, more importantly, an adaptive one that evolves constantly with the continually disruptive technology. But how does this compare to cities around the globe? Global cities have formulated different policy regulations for the sector, with each one of them enjoying varying degrees of success and failure. Utilizing a mixed-methods approach using qualitative and quantitative data, Singapore’s ride-hailing sector was benchmarked with chiefly nine global cities. The qualitative data was analyzed using the 3-element model of the social practice theory as an alternative to conventional behavioral studies, thereby eliminating bias on the commuters and rather shifting focus to the practice. The findings were validated by statistical analysis of quantitative data, namely, trip information from the ride-hailing sector in Singapore and driver earnings. The unique addition of the research to ride-hailing policy is the comprehension of the commonalities and patterns across industrial and technological disruption, practice and policy irrespective of sectoral variations thanks to the utilization of the social practice theory. The first-of-its-kind policy exercise in the sector can be repeated for any city, which is a direct testament to the simplicity and exhaustivity of the methodology, benefitting both operators and investors through equitable policy formulation.

Abstract

Download PDF(1.08M)

XML

4

65

Feb 10, 2021

A study of electrocatalytic ethanol oxidation of nanoporous PtSi alloy

In recent years, nanoporous alloys have presented the advantages of a large specific surface area, low density, and simple operation, and they have been widely used in the fields of catalysis, magnetism, and medicine. Nanoporous Pt-Si alloy was prepared by melt-spun and chemical dealloying, and was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscopy. Pt-Si alloys possess a three-dimensional bicontinuous structure and an average size of 5 nanometers. Compared with commercial Pt/C catalysts, nanoporous Pt-Si alloys exhibit excellent electrocatalytic activity and stability in ethanol-catalyzed oxidation reactions. It is taken into consideration to be a promising catalyst in direct ethanol fuel cells.

Abstract

Download PDF(1.22M)

XML

2

51

Aug 6, 2020

Study on the distribution pattern and influencing factors of shrinking cities in Northeast China based on the random forest model

Based on the population change data of 2005–2009, 2010–2014, 2015–2019 and 2005–2019, the shrinking cities in Northeast China are determined to analyze their spatial distribution pattern. And the influencing factors and effects of shrinking cities in Northeast China are explored by using multiple linear regression method and random forest regression method. The results show that: 1) In space, the shrinking cities in Northeast China are mainly distributed in the “land edge” areas represented by Changbai Mountain, Sanjiang Plain, Xiaoxing’an Mountain and Daxing’an Mountain. In terms of time, the contraction center shows an obvious trend of moving northward, while the opposite expansion center shows a trend of moving southward, and the shrinking cities gather further; 2) in the study of influencing factors, the results of multiple linear regression and random forest regression show that socio-economic factors play a major role in the formation of shrinking cities; 3) the precision of random forest regression is higher than that of multiple linear regression. The results show that per capita GDP has the greatest impact on the contraction intensity, followed by the unemployment rate, science and education expenses and the average wage of on-the-job workers. Among the four influencing factors, only the unemployment rate promotes the contraction, and the other three influencing factors inhibit the formation of shrinking cities to various degrees.

Abstract

Download PDF(1.81M)

XML

3

56

Jul 18, 2021

Template assisted nano-structured nickel for efficient methanol oxidation

Nanoporous nickel has been prepared by electrodeposition using non-ionic surfactant based liquid crystalline template under optimized processing conditions. Physicochemical properties of nanoporous nickel are systematically characterized through XRD, SEM and AFM analyses. Comparison of electrocatalytic activity of nanoporous nickel with smooth nickel was interrogated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) analyses. Distinctly enhanced electrocatalytic activity with improved surface poisoning resistance related to nanoporous nickel electrode towards methanol oxidation stems from unique nanoporous morphology. This nanoporous morphology with high surface to volume ratio is highly beneficial to promote active catalytic centers to offer readily accessible Pt catalytic sites for MOR, through facilitating mass and electron transports.

Abstract

Download PDF(1.33M)

XML

1

59

Jun 10, 2021

Basic residential neighborhood infrastructure financing in Nigeria urban cities: Community development associations (CDAs)-based approach

The study examined the community-based approach to finance basic public infrastructures in residential neighborhoods. The primary objectives of the study were to determine the condition of public infrastructures, the level of community engagement, the modalities of financing and the prominent influencing factors. The study adopted convenience sampling and questionnaire survey techniques. A total of 120 questionnaires were administered to residents of selected high-income communities (HICs) and low/medium-income communities (L/MICs), out of which 48 (80%) and 52 (86.67%) were retrieved, respectively, and analyzed. The study deployed descriptive statistics of mean and standard deviation models and mean weighted score to analyze the data. The study found that the residents were satisfied with the security of the neighborhoods but deplored the state of the public potable water infrastructure in both communities. However, the residents in the HICs enjoy a better condition of road infrastructure compared with L/MICs. The residents in both communities indicated a high level of involvement in the financing of public infrastructures, with major engagement in security and waste disposal/management infrastructures. However, the HICs engaged more in road grading/maintenance, while the provision of community potable water was given as a priority by the L/MICs. The major mode of financing basic communal infrastructures is through membership levy/contribution, and prominent influencing factors are cooperation among members, fundraising and income status. Therefore, while private-sector support funds, such as from the CDAs, help in cushioning the effects of basic infrastructure decay, governments at all levels should provide an enabling environment that will motivate mutual communal relationships through integrated infrastructure policies.

Abstract

Download PDF(1.20M)

XML

4