Controlled Etching of Internal and External Structures of SiO₂ Nanoparticles Using Hydrogen Bond of Polyelectrolytes

Islam, Md. Shahinul,Choi, Won San,Lee, Ha-Jin American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.12

<P>We have demonstrated a novel strategy for the synthesis of mesoporous silica nanoparticles (MSNPs) using a surfactant-free method under ambient conditions. By the simple addition of an amine-based polymer (polyethylenimine; PEI) with a high molecular weight to a silica nanoparticle (SNP) solution, two types of MSNPs, including rambutan-like MSNPs (R-MSNPs) and hollow MSNPs (H-MSNPs), were produced. The structural changes of the MSNPs were systematically studied using various reaction conditions (reaction time, molar ratio and molecular weight of PEI, etc.) and were observed using electron microscopic techniques. The formation mechanisms of both MSNPs were carefully investigated using XPS, Raman, and IR spectroscopies. Because the synthesized MSNPs are highly porous materials that contain internal organic/inorganic networks, we investigated the removal/adsorption properties of these MSNPs with respect to pollutants toward possible future use in environmental remediation applications. The H-MSNPs exhibited better environmental remediation capabilities relative to the R-MSNPs because PEI is present between the cobweb-like internal structures of the H-MSNPs, thereby providing a significant number of reaction sites for the adsorption of pollutants. The approach presented here can also be used as a direct method for the preparation of intraconnected networks within the substructures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-12/am501941c/production/images/medium/am-2014-01941c_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am501941c'>ACS Electronic Supporting Info</A></P>

Neuron-like polyelectrolyte–carbon nanotube composites for ultra-high loading of metal nanoparticles

Islam, Md. Shahinul,Choi, Won San,Bae, Tae Sung,Lee, Young Boo,Lee, Ha-Jin The Royal Society of Chemistry 2014 NEW JOURNAL OF CHEMISTRY Vol.38 No.10

<P>We report a simple protocol for the fabrication of multiwalled carbon nanotubes (MWCNTs) with a neuron-like structure for loading ultra-high densities of metal nanoparticles (NPs). The MWCNTs were initially coated with an anionic polyelectrolyte (PE), polystyrene sodium sulfonate (PSS), using a noncovalent interaction (CNT/PSS). The neuron-like structures were fabricated through the stepwise assembly of both the positively charged poly(allylamine) hydrochloride (PAH) and negatively charged poly(acrylic acid) (PAA) in a nonstoichiometric ratio on the CNT/PSS as a template. After three coatings with the PEs, the obtained neuron-shaped CNTs were used as a support for loading a high density of multi-metallic NPs. Moreover, a unique characteristic, tunable and side specific growth of the metal NPs, was also observed. Our neuron-like structures with high loadings of multi-metallic NPs were demonstrated to be catalytic materials for the conversion of 4-nitrophenol to 4-aminophenol and as convenient surface-enhanced Raman scattering substrates for biological tags and molecular detection.</P> <P>Graphic Abstract</P><P>We report a simple protocol for the fabrication of multiwalled carbon nanotubes (MWCNTs) with a neuron-like structure for loading ultra-high densities of metal nanoparticles (NPs). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4nj00638k'> </P>

Polyelectrolyte-mediated hierarchical mesoporous calcium silicates: a platform for drug delivery carrier with ultrahigh loading capacity and controlled release behavior

Islam, Md. Shahinul,Choi, Ha Neul,Choi, Won San,Lee, Ha-Jin The Royal Society of Chemistry 2015 Journal of Materials Chemistry B Vol.3 No.6

<P>We have developed a facile method for the poly(allylamine hydrochloride) (PAH)-assisted synthesis of mesoporous calcium silicate hydrates (PAH-CS) with a large specific surface area (BET = 348.4 m<SUP>2</SUP> g<SUP>−1</SUP>) and pore volume (<I>V</I>p = 1.42 cm<SUP>3</SUP> g<SUP>−1</SUP>). Tetraethyl orthosilicate (TEOS) was employed as a silicon source, which was rapidly hydrolyzed and reacted with the amine groups of PAH to form spherical SiO2 nanoparticles (PAH-Si). Subsequently, Ca<SUP>2+</SUP> ions reacted with the silicate anions produced during the dissolution of SiO2 in basic media, leading to the formation of the highly porous 3D networks of PAH-CS that were synthesized only under optimized reaction conditions. The PAH-CS containing an excess of Ca<SUP>2+</SUP> and NH3<SUP>+</SUP> enriched the surfaces with a very high cationic charge (<I>ζ</I> = +65.66 mV)and resulted in an extremely high loading capacity for anionic drugs and proteins. Ibuprofen (IBU) and FITC-labeled bovine albumin (FITC-Albumin) were chosen as a model drug and model protein, respectively, to test the loading and delivery efficiencies of the PAH-CS carriers. The ultrahigh drug loading capacities (DLC) and their release patterns were investigated under controlled pH conditions. Strikingly, the highest DLC reported to date (IBU or FITC-Albumin/carrier (3.35 g or 1 g g<SUP>−1</SUP>) was achieved in this work. The PAH-CS had no cytotoxic effect on osteoblast-like MC3T3-E1 cell lines evaluated by the LDH (Lactate dehydrogenase) assay in supernatant medium. Furthermore, the PAH-CS carriers could be entirely transformed to hydroxyapatite after releasing the drug in simulated body fluid (SBF), indicating good bioactivity and biodegradability of the PAH-CS carriers.</P>

Free-standing polymer nanoactuators, nanoshutters, and nanofilters

Islam, Md. Shahinul,Choi, Won San,Lee, Ha-Jin,Lee, Young Boo,Jeon, Il Cheol The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.17

<P>Our study demonstrates a facile approach for the synthesis of metal NP-embedded freestanding polyelectrolyte complexes (PECs) without sacrificial templates, which can be used as nanoactuators, nanoshutters, and nanofilters. The metal NP-PECs were prepared by mixing metal precursor-preadsorbed cation and anion PEs, using a nonstoichiometric ratio, followed by a controlled heat treatment. The metal NP-PECs showed reversible structural changes such as shrinking or swelling when they were exposed to various pH conditions. During the changes, they were also able to reversibly control the interparticle distance of the metal NPs embedded in the PECs, which has allowed the easy tuning of their catalytic and optical properties. By the reversible control of structural changes, the PECs can also be used as nanoshutters to reversibly control the flow of nanomaterials in the channels or pores. Furthermore, metal NP-embedded PECs, Au/Ag-PECs, were demonstrated to be useful as nanofilters for removing or transforming unwanted materials.</P> <P>Graphic Abstract</P><P>A facile approach for the synthesis of metal nanoparticle-embedded freestanding polyelectrolyte complexes, which can be used as nanoactuators, nanoshutters, and nanofilters, is demonstrated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm16179f'> </P>

Experimental Study on Strength Gaining Characteristics of Concrete using Portland Composite Cement

Md. Alhaz Uddin,Mohammed Jameel,Habibur Rahman Sobuz,Md. Shahinul Islam,Noor Md. Sadiqul Hasan 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.4

This study deals with experimental investigation of strength gaining characteristics of concrete made with Portland Composite Cement (PCC) and Ordinary Portland Cement (OPC). Compressive strength of concrete is often considered as a measure to determine the rate of strength gain of concrete with age and different cement composition. Strength developments of five concrete types have been investigated in terms of cement content and curing duration. Experimental observations on 495 specimens reveal that the early age strength of PCC concrete is lower than that of OPC concrete. Based on the test results, lack of proper pozzolanic reaction in the presence of fly ash in PCC concrete strength is lower at early age. The pozzolanic activity of fly ash also contributes to the strength gain at later stages of continuous curing. This study also concludes that drying ambient conditions reduce the strength potential of PCC concrete as the secondary (pozzolanic) reaction fails to contribute to the development of strength.

Biosensors on Array Chip by Dual-color Total Internal Reflection Fluorescence Microscopy

강성호,Md. Shahinul Islam 한국바이오칩학회 2009 BioChip Journal Vol.3 No.2

The noteworthy progress in biosensing technology during the last few decades has paved the way of the real-time detection, rapid screening, characterization and quantification of biological samples with supreme precision. Scientists in this distinct area have made it possible to enhance biochip-based biosensors using optical transducers. This review is meant to provide an overview of biosensors based on nanoarray biochips using polymer-modified glass surfaces and prism type dual-color total internal reflection fluorescence microscopy (TIRFM). It also endeavors to provide information on how the dual-color TIRFM system has made it possible to monitor theinteractions and to detect the colocalization of two different protein molecules (Alexa Fluor® 633 goat anti-rabbit IgG, anti-actin and Alexa Fluor® 488 conjugated actin) at the single-molecular level.

One-pot synthesis of layered double hydroxide hollow nanospheres with ultrafast removal efficiency for heavy metal ions and organic contaminants

Mubarak, Mahfuza,Jeon, Hyokyung,Islam, Md. Shahinul,Yoon, Cheolho,Bae, Jong-Seong,Hwang, Seong-Ju,Choi, Won San,Lee, Ha-Jin Elsevier 2018 CHEMOSPHERE - Vol.201 No.-

<P><B>Abstract</B></P> <P>Herein, Mg/Fe layered double hydroxide (MF-LDH) hollow nanospheres were successfully prepared by a one-step thermal method. After the thermal treatment of MF-LDH nanospheres at 400 °C, the MF-LDH was converted into the corresponding oxide, Mg/Fe layered double oxide (MF-LDO), which maintained the hollow nanosphere structure. The MF-LDO hollow nanospheres exhibited excellent adsorption efficiency for both As(V) and Cr(VI), showing 99% removal within 5 min and providing maximum removal capacities of 178.6 mg g<SUP>−1</SUP> [As(VI)] and 148.7 mg g<SUP>−1</SUP> [Cr(VI)]. Moreover, it met the maximum contaminant level requirements recommended by World Health Organization (WHO); 10 ppm for As(V) and 50 ppm for Cr(VI) in 10 and 20 min, respectively. Furthermore, Au nanoparticles were successfully introduced in the MF-LDO hollow nanospheres, and the products showed a conversion rate of 100% for the reduction of 4-nitrophenol into 4-aminophenol within 5 min. It is believed that these excellent and versatile abilities integrated with a facile synthetic strategy will facilitate the practical application of this material in cost-effective wastewater purification.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MF-LDH and MF-LDO hollow nanospheres were prepared by one-step thermal method. </LI> <LI> MF-LDH and MF-LDO showed ultrafast removal efficiency for As(V) and Cr(VI). </LI> <LI> MF-LDO purified contaminated water up to drinking water level within 20 min. </LI> <LI> Gold nanoparticles were successfully introduced into MF-LDO hollow nanosphere structure. </LI> <LI> Au-MF-LDO completely reduced 4-nitrophenol to 4-aminophenol within 5 min. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>