1
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Wang Q, Bao Y. Nanodelivery of natural isothiocyanates as a cancer therapeutic. Free Radic Biol Med 2021; 167:125-140. [PMID: 33711418 DOI: 10.1016/j.freeradbiomed.2021.02.044] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 01/31/2021] [Accepted: 02/26/2021] [Indexed: 12/18/2022]
Abstract
Natural isothiocyanates (ITCs) are phytochemicals abundant in cruciferous vegetables with the general structure, R-NCS. They are bioactive organosulfur compounds derived from the hydrolysis of glucosinolates by myrosinase. A significant number of isothiocyanates have been isolated from different plant sources that include broccoli, Brussels sprouts, cabbage, cauliflower, kale, mustard, wasabi, and watercress. Several ITCs have been demonstrated to possess significant pharmacological properties including: antioxidant, anti-inflammatory, anti-cancer and antimicrobial activities. Due to their chemopreventive effects on many types of cancer, ITCs have been regarded as a promising anti-cancer therapeutic agent without major toxicity concerns. However, their clinical application has been hindered by several factors including their low aqueous solubility, low bioavailability, instability as well as their hormetic effect. Moreover, the typical dietary uptake of ITCs consumed for promotion of good health may be far from their bioactive (or cytotoxic) dose necessary for cancer prevention and/or treatment. Nanotechnology is one of best options to attain enhanced efficacy and minimize hormetic effect for ITCs. Nanoformulation of ITCs leads to enhance stability of ITCs in plasma and emphasize on their chemopreventive effects. This review provides a summary of the potential bioactivities of ITCs, their mechanisms of action for the prevention and treatment of cancer, as well as the recent research progress in their nanodelivery strategies to enhance solubility, bioavailability, and anti-cancer efficacy.
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Affiliation(s)
- Qi Wang
- Norwich Medical School, University of East Anglia, Norwich NR4 7UQ, UK.
| | - Yongping Bao
- Norwich Medical School, University of East Anglia, Norwich NR4 7UQ, UK.
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2
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High Effective Preparation of Amorphous-Like Si Nanoparticles Using Spark Erosion Followed by Bead Milling. NANOMATERIALS 2021; 11:nano11030594. [PMID: 33673540 PMCID: PMC7997184 DOI: 10.3390/nano11030594] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/18/2021] [Accepted: 02/23/2021] [Indexed: 11/17/2022]
Abstract
This work aims to prepare the silicon nanoparticles with the nanocrystal-embedded amorphous structure through spark erosion followed by bead milling. Spark erosion breaks up monocrystal silicon ingots into micro/nanoparticles, refines the crystal grains, makes the crystals randomly disordered, and increases isotropic character. Bead milling further refines the crystal grains to a few nanometers and increases the amorphous portion in the structure, eventually forming an amorphous structure with the nanocrystals embedded. Spark erosion saves much time and energy for bead milling. The crystallite size and the amount of amorphous phase could be controlled through varying pulse durations of spark discharge and bead milling time. The final particles could contain the nanocrystals as small as 4 nm and the content of amorphous phase as high as 84% and could be considered as amorphous-like Si nanoparticles. This processing route for Si nanoparticles greatly reduced the production time and the energy consumption and, more importantly, is structure-controllable and scalable for mass production of the products with higher purity.
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Morozova S, Alikina M, Vinogradov A, Pagliaro M. Silicon Quantum Dots: Synthesis, Encapsulation, and Application in Light-Emitting Diodes. Front Chem 2020; 8:191. [PMID: 32318540 PMCID: PMC7154098 DOI: 10.3389/fchem.2020.00191] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 03/02/2020] [Indexed: 12/29/2022] Open
Abstract
Silicon quantum dots (SiQDs) are semiconductor Si nanoparticles ranging from 1 to 10 nm that hold great applicative potential as optoelectronic devices and fluorescent bio-marking agents due to their ability to fluoresce blue and red light. Their biocompatibility compared to conventional toxic Group II-VI and III-V metal-based quantum dots makes their practical utilization even more attractive to prevent environmental pollution and harm to living organisms. This work focuses on their possible use for light-emitting diode (LED) manufacturing. Summarizing the main achievements over the past few years concerning different Si quantum dot synthetic methods, LED formation and characteristics, and strategies for their stabilization by microencapsulation and modification of their surface by specific ligands, this work aims to provide guidance en route to the development of the first stable Si-based light-emitting diodes.
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Affiliation(s)
- Sofia Morozova
- Laboratory of Inkjet Printing of Functional Materials, SCAMT Institute, ITMO University, Saint-Petersburg, Russia
| | - Mariya Alikina
- Laboratory of Inkjet Printing of Functional Materials, SCAMT Institute, ITMO University, Saint-Petersburg, Russia
| | - Aleksandr Vinogradov
- Laboratory of Inkjet Printing of Functional Materials, SCAMT Institute, ITMO University, Saint-Petersburg, Russia
| | - Mario Pagliaro
- Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Palermo, Italy
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4
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Engineering of alkyl-terminated silicon nanoparticles for the selective filtration of copper ions. J IND ENG CHEM 2020. [DOI: 10.1016/j.jiec.2019.10.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Phatvej W, Datta HK, Wilkinson SC, Mutch E, Daly AK, Horrocks BR. Endocytosis and Lack of Cytotoxicity of Alkyl-Capped Silicon Quantum Dots Prepared from Porous Silicon. MATERIALS 2019; 12:ma12101702. [PMID: 31130663 PMCID: PMC6566257 DOI: 10.3390/ma12101702] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 05/17/2019] [Accepted: 05/19/2019] [Indexed: 12/16/2022]
Abstract
Freely-dissolved silicon quantum dots were prepared by thermal hydrosilation of 1-undecene at high-porosity porous silicon under reflux in toluene. This reaction produces a suspension of alkyl-capped silicon quantum dots (alkyl SiQDs) with bright orange luminescence, a core Si nanocrystal diameter of about 2.5 nm and a total particle diameter of about 5 nm. Previous work has shown that these particles are rapidly endocytosed by malignant cell lines and have little or no acute toxicity as judged by the standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for viability and the Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay for apoptosis. We have extended this work to the CACO-2 cell line, an established model for the human small intestinal mucosa, and demonstrate that neither acute nor chronic (14 days) toxicity is observed as judged by cell morphology, viability, ATP production, ROS production and DNA damage (single cell gel electrophoresis) at doses of 50–200 μg mL−1. Quantitative assessment of the extent of uptake of alkyl SiQDs by CACO-2, HeLa, HepG2, and Huh7 cell lines by flow cytometry showed a wide variation. The liver cell lines (HepG2 and Huh7) were the most active and HeLa and CACO-2 showed comparable activity. Previous work has reported a cholesterol-sensitivity of the endocytosis (HeLa), which suggests a caveolin-mediated pathway. However, gene expression analysis by quantitative real–time polymerase chain reaction (RT-PCR) indicates very low levels of caveolins 1 and 2 in HepG2 and much higher levels in HeLa. The data suggest that the mechanism of endocytosis of the alkyl SiQDs is cell-line dependent.
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Affiliation(s)
- Wipaporn Phatvej
- Thailand Institute of Scientific and Technological Research, Bangkok 10900, Thailand.
| | - Harish K Datta
- The James Cook University Hospital, Marton Road, Middlesbrough TS4 3BW, UK.
| | - Simon C Wilkinson
- Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle NE1 7RU, UK.
| | - Elaine Mutch
- Toxicology Unit, Medical School, Newcastle University, Newcastle NE1 7RU, UK.
| | - Ann K Daly
- Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle NE1 7RU, UK.
| | - Benjamin R Horrocks
- Chemical Nanoscience Laboratory, School of Natural and Environmental Sciences, Newcastle University, Newcastle NE1 7RU, UK.
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Koshida N, Nakamura T. Emerging Functions of Nanostructured Porous Silicon-With a Focus on the Emissive Properties of Photons, Electrons, and Ultrasound. Front Chem 2019; 7:273. [PMID: 31069217 PMCID: PMC6491725 DOI: 10.3389/fchem.2019.00273] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/02/2019] [Indexed: 11/13/2022] Open
Abstract
Recent topics of application studies on porous silicon (PS) are reviewed here with a focus on the emissive properties of visible light, quasiballistic hot electrons, and acoustic wave. By exposing PS in solvents to pulse laser, size-controlled nc-Si dot colloids can be formed through fragmentation of the PS layer with a considerably higher yield than the conventional techniques such as laser ablation of bulk silicon and sol-gel precursor process. Fabricated colloidal samples show strong visible photoluminescence (~40% in quantum efficiency in the red band). This provides an energy- and cost-effective route for production of nc-Si quantum dots. A multiple-tunneling transport mode through nc-Si dot chain induces efficient quasiballistic hot electron emission from an nc-Si diode. Both the efficiency and the output electron energy dispersion are remarkably improved by using monolayer graphene as a surface electrode. Being a relatively low operating voltage device compatible with silicon planar fabrication process, the emitter is applicable to mask-less parallel lithography under an active matrix drive. It has been demonstrated that the integrated 100 × 100 emitter array is useful for multibeam lithography and that the selected emission pattern is delineated with little distortion. Highly reducing activity of emitted electrons is applicable to liquid-phase thin film deposition of metals (Cu) and semiconductors (Si, Ge, and SiGe). Due to an extremely low thermal conductivity and volumetric heat capacity of nc-Si layer, on the other hand, thermo-acoustic conversion is enhanced to a practical level. A temperature fluctuation produced at the surface of nc-Si layer is quickly transferred into air, and then an acoustic wave is emitted without any mechanical vibrations. The non-resonant and broad-band emissivity with low harmonic distortions makes it possible to use the emitter for generating audible sound under a full digital drive and reproducing complicated ultrasonic communication calls between mice.
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Affiliation(s)
- Nobuyoshi Koshida
- Graduate School of Engineering, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Toshihiro Nakamura
- Department of Electrical and Electronic Engineering, Hosei University, Tokyo, Japan
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Liu P, Behray M, Wang Q, Wang W, Zhou Z, Chao Y, Bao Y. Anti-cancer activities of allyl isothiocyanate and its conjugated silicon quantum dots. Sci Rep 2018; 8:1084. [PMID: 29348534 PMCID: PMC5773486 DOI: 10.1038/s41598-018-19353-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 11/08/2017] [Indexed: 12/11/2022] Open
Abstract
Allyl isothiocyanate (AITC), a dietary phytochemical in some cruciferous vegetables, exhibits promising anticancer activities in many cancer models. However, previous data showed AITC to have a biphasic effect on cell viability, DNA damage and migration in human hepatoma HepG2 cells. Moreover, in a 3D co-culture of HUVEC with pericytes, it inhibited tube formation at high doses but promoted this at low doses, which confirmed its biphasic effect on angiogenesis. siRNA knockdown of Nrf2 and glutathione inhibition abolished the stimulation effect of AITC on cell migration and DNA damage. The biological activity of a novel AITC-conjugated silicon quantum dots (AITC-SiQDs) has been investigated for the first time. AITC-SiQDs showed similar anti-cancer properties to AITC at high doses while avoiding the low doses stimulation effect. In addition, AITC-SiQDs showed a lower and long-lasting activation of Nrf2 translocation into nucleus which correlated with their levels of cellular uptake, as detected by the intrinsic fluorescence of SiQDs. ROS production could be one of the mechanisms behind the anti-cancer effect of AITC-SiQDs. These data provide novel insights into the biphasic effect of AITC and highlight the application of nanotechnology to optimize the therapeutic potential of dietary isothiocyanates in cancer treatment.
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Affiliation(s)
- Peng Liu
- Norwich Medical School, University of East Anglia, Norwich, Norfolk, United Kingdom
| | - Mehrnaz Behray
- School of Chemistry, University of East Anglia, Norwich, Norfolk, United Kingdom
| | - Qi Wang
- Norwich Medical School, University of East Anglia, Norwich, Norfolk, United Kingdom
| | - Wei Wang
- Norwich Medical School, University of East Anglia, Norwich, Norfolk, United Kingdom
| | - Zhigang Zhou
- Norwich Medical School, University of East Anglia, Norwich, Norfolk, United Kingdom
| | - Yimin Chao
- School of Chemistry, University of East Anglia, Norwich, Norfolk, United Kingdom
| | - Yongping Bao
- Norwich Medical School, University of East Anglia, Norwich, Norfolk, United Kingdom.
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8
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Odo E, Britton D, Harting M. Sub-oxide passivation of silicon nanoparticles through rapid mechanical attrition. POWDER TECHNOL 2017. [DOI: 10.1016/j.powtec.2017.03.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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Yuan Z, Nakamura T, Adachi S, Matsuishi K. Luminescence color control and quantum-efficiency enhancement of colloidal Si nanocrystals by pulsed laser irradiation in liquid. NANOSCALE 2017; 9:1193-1200. [PMID: 28009922 DOI: 10.1039/c6nr08757d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate the emission color change of white-emitting chlorine-terminated silicon nanocrystals (Cl:Si-ncs) to blue-emitting carbon-terminated silicon nanocrystals (C:Si-ncs), together with the enhancement of the luminescence quantum efficiency from 7% to 13%, by post-laser ablation in 1-octene. Such changes of the PL properties are caused by the size reduction of Si-nc and efficient surface passivation by hydrocarbons, resulting from a high reactivity of 1-octene in the laser-ablation and subsequent nanoparticle-formation processes. Furthermore, the second post-laser irradiation of the C:Si-ncs in trichloroethylene reversibly results in the formation of the Cl:Si-ncs. The preparation yield of C:Si-ncs via the post-laser ablation of Cl:Si-ncs is higher than that of C:Si-ncs directly prepared only by the laser ablation of PSi in 1-octene. This high preparation yield is due to the high laser-ablation efficiency in trichloroethylene compared with 1-octene, which is attributed to the low heat loss of the solvent in the laser-ablation process.
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Affiliation(s)
- Ze Yuan
- Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
| | - Toshihiro Nakamura
- Graduate School of Science and Technology, Gunma University, Kiryu, Gunma 376-8515, Japan.
| | - Sadao Adachi
- Graduate School of Science and Technology, Gunma University, Kiryu, Gunma 376-8515, Japan.
| | - Kiyoto Matsuishi
- Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
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10
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Zhukhovitskiy AV, Mavros MG, Queeney KT, Wu T, Van Voorhis T, Johnson JA. Reactions of Persistent Carbenes with Hydrogen-Terminated Silicon Surfaces. J Am Chem Soc 2016; 138:8639-52. [DOI: 10.1021/jacs.6b04962] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | - K. T. Queeney
- Department of Chemistry, Smith College
, Northampton, Massachusetts 01063, United States
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11
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Behray M, Webster CA, Pereira S, Ghosh P, Krishnamurthy S, Al-Jamal WT, Chao Y. Synthesis of Diagnostic Silicon Nanoparticles for Targeted Delivery of Thiourea to Epidermal Growth Factor Receptor-Expressing Cancer Cells. ACS APPLIED MATERIALS & INTERFACES 2016; 8:8908-17. [PMID: 27007883 DOI: 10.1021/acsami.5b12283] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The novel thiourea-functionalized silicon nanoparticles (SiNPs) have been successfully synthesized using allylamine and sulforaphane, an important anticancer drug, followed by a hydrosilylation reaction on the surface of hydrogen terminated SiNPs. Their physiochemical properties have been investigated by photoluminescence emission, Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay has been employed to evaluate in vitro toxicity in human colorectal adenocarcinoma (Caco-2) cells and human normal colon epithelial (CCD) cells. The results show significant toxicity of thiourea SiNPs after 72 h of incubation in the cancer cell line, and the toxicity is concentration dependent and saturated for concentrations above 100 μg/mL. Confocal microscopy images have demonstrated the internalization of thiourea-functionalized SiNPs inside the cells. Flow cytometry data has confirmed receptor-mediated targeting in cancer cells. This nanocomposite takes advantage of the epidermal growth factor receptor (EGFR) active targeting of the ligand in addition to the photoluminescence properties of SiNPs for bioimaging purposes. The results suggest that this novel nanosystem can be extrapolated for active targeting of the receptors that are overexpressed in cancer cells such as EGFR using the targeting characteristics of thiourea-functionalized SiNPs and therefore encourage further investigation and development of anticancer agents specifically exploiting the EGFR inhibitory activity of such nanoparticles.
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Affiliation(s)
- Mehrnaz Behray
- School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Carl A Webster
- School of Pharmacy, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Sara Pereira
- School of Pharmacy, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Paheli Ghosh
- Nanoscale Energy and Surface Engineering Department of Engineering and Innovation, The Open University , Buckinghamshire MK7 6AA, United Kingdom
| | - Satheesh Krishnamurthy
- Nanoscale Energy and Surface Engineering Department of Engineering and Innovation, The Open University , Buckinghamshire MK7 6AA, United Kingdom
| | - Wafa T Al-Jamal
- School of Pharmacy, University of East Anglia , Norwich NR4 7TJ, United Kingdom
| | - Yimin Chao
- School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
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12
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Secret E, Leonard C, Kelly SJ, Uhl A, Cozzan C, Andrew JS. Size Control of Porous Silicon-Based Nanoparticles via Pore-Wall Thinning. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:1166-1170. [PMID: 26796986 DOI: 10.1021/acs.langmuir.5b04220] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Photoluminescent silicon nanocrystals are very attractive for biomedical and electronic applications. Here a new process is presented to synthesize photoluminescent silicon nanocrystals with diameters smaller than 6 nm from a porous silicon template. These nanoparticles are formed using a pore-wall thinning approach, where the as-etched porous silicon layer is partially oxidized to silica, which is dissolved by a hydrofluoric acid solution, decreasing the pore-wall thickness. This decrease in pore-wall thickness leads to a corresponding decrease in the size of the nanocrystals that make up the pore walls, resulting in the formation of smaller nanoparticles during sonication of the porous silicon. Particle diameters were measured using dynamic light scattering, and these values were compared with the nanocrystallite size within the pore wall as determined from X-ray diffraction. Additionally, an increase in the quantum confinement effect is observed for these particles through an increase in the photoluminescence intensity of the nanoparticles compared with the as-etched nanoparticles, without the need for a further activation step by oxidation after synthesis.
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Affiliation(s)
- Emilie Secret
- Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States
| | - Camille Leonard
- Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States
| | - Stefan J Kelly
- Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States
| | - Amanda Uhl
- Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States
| | - Clayton Cozzan
- Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States
| | - Jennifer S Andrew
- Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States
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13
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Wang DC, Hao HC, Chen JR, Zhang C, Zhou J, Sun J, Lu M. White light emission and optical gains from a Si nanocrystal thin film. NANOTECHNOLOGY 2015; 26:475203. [PMID: 26538479 DOI: 10.1088/0957-4484/26/47/475203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report a Si nanocrystal thin film consisting of free-standing Si nanocrystals, which can emit white light and show positive optical gains for its red, green and blue (RGB) components under ultraviolet excitation. Si nanocrystals with ϕ = 2.31 ± 0.35 nm were prepared by chemical etching of Si powder, followed by filtering. After being mixed with SiO2 sol-gel and thermally annealed, a broadband photoluminescence (PL) from the thin film was observed. The RGB ratio of the PL can be tuned by changing the annealing temperature or atmosphere, which is 1.00/3.26/4.59 for the pure white light emission. The origins of the PL components could be due to differences in oxygen-passivation degree for Si nanocrystals. The results may find applications in white-light Si lasing and Si lighting.
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Affiliation(s)
- Dong-Chen Wang
- Department of Optical Science and Engineering, and Shanghai Ultra-Precision Optical Manufacturing Engineering Centre, Fudan University, Shanghai 200433, People's Republic of China
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14
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Abualnaja KM, Šiller L, Horrocks BR. Metal-enhanced luminescence of silicon quantum dots: effects of nanoparticles and molecular electron donors and acceptors on the photofading kinetics. NANOTECHNOLOGY 2015; 26:145704. [PMID: 25785514 DOI: 10.1088/0957-4484/26/14/145704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Alkyl-capped silicon quantum dots (SiQDs) show enhanced luminescence when drop cast as films on glass slides in mixtures with Ag or Au nanoparticles or the electron donor ferrocene (Fc). Metal enhancement of quantum dot photoluminescence (PL) is known to arise from a combination of the intense near-field associated with the surface plasmon of the metal on the rate of absorption and the decrease in the lifetime of the excited state. Here we present evidence that an additional factor is also involved: electron transfer from the metal to the quantum dot. Under CW irradiation with an argon ion laser at 488 nm, SiQDs undergo a reversible photofading of the PL as the particles photoionize. A steady-state condition is established by the competition between photoionization and electron-hole recombination. The fading of the initial PL I0 to the steady-state value I∞ can be modelled by a simple first order decay with a lognormal distribution of rates, which reflects the heterogeneity of the sample. In the presence of Ag and Au nanoparticles, the modal rate constants of photofading increase by factors of up to 4-fold and the ratio I0/I∞ decreases by factors up to 5-fold; this is consistent with an increase in the rate of electron-hole recombination facilitated by the metal nanoparticles acting as sources of electrons. Further support for this interpretation comes from the enhancement in PL observed in photofading experiments with films of SiQDs mixed with Fc; this compound is a well-known one-electron donor, but shows no plasmon band which complicates the estimation of PL enhancement with Ag NPs.
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Affiliation(s)
- Khamael M Abualnaja
- School of Chemical Engineering and Advanced Materials, Herschel Building, Newcastle University, NE1 7RU, UK
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15
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Hajjaji H, Alekseev S, Guillot G, Blanchard NP, Monnier V, Chevolot Y, Brémond G, Querry M, Philippon D, Vergne P, Bluet JM. Luminescence nanothermometry with alkyl-capped silicon nanoparticles dispersed in nonpolar liquids. NANOSCALE RESEARCH LETTERS 2014; 9:94. [PMID: 24565261 PMCID: PMC3974062 DOI: 10.1186/1556-276x-9-94] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 02/19/2014] [Indexed: 06/03/2023]
Abstract
Silicon nanoparticles (Si NPs) with a diameter size ranging from 4 to 8 nm were successfully fabricated. They exhibit a visible photoluminescence (PL) due to the quantum confinement effect. Chemical functionalization of these Si NPs with alkyl groups allowed to homogeneously disperse them in nonpolar liquids (NPLs). In comparison to most of literature results for Si NPs, an important PL peak position variation with temperature (almost 1 meV/K) was obtained from 303 to 390 K. The influence of the liquid viscosity on the peak positions is also presented. These variations are discussed considering energy transfer between nanoparticles. The high PL thermal sensitivity of the alkyl-capped Si NPs paves the way for their future application as nanothermometers.
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Affiliation(s)
- Hamza Hajjaji
- Université de Lyon, CNRS, UMR 5270, INSA-Lyon, INL, Villeurbanne 69621, France
| | - Sergey Alekseev
- Chemistry Faculty, Kiev National Taras Shevchenko University, Kiev 01601, Ukraine
| | - Gérard Guillot
- Université de Lyon, CNRS, UMR 5270, INSA-Lyon, INL, Villeurbanne 69621, France
| | - Nicholas P Blanchard
- Université de Lyon, CNRS, UMR 5306, Université Claude Bernard Lyon1, ILM, Villeurbanne 69622, France
| | - Virginie Monnier
- Université de Lyon, CNRS, UMR 5270, EC-Lyon, INL, Ecully 69134, France
| | - Yann Chevolot
- Université de Lyon, CNRS, UMR 5270, EC-Lyon, INL, Ecully 69134, France
| | - Georges Brémond
- Université de Lyon, CNRS, UMR 5270, INSA-Lyon, INL, Villeurbanne 69621, France
| | - Michel Querry
- Université de Lyon, CNRS, UMR5259, INSA-Lyon, LaMCoS, Villeurbanne 69621, France
| | - David Philippon
- Université de Lyon, CNRS, UMR5259, INSA-Lyon, LaMCoS, Villeurbanne 69621, France
| | - Philippe Vergne
- Université de Lyon, CNRS, UMR5259, INSA-Lyon, LaMCoS, Villeurbanne 69621, France
| | - Jean Marie Bluet
- Université de Lyon, CNRS, UMR 5270, INSA-Lyon, INL, Villeurbanne 69621, France
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16
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Linehan K, Doyle H. Size controlled synthesis of silicon nanocrystals using cationic surfactant templates. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:584-590. [PMID: 24027115 DOI: 10.1002/smll.201301189] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 07/26/2013] [Indexed: 06/02/2023]
Abstract
Alkyl-terminated silicon nanocrystals (Si NCs) are synthesized at room temperature by hydride reduction of silicon tetrachloride (SiCl₄) within inverse micelles. Highly monodisperse Si nanocrystals with average diameters ranging from 2 to 6 nm are produced by variation of the cationic quaternary ammonium salts used to form the inverse micelles. Transmission electron microscopy imaging shows that the NCs are highly crystalline, while FTIR spectra confirm that the NCs are passivated by covalent attachment of alkanes, with minimal surface oxidation. UV-vis absorbance and photoluminescence spectroscopy show significant quantum confinement effects, with moderate absorption in the UV spectral range, and a strong blue emission with a marked dependency on excitation wavelength. The photoluminescence quantum yield (Φ) of the Si NCs exhibits an inverse relationship with the mean NC diameter, with a maximum of 12% recorded for 2 nm NCs.
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Affiliation(s)
- Keith Linehan
- Tyndall National Institute, University College Cork, Lee Maltings, Cork, Ireland
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17
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Coxon PR, Ahire JH, Ashby SP, Frogley MD, Chao Y. Amine-terminated nanoparticle films: pattern deposition by a simple nanostencilling technique and stability studies under X-ray irradiation. Phys Chem Chem Phys 2014; 16:5817-23. [DOI: 10.1039/c3cp55344b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Exploring the surface chemistry of nanopatterned amine-terminated nanoparticle films.
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Affiliation(s)
- P. R. Coxon
- Energy Materials Laboratory
- School of Chemistry
- University of East Anglia
- Norwich, UK
- Department of Materials Science & Metallurgy
| | - J. H. Ahire
- Energy Materials Laboratory
- School of Chemistry
- University of East Anglia
- Norwich, UK
| | - S. P. Ashby
- Energy Materials Laboratory
- School of Chemistry
- University of East Anglia
- Norwich, UK
| | | | - Y. Chao
- Energy Materials Laboratory
- School of Chemistry
- University of East Anglia
- Norwich, UK
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18
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Alsharif NH, Al-Said SAF, Birch MA, Horrocks BR, Datta HK. Real-time activity bioassay of single osteoclasts using a silicon nanocrystal-impregnated artificial matrix. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:3685-3692. [PMID: 23650249 DOI: 10.1002/smll.201203184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 03/05/2013] [Indexed: 06/02/2023]
Abstract
The lack of an in vitro real-time osteoclast (OC) activity assay has hampered mechanistic studies of bone resorption. Such an assay is developed, employing a hydroxyapatite matrix impregnated with alkyl-capped silicon nanocrystals, which is capable of monitoring the time-course of resorption by single osteoclasts. Resorption of the matrix by OC releases the nanocrystals, which are internalized by the cell and detected as an increase in OC luminescence. This particular choice of nanocrystals is motivated by their bright pH-independent luminescence, proportional to concentration, and by their rapid uptake without cytotoxicity. In this in vitro assay, OCs are inhibited by calcitonin (CT) and methyl-β-cyclodextrin (MCD), and stimulated by receptor activator of nuclear factor kappa-B ligand (RANKL) in the expected manner. The kinetics of the assay exhibit a lag phase representing cell attachment and commencement of resorption processes, followed by a growth of cell luminescence intensity, and the whole time-course is satisfactorily described by the logistic equation.
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Affiliation(s)
- Naif H Alsharif
- Musculoskeletal Research Group, Institute of Cellular Medicine, The Medical School, Framlington Place, Newcastle University, Newcastle upon Tyne, UK
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19
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Rajani KV, Daniels S, McNally PJ, Krishnamurthy S. Soft x-ray spectroscopic investigation of Zn doped CuCl produced by pulsed dc magnetron sputtering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:285501. [PMID: 23778949 DOI: 10.1088/0953-8984/25/28/285501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report on a systematic investigation of the electronic properties of UV-light emitting Zn doped CuCl thin films implemented using near edge x-ray absorption fine structures (NEXAFS) and high-resolution x-ray photoemission spectroscopy. A clear shift of the valence band maximum towards higher binding energy by 0.2 ± 0.1 eV was observed in Zn doped CuCl as compared to undoped CuCl. This shift is in correlation with the increase in conductivity measured by the Hall effect measurements. A decrease in the optical band gap of CuCl film is also observed as a function of Zn doping. The profound changes in the full width at half maximum and the gradual disappearance of satellite features of Cu 2p core level photoemission as a function of Zn dopant are attributed to the reduced presence of the surface layer of Cu(2+) species with d(9) configuration in the doped films. These investigations help us to understand the doping mechanisms and underlying physics. The reduced presence of the Cu(2+) related surface layer as a function of Zn doping is also verified using NEXAFS.
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Affiliation(s)
- K V Rajani
- National Centre for Plasma Science & Technology, Dublin City University, Dublin 9, Ireland.
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20
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Harun NA, Benning MJ, Horrocks BR, Fulton DA. Gold nanoparticle-enhanced luminescence of silicon quantum dots co-encapsulated in polymer nanoparticles. NANOSCALE 2013; 5:3817-3827. [PMID: 23519376 DOI: 10.1039/c3nr00421j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The preparation of two-component polymer composite nanoparticles encapsulating both Si quantum dots (SiQDs) and Au nanoparticles (AuNPs) by a single step miniemulsion polymerization of divinylbenzene is described. This simple and robust method affords well-defined polymer composite nanoparticles with mean diameters in a range of 100-200 nm and with narrow polydispersity indices as determined by dynamic light scattering and transmission electron microscopy. The successful encapsulation of AuNPs within poly(divinylbenzene) was confirmed by UV-visible spectroscopy and from TEM images. Plasmon-enhanced fluorescence of the luminescence of the SiQDs by AuNPs encapsulated within the polymer composite nanoparticles was evaluated by confocal microspectroscopy, and luminescence enhancements of up to 15 times were observed. These observations indicate that the luminescence of the SiQDs is enhanced by the proximity of the AuNPs. The polymer composite nanoparticles were successfully ink-jet printed onto a glass substrate, which demonstrates that these composites are processable in printing applications.
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Affiliation(s)
- Noor Aniza Harun
- Chemical Nanoscience Laboratory, School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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21
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Nakahara Y, Machiya K, Sato T, Nwe NT, Furuike T, Tamura H, Kimura K. Synthesis of Silicon Quantum Dots Functionalized Chemically with Monosaccharides and Their Use in Biological Fluorescence Imaging. CHEM LETT 2013. [DOI: 10.1246/cl.130068] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yoshio Nakahara
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Kazuki Machiya
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Toshiyuki Sato
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Ni Tar Nwe
- Faculty of Chemistry, Materials and Bioengineering, Kansai University
| | - Tetsuya Furuike
- Faculty of Chemistry, Materials and Bioengineering, Kansai University
| | - Hiroshi Tamura
- Faculty of Chemistry, Materials and Bioengineering, Kansai University
| | - Keiichi Kimura
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
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22
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A top–down strategy towards monodisperse colloidal lead sulphide quantum dots. Nat Commun 2013; 4:1695. [DOI: 10.1038/ncomms2637] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 02/21/2013] [Indexed: 12/15/2022] Open
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23
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Ahire JH, Wang Q, Coxon PR, Malhotra G, Brydson R, Chen R, Chao Y. Highly luminescent and nontoxic amine-capped nanoparticles from porous silicon: synthesis and their use in biomedical imaging. ACS APPLIED MATERIALS & INTERFACES 2012; 4:3285-3292. [PMID: 22624976 DOI: 10.1021/am300642m] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Stable and brightly luminescent amine-terminated Si nanoparticles (SiNPs) have been synthesized from electrochemically etched porous silicon (PSi). The surface amine termination was confirmed by FTIR, NMR, and XPS studies. The mean diameter of the crystal core of 4.6 nm was measured by transmission electron microscopy (TEM), which is in a good agreement with the size obtained by dynamic light scattering (DLS). The dry, amine-terminated product can be obtained from bulk silicon wafers in less than 4 h. This represents a significant improvement over similar routines using PSi where times of >10 h are common. The emission quantum yield was found to be about 22% and the nanoparticles exhibited an exceptional stability over a wide pH range (4-14). They are resistant to aging over several weeks. The amine-terminated SiNPs showed no significant cytotoxic effects toward HepG2 cells, as assessed with MTT assays.
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Affiliation(s)
- Jayshree H Ahire
- Energy Materials Laboratory, School of Chemistry, University of East Anglia , Norwich NR4 7TJ, United Kingdom
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24
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Wang Q, Bao Y, Zhang X, Coxon PR, Jayasooriya UA, Chao Y. Uptake and toxicity studies of poly-acrylic acid functionalized silicon nanoparticles in cultured mammalian cells. Adv Healthc Mater 2012. [PMID: 23184723 DOI: 10.1002/adhm.201100010] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Poly-acrylic acid (PAAc) terminated silicon nanoparticles (SiNPs) have been synthesized and employed as a synchronous fluorescent signal indicator in a series of cultured mammalian cells: HHL5, HepG2 and 3T3-L1. Their biological effects on cell growth and proliferation in both human and mouse cell lines have been studied. There was no evidence of in vitro cytotoxity in the cells exposed to PAAc terminated SiNPS when assessed by cell morphology, cell proliferation and viability, and DNA damage assays. The uptake of the nanocrystals by both HepG2 and 3T3-L1 cells was investigated by confocal microscopy and flow cytometry, which showed a clear time-dependence at higher concentrations. Reconstructed 3-D confocal microscope images exhibited that the PAAc-SiNPs were evenly distributed throughout the cytosol rather than attached to outer membrane. This study provides fundamental evidence for the safe application and further modification of silicon nanoparticles, which could broaden their application as cell markers in living systems and in micelle encapsulated drug delivery systems.
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Affiliation(s)
- Qi Wang
- Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
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25
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Zhang W, Peng H, Gao X, Ye J, Zhang Z, Chao Y. An in situ
chemical reaction approach to synthesize zinc picrate energetic thin film upon zinc oxide nanowires array. SURF INTERFACE ANAL 2012. [DOI: 10.1002/sia.4922] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Wenchao Zhang
- School of Chemical Engineering; Nanjing University of Science and Technology; Nanjing 210094 People's Republic of China
| | - Hongzheng Peng
- School of Chemical Engineering; Nanjing University of Science and Technology; Nanjing 210094 People's Republic of China
| | - Xiangdong Gao
- State Key Laboratory of High Performance Ceramics and Superfine Microstructures; Shanghai Institute of Ceramics of Chinese Academy of Sciences; Shanghai 200050 People's Republic of China
| | - Jiahai Ye
- School of Chemical Engineering; Nanjing University of Science and Technology; Nanjing 210094 People's Republic of China
| | - Zhongyuan Zhang
- School of Chemical Engineering; Nanjing University of Science and Technology; Nanjing 210094 People's Republic of China
| | - Yimin Chao
- Energy Materials Laboratory, School of Chemistry; University of East Anglia; Norwich Research Park NR4 7TJ UK
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26
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Harun NA, Horrocks BR, Fulton DA. A miniemulsion polymerization technique for encapsulation of silicon quantum dots in polymer nanoparticles. NANOSCALE 2011; 3:4733-4741. [PMID: 21984383 DOI: 10.1039/c1nr10938c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Miniemulsion polymerization techniques were used to encapsulate luminescent alkylated silicon quantum dots (Si-QDs) within polymer nanoparticles composed of styrene and 4-vinylbenzaldehyde monomers. The polymer nanoparticles had mean diameters in the range 90-150 nm depending on the reaction conditions, however all samples showed narrow particle size distributions, as determined by dynamic light scattering and atomic force microscopy. The Si-QDs were found to have a small, but beneficial effect on the polymerization process by reducing the polydispersity of the final polymer particles, which we attribute to co-surfactant action of the undecene used to form the alkyl capping layer on the Si-QDs. Confocal microspectroscopy was used to confirm that the luminescent alkylated Si-QDs were encapsulated within the polymer nanoparticles and also provided luminescence and Raman spectra which show peaks corresponding to both alkylated Si-QDs and the polymer nanoparticles. Treatment of the polymer nanoparticles with dilute aqueous sodium hydroxide solution, which is known to corrode Si and extinguish the luminescence of alkylated Si-QDs, results in only a partial reduction in luminescence suggesting that the majority of the alkylated Si-QDs are encapsulated sufficiently deep within the polymer matrix to protect them from alkaline attack. Miniemulsion polymerization of the monomers styrene and 4-vinylbenzaldehyde affords polymer nanoparticles displaying reactive aldehyde groups upon their surfaces, which could then be decorated with a selection of molecules through imine, oxime or hydrazone condensation reactions. We speculate that polymer-SiQD composite nanoparticles whose surfaces can be further decorated will increase the utility of luminescent Si-QDs in applications such as anti-counterfeiting and as probes of biological processes.
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Affiliation(s)
- Noor Aniza Harun
- Chemical Nanoscience Laboratory, School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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27
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Shirahata N. Colloidal Si nanocrystals: a controlled organic-inorganic interface and its implications of color-tuning and chemical design toward sophisticated architectures. Phys Chem Chem Phys 2011; 13:7284-94. [PMID: 21424017 DOI: 10.1039/c0cp02647f] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The optical use of colloidal silicon nanocrystals (Si NCs) has gained increasing attention for its possible contributions to building a sustainable society that ideally uses resources and energy with high efficiency without causing damage to the environment or human health. Si wafers (E(g) ≈ 1.1 eV) dominate modern microelectronics as an impressive electronic material, but they exhibit relatively poor optical performance owing to an indirect bandgap structure. Interestingly, however, full control of the size distribution and surface chemistry of the NCs yields size-dependent light emission in a very wide range from near-ultraviolet through visible to near-infrared wavelengths. In addition to such unique luminescence properties, Si exhibits a high chemical affinity to covalent linkages with carbon, oxygen, and nitrogen, thereby producing almost unlimited variations in organic-Si NCs architectures hybridized at the molecular level. To achieve this goal, I note some parameters, including interfacial chemistry, that are emerging as important elements for increasing our understanding of the effect of quantum confinement in nanostructured Si and for realizing efficient fluorescence emission. This article covers new aspects of derivatives of Si NCs in applications that utilize their optical absorption and emission features.
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Affiliation(s)
- Naoto Shirahata
- National Institute for MaterialsScience, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan.
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28
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Brooks-Kayal A. Molecular mechanisms of cognitive and behavioral comorbidities of epilepsy in children. Epilepsia 2011; 52 Suppl 1:13-20. [PMID: 21214535 DOI: 10.1111/j.1528-1167.2010.02906.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Intellectual and developmental disabilities (IDDs) such as autistic spectrum disorders (ASDs) and epilepsies are heterogeneous disorders that have diverse etiologies and pathophysiologies. The high rate of co-occurrence of these disorders, however, suggests potentially shared underlying mechanisms. A number of well-known genetic disorders share epilepsy, intellectual disability, and autism as prominent phenotypic features, including tuberous sclerosis complex, Rett syndrome, and fragile X syndrome. In addition, mutations of several genes involved in neurodevelopment, including ARX, DCX, neuroligins, and neuropilin 2 have been identified in children with epilepsy, IDDs, ASDs, or a combination of thereof. Finally, in animal models, early life seizures can result in cellular and molecular changes that could contribute to learning and behavioral disabilities. Increased understanding of the common genetic, molecular, and cellular mechanisms of IDDs, ASDs, and epilepsy may provide insight into their underlying pathophysiology and elucidate new therapeutic approaches for these conditions.
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Affiliation(s)
- Amy Brooks-Kayal
- Department of Pediatrics, University of Colorado Denver School of Medicine, Aurora, USA.
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29
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Žídek K, Trojánek F, Malý P, Ondič L, Pelant I, Dohnalová K, Šiller L, Little R, Horrocks BR. Femtosecond luminescence spectroscopy of core states in silicon nanocrystals. OPTICS EXPRESS 2010; 18:25241-25249. [PMID: 21164871 DOI: 10.1364/oe.18.025241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a study of ultrafast carrier transfer from highly luminescent states inside the core of silicon nanocrystal (due to quasidirect transitions) to states on the nanocrystal-matrix interface. This transfer leads to a sub-picosecond luminescence decay, which is followed by a slower decay component induced by carrier relaxation to lower interface states. We investigate the luminescence dynamics for two different surface passivation types and we propose a general model describing spectral dependence of ultrafast carrier dynamics. Our results stress the crucial role of the energy distribution of the interface states on surface-related quenching of quasidirect luminescence in silicon nanocrystals. We discuss how to avoid this quenching in order to bring the attractive properties of the quasidirect recombination closer to exploitation.
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Affiliation(s)
- K Žídek
- Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague, Czech Republic.
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30
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Brooks-Kayal A. Epilepsy and autism spectrum disorders: are there common developmental mechanisms? Brain Dev 2010; 32:731-8. [PMID: 20570072 DOI: 10.1016/j.braindev.2010.04.010] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 04/27/2010] [Indexed: 12/12/2022]
Abstract
Autistic spectrum disorders (ASD) and epilepsies are heterogeneous disorders that have diverse etiologies and pathophysiologies. The high rate of co-occurrence of these disorders suggest potentially shared underlying mechanisms. A number of well-known genetic disorders share epilepsy and autism as prominent phenotypic features, including tuberous sclerosis, Rett syndrome, and fragile X. In addition, mutations of several genes involved in neurodevelopment, including ARX, DCX, neuroligins and neuropilin2 have been identified in children with epilepsy, ASD or often both. Finally, in animal models, early-life seizures can result in cellular and molecular changes that could contribute to learning and behavioral disabilities as seen in ASD. Increased understanding of the common genetic, molecular and cellular mechanisms of ASD and epilepsy may provide insight into their underlying pathophysiology and elucidate new therapeutic approaches of both conditions.
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Affiliation(s)
- Amy Brooks-Kayal
- Department of Pediatrics, University of Colorado Denver School of Medicine, The Children's Hospital Denver, 13123 E 16th Avenue, B155, Aurora, CO 80045, United States.
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31
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Kůsová K, Cibulka O, Dohnalová K, Pelant I, Valenta J, Fucíková A, Zídek K, Lang J, Englich J, Matejka P, Stepánek P, Bakardjieva S. Brightly luminescent organically capped silicon nanocrystals fabricated at room temperature and atmospheric pressure. ACS NANO 2010; 4:4495-4504. [PMID: 20690596 DOI: 10.1021/nn1005182] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Silicon nanocrystals are an extensively studied light-emitting material due to their inherent biocompatibility and compatibility with silicon-based technology. Although they might seem to fall behind their rival, namely, direct band gap based semiconductor nanocrystals, when it comes to the emission of light, room for improvement still lies in the exploitation of various surface passivations. In this paper, we report on an original way, taking place at room temperature and ambient pressure, to replace the silicon oxide shell of luminescent Si nanocrystals with capping involving organic residues. The modification of surface passivation is evidenced by both Fourier transform infrared spectroscopy and nuclear magnetic resonance measurements. In addition, single-nanocrystal spectroscopy reveals the occurrence of a systematic fine structure in the emission single spectra, which is connected with an intrinsic property of small nanocrystals since a very similar structure has recently been observed in specially passivated semiconductor CdZnSe nanoparticles. The organic capping also dramatically changes optical properties of Si nanocrystals (resulting ensemble photoluminescence quantum efficiency 20%, does not deteriorate, radiative lifetime 10 ns at 550 nm at room temperature). Optically clear colloidal dispersion of these nanocrystals thus exhibits properties fully comparable with direct band gap semiconductor nanoparticles.
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Affiliation(s)
- Katerina Kůsová
- Institute of Physics of the ASCR, vvi, Cukrovarnicka 10, 162 53 Prague 6, Czech Republic.
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32
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Hybrid nanocomposites of semiconductor nanoparticles and conjugated polyelectrolytes and their application as fluorescence biosensors. POLYMER 2010. [DOI: 10.1016/j.polymer.2009.12.035] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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33
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Rostron RJ, Chao Y, Roberts G, Horrocks BR. Simultaneous photocharging and luminescence intermittency in silicon nanocrystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:235301. [PMID: 21825580 DOI: 10.1088/0953-8984/21/23/235301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Contemporaneous measurements of the time dependence of photoluminescence and concomitant electrical conduction in films of alkylated silicon nanocrystals (NCs) during and between periods of continuous-wave laser irradiation of arbitrary duration establish the role played by photoionization to a conducting state in the intermittent light emission from silicon nanocrystals. The luminescence and current generated by electron photoejection both decay to non-zero, steady-state values during irradiation with visible laser light at incident intensities in the range 0.25-0.30 ± 0.01 kW cm(-2); on cessation of irradiation, the non-conducting photoluminescent state of the NCs is substantially regained. These observations are consistent with a model in which the decay of photoluminescence is ascribed to autoionization of the silicon NCs with a most probable lifetime ⟨T(a)⟩, depending on particle size, and recovery of luminescence to electron-hole recombination characterized by a most probable lifetime ⟨T(eh)⟩. Values of ⟨T(a)⟩ = 1.08 ± 0.03 s and ⟨T(eh)⟩ = 770 ± 300 s are extracted from nonlinear least-squares fitting to the time dependence of the photoluminescence intensity. The temporal behavior of the transient photocurrent is found to be quantitatively consistent with a one-dimensional model of diffusion of charge carriers between NCs. Integration of the time dependence of the photocurrent response coupled with an estimate of the volume irradiated with the laser light suggests ionization of one electron per NC during photon irradiation.
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Affiliation(s)
- R J Rostron
- School of Natural Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
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34
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Siller L, Krishnamurthy S, Kjeldgaard L, Horrocks BR, Chao Y, Houlton A, Chakraborty AK, Hunt MRC. Core and valence exciton formation in x-ray absorption, x-ray emission and x-ray excited optical luminescence from passivated Si nanocrystals at the Si L(2,3) edge. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:095005. [PMID: 21817378 DOI: 10.1088/0953-8984/21/9/095005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Resonant inelastic x-ray scattering (RIXS), x-ray absorption spectroscopy and x-ray excited optical luminescence (XEOL) have been used to measure element specific filled and empty electronic states over the Si L(2,3) edge of passivated Si nanocrystals of narrow size distribution (diameter 2.2 ± 0.4 nm). These techniques have been employed to directly measure absorption and luminescence specific to the local Si nanocrystal core. Profound changes occur in the absorption spectrum of the nanocrystals compared with bulk Si, and new features are observed in the nanocrystal RIXS. Clear signatures of core and valence band exciton formation, promoted by the spatial confinement of electrons and holes within the nanocrystals, are observed, together with band narrowing due to quantum confinement. XEOL at 12 K shows an extremely sharp feature at the threshold of orange luminescence (i.e., at ∼1.56 eV (792 nm)) which we attribute to recombination of valence excitons, providing a lower limit to the nanocrystal band gap.
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Affiliation(s)
- L Siller
- School of Chemical Engineering and Advanced Materials, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK
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35
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Alsharif NH, Berger CEM, Varanasi SS, Chao Y, Horrocks BR, Datta HK. Alkyl-capped silicon nanocrystals lack cytotoxicity and have enhanced intracellular accumulation in malignant cells via cholesterol-dependent endocytosis. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:221-8. [PMID: 19058285 PMCID: PMC2962801 DOI: 10.1002/smll.200800903] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Revised: 08/08/2008] [Indexed: 05/20/2023]
Abstract
Nanocrystals of various inorganic materials are being considered for application in the life sciences as fluorescent labels and for such therapeutic applications as drug delivery or targeted cell destruction. The potential applications of the nanoparticles are critically compromised due to the well-documented toxicity and lack of understanding about the mechanisms involved in the intracellular internalization. Here intracellular internalization and toxicity of alkyl-capped silicon nanocrystals in human neoplastic and normal primary cells is reported. The capped nanocrystals lack cytotoxicity, and there is a marked difference in the rate and extent of intracellular accumulation of the nanoparticles between human cancerous and non-cancerous primary cells, the rate and extent being higher in the malignant cells compared to normal human primary cells. The exposure of the cells to the alkyl-capped nanocrystals demonstrates no evidence of in vitro cytotoxicity when assessed by cell morphology, apoptosis, and cell viability assays. The internalization of the nanocrystals by Hela and SW1353 cells is almost completely blocked by the pinocytosis inhibitors filipin, cytochalasin B, and actinomycin D. The internalization process is not associated with any surface change in the nanoparticles, as their luminescence spectrum is unaltered upon transport into the cytosol. The observed dramatic difference in the rate and extent of internalization of the nanocrystals between malignant and non-malignant cells therefore offers potential application in the management of human neoplastic conditions.
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Affiliation(s)
- Naif H Alsharif
- Musculoskeletal Research Group, Institute of Cellular Medicine Newcastle UniversityFramlington Place Newcastle upon Tyne, NE2 4HH (UK)
| | - Christine E M Berger
- A & R Biology Pfizer Limited500/1.826 IPC 675 Ramsgate Road Sandwich CT13 9NJ (UK)
| | - Satya S Varanasi
- Biomedical Tissue Research Group Department of Biology University of York YorkYO10 5DD (UK)
| | - Yimin Chao
- Faculty of Science Chemical Sciences and Pharmacy University of East AngliaNorwich NR4 7TJ (UK)
| | - Benjamin R Horrocks
- School of Natural Sciences, Bedson Building Newcastle UniversityNewcastle upon Tyne NE1 7RU (UK)
| | - Harish K Datta
- Musculoskeletal Research Group, Institute of Cellular Medicine Newcastle UniversityFramlington Place Newcastle upon Tyne, NE2 4HH (UK)
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36
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Lin SW, Chen DH. Synthesis of water-soluble blue photoluminescent silicon nanocrystals with oxide surface passivation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:72-76. [PMID: 18985673 DOI: 10.1002/smll.200800677] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Affiliation(s)
- Sheng-Wei Lin
- Department of Chemical Engineering and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan
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Dickinson FM, Alsop TA, Al-Sharif N, Berger CEM, Datta HK, Šiller L, Chao Y, Tuite EM, Houlton A, Horrocks BR. Dispersions of alkyl-capped silicon nanocrystals in aqueous media: photoluminescence and ageing. Analyst 2008; 133:1573-80. [DOI: 10.1039/b801921e] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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