Abstract:Few studies have investigated the two-photon properties of graphene quantum dots (GQDs) and GQD-conjugated polymers. The results of the present study revealed that conjugated polymers containing nitrogen and sulfur atoms caused higher quantum confinement of emissive energy to be trapped on the surface of nanomaterials, resulting in a high-photoluminescence quantum yield and notable two-photon properties. Additionally, the nanomaterials generated no reactive oxygen species-dependent oxidative stress on cells an… Show more
“…In contrast, one-layer GO-POAA and GO-chitosan sheets are 1.5 and 1.7 nm thick, respectively, because the POAA and chitosan is successfully adsorbed on the surfaces of the GO sheets (Fig. 1 h, i) [ 11 , 15 ]. Because of the presence of exposed carboxylic acid after oxidation, the zeta potential shows the surface charge of the GO to be around − 30.9 mV.…”
Section: Resultsmentioning
confidence: 99%
“…Glutathione (γ- l -glutamyl- l -cysteinyl-glycine, GSH), which is a thiol-tripeptide, can prevent damages to cellular components due to oxidation tress. The thiol group from GSH is oxidized to a disulfide bond, which converts GSH into glutathione disulfide [ 6 , 15 , 30 ]. In vitro GSH oxidation was also used to examine the generated O 2 · − anions that are generated from GO- and GO-based materials (10–100 μg mL −1 ) for bacteria that are treated with both culture media for 3 h of incubation (Additional file 1 : Figure S3) [ 6 ] and the oxidation is summarized in Tables 6 , 7 .…”
Section: Resultsmentioning
confidence: 99%
“…This was then incubated in a shaker for 2 h at 37 °C. The following experiments were then performed, as in previous studies [ 15 , 30 ]. Loss of GSH % = (absorbance of negative control − absorbance of sample)/absorbance of negative control × 100.…”
BackgroundThe results showed that the deciding factor is the culture medium in which the bacteria and the graphene oxide (GO) are incubated at the initial manipulation step. These findings allow better use of GO and GO-based materials more and be able to clearly apply them in the field of biomedical nanotechnology.ResultsTo study the use of GO sheets applied in the field of biomedical nanotechnology, this study determines whether GO-based materials [GO, GO-polyoxyalkyleneamine (POAA), and GO-chitosan] stimulate or inhibit bacterial growth in detail. It is found that it depends on whether the bacteria and GO-based materials are incubated with a nutrient at the initial step. This is a critical factor for the fortune of bacteria. GO stimulates bacterial growth and microbial proliferation for Gram-negative and Gram-positive bacteria and might also provide augmented surface attachment for both types of bacteria. When an external barrier that is composed of GO-based materials forms around the surface of the bacteria, it suppresses nutrients that are essential to microbial growth and simultaneously produces oxidative stress, which causes bacteria to die, regardless of whether they have an outer-membrane-Gram-negative-bacteria or lack an outer-membrane-Gram-positive-bacteria, even for high concentrations of biocompatible GO-POAA. The results also show that these GO-based materials are capable of inducing reactive oxygen species (ROS)-dependent oxidative stress on bacteria. Besides, GO-based materials may act as a biofilm, so it is hypothesized that they suppress the toxicity of low-dose chitosan.ConclusionGraphene oxide is not an antimicrobial material but it is a general growth enhancer that can act as a biofilm to enhance bacterial attachment and proliferation. However, GO-based materials are capable of inducing ROS-dependent oxidative stress on bacteria. The applications of GO-based materials can clearly be used in antimicrobial surface coatings, surface-attached stem cells for orthopedics, antifouling for biocides and microbial fuel cells and microbial electro-synthesis.Electronic supplementary materialThe online version of this article (10.1186/s12951-017-0328-8) contains supplementary material, which is available to authorized users.
“…In contrast, one-layer GO-POAA and GO-chitosan sheets are 1.5 and 1.7 nm thick, respectively, because the POAA and chitosan is successfully adsorbed on the surfaces of the GO sheets (Fig. 1 h, i) [ 11 , 15 ]. Because of the presence of exposed carboxylic acid after oxidation, the zeta potential shows the surface charge of the GO to be around − 30.9 mV.…”
Section: Resultsmentioning
confidence: 99%
“…Glutathione (γ- l -glutamyl- l -cysteinyl-glycine, GSH), which is a thiol-tripeptide, can prevent damages to cellular components due to oxidation tress. The thiol group from GSH is oxidized to a disulfide bond, which converts GSH into glutathione disulfide [ 6 , 15 , 30 ]. In vitro GSH oxidation was also used to examine the generated O 2 · − anions that are generated from GO- and GO-based materials (10–100 μg mL −1 ) for bacteria that are treated with both culture media for 3 h of incubation (Additional file 1 : Figure S3) [ 6 ] and the oxidation is summarized in Tables 6 , 7 .…”
Section: Resultsmentioning
confidence: 99%
“…This was then incubated in a shaker for 2 h at 37 °C. The following experiments were then performed, as in previous studies [ 15 , 30 ]. Loss of GSH % = (absorbance of negative control − absorbance of sample)/absorbance of negative control × 100.…”
BackgroundThe results showed that the deciding factor is the culture medium in which the bacteria and the graphene oxide (GO) are incubated at the initial manipulation step. These findings allow better use of GO and GO-based materials more and be able to clearly apply them in the field of biomedical nanotechnology.ResultsTo study the use of GO sheets applied in the field of biomedical nanotechnology, this study determines whether GO-based materials [GO, GO-polyoxyalkyleneamine (POAA), and GO-chitosan] stimulate or inhibit bacterial growth in detail. It is found that it depends on whether the bacteria and GO-based materials are incubated with a nutrient at the initial step. This is a critical factor for the fortune of bacteria. GO stimulates bacterial growth and microbial proliferation for Gram-negative and Gram-positive bacteria and might also provide augmented surface attachment for both types of bacteria. When an external barrier that is composed of GO-based materials forms around the surface of the bacteria, it suppresses nutrients that are essential to microbial growth and simultaneously produces oxidative stress, which causes bacteria to die, regardless of whether they have an outer-membrane-Gram-negative-bacteria or lack an outer-membrane-Gram-positive-bacteria, even for high concentrations of biocompatible GO-POAA. The results also show that these GO-based materials are capable of inducing reactive oxygen species (ROS)-dependent oxidative stress on bacteria. Besides, GO-based materials may act as a biofilm, so it is hypothesized that they suppress the toxicity of low-dose chitosan.ConclusionGraphene oxide is not an antimicrobial material but it is a general growth enhancer that can act as a biofilm to enhance bacterial attachment and proliferation. However, GO-based materials are capable of inducing ROS-dependent oxidative stress on bacteria. The applications of GO-based materials can clearly be used in antimicrobial surface coatings, surface-attached stem cells for orthopedics, antifouling for biocides and microbial fuel cells and microbial electro-synthesis.Electronic supplementary materialThe online version of this article (10.1186/s12951-017-0328-8) contains supplementary material, which is available to authorized users.
“…As the latest member of the graphene family, graphene quantum dots (GQDs), which can be a promising alternative to traditional semiconductor quantum dots, show promising applications and potential developments in terms of bioimaging, electrochemical biosensors, photovoltaic devices and in the biomedical field, among many others [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. GQDs are generally derived from glucose, carbon fibers, graphite, graphene oxides, and synthesized or fabricated by methods like electrochemical oxidation, lithographic patterning, hydrothermal, microwave, acidic oxidation and supercritical fluid treatment [ 15 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. The high price of the carbon source (graphite, carbon fibers, and carbon nanotubes), long processing time (24–48 h), post-purification procedure (3–5 days) and the harsh reaction conditions (nitrating mixture or oxidizing supercritical water) for the large-scale production of GQDs are uneconomic and unreasonable, so it is imperative and desirable to prepare GQDs in a more facile, milder and more environmentally-friendly method [ 18 , 19 , 21 , 23 , 24 , 29 , 30 ].…”
Coal tar pitch (CTP), a by-product of coking industry, has a unique molecule structure comprising an aromatic nucleus and several side chains bonding on this graphene-like nucleus, which is very similar to the structure of graphene quantum dots (GQDs). Based on this perception, we develop a facile approach to convert CTP to GQDs only by oxidation with hydrogen peroxide under mild conditions. One to three graphene layers, monodisperse GQDs with a narrow size distribution of 1.7 ± 0.4 nm, are obtained at high yield (more than 80 wt. %) from CTP. The as-produced GQDs are highly soluble and strongly fluorescent in aqueous solution. This simple strategy provides a feasible route towards the commercial synthesis of GQDs for its cheap material source, green reagent, mild condition, and high yield.
“…1d, the D band at ≈ 1360 cm −1 and G band at ≈ 1600 cm −1 could also be observed, which are attributed to the sp 2 graphitized structure and local defects/disorders of carbonaceous materials, respectively. The high ratio of D/G peak intensity demonstrated that large amounts of defects and disorders existed in the edge or surface of the GQDs structure [31]. Fig.…”
A novel isotype heterojunction ultraviolet photodetector was fabricated by growing n-ZnO nanorod arrays on n-GaN thin films and then spin-coated with graphene quantum dots (GQDs). Exposed to UV illumination with a wavelength of 365 nm, the time-dependent photoresponse of the hybrid detectors manifests high sensitivity and consistent transients with a rise time of 100 ms and a decay time of 120 ms. Meanwhile, an ultra-high specific detectivity (up to ~ 1012 Jones) and high photoresponsivity (up to 34 mA W−1) are obtained at 10 V bias. Compared to the bare heterojunction detectors, the excellent performance of the GQDs decorated n-ZnO/n-GaN heterostructure is attributed to the efficient immobilization of GQDs on the ZnO nanorod arrays. GQDs were exploited as a light absorber and act like an electron donor to effectively improve the effective carrier concentration in interfacial junction. Moreover, appropriate energy band alignment in GQDs decorated ZnO/GaN hybrids can also be a potential factor in facilitating the UV-induced photocurrent and response speed.
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