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1.
Talanta ; 201: 143-148, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122404

RESUMO

The current study proposes a fast one-pot microwave assisted synthesis of new carbon dots (CDs) based on glycerol and urea. The novel carbon nanoparticles (GUCDs) have been appropriately characterized and exhibited good luminescent properties with a quantum yield of about 9.8%. Interestingly, the GUCDs are able to selectively interact with tetracycline class antibiotics, which produce a decrease in the native fluorescence of the CDs. On the base of these features, a new analytical method has been developed for the determination of tetracycline. The proposed method has shown satisfactory analytical parameters, such as good linearity range -between 0.5 and 25 µM (R2 = 0.9997)- and an acceptable detection limit (165 nM). Moreover, the new method has been successfully applied for tetracycline determination in urine samples with good recoveries (94.7-103%) and precision (4.6 RSD%).


Assuntos
Carbono/química , Pontos Quânticos/química , Tetraciclina/urina , Carbono/efeitos da radiação , Fluorescência , Fluorometria/métodos , Glicerol/química , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Pontos Quânticos/efeitos da radiação , Raios Ultravioleta , Ureia/química
2.
Talanta ; 201: 82-89, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122464

RESUMO

Using chloroauric acid as precursor and ß-cyclodextrin (ß-CD) as reducing agent and stabilizer, ß-CD@AuNPs with negative charge were synthesized by one-step colloidal synthesis method. The positive charged carbon quantum dots (CQDs) were synthesized by one-step of sonication of cetylpyridinium chloride. Under the role of static electricity, the fluorescence resonance energy transfer (FRET) occurred between CQDs and ß-CD@AuNPs. CQDs and ß-CD@AuNPs served as the fluorescence energy donors and receptors, respectively, i.e., the fluorescence of CQDs was turned off by ß-CD@AuNPs. Based on the specific host-guest recognition between the inner cavity of ß-CD and cholesterol, CQDs was replaced by cholesterol, the FRET could be interrupted, and then the fluorescence of CQDs was turned on. A good linear relationship between cholesterol concentration (10-210 µmol L-1) and fluorescence intensity was obtained and the LOD was 343.48 nmol L-1. Because of excellent fluorescence quenching ability of FRET, the analytical performance (including LOD and linear scope) of such a turn off-on fluorescent nanosensor (e.g., CQDs/ß-CD@AuNPs) was better than nanosensor only via competitive host-guest recognition (e.g., ß-CD functionalized CQDs). The synergistic effect of competitive host-guest recognition and FRET was proved. Because of selective recognition, ultrasensitive, wide linear range, and strong anti-interference ability, CQDs/ß-CD@AuNPs as a turn off-on fluorescent nanosensor was developed to determine cholesterol in porcine serum.


Assuntos
Colesterol/sangue , Corantes Fluorescentes/química , Nanopartículas Metálicas/química , Pontos Quânticos/química , beta-Ciclodextrinas/química , Animais , Carbono/química , Carbono/efeitos da radiação , Fluorescência , Transferência Ressonante de Energia de Fluorescência/métodos , Ouro/química , Limite de Detecção , Tamanho da Partícula , Pontos Quânticos/efeitos da radiação , Suínos , Raios Ultravioleta
4.
Methods Appl Fluoresc ; 7(2): 022002, 2019 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-30822759

RESUMO

The right choice of a fluorescent probe is essential for successful luminescence imaging and sensing and especially concerning in vivo and in vitro applications, the development of new classes have gained more and more attention in the last years. One of the most promising class are upconversion nanoparticles (UCNPs)-inorganic nanocrystals capable to convert near-infrared light in high energy radiation. In this review we will compare UCNPs with other fluorescent probes in terms of (a) the optical properties of the probes, such as their brightness, photostability and excitation wavelength; (b) their chemical properties such as the dispersibility, stability under experimental or physiological conditions, availability of chemical modification strategies for labelling; and (c) the potential toxicity and biocompatibility of the probe. Thereby we want to provide a better understanding of the advantages and drawbacks of UCNPs and address future challenges in the design of the nanocrystals.


Assuntos
Carbono/química , Corantes Fluorescentes/química , Proteínas de Fluorescência Verde/química , Elementos da Série dos Lantanídeos/química , Nanopartículas/química , Pontos Quânticos/química , Animais , Linhagem Celular Tumoral , Fluorescência , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/efeitos da radiação , Proteínas de Fluorescência Verde/síntese química , Proteínas de Fluorescência Verde/efeitos da radiação , Humanos , Elementos da Série dos Lantanídeos/efeitos da radiação , Luz , Nanopartículas/efeitos da radiação , Imagem Óptica , Pontos Quânticos/efeitos da radiação
5.
Anal Chim Acta ; 1058: 1-8, 2019 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-30851843

RESUMO

Most of the photoelectrochemical (PEC) bioassays need to immobilize biomolecules on electrodes, which lead to tedious modification processes, damaged biomolecules, as well as crippled sensitivity/accuracy and low throughput of the performances. To overcome these drawbacks, we now introduce an exquisitely split-mode (which separates the bioreaction (performed in microplates) from the PEC detection (conducted in PEC cell)) cathodic photoelectrochemistry for probing versatile biocatalytic events with high throughput. Specifically, the enzymatically in situ generated 1,2-bezoquinone was covalently attached onto the PbSe quantum dots (QDs) modified indium tin oxide (ITO) (ITO/PbSe) photocathode through the connector of chitosan (CS). And the attached 1,2-bezoquinone acted as an efficient electron acceptor to promote the cathodic photocurrent of the ITO/PbSe electrode, enabling us to probe quinones-generating oxidoreductase (by taking horseradish peroxidase (HRP) as a model) coupled biocatalytic cascades including the alkaline phosphatase (ALP)/HRP and the glucose oxidase (GOx)/HRP cascades. Quantitative probing for ALP activity in a wide linear range of 5.0 × 10-3 to 10 U/L with the detection limit of 1.2 × 10-3 U/L was realized. While a wide linear range of 5.0 × 10-8 to 1.0 × 10-4 moL/L with a quite low detection limit of 1.0 × 10-8 moL/L was obtained for the glucose assay. In addition, this testing protocol was also extended to an immunoassay (taking carcinoembryonic antigen (CEA) as an example) using HRP as a catalytic tracer. The developed bioassays show high sensitivity and good selectivity for CEA detection in the linear range from 0.1 pg/mL to 100 ng/mL with a detection limit of 0.02 pg/mL. Moreover, the proposed detection has distinctive merits because it not only avoids the adverse effects of the surface confined biomolecules for crippling the signal transduction, but also it has enhanced throughput.


Assuntos
Benzoquinonas/química , Antígeno Carcinoembrionário/análise , Técnicas Eletroquímicas/métodos , Chumbo/química , Fotoquímica/métodos , Pontos Quânticos/química , Compostos de Selênio/química , Fosfatase Alcalina/química , Anticorpos/imunologia , Armoracia/enzimologia , Benzoquinonas/síntese química , Antígeno Carcinoembrionário/imunologia , Quitosana/química , Enzimas Imobilizadas/química , Glucose Oxidase/química , Ouro/química , Peroxidase do Rábano Silvestre/química , Imunoensaio/métodos , Raios Infravermelhos , Chumbo/efeitos da radiação , Limite de Detecção , Nanopartículas Metálicas/química , Pontos Quânticos/efeitos da radiação , Reprodutibilidade dos Testes , Compostos de Selênio/efeitos da radiação
7.
ACS Appl Mater Interfaces ; 11(5): 4858-4866, 2019 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-30628779

RESUMO

Molybdenum disulfide (MoS2) nanosheets have received considerable interest due to their superior physicochemical performances to graphene nanosheets. As the lateral size and layer thickness decrease, the formed MoS2 quantum dots (QDs) show more promise as photocatalysts, endowing them with potential antimicrobial properties under environmental conditions. However, studies on the antibacterial photodynamic therapy of MoS2 QDs have rarely been reported. Here, we show that MoS2 QDs more effectively promote the creation and separation of electron-hole pair than MoS2 nanosheets, resulting in the formation of multiple reactive oxygen species (ROS) under simulated solar light irradiation. As a result, photoexcited MoS2 QDs show remarkably enhanced antibacterial activity, and the ROS-mediated oxidative stress plays a dominant role in the antibacterial mechanism. The in vivo experiments showed that MoS2 QDs are efficacious in wound healing under simulated solar light irradiation and exert protective effects on normal tissues, suggesting good biocompatibility properties. Our findings provide a full description of the photochemical behavior of MoS2 QDs and the resulting antibacterial activity, which might advance the development of MoS2-based nanomaterials as photodynamic antibacterial agents under environmental conditions.


Assuntos
Antibacterianos , Dissulfetos , Molibdênio , Pontos Quânticos , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Antibacterianos/efeitos da radiação , Antibacterianos/toxicidade , Bactérias/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Dissulfetos/química , Dissulfetos/farmacologia , Dissulfetos/toxicidade , Células Endoteliais da Veia Umbilical Humana , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Molibdênio/química , Molibdênio/farmacologia , Molibdênio/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Processos Fotoquímicos , Pontos Quânticos/química , Pontos Quânticos/efeitos da radiação , Pontos Quânticos/toxicidade , Espécies Reativas de Oxigênio , Infecção dos Ferimentos
8.
Anal Chim Acta ; 1048: 42-49, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30598156

RESUMO

A novel enhanced photoelectrochemical (PEC) DNA biosensor, based on a compact heterojunction g-C3N4/MoS2 and co-sensitization effect with CdSe quantum dots (QDs), was first proposed for simple and accurate analysis of a short ssDNA. In this work, the g-C3N4/MoS2 was successfully synthesized and used as the electrode matrix material to construct PEC biosensor. 2D/2D heterojunction was formed between g-C3N4 and MoS2, which could promote the separation of photogenerated electron-hole pairs resulting in an enhanced photocurrent. In the presence of target DNA, CdSe QDs labeled reporter DNA was complementary pairing with target DNA which was specific recognized by capture DNA loading on self-assembled CdS QDs film, leading to close contact between CdSe QDs and g-C3N4/MoS2 modified electrode surface, thereby resulting in the enhanced photocurrent intensity due to the co-sensitization effect. Under the optimal operating conditions, the photoelectrochemical biosensor demonstrated favorable accuracy and could respond to 0.32 pM (S/N = 3) with a linear concentration range from 1.0 pM to 2.0 µM. Moreover, the proposed PEC DNA biosensor exhibits high sensitivity, excellent specificity, acceptable reproducibility and accuracy, showing a promising potential in DNA bioanalysis and other relative fields.


Assuntos
Técnicas Biossensoriais/métodos , DNA de Cadeia Simples/análise , Técnicas Eletroquímicas/métodos , Fotoquímica/métodos , Pontos Quânticos/química , Compostos de Cádmio/química , Compostos de Cádmio/efeitos da radiação , DNA de Cadeia Simples/genética , Dissulfetos/química , Eletrodos , Luz , Limite de Detecção , Molibdênio/química , Nitrilos/química , Hibridização de Ácido Nucleico , Pontos Quânticos/efeitos da radiação , Compostos de Selênio/química , Compostos de Selênio/efeitos da radiação
9.
Talanta ; 188: 35-40, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30029387

RESUMO

A hydrothermal synthetic approach is developed for the preparation of graphitic carbon nitride quantum dots (g-C3N4 QDs) from human urine. The reported synthetic method is green, simple, low-cost, less time-consuming, and can be used for the large-scale production of the g-C3N4 QDs. The as-prepared g-C3N4 QDs possess a high quantum yield of 15.7% by using quinine sulfate as a reference, and display excitation-wavelength dependent fluorescent emission. In addition, the g-C3N4 QDs exhibit high photostability, low cytotoxicity. and are successfully used as fluorescent probes for cell multicolor imaging. It is believed that the valuable nanomaterials, g-C3N4 QDs, which are transformed from the human bodily wastes, are promising in diverse chemical applications.


Assuntos
Corantes Fluorescentes/síntese química , Grafite/síntese química , Química Verde/métodos , Nitrilos/síntese química , Pontos Quânticos/química , Urina/química , Técnicas de Química Sintética/métodos , Fluorescência , Corantes Fluorescentes/metabolismo , Corantes Fluorescentes/efeitos da radiação , Corantes Fluorescentes/toxicidade , Grafite/metabolismo , Grafite/efeitos da radiação , Grafite/toxicidade , Células Hep G2 , Humanos , Microscopia de Fluorescência , Nitrilos/metabolismo , Nitrilos/efeitos da radiação , Nitrilos/toxicidade , Imagem Óptica/métodos , Pontos Quânticos/efeitos da radiação , Pontos Quânticos/toxicidade
10.
Phys Chem Chem Phys ; 20(24): 16501-16509, 2018 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-29878021

RESUMO

In this study, we demonstrated a prompt and sensitive detection technique for cardiac troponin T (cTnT) in buffer and biological fluid (serum) using an NIR-active fluorescent anti-cTnT-labelled carbon dot (CD) and molybdenum disulfide (MoS2)-based nano-couple. Exfoliated MoS2 nanosheets strongly grasp the anti-cTnT-labelled CDs over their surface, and an excited-state non-radiative energy transfer mechanism takes place from CDs to MoS2, thereby quenching the upconversion fluorescence. The nonlinear and upward Stern-Volmer relationship is observed, which indicates a combined static and dynamic quenching. Static and time-resolved fluorescence measurements predict distance-dependent Förster resonance energy transfer (FRET) dynamics, which control the detection process. In the presence of cTnT, the energy transfer process gets hindered due to strong antibody/antigen (anti-cTnT/cTnT) interaction. The cTnT molecules affect the positions of the nano-couple and cause effective detachment of CDs from the MoS2 surface. This results hindrance in the energy transfer process with consequent restoration of upconversion intensity. A linear response is observed between the cTnT concentration and the restored fluorescence intensity in the concentration range of 0.1-50 ng mL-1 with a limit of detection of 0.12 ng mL-1 and a limit of quantification of 0.38 ng mL-1. Statistical analysis shows that the present assay possesses an accuracy of 101.4 ± 3.76 with a co-relation co-efficient of 0.99. Thus, CD/MoS2 provides a promising platform for the sensitive detection of cTnT.


Assuntos
Carbono/efeitos da radiação , Dissulfetos/efeitos da radiação , Molibdênio/efeitos da radiação , Pontos Quânticos/efeitos da radiação , Troponina T/sangue , Anticorpos/imunologia , Técnicas Biossensoriais/métodos , Carbono/química , Dissulfetos/química , Fluorescência , Transferência Ressonante de Energia de Fluorescência/métodos , Humanos , Técnicas Imunológicas/métodos , Luz , Limite de Detecção , Molibdênio/química , Pontos Quânticos/química , Troponina T/imunologia
11.
Chem Commun (Camb) ; 54(47): 6060-6063, 2018 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-29808876

RESUMO

Black phosphorus quantum dots are incorporated into liposomal bilayers to produce a drug delivery system with excellent near-infrared (NIR) photothermal properties and drug release capability controlled by light. In vitro experiments demonstrate its good biocompatibility and NIR-light-induced chemo-photothermal antitumor efficiency.


Assuntos
Antineoplásicos/farmacologia , Doxorrubicina/farmacologia , Bicamadas Lipídicas/química , Lipossomos/química , Fósforo/química , Pontos Quânticos/efeitos da radiação , Animais , Colesterol/química , Colesterol/toxicidade , Liberação Controlada de Fármacos , Calefação , Humanos , Raios Infravermelhos , Bicamadas Lipídicas/toxicidade , Lipossomos/toxicidade , Células MCF-7 , Camundongos , Microscopia Confocal , Tamanho da Partícula , Fosfatidilcolinas/química , Fosfatidilcolinas/toxicidade , Fósforo/toxicidade , Pontos Quânticos/química , Pontos Quânticos/toxicidade
12.
Chem Rev ; 116(22): 13043-13233, 2016 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-27933768

RESUMO

The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the function of optical power limiting. All known mechanisms of optical limiting have been analyzed and discussed for the different types of materials.


Assuntos
Complexos de Coordenação/efeitos da radiação , Luz , Nanoestruturas/efeitos da radiação , Dispositivos Ópticos , Carbono/química , Carbono/efeitos da radiação , Corantes/química , Corantes/efeitos da radiação , Complexos de Coordenação/química , Dendrímeros/química , Dendrímeros/efeitos da radiação , Nanopartículas Metálicas/química , Nanopartículas Metálicas/efeitos da radiação , Nanoestruturas/química , Fenômenos Ópticos , Óptica e Fotônica , Porfirinas/química , Porfirinas/efeitos da radiação , Pontos Quânticos/química , Pontos Quânticos/efeitos da radiação
13.
Aquat Toxicol ; 176: 197-207, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27162069

RESUMO

Cadmium-based quantum dots (QDs) are increasingly applied in existent and emerging technologies, especially in biological applications due to their exceptional photophysical and functionalization properties. However, they are very toxic compounds due to the high reactive and toxic cadmium core. The present study aimed to determine the toxicity of three different QDs (CdS 380, CdS 480 and CdSeS/ZnS) before and after the exposure of suspensions to sunlight, in order to assess the effect of environmentally relevant irradiation levels in their toxicity, which will act after their release to the environment. Therefore, a battery of ecotoxicological tests was performed with organisms that cover different functional and trophic levels, such as Vibrio fischeri, Raphidocelis subcapitata, Chlorella vulgaris and Daphnia magna. The results showed that core-shell type QDs showed lower toxic effects to V. fischeri in comparison to core type QDs before sunlight exposure. However, after sunlight exposure, there was a decrease of CdS 380 and CdS 480 QD toxicity to bacterium. Also, after sunlight exposure, an effective decrease of CdSeS/ZnS and CdS 480 toxicity for D. magna and R. subcapitata, and an evident increase in CdS 380 QD toxicity, at least for D. magna, were observed. The results of this study suggest that sunlight exposure has an effect in the aggregation and precipitation reactions of larger QDs, causing the degradation of functional groups and formation of larger bulks which may be less prone to photo-oxidation due to their diminished surface area. The same aggregation behaviour after sunlight exposure was observed for bare QDs. These results further emphasize that the shell of QDs seems to make them less harmful to aquatic biota, both under standard environmental conditions and after the exposure to a relevant abiotic factor like sunlight.


Assuntos
Compostos de Cádmio/toxicidade , Pontos Quânticos/toxicidade , Sulfetos/toxicidade , Luz Solar , Poluentes Químicos da Água/toxicidade , Aliivibrio fischeri/efeitos dos fármacos , Animais , Compostos de Cádmio/efeitos da radiação , Clorófitas/efeitos dos fármacos , Daphnia/efeitos dos fármacos , Pontos Quânticos/efeitos da radiação , Sulfetos/efeitos da radiação , Compostos de Zinco/toxicidade
14.
Talanta ; 142: 131-9, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26003702

RESUMO

Nitrogen doping has been a powerful method to modulate the properties of carbon materials for various applications, and N-doped graphene quantum dots (GQDs) have gained remarkable interest because of their unique chemical, electronic, and optical properties. Herein, we introduce a facile one-pot solid-phase synthesis strategy for N-doped GQDs using citric acid (CA) as the carbon source and 3,4-dihydroxy-L-phenylalanine (L-DOPA) as the N source. The as-prepared N-GQDs with oxygen-rich functional groups are uniform with an average diameter of 12.5 nm. Because of the introduction of nitrogen atoms, N-GQDs exhibit excitation-wavelength-independent fluorescence with the maximum emission at 445 nm, and a high quantum yield of 18% is achieved at an excitation wavelength of 346 nm. Furthermore, a highly efficient fluorosensor based on the as-prepared N-GQDs was developed for the detection of Hg(2+) because of the effective quenching effect of metal ions via nonradiative electron transfer. This fluorosensor exhibits high sensitivity toward Hg(2+) with a detection limit of 8.6 nM. The selectivity experiments reveal that the fluorescent sensor is specific for Hg(2+). Most importantly, the practical use of the sensor based on N-GQDs for Hg(2+) detection was successfully demonstrated in river-water samples.


Assuntos
Mercúrio/análise , Pontos Quânticos/química , Poluentes Químicos da Água/análise , Ácido Cítrico/química , Grafite/química , Grafite/efeitos da radiação , Concentração de Íons de Hidrogênio , Levodopa/química , Luminescência , Mercúrio/química , Nitrogênio/química , Nitrogênio/efeitos da radiação , Oxigênio/química , Oxigênio/efeitos da radiação , Pontos Quânticos/efeitos da radiação , Rios/química , Raios Ultravioleta , Poluentes Químicos da Água/química
15.
Talanta ; 135: 27-33, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25640122

RESUMO

A new chemiluminescence (CL) flow method for persulfate determination was developed based on luminol oxidation by in-line generated radicals. Reactive oxygen species (ROS) generated by CdTe quantum dots (QDs) under a low energetic radiation (visible light emitted by LEDs) promoted the decomposition of persulfate ion (S2O8(2-)) into sulfate radical (SO4(∙-)), leading to subsequent radical chain reactions that yield the emission of light. Due to the inherent radical short lifetimes and the transient behavior of CL phenomena an automated multi-pumping flow system (MPFS) was proposed to improve sample manipulation and reaction zone implementation ensuring reproducible analysis time and high sampling rate. The developed approach allowed up to 60 determinations per hour and determine S2O8(2-) concentrations between 0.1 and 1 mmol with good linearity (R=0.9999). The method has shown good repeatability with relative standard deviations below 2.5% (n=3) for different persulfate concentrations (0.1 and 0.625 mmol L(-1)). Limits of detection (3σ) and quantification (10σ) were 2.7 and 9.1 µmol L(-1), respectively. The MPFS system was applied to persulfate determination in bench scale UV/S2O8(2-) drug degradation processes of model samples showing good versatility and providing real time information on the persulfate consumption in photo-chemical degradation methodologies.


Assuntos
Ácido 3-Mercaptopropiônico/efeitos da radiação , Compostos de Cádmio/efeitos da radiação , Luminol/química , Compostos de Potássio/efeitos da radiação , Pontos Quânticos/efeitos da radiação , Espécies Reativas de Oxigênio/química , Sulfatos/efeitos da radiação , Telúrio/efeitos da radiação , Ácido 3-Mercaptopropiônico/química , Compostos de Cádmio/química , Luz , Nanopartículas/química , Oxirredução , Compostos de Potássio/química , Pontos Quânticos/química , Sulfatos/química , Telúrio/química
16.
ChemSusChem ; 8(4): 642-9, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25470751

RESUMO

A visible-light-induced hydrogen evolution system based on a CdSe quantum dots (QDs)-TiO2 -Ni(OH)2 ternary assembly has been constructed under an ambient environment, and a bifunctional molecular linker, mercaptopropionic acid, is used to facilitate the interaction between CdSe QDs and TiO2 . This hydrogen evolution system works effectively in a basic aqueous solution (pH 11.0) to achieve a hydrogen evolution rate of 10.1 mmol g(-1) h(-1) for the assembly and a turnover frequency of 5140 h(-1) with respect to CdSe QDs (10 h); the latter is comparable with the highest value reported for QD systems in an acidic environment. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and control experiments demonstrate that Ni(OH)2 is an efficient hydrogen evolution catalyst. In addition, inductively coupled plasma optical emission spectroscopy and the emission decay of the assembly combined with the hydrogen evolution experiments show that TiO2 functions mainly as the electron mediator; the vectorial electron transfer from CdSe QDs to TiO2 and then from TiO2 to Ni(OH)2 enhances the efficiency for hydrogen evolution. The assembly comprises light antenna CdSe QDs, electron mediator TiO2 , and catalytic Ni(OH)2 , which mimics the strategy of photosynthesis exploited in nature and takes us a step further towards artificial photosynthesis.


Assuntos
Compostos de Cádmio/química , Hidrogênio/química , Hidróxidos/química , Níquel/química , Pontos Quânticos/química , Compostos de Selênio/química , Compostos de Sulfidrila/química , Titânio/química , Compostos de Cádmio/efeitos da radiação , Catálise , Hidróxidos/efeitos da radiação , Luz , Níquel/efeitos da radiação , Pontos Quânticos/efeitos da radiação , Compostos de Selênio/efeitos da radiação , Titânio/efeitos da radiação
17.
Chem Commun (Camb) ; 50(77): 11370-3, 2014 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-25122582

RESUMO

Herein, positively charged QDs were initially prepared by covalently linking to poly(allylamine hydrochloride) (PAH). The resulting PAH-modified QDs in conjunction with MMT nanosheets were utilized to fabricate QDs/MMT UTFs via LBL assembly. Strong photoluminescence, temperature responsiveness, long-term stability and high uniformity make these films potential candidates for a wide range of applications.


Assuntos
Bentonita/química , Polímeros/química , Pontos Quânticos/química , Alilamina , Luminescência , Nanoestruturas/química , Pontos Quânticos/efeitos da radiação , Temperatura Ambiente , Raios Ultravioleta
18.
ACS Appl Mater Interfaces ; 5(16): 8105-10, 2013 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-23855339

RESUMO

A new method to enhance the stability of quantum dots (QDs) in aqueous solution by encapsulating them with conducting polymer polyaniline was reported. The polyaniline-encapsulated QDs were then decorated onto graphene through π-π interactions between graphene and conjugated polymer shell of QDs, forming stable polyaniline/QD/graphene hybrid. A testing electronic device was fabricated using the hybrid in order to investigate the photoinduced charge transfer between graphene and encapsulated QDs within the hybrid. The charge transfer mechanism was explored through cyclic voltammetry and spectroscopic studies. The hybrid shows a clear response to the laser irradiation, presenting a great advantage for further applications in optoelectronic devices.


Assuntos
Compostos de Anilina/química , Grafite/química , Pontos Quânticos , Lasers , Polímeros/química , Pontos Quânticos/química , Pontos Quânticos/efeitos da radiação , Soluções , Água/química
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