Photodynamic therapy (PDT) is a noninvasive and site-specific therapeutic technique for the clinical treatment of various of superficial diseases. In order to tuning the operation wavelength and improve the tissue penetration of PDT, rare-earth doped upconversion nanoparticles (UCNPs) with strong anti-stokes emission are introduced in PDT recently. However, the conventional Yb³⁺-sensitized UCNPs are excited at 980 nm which is overlapped with the absorption of water, thus resulting in strong overheating effect. Herein, a convenient but effective design to obtain highly emissive 795 nm excited Nd³⁺-sensitized UCNPs (NaYF₄:Yb,Er@NaYF₄:Yb_0.1Nd_0.4@NaYF₄) is reported, which provides about six times enhanced upconversion luminescence, comparing with traditional UCNPs (NaYF₄:Yb,Er@NaYF₄). A colloidal stable and non-leaking PDT nanoplatform is fabricated later through a highly PEGylated mesoporous silica layer with covalently linked photosensitizer (Rose Bengal derivative). With as-prepared Nd³⁺-sensitized UCNPs, the nanoplatform can produce singlet oxygen more effective than traditional UCNPs. Significant higher penetration depth and lower overheating are demonstrated as well. All these features make as-prepared nanocomposites excellent platform for PDT treatment. In addition, the nanoplatform with uniform size, high surface area, and excellent colloidal stability can be extended for other biomedical applications, such as imaging probes, biosensors, and drug delivery vehicles.

The design of an ideal drug delivery system with targeted recognition and zero premature release, especially controlled and specific release that is triggered by an exclusive endogenous stimulus, is a great challenge. A traceable and aptamer-targeted drug nanocarrier has now been developed; the nanocarrier was obtained by capping mesoporous silica-coated quantum dots with a programmable DNA hybrid, and the drug release was controlled by microRNA. Once the nanocarriers had been delivered into HeLa cells by aptamer-mediated recognition and endocytosis, the overexpressed endogenous miR-21 served as an exclusive key to unlock the nanocarriers by competitive hybridization with the DNA hybrid, which led to a sustained lethality of the HeLa cells. If microRNA that is exclusively expressed in specific pathological cell was screened, a combination of chemotherapy and gene therapy should pave the way for a targeted and personalized treatment of human diseases.

A new nanostructured graphene/TiO₂ (G/TiO₂) hybrid was synthesized by a facile microwave-assisted solvothermal process in which amorphous TiO₂ was assembled on graphene in situ. The resulting G/TiO₂ hybrids were characterized by XRD, SEM, TEM, Raman spectroscopy, and N₂ adsorption/desorption analysis. The electrochemical properties of the hybrids as anode materials for Shewanella-inoculated microbial fuel cells (MFCs) were studied for the first time, and they proved to be effective in improving MFC performance. The significantly improved bacterial attachment and extracellular electron-transfer efficiency could be attributed to the high specific surface area, active groups, large pore volume, and excellent conductivity of the nanostructured G/TiO₂ hybrid, and this suggests that it could be a promising candidate for high-performance MFCs.

A graphene/poly(3,4-ethylenedioxythiophene) (G/PEDOT) hybrid was prepared by the in situ polymerization of 3,4-ethylenedioxythiophene using the precursor of graphene, graphene oxide, as an oxidant under microwave heating. The G/PEDOT hybrid was characterized by ultraviolet–visible absorption spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. The electrochemical properties of G/PEDOT hybrid electrodes were investigated by cyclic voltammetry and galvanostatic charge–discharge measurements. The G/PEDOT hybrid as a supercapacitor electrode material afforded high specific capacitance and good cycling stability (93 % retention after 10 000 cycles at a high current density of 5 A g⁻¹) during the charge–discharge process. A maximum specific capacitance as high as 270 F g⁻¹ at a current density of 1 A g⁻¹ was achieved in 1 M H₂SO₄ electrolyte solution. In addition, the energy density of the G/PEDOT hybrid reached 34 W h kg⁻¹ at a power density of 25 kW kg⁻¹.

A microbial fuel cell (MFC) is an innovative power-output device, which utilizes microorganisms to metabolize fuel and transfers electrons to the electrode surface. In this study, we decorated the surface of graphene (G) with a conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), through galvanostatic electropolymerization to fabricate a G/PEDOT hybrid anode for an Escherichia coli MFC. Cyclic voltammetry and electrochemical impedance spectroscopy analyses illustrated that the G/PEDOT hybrid anode possesses a larger active surface area and lower charge-transfer resistance than three other kinds of anodes, namely, carbon paper (CP), graphene-modified carbon paper (CP/G), and PEDOT-modified carbon paper (CP/PEDOT). Scanning electron microscopy was used to investigate the bacteria growth on the four anodes. A compact biofilm was formed on the hybrid anode owing to the electrostatic interaction between the negatively charged bacteria and positively charged PEDOT backbone. The constant-load (1 KΩ) discharge curves of MFCs with CP, CP/G, CP/PEDOT, and G/PEDOT anodes revealed that the G/PEDOT electrode had good stability and high voltage output. The G/PEDOT anode generated a maximum power density of 873 mW m⁻², which is about 15 times higher than that of CP (55 mW m⁻²) in an H-shaped dual-chamber MFC. All the experimental results suggest that the performance of the G/PEDOT hybrid anode is superior to the CP, CP/G, or CP/PEDOT anode.

A novel strategy is developed for the fabrication of graphene–CdS (G–CdS) nanocomposites by in situ growth of CdS nanoparticles onto simultaneously reduced graphite oxide, which is noncovalently functionalized by sodium 1-pyrene sulfonate through strong π–π stacking interactions. Subsequently, cobalt 2,9,16,23-tetraaminophthalocyanine (CoTAPc) is self-assembled on the G–CdS nanocomposites through electrostatic interactions to produce phthalocyanine-sensitized G–CdS nanocomposites. The photoactive superstructure enhances the photocurrent generation capability, and presents an efficient photoelectrochemical immunosensing platform for the ultrasensitive detection of the prostate-specific antigen (PSA). The quantitative measurement of PSA is based on the decrease in the photocurrent intensity of the phthalocyanine-sensitized G–CdS nanocomposites, which results from an increase in the steric hindrance due to the formation of the immunocomplex. A linear relationship between the photocurrent decrease and the PSA concentration is obtained in the wide range from 1 pg mL⁻¹ to 5 μg mL⁻¹ with a detection limit of 0.63 pg mL⁻¹. The proposed sensor shows high sensitivity, stability, reproducibility, and can become a promising platform for other biomolecular detection.

With the assistance of microwave irradiation, greenish-yellow luminescent graphene quantum dots (gGQDs) with a quantum yield (QY) up to 11.7% are successfully prepared via cleaving graphene oxide (GO) under acid conditions. The cleaving and reduction processes are accomplished simultaneously using microwave treatment without additional reducing agent. When the gGQDs are further reduced with NaBH₄, bright blue luminescent graphene quantum dots (bGQDs) are obtained with a QY as high as 22.9%. Both GQDs show well-known excitation-dependent PL behavior, which could be ascribed to the transition from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) with a carbene-like triplet ground state. Electrochemiluminescence (ECL) is observed from the graphene quantum dots for the first time, suggesting promising applications in ECL biosensing and imaging. The ECL mechanism is investigated in detail. Furthermore, a novel sensor for Cd²⁺ is proposed based on Cd²⁺ induced ECL quenching with cysteine (Cys) as the masking agent.

Graphene–CdS (GR–CdS) nanocomposites were prepared in a one-step synthesis in aqueous solution. The synthetic approach was simple and fast, and it may be extended for the synthesis of other GR–metal-sulfide nanocomposites. The as-prepared GR–CdS nanocomposite films inherited the excellent electron-transport properties of GR. In addition, the heteronanostructure of the GR–CdS nanocomposites facilitated the spatial separation of the charge carriers, thus resulting in enhanced photocurrent intensity, which makes it a promising candidate for photoelectrochemical applications. This strategy was used for the fabrication of an advanced photoelectrochemical cytosensor, based on these GR–CdS nanocomposites, by using a layer-by-layer assembly process. This photoelectrochemical cytosensor showed a good photoelectronic effect and cell-capture ability, and had a wide linear range and low detection limit for Hela cells. The as-synthesized GR–CdS nanocomposites exhibited obviously enhanced photovoltaic properties, which could be an efficient platform for many other high-performance photovoltaic devices.

A novel strategy is reported for the fabrication of poly(diallyldimethylammonium chloride) (PDDA)-protected graphene–CdSe (P-GR-CdSe) composites. An advanced electrogenerated chemiluminescence (ECL) immunosensor is proposed for the sensitive detection of human IgG (HIgG) by using the as-prepared P-GR-CdSe composites. The P-GR-CdSe composite film shows high ECL intensity, good electronic conductivity, fast response, and satisfactory stability, all of which holds great promise for the fabrication of ECL biosensors with improved sensitivity. After two successive steps of amplification via the conjugation of PDDA and gold nanoparticles (GNPs) in the film, high ECL intensity is observed. The ECL immunosensor has an extremely sensitive response to HIgG in a linear range of 0.02–2000 pg mL⁻¹ with a detection limit of 0.005 pg mL⁻¹. The proposed sensor exhibits high specificity, good reproducibility, and long-term stability, and may become a promising technique for protein detection.

The catalytic activity of nanocrystal catalysts depends strongly on their structures. Herein, we report three distinct structures of Fe₃O₄ nanocrystals, cluster spheres, octahedra, and triangular plates, prepared by a similar hydrothermal procedure. Additionally, the three Fe₃O₄ nanostructures were used as peroxidase nanomimetics and the correlation between the catalytic activities and the structures was first explored by using 3,3′,5,5′-tetramethylbenzidine and H₂O₂ as peroxidase substrates. The results showed that the peroxidase-like activities of the Fe₃O₄ nanocrystals were structure dependent and followed the order cluster spheres>triangular plates>octahedra; this order was closely related to their preferential exposure of catalytically active iron atoms or crystal planes. Such investigation is of great significance for peroxidase nanomimetics with enhanced activity and utilization.

A combined hydrothermal/hydrogen reduction method has been developed for the mass production of helical carbon nanotubes (HCNTs) by the pyrolysis of acetylene at 475 °C in the presence of Fe₃O₄ nanoparticles. The synthesized HCNTs have been characterized by high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction analysis, vibrating sample magnetometry, and contact-angle measurements. The as-prepared helical-structured carbon nanotubes have a large specific surface area and high peroxidase-like activity. Catalysis was found to follow Michaelis–Menten kinetics and the HCNTs showed strong affinity for both H₂O₂ and 3,3′,5,5′,-tetramethylbenzidine (TMB). Based on the high activity, the HCNTs were firstly used to develop a biocatalyst and amperometric sensor. At pH 7.0, the constructed amperometric sensor showed a linear range for the detection of H₂O₂ from 0.5 to 115 μM with a correlation coefficient of 0.999 without the need for an electron-transfer mediator. Because of their low cost and high stability, these novel metallic HCNTs represent a promising candidate as mimetic enzymes and may find a wide range of new applications, such as in biocatalysis, immunoassay, and environmental monitoring.

Multifunctional manganese carbonate microspheres with superparamagnetic and fluorescent properties were fabricated and used as biological labels. The Fe₃O₄@MnCO₃ microspheres were synthesized by direct co-precipitation without any linker shell. The Fe₃O₄@MnCO₃ microspheres have uniform size distribution and rough surface, which provides a promising template for the assembly of polyelectrolytes (PEs) and CdTe quantum dots (QDs). A luminescent CdTe shell was observed in Fe₃O₄@MnCO₃@PE-CdTe spheres by confocal fluorescence imaging. With excellent solubility in water and rough surfaces, the multifunctional microsphere offers a friendly microenvironment for immobilization of α-fetoprotein (AFP) antibodies (Ab₂) to fabricate Fe₃O₄@MnCO₃@PE-CdTe-Ab₂ architecture. By using the Fe₃O₄@MnCO₃@PEs-CdTe-Ab₂ bioconjugate as a label, a promising and versatile platform for fluorescence imaging and electrochemical immunosensing of cancer biomarker AFP was developed. The prepared electrochemical immunosensor shows high sensitivity and selectivity with a detection limit of 0.3 pg mL⁻¹.

A 3D ordered macroporous (3DOM) ionic-liquid-doped polyaniline (IL-PANI) inverse opaline film is fabricated with an electropolymerization method and gold nanoparticles (AuNPs) are assembled on the film by electrostatic adsorption, which offers a promising basis for biomolecular immobilization due to its satisfactory chemical stability, good electronic conductivity, and excellent biocompatibility. The AuNP/IL-PANI inverse opaline film could be used to fabricate an electrochemical impedance spectroscopy (EIS) immunosensor for the determination of Hepatitis B surface antigen (HBsAg). The concentration of HBsAg is measured using the EIS technique by monitoring the corresponding specific binding between HBsAg and HBsAb (surface antibody). The increased electron transfer resistance (R_et) values are proportional to the logarithmic value of the concentration of HBsAg. This novel immunoassay displays a linear response range between 0.032 pg mL⁻¹ and 31.6 pg mL⁻¹ with a detection limit of 0.001 pg mL⁻¹. The detection of HBsAg levels in several sera showed satisfactory agreement with those using a commercial turbidimetric method.

A rapid microwave-hydrothermal method has been developed to prepare monodisperse colloidal carbon nanospheres from glucose solution, and gold nanoparticles (AuNPs) are successfully assembled on the surface of the colloidal carbon nanospheres by a self-assembly approach. The resulting AuNP/colloidal carbon nanosphere hybrid material (AuNP/C) has been characterized and is expected to offer a promising template for biomolecule immobilization and biosensor fabrication because of its satisfactory chemical stability and the good biocompatibility of AuNPs. Herein, as an example, it is demonstrated that the as-prepared AuNP/C hybrid material can be conjugated with horseradish peroxidase-labeled antibody (HRP-Ab₂) to fabricate HRP-Ab₂-AuNP/C bioconjugates, which can then be used as a label for the sensitive detection of protein. The amperometric immunosensor fabricated on a carbon nanotube-modified glass carbon electrode was very effective for antibody immobilization. The approach provided a linear response range between 0.01 and 250 ng mL⁻¹ with a detection limit of 5.6 pg mL⁻¹. The developed assay method was versatile, offered enhanced performances, and could be easily extended to other protein detection as well as DNA analysis.

A Hemoglobin-CdTe-CaCO₃@polyelectrolyte 3D architecture is synthesized by a stepwise layer-by-layer method and is further used to fabricate an electrochemistry biosensor. While the calcium carbonate (CaCO₃) microsphere acts as an effective host for the loading of cadmium telluride (CdTe) quantum dots due to its channel-like structure, the polyelectrolyte layers further increase the loading amount and help in the formation of a thick and uniform quantum-dot “shell”, which not only improves the stability of the spheres in water, but also contributes to the fast and effective direct electron transfer between the protein redox center and the macroscopic electrode. The materials are characterized and compared, and the possible mechanism for the direct electrochemistry phenomenon is hypothesized. Our work not only provides a facile and effective route for the preparation of quantum-dot-loaded spheres, but also sets an example of how the structure of functional materials can be tuned and related to their applications. In addition, it is one of the few examples of using CaCO₃ microspheres in quantum-dot loading and biosensing.

Luminescent cadmium(II) (8-hydroxyquinoline) chloride (CdqCl) complex nanowires are synthesized via a sonochemical solution route. The results of X-ray photoelectron spectroscopy, energy dispersive X-ray analysis, infrared spectroscopy, elemental analysis (EA), and atomic absorption spectroscopy demonstrate that the chemical composition of the product is Cd(C₉H₆NO)Cl. Transmission electron microscopy and scanning electron microscopy images show that the CdqCl product is wire-like in structure, with a diameter of approximately 50 nm and an approximate length of 2–4 µm. The morphology and composition of the product can be transformed from Cdq₂ micrometer-scaled flakes to CdqCl nanowires by increasing the ratio of CdCl₂/q. A new fluorescent sensing strategy for detecting H₂O₂ and glucose is developed and is based on the combination of the luminescent nanowires and the biocatalytic growth of Au nanoparticles. The quenching effects of Au nanoparticles and on the fluorescence of CdqCl nanowires are investigated. The dominant factor for the fluorescence quenching of CdqCl nanowires is that the Stern–Volmer quenching constant of Au nanoparticles is larger than that of .