•Flexible photodetectors based on HfSe3/GO and HfSe3/RGO composites were fabricated.•Flexible photodetectors based on HfS3/GO and HfS3/RGO composites were fabricated.•These photodetectors showed good photoresponse from 405 to 980 nm.•The photodetectors of the composites showed enhanced photoresponse.Flexible photodetectors from 405 to 980 nm based on HfSe3 or HfS3 nanobelts (NBs)/graphene composites were fabricated on polypropylene (PP) films. Compared with HfSe3 or HfS3 NB photodetectors, the flexible composite photodetector showed enhancement of photoresponsivity. For substance, under the illumination light of 405 nm (14.4 mW/cm2), the responsivities of HfSe3 NBs, HfSe3 NBs/GO (graphene oxide) and HfSe3 NBs/RGO (reduced graphene oxide) photodetectors were 1.1 × 10−4, 4.3 × 10−3 and 0.5 (mA/W), respectively, while those of HfS3 NBs, HfS3 NBs/GO and HfS3 NBs/RGO photodetectors were 0.11, 0.92 and 0.55 (mA/W), respectively. Meanwhile, these photodetectors exhibited excellent durability and stability after they were placed for 3 months and bended 500 times. So the composites are promising optoelectronic materials, and the flexible photodetectors are high-performance photodetectors from visible to near-infrared.Download high-res image (182KB)Download full-size image

•We study the nonlinear absorption properties of SnS2 and SnSe2 for the first time.•We find SnS2 have excellent optical limiting for the first time.•The optical limiting threshold Fth of SnS2 is only about 0.23 J/cm2.Tin-based dichalcogenides such as SnS2 and SnSe2 have attracted wide attention due to their significant potential for the next-generation optoelectronic and photonic devices in nanotechnology. We investigate the nonlinear absorption of SnS2 and SnSe2 nanosheets using the Z-scan technique with nanosecond pulse and picosecond pulse at 532 nm for the first time. Z-scan measurement reveals that SnS2 nanosheets dispersions exhibit reverse saturable absorption (RSA) behavior under different pulses, which is in contrast to the saturable absorption (SA) observed in the SnSe2 nanosheets dispersions resulted from different band gaps. The nonlinear absorption coefficient (β) and the figures of merit (FOM) of SnS2 dispersed in ethanol with linear transmittances of 0.75 at input energy of 6.16 μJ in the nanosecond regime are 12.78 × 10−10 m/W and 8.71 × 10−11 esu⋅cm, respectively. As for SnSe2 nanosheet dispersions, β and FOM are −12.58 × 10−10 m/W and 11.98 × 10−11 esu⋅cm at the same input energy, respectively. The RSA behavior coupled to the smaller optical limiting threshold Fth (0.23 J/cm2) proves SnS2 a promising 2D material for protecting sensitive optical components or eyes from laser-induced damage. The SA performance indicates SnSe2 nanosheets prospective candidates for high-performance nanoscale nanophotonic devices like optical switches.The nonlinear absorption performance of SnX2 (X = S, Se) was measured by Z-Scan technique at nanosecond pulse and picosecond pulse, the results show that SnS2 nanosheets have excellent optical limiting property and optical limiting threshold Fth is about 0.23 J/cm2. However, SnSe2 nanosheets exhibit saturable absorption behavior.Download high-res image (171KB)Download full-size image

The nonlinear optical (NLO) properties of a ZrS3 nanobelt were measured with a 6.5 ns pulse laser at 532 nm. Its optical response to the incident light exhibits good optical absorptive and refractive effects, with the nonlinear absorption coefficient β = 4.42 × 10−10 m W−1 and the nonlinear refraction coefficient γ = 5.86 × 10−17 m2 W−1 for the ZrS3 nanobelt in ethanol dispersions at an input energy of 34.25 μJ. In addition, the β values and γ values have dependence on input energy. Results show that the ZrS3 nanobelts have an excellent reverse saturable absorption (RSA) performance in nanosecond pulses, demonstrating that ZrS3 nanobelts are an extraordinarily promising novel optical power limiting material. Meanwhile, compared to the pure ZrS3, graphene oxide (GO) and reduced graphene oxide (RGO), composites (ZrS3/GRO) exhibit an enhanced nonlinear absorption response at the same input energy.

•We synthesized pure HfS3 nanobelts by chemical vapor transport in a short time.•The nanobelts have good photoluminescence under the excitation at 400 nm.•A flexible UV–vis photodetector was fabricated on the basis of HfS3 nanobelt film.•The photodetector showed high photoresponse and high selectivity.HfS3 nanobelts with a width of 700 − 70 nm, a thickness of about 10–30 nm and a length of more than 10 μm, were directly synthesized at 650 °C for 5 h by a facile chemical vapor transport (CVT) method. The direct and indirect optical energy gaps of the nanobelts were measured as 2.19 and 1.73 eV, respectively. The nanobelts have good photoluminescence (PL), i. e. there are strong emissions at 483, 540 and 600 nm under excitation at 400 nm. The nanobelts were dispersed in enthanol and adhered to a transparent polypropylene (PP) film by double-side adhesive tape, and then two separate electrodes (Ti/Au) were evaporated on the surface with a mask, removing the mask to form a flexible photodetector. The detector demonstrated an excellent photoresponse from ultraviolet to visible light. Under illumination of 405 nm with 6.32 mW, the light on/off current ratio is 12, and response time is less than 0.2 s. It suggested that the HfS3 nanobelts are promising for applications in optoelectronic nanodevices, and the flexible photodetector can be used in practical photodetection.

•We synthesized the SnS2 ultrathin nanosheets by an ultrasonic chemical method for first time.•The photodetector was fabricated on the basis of the SnS2 ultrathin nanosheet film.•The photodetectors showed decent photoresponse from ultraviolet to near infrared.Ultrathin SnS2 nanosheets are synthesized for the first time by a simple ultrasonic method, and then fabricated onto a SiO2/Si substrate to form nanosheet-based phototransistor which exhibits a broad photoresponse from 254 to 980 nm, dependence of photocurrent on optical power and wavelength, fast-response, and long-term stability. Under illumination of 532-nm light with an optical power of 19.3 mW/cm2 (0.68 nW), the photoswitch current ratio (PCR) is about 8.7, while the photoresponsivity, external quantum efficiency, and detectivity are 0.65 mA/W, 0.15%, and 1.13 × 108 J, respectively. Compared with the reported SnS2-based photodetectors, the SnS2-nanosheet phototransistor shows an enhanced photosensitive performance.

Zinc triselenide (ZrSe3) and hafnium triselenide (HfSe3) nanobelts were synthesized using a chemical vapor transport method. Photodetectors based on individual nanobelts of ZrSe3 and HfSe3 were fabricated on SiO2/Si substrates, respectively, and the optoelectronic properties of both were evaluated. The ZrSe3 nanobelt photodetector showed a good photoresponse to wavelengths ranging from 405 nm to 780 nm. Under illumination with 650 nm light, the ratio of photoswitch currents reached 1.97 with a light on/off period of 50 s at a bias voltage of 5 V. The HfSe3 nanobelt photodetector also showed good photoresponse to wavelengths ranging from 405 nm to 650 nm, and the ratio of photoswitch currents, under illumination with 532 nm light, reached 2.2 with a light on/off period of 50 s at a bias voltage of 5 V. The photoresponse time of both the photodetectors was less than 0.4 s. The results demonstrated that ZrSe3 and HfSe3 nanobelts possessed excellent photoconductivity, and suggested that these photodetectors would have potential applications under a range of visible light conditions.

A new flexible ultraviolet (UV) to near infrared (NIR) photodetector based on a SnS2 nanosheet self-assembled microsphere film has been fabricated onto a transparent polypropylene (PP) film using double-side adhesive tape, and its light-induced electric properties were investigated in detail. The detector demonstrates a remarkable photoresponse from 300 to 830 nm, a remarkable photocurrent depending on the optical power and light wavelength, as well as an excellent photoswitch effect and stability. In addition, another new rigid photodetector based on the same SnS2 microsphere film has been fabricated on a SiO2/Si substrate, showing similar photosensitive properties. It suggests that SnS2 nanosheet microspheres are potential candidates for high-performance nanoscale optoelectronic devices, and the SnS2-microsphere-based photodetector can be applied as a photodetector in the range of UV to NIR light because of its low cost and nontoxicity.

A novel aptasensor was fabricated for the detection of lysozyme and DNA based on the fluorescence resonance energy transfer (FRET) technique between upconversion nanoparticles (UCNPs) and a dye labeled aptamer. UCNPs can act as excellent emitters due to their low autofluorescence and high penetration depth of biosamples. NaYF4:Yb, Er nanoparticles as UCNPs were synthesized and attached with a dye labeled aptamer through a cationic polymer as an electrostatic linker to quench the upconversion fluorescence intensity. The intensity can be restored after the addition of lysozyme or the complementary DNA (target DNA) because of their strong interaction with the aptamer. The sensor provided a linear concentration range from 30 to 210 nM for lysozyme and 40 to 200 nM for the target DNA, the limit of detection was 2.5 nM and 2.8 nM, respectively. The sensor was also used to monitor the lysozyme level in both human saliva and serum samples, and the results were consistent with the reported values. The method was simple and convenient without the extra procedure of bioconjugation, and could be put to use for the determination of various targets in the future.

Phototransistors based on single and three ZrS3 nanobelts were fabricated on SiO2/Si wafers by photolithography and the lift-off technique, respectively, and their light-induced electric properties were investigated in detail. Both the devices demonstrate a remarkable photoresponse from ultraviolet to near infrared light. The photoswitch current ratio (PCR) of the single-nanobelt phototransistor is 13 under the illumination of 405 nm light with an optical power of 10.5 mW cm−2 at a bias of 5 V, while the PCR of the three-nanobelt device is 210 under the illumination of 405 nm light with an optical power of 5.57 mW cm−2 at a bias of 1 V. On comparison of the photoresponses under the same conditions, the latter is found to be superior to the former, and both the devices show a much better photoresponse than the reported flexible ZrS3-nanobelt-film photodetector.

A novel fluorescent resonant energy transfer (FRET) biosensor was fabricated for the detection of hepatitis B virus (HBV) DNA using poly(ethylenimine) (PEI) modified upconversion nanoparticles (NH2-UCNPs) as energy donor and gold nanoparticles (Au NPs) as acceptor. The PEI modified upconversion nanoparticles were prepared directly with a simple one-pot hydrothermal method, which provides high quality amino-group functionalized UCNPs with uniform morphology and strong upconversion luminescence. Two single-stranded DNA strands, which were partially complementary to each other, were then conjugated with NH2-UCNPs and Au NPs. When DNA conjugated NH2-UCNPs and Au NPs are mixed together, the hybridization between complementary DNA sequences on UCNPs and Au NPs will lead to the quenching of the upconversion luminescence due to the FRET process. Meanwhile, upon the addition of target DNA, Au NPs will leave the surface of the UCNPs and the upconversion luminescence can be restored because of the formation of the more stable double-stranded DNA on the UCNPs. The sensor we fabricated here for target DNA detection shows good sensitivity and high selectivity, which has the potential for clinical applications in the analysis of HBV and other DNA sequences.

Being confined within nanoscale space, substances may exhibit unique physicochemical properties. The effect of nanoconfinement on molecular interactions is of significance, but a sound understanding has not been established yet. Here we present a quantitative study on boronate affinity (covalent) and electrostatic (non-covalent) interactions confined within mesoporous silica. We show that both interactions were enhanced by the confinement and that the enhancement depended on the closeness of the interacting location, as well as on the difference between the pore size and the molecular size. The overall enhancement could reach 3 orders of magnitude.

HfS3 nanobelts were directly synthesized via a simple chemical vapor transport method. A field-effect transistor and photodetector was further fabricated based on an individual HfS3 nanobelt, and its electrical and optoelectronic properties were evaluated. The output characteristic curves of the FET revealed a typical p-type semiconducting behavior. The photodetector has an ultralow dark current (0.04 pA) and a large on/off ratio (337.5) illuminated by 405 nm light with 1.2 mW cm−2. It demonstrated excellent stability and sensitivity to 405 nm light. The results suggest that the HfS3 nanobelts are promising for application in nanoscale electronic and optoelectronic devices. The research will play a positive role in nanodevice research of one-dimensional transition-metal trichalcogenide nanostructure.

Low-toxicity, highly luminescent, and water-soluble AgInS2/ZnS nanocrystals (NCs) have been synthesized via a microwave-assisted approach. The structure and optical features of the AgInS2/ZnS NCs were characterized by X-ray diffraction, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet visible absorption spectroscopy and photoluminescence (PL) spectroscopy. The as-synthesized AgInS2/ZnS NCs exhibited high PL quantum yields (40%) and long PL lifetimes (424.5 ns). Furthermore, the dynamic changes of the intracellular copper(II) levels in HeLa cells were monitored using the AgInS2/ZnS NCs as fluorescent probes. The results showed that the AgInS2/ZnS NCs as promising fluorescent probes can be used in the detection of intracellular copper ions in living cells.

In this Article, we present a facile microwave-assisted synthesis route for the preparation of water-soluble and high-quality CuInS2/ZnS nanocrystals (NCs) with glutathione as the stabilizer. The as-prepared CuInS2/ZnS NCs exhibited small particle sizes (∼3.3 nm), long photoluminescence lifetimes, and color-tunable properties ranging from the visible to the near-infrared by varying the initial ratio of Cu/In in the precursors. The low-toxicity, highly luminescent and biocompatible CuInS2/ZnS NCs were applied to cell imaging, showing that they could be used as promising fluorescent probes. Furthermore, the CuInS2/ZnS NCs were used as the signal labels for a fluoroimmunoassay of the biomarker IL-6, showing their great potential for use as reliable point-of-care diagnostics for biomarkers of cancer and other diseases.Keywords: color tunable; CuInS2/ZnS nanocrystals; fluoroimmunoassay; human interleukin-6; microwave assisted;

Mesoporous ZrO2 nanobelts (MZNs) have been prepared by a calcination route of ZrS3 nanobelts in air. The nanobelts prepared at 400–600 °C are the mixtures of tetragonal and monoclinic phases, and have well-distributed mesopores (pore diameter of about 3.4–3.6 nm). As the calcination temperature increased from 400 to 1200 °C, the structures changed from tetragonal to monoclinic phase, while the morphologies turned from regular nanobelts to bead-like nanowires, and the mesopores disappeared bit by bit. Fe-doped and Fe2O3-loaded MZNs have been prepared to compare the catalytic activities of Fe-doped, Fe2O3-loaded, and pure MZNs for methane combustion. The results showed that Fe2O3-loaded MZNs have rather high catalytic activity, suggesting its potential application in practice. Methane combustion data over the catalysts are well fitted by a first-order kinetic expression.Graphical abstractMesoporous ZrO2 nanobelts (MZNs) have been prepared by a calcination route of ZrS3 nanobelts in air. Fe-doped and Fe2O3-loaded MZNs have been prepared to compare the catalytic activities of Fe-doped, Fe2O3-loaded, and pure MZNs for methane combustion. The results showed that Fe2O3-loaded MZNs have rather high catalytic activity.Highlights► Novel method preparing mesoporous zirconia nanobelts (MZNs) was introduced. ► Fe-doped, Fe2O3-loaded, and pure MZNs were used as catalysts for methane combustion. ► Fe2O3-loaded MZNs showed enhancing catalytic activity. ► Kinetic data over the catalysts were well fitted by a first-order kinetic equation.

Highly ordered SrMoO4 3D spherical superstructure assembled with nanosheets was synthesized via a facile and fast sonochemical route without any template. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and selected-area electron diffraction. The results showed that the as-synthesized self-assembled SrMoO4 spheres were composed of nanosheets with thickness of about 40−60 nm and width of 1 μm. The pH values and surfactants play an important role in the morphologies of the final sample. The possible mechanism for the formation of self-assembled SrMoO4 spherical superstructure is proposed. The luminescence properties of these SrMoO4 samples with different morphologies have also been investigated.

Silica hollow spheres were synthesized by sol–gel process using carbon microspheres as templates, and used as supports for CuO/SiO2 catalysts. The samples were characterized by TEM, nitrogen adsorption–desorption, XRD and TPR, and furthermore, the catalytic performance for CO oxidation was approached. The results indicated that the catalytic activity of CuO supported on SiO2 hollow spheres exhibited much higher as compared to that supported on commercial SiO2. Enhancement of the catalytic activity may be attributed to the fact that the unique hollow spherical texture should facilitate the formation of main active species and gas diffusion in catalysts.

Zinc triselenide (ZrSe3) and hafnium triselenide (HfSe3) nanobelts were synthesized using a chemical vapor transport method. Photodetectors based on individual nanobelts of ZrSe3 and HfSe3 were fabricated on SiO2/Si substrates, respectively, and the optoelectronic properties of both were evaluated. The ZrSe3 nanobelt photodetector showed a good photoresponse to wavelengths ranging from 405 nm to 780 nm. Under illumination with 650 nm light, the ratio of photoswitch currents reached 1.97 with a light on/off period of 50 s at a bias voltage of 5 V. The HfSe3 nanobelt photodetector also showed good photoresponse to wavelengths ranging from 405 nm to 650 nm, and the ratio of photoswitch currents, under illumination with 532 nm light, reached 2.2 with a light on/off period of 50 s at a bias voltage of 5 V. The photoresponse time of both the photodetectors was less than 0.4 s. The results demonstrated that ZrSe3 and HfSe3 nanobelts possessed excellent photoconductivity, and suggested that these photodetectors would have potential applications under a range of visible light conditions.

Low-toxicity, highly luminescent, and water-soluble AgInS2/ZnS nanocrystals (NCs) have been synthesized via a microwave-assisted approach. The structure and optical features of the AgInS2/ZnS NCs were characterized by X-ray diffraction, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet visible absorption spectroscopy and photoluminescence (PL) spectroscopy. The as-synthesized AgInS2/ZnS NCs exhibited high PL quantum yields (40%) and long PL lifetimes (424.5 ns). Furthermore, the dynamic changes of the intracellular copper(II) levels in HeLa cells were monitored using the AgInS2/ZnS NCs as fluorescent probes. The results showed that the AgInS2/ZnS NCs as promising fluorescent probes can be used in the detection of intracellular copper ions in living cells.

HfS3 nanobelts were directly synthesized via a simple chemical vapor transport method. A field-effect transistor and photodetector was further fabricated based on an individual HfS3 nanobelt, and its electrical and optoelectronic properties were evaluated. The output characteristic curves of the FET revealed a typical p-type semiconducting behavior. The photodetector has an ultralow dark current (0.04 pA) and a large on/off ratio (337.5) illuminated by 405 nm light with 1.2 mW cm−2. It demonstrated excellent stability and sensitivity to 405 nm light. The results suggest that the HfS3 nanobelts are promising for application in nanoscale electronic and optoelectronic devices. The research will play a positive role in nanodevice research of one-dimensional transition-metal trichalcogenide nanostructure.

A new flexible ultraviolet (UV) to near infrared (NIR) photodetector based on a SnS2 nanosheet self-assembled microsphere film has been fabricated onto a transparent polypropylene (PP) film using double-side adhesive tape, and its light-induced electric properties were investigated in detail. The detector demonstrates a remarkable photoresponse from 300 to 830 nm, a remarkable photocurrent depending on the optical power and light wavelength, as well as an excellent photoswitch effect and stability. In addition, another new rigid photodetector based on the same SnS2 microsphere film has been fabricated on a SiO2/Si substrate, showing similar photosensitive properties. It suggests that SnS2 nanosheet microspheres are potential candidates for high-performance nanoscale optoelectronic devices, and the SnS2-microsphere-based photodetector can be applied as a photodetector in the range of UV to NIR light because of its low cost and nontoxicity.

A novel aptasensor was fabricated for the detection of lysozyme and DNA based on the fluorescence resonance energy transfer (FRET) technique between upconversion nanoparticles (UCNPs) and a dye labeled aptamer. UCNPs can act as excellent emitters due to their low autofluorescence and high penetration depth of biosamples. NaYF4:Yb, Er nanoparticles as UCNPs were synthesized and attached with a dye labeled aptamer through a cationic polymer as an electrostatic linker to quench the upconversion fluorescence intensity. The intensity can be restored after the addition of lysozyme or the complementary DNA (target DNA) because of their strong interaction with the aptamer. The sensor provided a linear concentration range from 30 to 210 nM for lysozyme and 40 to 200 nM for the target DNA, the limit of detection was 2.5 nM and 2.8 nM, respectively. The sensor was also used to monitor the lysozyme level in both human saliva and serum samples, and the results were consistent with the reported values. The method was simple and convenient without the extra procedure of bioconjugation, and could be put to use for the determination of various targets in the future.