Analysis of characteristics and changes in three-dimensional spatial and temporal distribution of aerosol types in Central Asia.

Atmospheric aerosol types and characteristics have regional and seasonal characteristics mainly due spatial and temporal differences in emission sources and diffuse transport conditions. We explored regional three-dimensional spatial and temporal distribution characteristics of aerosol types in Central Asia from daytime to nighttime by using long-term (2007-2021) CALIPSO lidar measurements. The three results are as follows: (1) Average aerosol optical depth (AOD) values during the 14 years were 0.44 and 0.47 during daytime and nighttime, respectively, with an overall decreasing trend, among which the AOD in spring in the southern border region and in winter in the northern border region showed high values, 0.66 and 0.31 during daytime and 0.69 and 0.33 during nighttime, respectively, and nighttime AOD values were higher than those of daytime, possibly due to the lower signal-to-noise ratio of the CALIPSO during the daytime than during the nighttime. (2) The primary representative aerosol type in the Taklamakan Desert region being pure sand and dust, and more apparent winter-polluted sand and dust exist along the northern slope of the Tianshan Mountains in Xinjiang in winter than in other areas. High-altitude soot mainly existed below 4 km and was primarily concentrated in northern Central Asia, with the highest values (0.016 and 0.003) in summer and winter, respectively, which may be due to different diffusion and transport conditions. (3) Dust aerosols in spring were mainly concentrated in the region of 2-6 km in the Taklamakan Desert area; pure dust particles in summer and fall lifted height diffusion and gradually moved to the northern border region; polluted dust was mainly in northern Xinjiang in fall and winter and spread to northern Central Asia; and the average top height of aerosols in the transmission process reached the top of the troposphere, and transmission height was higher than source area.

A novel electrochemiluminescence biosensor based on Ru(bpy)32+-functionalized MOF composites and cycle amplification technology of DNAzyme walker for ultrasensitive detection of kanamycin.

An electrochemiluminescence (ECL) sensing platform for ultrasensitive and highly selective detection of kanamycin (KANA) was developed based on the prepared Ru(bpy)32+-functionalized MOF (Ru@MOF) composites by hydrothermal synthesis and Ag+-dependent DNAzyme. In this sensor, the stem-loop DNA (HP) with the ferrocene (Fc) was used as substrate chain to quench the ECL emission generated by the Ru@MOF. Using the specific recognition effect between KANA and the KANA aptamer (Apt) and the DNAzyme dependence on Ag+, the KANA aptamer as the pendant strand of the DNAzyme was assembled on Ru@MOF/GCE with the aptamer. When both Ag+ and KANA were present simultaneously, KANA specifically was binded to KANA aptamer as a pendant chain. Subsequently, Ag+-dependent DNAzyme walker continuously cleaved the HP chain and released the modified end of Fc to restore the ECL signal of Ru@MOF composites, thus achieving selective and ultrasensitive detection of KANA. The constructed KANA biosensor exhibits a wide detection range (30 pM to 300 µM) accompanied by a low detection limit (13.7 pM). The KANA in seawater and milk samples are determined to evalute the practical application results of the sensor. This ECL detection strategy could be used for detecting other similar analytes and has broad potential application in biological analysis.

A signal "on-off-on"-type electrochemiluminescence aptamer sensor for detection of sulfadimethoxine based on Ru@Zn-oxalate MOF composites.

An "on-off-on"-type electrochemiluminescence (ECL) aptamer sensor based on Ru@Zn-oxalate metal-organic framework (MOF) composites is constructed for sensitive detection of sulfadimethoxine (SDM). The prepared Ru@Zn-oxalate MOF composites with the three-dimensional structure provide good ECL performance for the "signal-on." The MOF structure with a large surface area enables the material to fix more Ru(bpy)32+. Moreover, the Zn-oxalate MOF with three-dimensional chromophore connectivity provides a medium which can accelerate excited-state energy transfer migration among Ru(bpy)32+ units, and greatly reduces the influence of solvent on chromophore, achieving a high-energy Ru emission efficiency. The aptamer chain modified with ferrocene at the end can hybridize with the capture chain DNA1 fixed on the surface of the modified electrode through base complementary pairing, which can significantly quench the ECL signal of Ru@Zn-oxalate MOF. SDM specifically binds to its aptamer to separate ferrocene from the electrode surface, resulting in a "signal-on" ECL signal. The use of the aptamer chain further improves the selectivity of the sensor. Thus, high-sensitivity detection of SDM specificity is realized through the specific affinity between SDM and its aptamer. This proposed ECL aptamer sensor has good analytical performance for SDM with low detection limit (27.3 fM) and wide detection range (100 fM-500 nM). The sensor also shows excellent stability, selectivity, and reproducibility, which proved its analytical performance. The relative standard deviation (RSD) of SDM detected by the sensor is between 2.39 and 5.32%, and the recovery is in the range 97.23 to 107.5%. The sensor shows satisfactory results in the analysis of actual seawater samples, which is expected to play a role in the exploration of marine environmental pollution.

An enhanced photoelectrochemical sensor for aflatoxin B1 detection based on organic-inorganic heterojunction nanomaterial: poly(5-formylindole)/NiO.

A new strategy for enhancing the photoelectric activity of poly(5-formylindole) (P5FIn) was developed by introducing the inorganic semiconductor material (NiO) to form organic-inorganic heterojunctions. P5FIn/NiO heterojunctions were firstly prepared by combining hydrothermal synthesis and electrochemical polymerization. Due to the synergistic effect between P5FIn and NiO, the photoelectrochemical (PEC) performance of this heterojunction was significantly enhanced compared to pure P5FIn and NiO. The reason for the enhanced PEC performance is mainly attributed to the increased visible light utilization and the bandgap matching effect of the P5FIn/NiO heterojunctions. Based on the prepared P5FIn/NiO heterojunctions, a novel PEC sensor for aflatoxin B1 (AFB1) detection was also constructed with a wide linear range of 0.005-50 ng mL-1 and a limit of detection (LOD) of 0.0015 ng mL-1. Moreover, this constructed PEC sensor also had good stability, reproducibility, selectivity, and satisfactory actual sample detection ability. This strategy may inspire more design and application of high-performance photoelectric active material based on inorganic semiconductor and organic conducting polymer heterojunctions. Graphical abstract.

Simple "signal-on" photoelectrochemical aptasensor for ultrasensitive detecting AFB1 based on electrochemically reduced graphene oxide/poly(5-formylindole)/Au nanocomposites.

A simple "signal-on" photoelectrochemical (PEC) aptasensor is constructed for Aflatoxin B1 (AFB1) detection based on electrochemically reduced graphene oxide/poly(5-formylindole)/Au (erGO/P5FIn/Au) nanocomposites. The nanocomposites are synthesized by simple electrochemical deposition method and show good photoelectrochemical performance. Poly(5-formylindole) (P5FIn) can generate electron-hole pairs under light irradiation, leading to the formation of robust cathode photocurrent. Au can be acted as signal amplifier due to the high conductivity. The erGO is used to immobilize AFB1 aptamer chain by π-π stacking interaction between the carbon six-membered ring in graphene and the C-N heterocyclic ring in nucleobases of ssDNA. After the insulating AFB1 aptamer chain is fixed to the electrode, the signal of PEC sensor is "OFF". In the process of AFB1 detection, the aptamer chain detaches from the surface of erGO, which results in "ON" of the sensor signal. Based on this design, this constructed PEC aptasensor shows a high sensitivity for AFB1 with a wide linear detection range (LDR) from 0.01 ng mL-1 to 100 ng mL-1. The limit of detection (LOD) is 0.002 ng mL-1. This PEC sensor also exhibits good stability, selectivity, specificity, and satisfactory practical sample analysis ability. This work may provide a new promising PEC platform for AFB1 detection as well as some other small molecules analysis.

High-Performance Asymmetric Electrochromic-Supercapacitor Device Based on Poly(indole-6-carboxylicacid)/TiO2 Nanocomposites.

A difunctional porous network of poly(indole-6-carboxylicacid) (PICA)/TiO2 nanocomposites is first prepared using TiO2 nanorod arrays as the scaffold. Because of the synergistic effect of PICA and TiO2, the nanocomposites show good electrochemical performance, a high specific capacitance value (23.34 mF cm-2), and excellent galvanostatic charge-discharge stability. Meanwhile, this nanocomposite can be reversibly switched (yellow, green, brown) with a high coloration efficiency (124 cm2 C-1). An asymmetric electrochromic-supercapacitor device (ESD) is also constructed using the PICA/TiO2 nanocomposites as the anode material and poly(3,4-ethylenedioxythiophene) as the cathode material. This ESD has robust cycle stability and a high specific capacitance value (9.65 mF cm-2), which can be switched from light green to dark blue. After charging, the device can light up a single LED for 108 s, and the energy storage level can also be monitored by the corresponding color changes. This constructed ESD will have great potential applications in intelligent energy storage and other smart electronic fields.

Label-free photoelectrochemical immunosensing platform for detection of carcinoembryonic antigen through photoactive conducting poly(5-formylindole) nanocomposite.

Poly(5-formylindole)/electrochemically reduced graphene oxide (P5FIn/erGO) nanocomposite is firstly used to construct a label-free photoelectrochemical (PEC) immunosensor to detect carcinoembryonic antigen (CEA). As photoactive material and electroactive mediator, the prepared P5FIn/erGO nanocomposite exhibits high photocurrent intensity under visible-light irradiation due to the synergistic effect of P5FIn and erGO. The anti-CEA is connected to the P5FIn/erGO modified electrode surface, and gold nanoparticles (AuNP) is used as cross-linking in the process. The linear decrease of photocurrent is caused by the specific recognition of anti-CEA and CEA. This PEC immunosensor shows a wide linear response to CEA ranging from 0.0005 to 50 ng mL-1 with a low detection limit of 0.14 pg mL-1. The proposed immunosensor has good stability, reproducibility and high specificity. The satisfied results are also obtained when this immunosensor is used to detect CEA in actual human serum samples analysis, thus opening up a new promising PEC analysis platform based on conducting polymers.

A graphene quantum dots based electrochemiluminescence immunosensor for carcinoembryonic antigen detection using poly(5-formylindole)/reduced graphene oxide nanocomposite.

A novel electrochemiluminescence (ECL) immunosensor for ultrasensitive detection of carcinoembryonic antigen (CEA) was developed using signal amplification strategy based on poly(5-formylindole)/reduced graphene oxide nanocomposite (P5FIn/erGO) and Au nanoparticle (AuNP) decorated graphene quantum dots (GQDs) (GQDs@AuNP). As an effective matrix for immobilization of primary antibody (Ab1), P5FIn/erGO nanocomposite facilitated the ion transport during the redox reactions and provided larger surface areas for the immobilization of Ab1. GQDs@AuNP was used as labels to conjugate with secondary antibody (Ab2), which improved electron transfer capability with stable ECL intensity. The multiple amplification of P5FIn/erGO and GQDs@AuNP made the ECL immunosensor have a broad linear range from 0.1pgmL-1 to 10ngmL-1 and a low detection limit with 3.78fgmL-1. In addition, this ECL immunosensor performed with admirable stability and good selectivity and reproducibility as well. When this immunosensor was used for the analysis of CEA in human serum, good recoveries were obtained. Thus, there will be a promising future in the early diagnosis of cancer to detect CEA.