With the continuous industrialization, as one of the most common air pollutants found in fossil fuels and automobile exhausts, nitride oxide (NO ₂ ) monitor is very essential for ensuring good air quality and our body health. 2D materials attract more attention for its special surface and electron structures. MoS ₂ shows small gas sensing response for its less surface dangling bonds. Here, we introduce a facile method to modify MoS ₂ with SnO ₂ as a NO ₂ receptor via mechanical composite. The MoS ₂ nanoflowers prepared with a hydrothermal method depicted a high surface/volume ratio and the SnO ₂ fabricated using a solvothermal method. Mixing ratio and annealing temperature was systematic researched for screening optimal parameters for gas sensor fabrication. The response was enhanced 1.5 time after modification with fast response and recovery time. The p-n heterostructure also provide good selectivity towards NO ₂ for gas sensing. This work provides a facile alternative for fast and stable response NO ₂ gas sensor at room temperature.

We propose an ultrasensitive leaky surface acoustic wave (LSAW) immunosensor based on molybdenum disulfide @ cuprous oxide—gold (MoS₂@Cu₂O-Au) nanoparticles and subsequent gold staining for the detection of alpha-fetoprotein (AFP). MoS₂@Cu₂O-Au nanoparticles, with their large specific surface area and good biocompatibility, not only capture the secondary antibodies (Ab₂) but also amplify the mass loading effect of the acoustic wave sensor in the detection of AFP. The immunosensor signals are further amplified upon injection of gold staining solution. The developed immunosensor achieved a low detection limit of 5.5 and 25.0 pg/mL with and without gold staining, respectively. The immunosensor demonstrated its efficiency for the quantitative detection of AFP in complex biological fluids, including human serum and saliva samples, with excellent selectivity and long-term stability, showing great potential for the quantification of AFP in clinical diagnosis.

Herein, a highly sensitive, sandwich-type quartz crystal microbalance (QCM) immunosensor is proposed for the quantitative monitoring of alpha-fetoprotein (AFP), a representative tumor marker for hepatocellular carcinoma. A cuprous oxide @ molybdenum disulfide (Cu ₂ O@MoS ₂ ) nanohybrid was synthesized and combined with gold nanoparticles. The yield, a Cu ₂ O@MoS ₂ –Au nanocomposite, exhibited coral morphology with an increased surface area for loading more secondary antibodies (Ab ₂ ), which amplified the mass loading on the QCM electrode’s surface. The immunosensor’s sensitivity was further enhanced by injecting the gold-staining solution for signal amplification. A self-assembled monolayer of primary antibody (Ab ₁ ) was also fabricated on the QCM electrode’s surface via mercaptoacetic acid immobilization in EDC and NHS. The immunosensor’s limit of detection dropped to 35 pg/mL and 90 pg/mL with and without the gold enhancement, respectively. When used to detect AFP in human saliva and serum samples, the immunosensor displayed high selectivity and long-term stability, which indicates its potential for clinically monitoring of biomarkers.

Thrombin plays a crucial role in regulating normal hemostatic function and various internal body processes but is rarely in-vivo detected because anticoagulant substances in the blood can quickly neutralize it after early-stage coagulation. In this paper, we designed a novel perovskite semiconductor Ba _0.5 Sr _0.5 FeO ₃ -δ by a one-step hydrothermal method as a sensing-platform maintaining electroactive characteristics that can be used to conjugate the bio-recognition of aptamers and auto-probing of binding events for highly sensitive thrombin detection. In particular, the introduction of 10%Sb-dopant into Ba _0.5 Sr _0.5 FeO ₃ -δ semiconductor to tune the energy band structure for fast transport of charged species. Further, the synthesized Ba _0.5 Sr _0.5 Sb _x Fe _1.0-x O ₃ -δ (x=0-0.1) materials are physically characterized via XRD, FE-SEM, HR-TEM assisted by EDS, XPS, UV-Vis, and UPS. Moreover, aptamer plays a key role in amplifying the electrical signal, where the prepared BaSrFeSb _0.1 O ₃ -δ particles show dispersion and aggregation upon binding with aptamers and target analyte thrombin, respectively, thereby increasing the sensitivity of the aptasensor. The electrostatic forces are responsible to make complex between aptamers and particles, while conformational changes in aptamers pursue bio-molecular binding of aptamer with thrombin. Accordingly, the electrochemical aptasensor for thrombin detection shows an impressive low limit-of-detection (LOD) of 0.02 pM in a dynamic linear range (0.05 pM–0.3 nM). The proposed electrochemical aptasensor does not require special labeling of oligonucleotides or particle surface decoration.