The electrodes of two-dimensional (2D) titanium dioxide (TiO₂) nanosheet arrays were successfully fabricated for microRNA-155 detection. The (001) highly active crystal face was exposed to catalyze signaling molecules ascorbic acid (AA). Zero-dimensional (0D) titanium carbide quantum dots (Ti₃C₂T_x QDs) were modified to the electrode as co-catalysts and reduced the recombination rate of the charge carriers. Spectroscopic methods were used to determine the band structure of TiO₂ and Ti₃C₂T_x QDs, showing that a type Ⅱ heterojunction was built between TiO₂ and Ti₃C₂T_x QDs. Benefiting the advantages of materials, the sensing platform achieved excellent detection performance with a wide liner range, from 0.1 pM to 10 nM, and a low limit of detection of 25 fM (S/N = 3).

A photoelectrochemical (PEC) detection platform was built based on the branched rutile/anatase titanium dioxide (RA-TiO₂) electrode. Theoretical calculations proved that the type-II band alignment of rutile and anatase could facilitate charge separation in the electrode. The self-generated electric field at the interface of two phases can enhance the electron transfer efficiency of the electrode. Carboxylated CdTe quantum dots (QDs) were applied as signal amplification factors. Without the target DNA presence, the CdTe QDs were riveted to the surface of the electrode by the hairpin probe DNA. The sensitization of CdTe QDs increased the photocurrent of the electrode significantly. When the target DNA was present, the structural changes of the hairpin probe DNA resulted in the failure of the sensitized structure. Benefiting from excellent electrode structure design and CdTe QDs sensitization strategy, the PEC assays could achieve highly sensitive and specific detection of target DNA in the range of 1 fM to 1 nM, with a detection limit of 0.23 fM. The electrode construction method proposed in this article can open a new avenue for the preparation of more efficient PEC sensing devices.

With the rapid development of modern science and technology and the diversification of social needs, traditional single-performance materials struggle to meet the complex and changeable application scenarios. To address the multifaceted requirements of biomedical applications, such as disease diagnosis and treatment, scientists are dedicated to developing new multifunctional biomaterials with multiple activities. Bi₄Ti₃O₁₂ (BTO), despite its versatility and application potential, has insufficient photocatalytic performance. Silver nanoparticles (Ag) and Ti₃C₂T_x are particularly effective as antibacterial materials but they have relatively single functions. In this study, BTO/Ag/Ti₃C₂T_x biomultifunctional materials were constructed by combining BTO with Ag and Ti₃C₂T_x. We discovered that the addition of Ag and Ti₃C₂T_x effectively optimized the visible light absorption characteristics of BTO, reduced the electron transfer resistance, and increased the carrier concentration, thus significantly improving the photocatalytic performance of composite material, thereby markedly improving the composite’s photocatalytic performance and its efficacy in photochemical sensing and photodegradation. At the same time, BTO, as a carrier, effectively avoids Ag and Ti₃C₂T_x agglomeration and gives full play to its antibacterial properties. In the specific performance studies, ascorbic acid and MB were used as the subjects of photochemical sensing and photodegradation properties, while Escherichia coli and Staphylococcus aureus were tested for antibacterial properties. The BTO/Ag/Ti₃C₂T_x composite showed remarkable results in all assessments, demonstrating its potential as a versatile antibacterial and photocatalytic material.