Few-layer black phosphorous (BP) has emerged as a promising candidate for next-generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo-oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo-oxidative degradation, imidazolium-based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.

This study addresses the need for rapid pesticide (acetamiprid) detection by reporting a new colorimetric biosensing assay. Our approach combines the inherent peroxidase-like nanozyme activity of gold nanoparticles (GNPs) with high affinity and specificity of an acetamiprid-specific S-18 aptamer to detect this neurotoxic pesticide in a highly rapid, specific, and sensitive manner. It is shown that the nanozyme activity of GNPs can be inhibited by its surface passivation with target-specific aptamer molecules. Similar to an enzymatic competitive inhibition process, in the presence of a cognate target, these aptamer molecules leave the GNP surface in a target concentration-dependent manner, reactivating GNP nanozyme activity. This reversible inhibition of the GNP nanozyme activity can either be directly visualized in the form of color change of the peroxidase reaction product or can be quantified using UV-visible absorbance spectroscopy. This approach allowed detection of 0.1 ppm acetamiprid within an assay time of 10 min. This reversible nanozyme activation/inhibition strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest.

A new ultrafast and highly sensitive 'turn-off/turn-on' biosensing approach that combines the intrinsic peroxidase-like activity of gold nanoparticles (GNPs) with the high affinity and specificity of a ssDNA aptamer is presented for the efficient detection of a model small molecule kanamycin.

Human norovirus (NoV) remains the most common cause of viral gastroenteritis and the leading cause of viral foodborne outbreaks globally. NoV is highly pathogenic with an estimated median viral infective dose (ID 50 ) ranging from 18 to 1015 genome copies. For NoV detection, the only reliable and sensitive method available for detection and quantification is reverse transcription quantitative polymerase chain reaction (RTqPCR). NoV detection in food is particularly challenging, requiring matrix specific concentration of the virus and removal of inhibitory compounds to detection assays. Hence, the RTqPCR method poses some challenges for rapid in-field or point-of-care diagnostic applications. We propose a new colorimetric NanoZyme aptasensor strategy for rapid (10 min) and ultrasensitive (calculated Limit of Detection (LoD) of 3 viruses per assay equivalent to 30 viruses/mL of sample and experimentally demonstrated LoD of 20 viruses per assay equivalent to 200 viruses/mL) detection of the infective murine norovirus (MNV), a readily cultivable surrogate for NoV. Our approach combines the enzyme-mimic catalytic activity of gold nanoparticles with high target specificity of an MNV aptamer to create sensor probes that produce a blue color in the presence of this norovirus, such that the color intensity provides the virus concentrations. Overall, our strategy offers the most sensitive detection of norovirus or a norovirus surrogate achieved to date using a biosensor approach, enabling for the first time, the detection of MNV virion corresponding to the lower end of the ID 50 for NoV. We further demonstrate the robustness of the norovirus NanoZyme aptasensor by testing its performance in the presence of other nontarget microorganisms, human serum and shellfish homogenate, supporting the potential of detecting norovirus in complex matrices. This new assay format can, therefore, be of significant importance as it allows ultrasensitive norovirus detection rapidly within minutes, while also offering the simplicity of use and need for nonspecialized laboratory infrastructure.

The rapid emergence of antibiotic-resistant bacterial strains warrants new strategies for infection control. NanoZymes are emerging as a new class of catalytic nanomaterials that mimic the biological action of natural enzymes. The development of photoactive NanoZymes offers a promising avenue to use light as a “trigger” to modulate the bacterial activity. Visible light activity is particularly desirable because it contributes to 44% of the total solar energy. Here we show that the favorable band structure of a CuO-nanorod-based NanoZyme catalyst (band gap of 1.44 eV) allows visible light to control the antibacterial activity. Photomodulation of the peroxidase-mimic activity of CuO nanorods enhances its affinity to H2O2, thereby remarkably accelerating the production of reactive oxygen species (ROS) by 20 times. This photoinduced NanoZyme-mediated ROS production catalyzes physical damage to the bacterial cells, thereby enhancing the antibacterial performance against Gram-negative-indicator bacteria Escherichia coli.

Gd-based nanomaterials offer interesting magnetic properties and have been heavily investigated for magnetic resonance imaging. The applicability of these materials beyond biomedical imaging remains limited. The current study explores the applicability of these rare-earth nanomaterials as nanozyme-mediated catalysts for colorimetric sensing of l-cysteine, an amino acid of high biomedical relevance. We show a facile solution-based strategy to synthesize two Gd-based nanomaterials viz. Gd(OH) and GdO nanorods. We further establish the catalytic peroxidase-mimic nanozyme activity of these Gd(OH) and GdO nanorods. This catalytic activity was suppressed specifically in the presence of l-cysteine that allowed us to develop a colorimetric sensor to detect this biologically relevant molecule among various other contaminants. This suppression, which could either be caused due to catalyst poisoning or enzyme inhibition, prompted extensive investigation of the kinetics of this catalytic inhibition in the presence of cysteine. This revealed a competitive inhibition process, a mechanism akin to those observed in natural enzymes, bringing nanozymes a step closer to the biological systems.

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