ABSTRACT
The work was based on N-(4-Aminobutyl)-N-ethylisoluminol (ABEI)-functionalized Fe-MIL-101 and gold nanoparticles (AuNPs) as sensing materials, and an electrochemiluminescence (ECL) aptasensor was constructed for detecting acetamiprid. As a metal-organic framework (MOF) material, Fe-MIL-101, was renowned for its unique three-dimensional network structure and efficient catalytic capability. ABEI, a common ECL reagent, was widely applied. ABEI was introduced into the Fe-MIL-101 structure as a luminescence functionalization reagent to form Fe-MIL-101@ABEI. This approach avoided limitations on the loading capacity of luminescent reagents imposed by modification and encapsulation methods. With character of excellent catalytic activity and ease of bioconjugation, AuNPs offered significant advantages in biosensing. Leveraging the reductive properties of ABEI, AuNPs were reduced around Fe-MIL-101@ABEI, resulting in the modified luminescent functionalized material denoted as Fe-MIL-101@ABEI@AuNPs. An aptamer was employed as a recognition element and was modified accordingly. The aptamer was immobilized on Fe-MIL-101@ABEI@AuNPs through gold-sulfur (Au-S) bonds. After capturing acetamiprid, the aptamer induced a decrease in the ECL signal intensity within the ABEI-hydrogen peroxide (H2O2) system, enabling the quantitative detection of acetamiprid. The aptasensor displayed remarkable stability and repeatability, featured a detection range of 1×10-3-1×102 nM, and had a limit of detection (LOD) of 0.3 pM (S/N=3), which underscored its substantial practical application potential.
Subject(s)
Aptamers, Nucleotide , Biosensing Techniques , Electrochemical Techniques , Gold , Limit of Detection , Luminescent Measurements , Metal Nanoparticles , Metal-Organic Frameworks , Neonicotinoids , Neonicotinoids/analysis , Neonicotinoids/chemistry , Metal-Organic Frameworks/chemistry , Biosensing Techniques/methods , Metal Nanoparticles/chemistry , Gold/chemistry , Aptamers, Nucleotide/chemistry , Luminescent Measurements/methods , Electrochemical Techniques/methods , Vegetables/chemistry , Luminol/chemistry , Luminol/analogs & derivatives , Pesticide Residues/analysis , Pesticide Residues/isolation & purification , Food Contamination/analysisABSTRACT
Speech recognition crucially relies on slow temporal modulations (<16 Hz) in speech. Recent studies, however, have demonstrated that the long-delay echoes, which are common during online conferencing, can eliminate crucial temporal modulations in speech but do not affect speech intelligibility. Here, we investigated the underlying neural mechanisms. MEG experiments demonstrated that cortical activity can effectively track the temporal modulations eliminated by an echo, which cannot be fully explained by basic neural adaptation mechanisms. Furthermore, cortical responses to echoic speech can be better explained by a model that segregates speech from its echo than by a model that encodes echoic speech as a whole. The speech segregation effect was observed even when attention was diverted but would disappear when segregation cues, i.e., speech fine structure, were removed. These results strongly suggested that, through mechanisms such as stream segregation, the auditory system can build an echo-insensitive representation of speech envelope, which can support reliable speech recognition.
Subject(s)
Auditory Cortex , Speech Perception , Humans , Speech Perception/physiology , Speech Intelligibility/physiology , Brain , Auditory Cortex/physiology , Attention , Acoustic StimulationABSTRACT
Temporal modulations provide critical cues for speech recognition. When the temporal modulations are distorted by, e.g., reverberations, speech intelligibility drops, and the drop in speech intelligibility can be explained by the amount of distortions to the speech modulation spectrum, i.e., the spectrum of temporal modulations. Here, we test a condition in which speech is contaminated by a single echo. Speech is delayed by either 0.125 s or 0.25 s to create an echo, and these two conditions notch out the temporal modulations at 2 or 4 Hz, respectively. We evaluate how well young and older listeners can recognize such echoic speech. For young listeners, the speech recognition rate is not influenced by the echo, even when they are exposed to the first echoic sentence. For older listeners, the speech recognition rate drops to less than 60% when listening to the first echoic sentence, but rapidly recovers to above 75% with exposure to a few sentences. Further analyses reveal that both age and the hearing threshold influence the recognition of echoic speech for the older listeners. These results show that the recognition of echoic speech cannot be fully explained by distortions to the modulation spectrum, and suggest that the auditory system has mechanisms to effectively compensate the influence of single echoes.
