A comprehensive review on the development and state of the art of colorimetric and fluorometric sensor arrays is presented. Chemical sensing aims to detect subtle changes in the chemical environment ...by transforming relevant chemical or physical properties of molecular or ionic species (i.e., analytes) into an analytically useful output. Optical arrays based on chemoresponsive colorants (dyes and nanoporous pigments) probe the chemical reactivity of analytes, rather than their physical properties (e.g., mass). The chemical specificity of the olfactory system does not come from specific receptors for specific analytes (e.g., the traditional lock-and-key model of substrate–enzyme interactions), but rather olfaction makes use of pattern recognition of the combined response of several hundred olfactory receptors. In a similar fashion, arrays of chemoresponsive colorants provide high-dimensional data from the color or fluorescence changes of the dyes in these arrays as they are exposed to analytes. This provides chemical sensing with high sensitivity (often down to parts per billion levels), impressive discrimination among very similar analytes, and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, in both the gas and liquid phases. Design of both sensor arrays and instrumentation for their analysis are discussed. In addition, the various chemometric and statistical analyses of high-dimensional data (including hierarchical cluster analysis (HCA), principal component analysis (PCA), linear discriminant analysis (LDA), support vector machines (SVMs), and artificial neural networks (ANNs)) are presented and critiqued in reference to their use in chemical sensing. A variety of applications are also discussed, including personal dosimetry of toxic industrial chemical, detection of explosives or accelerants, quality control of foods and beverages, biosensing intracellularly, identification of bacteria and fungi, and detection of cancer and disease biomarkers.
Recent advances in nanostructured materials have been led by the development of new synthetic methods that provide control over size, morphology, and nano/microstructure. The utilization of high ...intensity ultrasound offers a facile, versatile synthetic tool for nanostructured materials that are often unavailable by conventional methods. The primary physical phenomena associated with ultrasound that are relevant to materials synthesis are cavitation and nebulization. Acoustic cavitation (the formation, growth, and implosive collapse of bubbles in a liquid) creates extreme conditions inside the collapsing bubble and serves as the origin of most sonochemical phenomena in liquids or liquid‐solid slurries. Nebulization (the creation of mist from ultrasound passing through a liquid and impinging on a liquid‐gas interface) is the basis for ultrasonic spray pyrolysis (USP) with subsequent reactions occurring in the heated droplets of the mist. In both cases, we have examples of phase‐separated attoliter microreactors: for sonochemistry, it is a hot gas inside bubbles isolated from one another in a liquid, while for USP it is hot droplets isolated from one another in a gas. Cavitation‐induced sonochemistry provides a unique interaction between energy and matter, with hot spots inside the bubbles of ∼5000 K, pressures of ∼1000 bar, heating and cooling rates of >1010 K s−1; these extraordinary conditions permit access to a range of chemical reaction space normally not accessible, which allows for the synthesis of a wide variety of unusual nanostructured materials. Complementary to cavitational chemistry, the microdroplet reactors created by USP facilitate the formation of a wide range of nanocomposites. In this review, we summarize the fundamental principles of both synthetic methods and recent development in the applications of ultrasound in nanostructured materials synthesis.
Ultrasound is a versatile tool for the synthesis of nanostructured materials. For both sonochemistry and ultrasonic spray pyrolysis (USP), the reaction sites are isolated nanoscale reactors: for sonochemistry, the hot spot inside a collapsing cavitation bubble, whereas for USP, a heated liquid droplet. In each case, unique reaction conditions are created: e.g., acoustic cavitation produces transient temperatures of >5000 K, pressures of ∼1000 bar, and cooling rates of >1010 K s−1.
The Optoelectronic Nose Li, Zheng; Suslick, Kenneth S
Accounts of chemical research,
02/2021, Volume:
54, Issue:
4
Journal Article
Peer reviewed
Conspectus How does one tell the difference between one molecule or mixture of molecules from another? Chemical sensing seeks to probe physical or chemical properties of molecular or ionic species ...(i.e., analytes) and transform that information into a useful and distinguishable output. The olfactory system of animals is the prototype of chemical sensing. Even for human beings (who are generally more visual than olfactory creatures), the sense of smell is one of our most basic capabilities, and we can discriminate among many thousands, and possibly even billions, of different odors. The chemical specificity of the olfactory system does not come from specific receptors for specific analytes (i.e., the traditional lock-and-key model of enzyme–substrate interactions), but rather olfaction uses pattern recognition of the combined responses of several hundred olfactory receptors. In analogy to olfaction, colorimetric sensor arrays provide high dimensional data from the color changes of chemically responsive colorants as they are exposed to analytes. These colorants include pH responsive dyes, Lewis acid/base indicators, redox dyes, vapochromics, and surface-modified silver nanoparticles. The color difference maps so created provide chemical sensing with high sensitivity (often down to ppb levels), impressive discrimination among very similar analytes, and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, both in the gas and liquid phases. Such colorimetric arrays probe a wide range of the chemical reactivity of analytes, rather than the limited dimensionality of physical properties (e.g., mass) or physisorption (e.g., traditional electronic noses). Our sensor arrays are disposable and simple to produce by either inkjet or robotic dip-pen printing onto the surface of porous polymer membranes or even paper. Design of both sensor arrays and optical readers for their analysis has advanced to a fully self-contained pocket-sized instrument, the optoelectronic nose. Quantitative analysis requires appropriate chemometric methods for pattern recognition of data with inherently high dimensionality, e.g., hierarchical cluster analysis and support vector machines. A wide range of applications for the colorimetric sensor arrays has been developed, including personal dosimetry of toxic industrial chemicals, detection of explosives or fire accelerants, monitoring pollutants for artwork and cultural heritage preservation, quality control of foods and beverages, rapid identification of bacteria and fungi, and detection of disease biomarkers in breath or urine. The development of portable, high-accuracy instrumentation using standard imaging devices with the capability of onboard, real-time analysis has had substantial progress and increasingly meets the expectations for real-world use.
We have observed solid‐state growth of pre‐existing silver nanoparticles (AgNPs) upon exposure to trace (ppb) concentrations of reactive gases at room temperature. The consequent change in localized ...surface plasmon resonances alters the visible absorbance of dried, printed sensor spots made from inks of 10 nm‐AgNPs and provides a novel mechanism for trace detection and dosimetry of reactive gases. Colorimetric sensor arrays based on these AgNP inks offer dosimetric identification of acidic and oxidizing gases and other reactive vapors with limits of detection below ppb levels for 1 h exposures. For an array of AgNP inks with various capping agents, a unique color response pattern is observed for each specific analyte. Excellent discrimination among 11 reactive gases was demonstrated using standard chemometric methods. The chemically induced sintering of NPs paves the way for novel solid‐state sensors for the ultrasensitive detection of reactive gases and their application to the monitoring of trace airborne pollutants.
Sintering sensors: The solid‐state growth of pre‐existing silver nanoparticles (AgNPs) upon exposure to trace (ppb) concentrations of reactive gases at room temperature is reported. The consequent change in localized surface plasmon resonances alters the visible absorbance of dried, printed sensor spots made from inks of 10 nm AgNPs and provides a novel mechanism for trace detection and dosimetry of reactive gases.
Ag nanoclusters consist of several to roughly a hundred atoms and possess sizes comparable to the Fermi wavelength of electrons; they exhibit molecule‐like properties, including discrete electronic ...transitions and strong fluorescence. These nanoclusters are of significant interest because they provide the bridge between atomic and nanoparticle behavior in noble metals. Since the first observations of photoluminescence from Ag nanoclusters, substantial effort has been made to prepare Ag nanoclusters and explore their potential applications. The synthesis of well‐defined Ag nanoclusters, however, is difficult due to aggregation of nanoclusters, especially in aqueous solutions. In this Research News article, we highlight some recent progress on solution‐based synthesis of water‐soluble Ag nanoclusters using radiolytic, chemical reduction and photochemical approaches to prepare fluorescent Ag nanoclusters.
Water‐soluble fluorescent Ag nanoclusters have been successfully prepared using radiolytic, chemical reduction and photochemical approaches. The optical and photoluminescence properties of the Ag nanoclusters are easily controlled by the synthetic conditions.
A comprehensive review is presented on the development and state of the art of colorimetric and fluorometric sensor arrays. Optical arrays based on chemoresponsive colorants (dyes and nanoporous ...pigments) probe the chemical reactivity of analytes, rather than their physical properties. This provides a high dimensionality to chemical sensing that permits high sensitivity (often down to ppb levels), impressive discrimination among very similar analytes and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, both in the gas and liquid phases.
The use of colorimetric and fluorometric sensor arrays has given rise to a new analytical technique: the optoelectronic nose.
The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. ...Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 °C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures.
Highly fluorescent, stable, water-soluble Ag nanoclusters have been successfully prepared via a convenient sonochemical approach using a simple polyelectrolyte, polymethylacrylic acid (PMAA), as a ...capping agent. The optical and fluorescence properties of the Ag nanoclusters can be easily controlled by varying the synthetic conditions, such as sonication time, stoichiometry of the carboxylate groups to Ag+, and polymer molecular weight.
Sonochemical synthesis of nanomaterials Xu, Hangxun; Zeiger, Brad W; Suslick, Kenneth S
Chemical Society reviews,
2013-Apr-07, Volume:
42, Issue:
7
Journal Article
Peer reviewed
Open access
High intensity ultrasound can be used for the production of novel materials and provides an unusual route to known materials without bulk high temperatures, high pressures, or long reaction times. ...Several phenomena are responsible for sonochemistry and specifically the production or modification of nanomaterials during ultrasonic irradiation. The most notable effects are consequences of acoustic cavitation (the formation, growth, and implosive collapse of bubbles), and can be categorized as primary sonochemistry (gas-phase chemistry occurring inside collapsing bubbles), secondary sonochemistry (solution-phase chemistry occurring outside the bubbles), and physical modifications (caused by high-speed jets or shock waves derived from bubble collapse). This tutorial review provides examples of how the chemical and physical effects of high intensity ultrasound can be exploited for the preparation or modification of a wide range of nanostructured materials.
This paper offers a perspective on mechanochemistry and offers summarizing commentary on the
Faraday Discussion
170
, "Mechanochemistry: From Functional Solids to Single Molecules". The connection ...between the mechanical and the chemical worlds dates back to our earliest written records and beyond, but its renaissance over the past decade or so has had an impact on a huge swathe of modern science and engineering: from metallurgists to polymer scientists to synthetic organic and inorganic chemists to cellular biologists. Connections among the different subfields of mechanochemistry (tribochemistry, trituration, macromolecular, and sonochemistry) are drawn out and the common themes and open questions are considered.
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