Editing Nanosensor (section)

=== Food and the environment ===
Nanosensors can improve various sub-areas within food and environment sectors including food processing, agriculture, air and water quality monitoring, and packaging and transport.  Due to their sensitivity, as well as their tunability and resulting binding selectivity, nanosensors are very effective and can be designed for a wide variety of environmental applications. Such applications of nanosensors help in a convenient, rapid, and ultrasensitive assessment of many types of environmental pollutants.<ref>{{Cite journal|last1=Handford|first1=Caroline E.|last2=Dean|first2=Moira|last3=Henchion|first3=Maeve|last4=Spence|first4=Michelle|last5=Elliott|first5=Christopher T.|last6=Campbell|first6=Katrina|date=December 2014|title=Implications of nanotechnology for the agri-food industry: Opportunities, benefits and risks|journal=Trends in Food Science & Technology|language=en|volume=40|issue=2|pages=226–241|doi=10.1016/j.tifs.2014.09.007}}</ref>

Chemical sensors are useful for analyzing odors from [[food sampling|food samples]] and detecting atmospheric gases.<ref>{{cite web| title = Advanced Environmental Monitoring Systems| url = https://www.sensigent.com/msem.html| website = sensigent.com| date = 12 March 2018| access-date = 17 July 2023}}</ref>&nbsp;The "electronic nose" was developed in 1988 to determine the quality and freshness of food samples using traditional sensors, but more recently the sensing film has been improved with nanomaterials. A sample is placed in a chamber where volatile compounds become concentrated in the gas phase, whereby the gas is then pumped through the chamber to carry the aroma to the sensor that measures its unique fingerprint. The high surface area to volume ratio of the nanomaterials allows for greater interaction with analytes and the nanosensor's fast response time enables the separation of interfering responses.<ref>Ramgir, N. S. ISRN Nanomaterials 2013, 2013, 1–21.</ref>  Chemical sensors, too, have been built using [[Chemiresistor#Carbon nanotubes|nanotubes]] to detect various properties of gaseous molecules. Many carbon nanotube based sensors are designed as field effect transistors, taking advantage of their sensitivity. The electrical conductivity of these nanotubes will change due to charge transfer and chemical doping by other molecules, enabling their detection. To enhance their selectivity, many of these involve a system by which nanosensors are built to have a specific pocket for another molecule. Carbon nanotubes have been used to sense [[ionization]] of gaseous molecules while nanotubes made out of titanium have been employed to detect atmospheric concentrations of hydrogen at the molecular level.<ref name="F7">{{cite journal |author=Modi A|author2=Koratkar N|author3=Lass E|author4= Wei B|author5=Ajayan PM|title= Miniaturized Gas Ionization Sensors using Carbon Nanotubes|journal= Nature |volume=424|issue=6945|pages=171–174|date=2003|doi=10.1038/nature01777|pmid=12853951|bibcode=2003Natur.424..171M|s2cid=4431542}}</ref><ref name="F8">{{cite journal |author= Kong J|author2= Franklin NR|author3= Zhou C|author4= Chapline MG|author5= Peng S|author6=  Cho K|author7=  Dai H.|title= Nanotubes Molecular Wires as Chemical Sensors |journal= Science |volume=287 |issue=5453 |pages=622–625|date=2000 |doi=10.1126/science.287.5453.622|pmid= 10649989|bibcode= 2000Sci...287..622K}}</ref> Some of these have been designed as field effect transistors, while others take advantage of optical sensing capabilities. Selective analyte binding is detected through spectral shift or fluorescence modulation.<ref name="F3">{{cite book|date=2003|title=Nanotechnology: A Gentle Introduction to the Next Big Idea|place=Upper Saddle River|publisher=Prentice Hall|isbn=0-13-101400-5|author=Ratner MA|author2=Ratner D|author3=Ratner M.|url-access=registration|url=https://archive.org/details/nanotechnologyge00ratn_0}}</ref> In a similar fashion, Flood et al. have shown that [[supramolecular chemistry|supramolecular]] host–guest chemistry offers quantitative sensing using [[Raman spectroscopy|Raman scattered light]]<ref>{{cite journal |title=Determination of Binding Strengths of a Host–Guest Complex Using Resonance Raman Scattering |first9=Amar H. |last9=Flood |first8=Lasse |last8=Jensen |first7=Eric W. |last7=Wong |first6=Jan O. |last6=Jeppesen |first5=Sune D. |last5=Nygaard |first4=Thomas S. |last4=Hansen |first3=Martin |last3=Christensen |first2=Stinne W. |last2=Hansen |first1=Edward H. |last1=Witlicki  |date=2009 |volume=113 |pages=9450–9457 |doi=10.1021/jp905202x |journal=[[J. Phys. Chem. A]] |issue=34|pmid=19645430 |bibcode=2009JPCA..113.9450W }}</ref> as well as [[surface enhanced Raman spectroscopy|SERS]].<ref>{{cite journal |title=Turning on Resonant SERRS Using the Chromophore-Plasmon Coupling Created by Host–Guest Complexation at a Plasmonic Nanoarray |first7=Amar H. |last7=Flood |first6=Lasse |last6=Jensen |first5=Eric W. |last5=Wong |first4=Jan O. |last4=Jeppesen |first3=Stinne W. |last3=Hansen |first2=Sissel S. |last2=Andersen |first1=Edward H. |last1=Witlicki  |journal=[[J. Am. Chem. Soc.]] |date=2010 |volume=132 |pages=6099–6107 |doi=10.1021/ja910155b |issue=17|pmid=20387841 }}</ref>

Other types of nanosensors, including [[quantum dot]]s and [[gold nanoparticles]], are currently being developed to detect pollutants and toxins in the environment. These take advantage of the [[Localized surface plasmon|localized surface plasmon resonance]] (LSPR) that arises at the nanoscale, which results in wavelength specific absorption.<ref>{{Cite journal|last1=Yonzon|first1=Chanda Ranjit|last2=Stuart|first2=Douglas A.|last3=Zhang|first3=Xiaoyu|last4=McFarland|first4=Adam D.|last5=Haynes|first5=Christy L.|last6=Van Duyne|first6=Richard P.|date=2005-09-15|title=Towards advanced chemical and biological nanosensors—An overview|url=http://www.sciencedirect.com/science/article/pii/S0039914005003504|journal=Talanta|series=Nanoscience and Nanotechnology|language=en|volume=67|issue=3|pages=438–448|doi=10.1016/j.talanta.2005.06.039|pmid=18970187|issn=0039-9140|url-access=subscription}}</ref> This LSPR spectrum is particularly sensitive, and its dependence on nanoparticle size and environment can be used in various ways to design optical sensors. To take advantage of the LSPR spectrum shift that occurs when molecules bind to the nanoparticle, their surfaces can be functionalized to dictate which molecules will bind and trigger a response.<ref name=":7">{{Cite journal|last1=Riu|first1=Jordi|last2=Maroto|first2=Alicia|last3=Rius|first3=F. Xavier|date=2006-04-15|title=Nanosensors in environmental analysis|url=http://www.sciencedirect.com/science/article/pii/S0039914005006570|journal=Talanta|series=1st Swift-WFD workshop on validation of Robustness of sensors and bioassays for Screening Pollutants|language=en|volume=69|issue=2|pages=288–301|doi=10.1016/j.talanta.2005.09.045|pmid=18970568|issn=0039-9140|url-access=subscription}}</ref> For environmental applications, quantum dot surfaces can be modified with antibodies that bind specifically to microorganisms or other pollutants. Spectroscopy can then be used to observe and quantify this spectrum shift, enabling precise detection, potentially on the order of molecules.<ref name=":7" /> Similarly, fluorescent semiconducting nanosensors may take advantage of [[Förster resonance energy transfer|fluorescence resonance energy transfer]] (FRET) to achieve optical detection. Quantum dots can be used as donors, and will transfer electronic excitation energy when positioned near acceptor molecules, thus losing their fluorescence. These quantum dots can be functionalized to determine which molecules will bind, upon which fluorescence will be restored. Gold nanoparticle-based optical sensors can be used to detect heavy metals very precisely; for example, mercury levels as low as 0.49 nanometers. This sensing modality takes advantage of FRET, in which the presence of metals inhibits the interaction between quantum dots and gold nanoparticles, and quenches the FRET response.<ref>{{cite journal | last1 = Long | first1 = F. | last2 = Zhu | first2 = A. | last3 = Shi | first3 = H | year = 2013 | title =  Recent Advances in Optical Biosensors for Environmental Monitoring and Early Warning| journal = Sensors | volume = 13 | issue = 10| pages = 13928–13948 | doi = 10.3390/s131013928 | pmid = 24132229 | pmc = 3859100 | bibcode = 2013Senso..1313928L | doi-access = free }}</ref> Another potential implementation takes advantage of the size dependence of the LSPR spectrum to achieve ion sensing. In one study, Liu et al. functionalized gold nanoparticles with a Pb<sup>2+</sup> sensitive enzyme to produce a lead sensor. Generally, the gold nanoparticles would aggregate as they approached each other, and the change in size would result in a color change. Interactions between the enzyme and Pb<sup>2+</sup> ions would inhibit this aggregation, and thus the presence of ions could be detected.

The main challenge associated with using nanosensors in food and the environment is determining their associated toxicity and overall effect on the environment. Currently, there is insufficient knowledge on how the implementation of nanosensors will affect the soil, plants, and humans in the long-term. This is difficult to fully address because nanoparticle toxicity depends heavily on the type, size, and dosage of the particle as well as environmental variables including pH, temperature, and humidity. To mitigate potential risk, research is being done to manufacture safe, nontoxic nanomaterials, as part of an overall effort towards green nanotechnology.<ref>{{cite journal | last1 = Omanovic-Miklicanin | first1 = E. | last2 = Maksimovic | first2 = M. | year = 2016 | journal = Bulletin of the Chemists and Technologists of Bosnia and Herzegovina | volume = 47 | pages = 59–70 }}</ref>