Gold Nanostar Substrates for Metal-Enhanced Fluorescence through the First and Second Near-Infrared Windows

Theodorou, Ioannis G.; Jawad, Zaynab; Jiang, Qianfan; Aboagye, Eric O.; Porter, Alexandra E.; Ryan, Mary P.; Xie, Fang

doi:10.1021/acs.chemmater.7b02313

Cited by 74 publications

(89 citation statements)

References 78 publications

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“…Interestingly, instead of complete overlap, it has been shown that enhanced fluorescence occurs when the fluorophore emission peaks at a slightly longer wavelength than the LSPR peak. 23,24 In the past decade, there have been plentiful novel nanoparticle structures showing an ability to improve both the fluorescence intensity and the photostability of fluorophores via this mechanism, including nanorods, 25 nanocubes, 26 nanodisks, 27 nanotriangles 28 and nanostars 29 (Fig. 3A 30 ).…”

Section: General Criteria For a Mef Based Biosensormentioning

confidence: 99%

Metal enhanced fluorescence biosensing: from ultra-violet towards second near-infrared window

2018

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Section: General Criteria For a Mef Based Biosensormentioning

confidence: 99%

Metal enhanced fluorescence biosensing: from ultra-violet towards second near-infrared window

2018

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“…This leads to larger field enhancement at the LSPR, leading to a larger excitation enhancement in MEF. The LSPR is dependent not just upon material but also on the shape of the nanoparticle, and MEF has been successfully demonstrated in the NIR using triangular-like Ag nanoparticles immobilized on glass substrate [26,27], nanocylinders [22], and Nanostar [23]. Table 1 summarizes some of the results presented in published work by the Xie group at Imperial College for MEF in the NIR, for both Au and Ag nanoparticles, for excitation wavelengths up to 780 nm.…”

Section: Of 13mentioning

confidence: 97%

“…One application that exploits the LSPR, which has received much attention for the purpose of bio-sensing, is metal enhanced fluorescence (MEF) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. MEF is now a well-recognized form of technology wherein the near-field interaction of fluorophores with metallic nanostructures can lead to substantial fluorescence enhancement.…”

Section: Introductionmentioning

confidence: 99%

Infra-Red Plasmonic Sensors

Centeno

Aid²,

Xie

2018

Chemosensors

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Plasmonic sensors exploiting the localized surface plasmon resonance (LSPR) of noble metal nanoparticles are common in the visual spectrum. However, bio-sensors near the infra-red (NIR) windows (600-900 nm and 1000-1400 nm) are of interest, as in these regions the absorption coefficients of water, melanin deoxyglobin, and hemoglobin are all low. The first part of this paper reviews the work that has been undertaken using gold (Au) and silver (Ag) particles in metal enhanced fluorescence (MEF) in the NIR. Despite this success, there are limitations, as there is only a narrow band in the visual and NIR where losses are low for traditional plasmonic materials. Further, noble metals are not compatible with standard silicon manufacturing processes, making it challenging to produce on-chip integrated plasmonic sensors with Au or Ag. Therefore, it is desirable to use different materials for plasmonic chemical and biological sensing, that are foundry-compatible with silicon (Si) and germanium (Ge). One material that has received significant attention is highly-doped Ge, which starts to exhibit metallic properties at a wavelength as short as 6 µm. This is discussed in the second part of the paper and the results of recent analysis are included.Fluorescent molecules emitting at wavelengths in the infra-red window, in which penetration depth is high and the autofluorescence minimum is of particular interest, are potentially an attractive technology for bio-applications [27]. However, the low quantum yield and poor photostability of near infra-red (NIR) dyes currently limits their applicability. Design and synthesis of NIR dyes with high quantum yield and photostability have proved to be extremely challenging, due to the complex synthetic routes required for these large, complex molecules [27]. The amplification of light from NIR fluorophores by MEF is a promising strategy for dramatically improving both the detection sensitivity and image enhancement, thereby realizing the potential advantages of the NIR fluorophores. Section 2 of this paper discusses the physical process of MEF and reviews some of the published work by the authors.NIR losses arise in Au and Ag from intraband (or Drude) losses. There is, therefore, only a narrow band in the visual and NIR range where losses are low for traditional plasmonic materials. A further challenge associated with noble metals is that they are not compatible with standard silicon manufacturing processes. Further, noble metals diffuse into the semiconductor, forming deep-level traps which have an adverse effect on device performance. While Au and Ag are the obvious choice for visible and NIR applications, there is a desire and need for chemical and biological sensing in the mid-infrared (MIR) range [29][30][31] using materials that are foundry-compatible with silicon (Si) and germanium (Ge), that might lead to on-chip integration of devices governed by plasmonic effects [25,26]. One material that has received significant attention as a potential plasmonic material in the MIR is highly-...

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“…On the other hand, the sensitivities of current fluorescence indicator paper and sensors are still expected to improve because a higher sensitivity can respond to target solutions with a lower concentration, which will benefit the application of trace detection. [16,17] Superhydrophobicity signifies that the material does not readily become damp, with a water contact angle over 150°. [12,13] Moreover, fluorophores with stronger fluorescence can suppress background noise and autofluorescence, bringing about more sensitive detection.…”

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“…[12,13] Moreover, fluorophores with stronger fluorescence can suppress background noise and autofluorescence, bringing about more sensitive detection. [16,17] Superhydrophobicity signifies that the material does not readily become damp, with a water contact angle over 150°. [16,17] Superhydrophobicity signifies that the material does not readily become damp, with a water contact angle over 150°.…”

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Ultrasensitive and Recyclable Upconversion‐Fluorescence Fibrous Indicator Paper with Plasmonic Nanostructures for Single Droplet Detection

Zhang

et al. 2019

Advanced Optical Materials

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attention due to their extensive biological and medical applications. [1][2][3][4][5] Conventional indicator paper such as pH paper is disposable after use. Similarly, a traditional particulate-based fluorescence sensor is also not reusable because it usually suspends fluorescent nanoparticles such as quantum dots and upconversion nanocrystals in the target solution to initiate detection, [6][7][8][9] which are often unstable and irreproducible when contaminated by the target solution. Additionally, these indicator papers and fluorescence sensors usually need large amounts of the target solutions, which severely restricts their widespread application, especially for small amounts of target solutions, such as a single droplet. On the other hand, the sensitivities of current fluorescence indicator paper and sensors are still expected to improve because a higher sensitivity can respond to target solutions with a lower concentration, which will benefit the application of trace detection. [10,11] Therefore, it is highly desired to develop fluorescence indicator paper or sensor that simultaneously possesses excellent sensitivity and recyclability for single droplet detection.Among fluorescent nanoparticles, upconversion nanocrystals, compared with quantum dots, are attractive candidates because they can be excited by near-infrared light, which has a high penetration depth in biological tissues. [12,13] Moreover, fluorophores with stronger fluorescence can suppress background noise and autofluorescence, bringing about more sensitive detection. [14,15] To achieve stronger fluorescence, plasmonic nanostructures are good choices because they can produce strong localized electric fields, affecting excitation or emission process of nearby fluorophores to enhance their fluorescence; this process must not change the chemical construction of fluorophores, which is not an easy task. [16,17] Superhydrophobicity signifies that the material does not readily become damp, with a water contact angle over 150°. [18] To achieve recyclability, immediate contact of fluorescent nanoparticles with target solutions must be avoided. Utilizing electrospinning is a good method to achieve this, because it can easily incorporate nanoparticles into superhydrophobic nanofibers during the electrospinning process, [19][20][21][22] which endows them with a self-cleaning property. In addition, the large specific surface area of electrospun Conventional indicator paper is disposable after use and requires a large amount of target solution. Herein, recyclable upconversion fluorescence indicator papers consisting of upconversion nanorods and plasmonic nanostructures are fabricated by electrospinning. This recyclable indicator paper exhibits good flexibility and superhydrophobicity with enhanced upconversion fluorescence. Rhodamine B (RhB) is selected as the target solution because it is prohibited as a food additive but often occurs in food, and conventional detection methods usually need a large volume of solution (>1 mL) to refine to higher concentratio...

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Gold Nanostar Substrates for Metal-Enhanced Fluorescence through the First and Second Near-Infrared Windows

Cited by 74 publications

References 78 publications

Metal enhanced fluorescence biosensing: from ultra-violet towards second near-infrared window

Metal enhanced fluorescence biosensing: from ultra-violet towards second near-infrared window

Infra-Red Plasmonic Sensors

Ultrasensitive and Recyclable Upconversion‐Fluorescence Fibrous Indicator Paper with Plasmonic Nanostructures for Single Droplet Detection

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