ExcitonâPlasmon Interactions between CdS@g-C3N4 Heterojunction

Subscriber access provided by University of Sussex Library

Article

Exciton-plasmon interactions between CdS@g-C3N4 heterojunction and Au@Ag nanoparticles coupled with DNAase-triggered signal amplification: toward highly sensitive photoelectrochemical bioanalysis of microRNA Yu-Xiang Dong, Juntao Cao, Bing Wang, Shu-Hui Ma, and Yan Ming Liu ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b02774 • Publication Date (Web): 22 Sep 2017 Downloaded from http://pubs.acs.org on September 22, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Sustainable Chemistry & Engineering is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

1

Exciton-plasmon

interactions

2

heterojunction

3

DNAase-triggered signal amplification: toward highly sensitive

4

photoelectrochemical bioanalysis of microRNA

5

Yu-Xiang Donga,b, Jun-Tao Caoa,b∗, Bing Wanga,b, Shu-Hui Mac, and Yan-Ming Liua,b∗

6

a

7

Nanhu Road, Xinyang 464000, China

8

b

9

Xinyang Normal University, 237 Nanhu Road, Xinyang 464000, China

and

Au@Ag

between nanoparticles

CdS@g-C3N4 coupled

with

College of Chemistry and Chemical Engineering, Xinyang Normal University, 237

Institute for Conservation and Utilization of Agro-bioresources in Dabie Mountains,

10

c

11

* Corresponding author:

12

* Tel/Fax: +86-376-6392889. Email: [email protected] (Y.-M. Liu)

13

* Tel/Fax: +86-376-6391172. Email: [email protected] (J.-T. Cao)

Xinyang Central Hospital, 1 Siyi Road, Xinyang 464000, China

14 15

ABSTRACT

16

Novel exciton-plasmon interactions (EPI) between CdS@g-C3N4 heterojunction

17

and Au@Ag nanoparticles (NPs) was introduced for the first time into the

18

photoelectrochemical (PEC) biosensing system for highly sensitive microRNA-21

19

detection using duplex-specific nuclease-assisted cycle amplification for sensitivity

20

enhancement. The photoelectrode of CdS@g-C3N4 nanowires could generate a great

21

photocurrent because of the formation of the p-n heterojunction. Due to the natural

22

absorption overlap, the exciton of CdS@g-C3N4 and the plasmon of Au@Ag NPs

23

could be induced simultaneously to form EPI. Specifically, the perfect overlap of the

24

wide absorption spectrum of Au@Ag NPs with the photoluminescence spectrum of

25

CdS@g-C3N4 allows the resonance energy transfer and EPI between CdS@g-C3N4

26

nanowire and Au@Ag NPs simultaneously. The effective EPI renders the signal

27

change modulated by the interparticle distance significantly. Such a signaling

28

mechanism was then used to construct the PEC biosensor for microRNA-21 detection, 1

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 23

1

within which the duplex-specific nuclease (DSN) was further introduced to enhance

2

the sensitivity. The constructed PEC biosensor exhibits the sub-fM level (0.05 fM)

3

detection of microRNA-21 with a wide range from 0.1 fM to 1.0 nM. In complex

4

biological samples, the proposed method also possesses good specificity,

5

reproducibility, and stability.

6

Keywords:

7

amplification, Exciton-plasmon interactions, Heterojunction

Photoelectrochemistry,

MicroRNA-21,

Enzyme-assited

cycle

8 9

INTRODUCTION

10

Photoeletrochemical (PEC) bioanalysis as a newly emerged yet dynamically

11

developing methodology has been proved to be an elegant route for biodetection

12

applications.1-3 Currently, many PEC detection formats have been developed for the

13

biomolecular detection.4 The signaling strategies are mainly relied on the changed

14

photocurrent signal caused by the steric-hindrance effect,5 biocatalytic precipitation,6

15

sensitization effects,7 in situ generation of electron donor or acceptor by the catalysis

16

of enzyme,8,9 and energy transfer (ET).10 Of these, ET as an effective tool has been

17

adopted for the sensitive detection of various biomolecules11-13 since the first report

18

on the ET between quantum dots (QDs) and gold nanoparticles (Au NPs) for PEC

19

biosensing application in 2011.14 In such a system, the ET is highly limited to the

20

interplay between CdS QDs and Au NPs. In 2012, Zhao et al. demonstrated the

21

existence of the more efficient interparticle interplay between CdS QDs and Ag NPs

22

based on exciton-plasmon interactions (EPI).15 Very recently, on the basis of the

23

transition of the interparticle interplay from the CdS QDs-Au NPs to the CdS QDs-Ag

24

NPs system, they further reported a highly efficient EPI with strong quenching effect

25

for the PEC microRNA bioassay.16 Due to the short development time of this field, the

26

ET-based PEC bioanalysis is still in its early stage and great potential exists in its

27

future investigations.

28

Nanostructure photoactive materials have long been of interest as one of important

29

element in improving the performance of PEC bioanalysis.17 Among various 2


Page 3 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

candidates, CdS with relatively narrow band gap (2.4 eV) is an important

2

visible-light-responsive material.18 Up to now, a variety of approaches has been

3

proposed to enhance the photoelectric activity of CdS, including controlling the

4

crystal phases,19 designing morphologies20 and constructing heterojunction.21 Of these,

5

semiconductor heterojunctions have been verified to be an ingenious transducer in the

6

broad PEC analytical field since the first report using BiOI nanoflakes/TiO2

7

nanoparticles p-n heterojunction as photoelectrode for PEC bioanalysis developed by

8

Zhao et al.22 Zang et al developed a CdS/MoS2 heterojunction-based PEC biosensor

9

for sensitive DNA detection.21 The heterostructure-based photoelectrode achieved

10

about 280% increasing of photocurrent compared to pure CdS QDs electrode. The

11

formation of heterojunction not only increases the enterable area for efficient charge

12

transfer across the interface, but also shortens the charge transport time and distance

13

for directional face-to-face migration of photogenerated charge, thus greatly promote

14

electron–hole

15

recombination.23,24 Recently, graphitic carbon nitride (g-C3N4) benefited from its good

16

water solubility, highly chemical stability, and especially the intrinsic visible light

17

response has attracted much attention.25 So, how about constructing a linear

18

heterojunction

19

(CdS-NW/g-C3N4-NS) for biochemical analysis? To the best of our knowledge, such

20

heterojunctions-based PEC bioanalysis is still very few and explore of EPI in PEC

21

bioanalysis using heterojunction as photoactive material has not yet been reported.

separation

to

comprising

minimize

the

CdS

the

energy

nanowire

waste

and

of

g-C3N4

electron–hole

nanosheets

22

MicroRNAs (miRNAs) are a class of short (approximately 19-25 nucleotides),

23

single-stranded, endogenous noncoding RNAs, which has been regarded as the good

24

candidate biomarkers in the early diagnosis of cancers and prognostic processes. The

25

traditional quantification methods including RT-PCR,26 northern blotting27 and

26

microarray28 have been employed in the miRNA detection. However, these methods

27

usually required expensive equipment or complex operations. The new strategies

28

combining the techniques of colorimetry, electrochemistry, chemiluminescence,

29

electrochemiluminescence, and PEC with the unique features of functional 3



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

nanomaterials have witnessed their potentials in miRNAs detection. The unique

2

characteristics of miRNAs with low abundance in serum or cell, small size and

3

similarity among other family members make the specific and sensitive detection of

4

miRNAs challenging. So, developing ingenious method by integrating the

5

heterojunction-based EPI process with some signal amplification strategies for highly

6

sensitive detection of miRNA is highly desirable.

7

Enzyme-assisted cycle amplification as one of important recycling strategies, has

8

been applied in bioassays for signal amplification and sensitive detection of target.29-31

9

Duplex-specific nuclease (DSN), with unique property of specific digestion DNA in

10

DNA-RNA duplexes to release RNA, has been developed for miRNAs detection,

11

which possess the advantages of high detection specificity and sensitivity.32 These

12

excellent characteristics have made the DSN as a efficient signal amplification tool

13

for miRNAs detection in numbers of analysis method, such as fluorescence,33

14

electrochemiluminescence,34 electrochemistry,35 etc. As far as we know, there are few

15

reports focusing on the DSN to amplify photocurrent signal in PEC bioanalysis.

16

Herein, we report a novel and sensitive PEC bioassay of miRNA-21 based on the

17

EPI between CdS@g-C3N4 nanowire and Au@Ag NP and DSN-assisted target

18

recycling amplification strategy. As illustrated in Figure 1A, the heterojunction of

19

CdS@g-C3N4 nanowire was prepared by immobilizing the g-C3N4 on the surface of

20

CdS nanowire and used as electrode matrix for accommodating the biorecognition

21

events. The hairpin structure molecular beacon (MB) immobilized on the

22

CdS@g-C3N4 nanowire was used for the specific recognizing of miRNA-21 and

23

subsequent DSN-assisted target recycling amplification. Upon the addition of

24

miRNA-21, MB specifically hybridized with miRNA-21. The formed MB-miRNA

25

duplex on the interface of the electrode will become the substrate for DSN cleavage.

26

Since DSN only cleaves DNA in the duplexes, the miRNA-21 subseqently released to

27

hybrided with another MB, leading to a cyclic reaction and target signal amplification.

28

In this case, the probe DNA functionalized Au@Ag as tags specifically hybrids with

29

the sheared MB and an EPI between CdS@g-C3N4 nanowire and Au@Ag NPs occurs 4


Page 4 of 23

Page 5 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

under light illumination, leading to a sharp decrease of the PEC intensity. The

2

effective EPI signaling mechanism, together with the cyclic DSN-assisted signal

3

amplification, gives rise to the high sensitivity of the assay. To the best of our

4

knowledge, both the signaling mechanism based on EPI between CdS@g-C3N4

5

nanowire and Au@Ag NPs and the PEC bioanalytical strategy has never been

6

reported.

7 8

Figure 1. (A) Schematic illustration of the fabrication process of the PEC biosensor； 5



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

(B) Schematic illustration for the energy bands of CdS@g-C3N4 before and after

2

coupling; (C) Charge transfer process at the formed heterojunction under light

3

illumination.

4

EXPERIMENTAL SECTION

5

The sequence of DNA probes (Table S1), Chemicals and materials, and

6

instrumentation utilized in this work were described in the Supporting Information.

7

Preparation of core/shell CdS@g-C3N4 nanowires

8

CdS nanowires were synthesized via a solvothermal method.36 Briefly, 3.205 g

9

Cd(NO3)2·4H2O and 2.37 g thiourea were added into a dried beaker. 50 mL of

10

ethylenediamine was subsequently injected into the beaker. The solution was stirred

11

and transferred to Teflon-lined autoclave. After maintained at 180 ℃ for 72 h, the

12

autoclave was quenched rapidly to room temperature. The obtained yellow

13

precipitates were centrifuged, rinsed with ethanol and water three times, and then

14

dried in a vacuum oven at 60 ℃.

15

Water-dispersible g-C3N4 was prepared according to the previous work.37 First,

16

bulk C3N4 (b-C3N4) was synthesized by annealing 5.0 g of melamine in a semiclosed

17

system at 550 ℃ for 4 h. Then, 1.0 g of as-prepared b-C3N4 powder was refluxed in

18

100 mL of 5 M HNO3 at 125 ℃ for 12 h and kept overnight. The formed precipitate

19

was centrifuged, washed repeatedly with water until the pH of the solution was 7.0,

20

and dried at 60 ℃. Thus, water dispersible g-C3N4 was obtained.

21

Core/shell CdS@g-C3N4 nanowires were obtained via a self-assembly procedure.38

22

Certain amount of as prepared g-C3N4 was added into 25 mL of methanol. After being

23

ultrasonically treated for 30 min, CdS nanowires were dispersed in the suspension and

24

stirred at room temperature for 24 h. After removing residual methanol by

25

centrifugation, the obtained yellow precipitate was collected and dried in a vacuum

26

oven at 60 ℃. Core/shell CdS@g-C3N4 nanowires with different weight ratios of

27

g-C3N4 to CdS (0, 0.5, 1, 2, 3, and 4 wt %) were labeled as CN0 (pristine CdS

28

nanowire), CN0.5, CN1, CN2, CN3, and CN4, respectively.

29

Synthesis of Au@Ag NPs and pDNA-Au@Ag NPs 6


Page 6 of 23

Page 7 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Au@Ag NPs were prepared according to literature.39 First, 1% trisodium citrate (1.0

2

mL) was quickly added into 0.01% HAuCl4 solution (0.01%, 100 mL) under vigorous

3

stirring. The color of the solution turning from gray to deep wine-red indicated the

4

formation of Au NPs, and then kept stirring for 10 min. Next, 50 mL of the obtained

5

Au NPs solution was added in double neck flask and refluxed at 135 ℃ under stirring.

6

Then, 1 mL AgNO3 (4.0 mg/mL) was added. After that, 1% trisodium citrate (1 mL)

7

was added dropwise. The reaction solution was refluxed for 1 h. Au@Ag NPs were

8

eventually obtained after cooling.

9

pDNA-Au@Ag NPs were parepared as follows. Briefly, 10 µL of 100 µM

10

HS-modified DNA was mixed with 800 µL Au@Ag NPs and gentle shaken for 16 h at

11

room temperature. The resulted solution was centrifuged for 10 min at 10000 rpm.

12

After removal of the supernatant, the precipitate was resuspended in 500 µL PBS.

13

Fabrication of PEC biosensor

14

The preparation process of PEC biosensor is shown in Figure 1. The ITO slices as the

15

working electrode were washed with acetone/ethanol and water, respectively. Then,

16

20 µL of 0.5 mg/mL CN2 (dissolved in 0.1 mg/mL CS) was coated on an ITO

17

electrode surface and dried at 55 ℃. Subsequently, 20 µL of 2.5% (v/v) GA in PBS

18

was spreaded onto the electrode for 2 h at room temperature. After rinsed with PBS,

19

0.5 µM MB was dropped on the electrode at 37 ℃ for 1 h and washed with PBS. The

20

gained electrode was immediately added 20 µL PBS buffer containing 5.0 mM Mg2+,

21

different concentrations of miRNA-21, and 0.01 U/µL DSN at 37 ℃ for 60 min, and

22

DSN stop solution was used to end the enzyme amplification reaction. After washing

23

with PBS thoroughly, the resulted electrode was incubated with pDNA-Au@Ag NPs

24

at 37 ℃ for 60 min.

25

RESULTS AND DISCUSSION

26

PEC mechanism of the biosensor

27

The exploration of EPI in PEC bioanalysis using heterojunction as photoactive

28

material has not been reported so far. Thus, exploitation of heterojunction in this work

29

is very meaningful and potentially broadens the applicability of the heterojunction in 7



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

PEC field. Figure 1B illustrated the schematic representation of the energy-level

2

configuration and the photo-transfer process in CdS@g-C3N4 heterojunction.18,36

3

Under irradiation, light induced electron-hole pairs separation of g-C3N4, and the

4

reformed band edge in the p-n junction facilitate the photoelectrons transfer from

5

g-C3N4 to CdS. On the contrary, the holes of the latter would migrate to the valence

6

band (VB) of the former. Evidently, the formation of heterojunction could promote the

7

spatial charge separation as well as increase the photoelectron lifetime, hence improve

8

the analytical performance of the following biosensor.

9

In Figure 1C, upon light irradiation, the excitonic responses in CdS@g-C3N4

10

occurred immediately and electron-hole (e--h+) pair generated at the same time.

11

However, the generated e--h+ pair would be destined for recombination. This process

12

may lead to rapid energy recession (i.e. radiative decay (rD), nonradiative decay (nD)

13

and spatial electron transfer). To inhibit the corrosion (lattice dissolution) of

14

CdS@g-C3N4 under illumination and yield stable photocurrent signal, electron donor

15

(AA, in this work) is necessary. On the other hand, because of the collective

16

oscillation of conduction electrons driven by the applied electromagnetic field of

17

incident light, the surface plasmon resonance (SPR) of Au@Ag NPs would be

18

stimulated. When EPI happens in the PEC system, the excitonic response in

19

CdS@g-C3N4 could be modulated greatly and thus generate a weak photocurrent. The

20

weak of the current could be attribute to the following reasons: (i) the EPI effect

21

between Au@Ag NPs and CdS@g-C3N4 enhances the e--h+ recombination of the

22

CdS@g-C3N4, hence yield a low photoelectric conversion efficiency15; (ii) the steric

23

hindrance of pDNA partly obstructs the diffusion of the electron donor, i.e. ascorbic

24

acid, to the surface of photoelectrode, which make the depleting efficiency of the

25

photogenerated holes decrease, leading to a declined photocurrent intensity.40

26

Characterization of CdS@g-C3N4 nanowires

27

Figure 2A presents the SEM image of the CdS nanowires, and the inset is the

28

corresponding TEM image. It can be seen that the nanowires have an average

29

diameter of ca. 50 nm and a length of about 1 − 3 µm. Figure 2B displays the SEM 8


Page 8 of 23

Page 9 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

image of the g-C3N4 nanosheets, and the inset is the corresponding TEM image. It can

2

be seen that the nanosheets have a typical thin laminar structure.

3 4

Figure 2. (A) SEM image of CdS (the inset is the corresponding TEM image). (B)

5

SEM image of g-C3N4 (the inset is the corresponding TEM image).

6

After a spontaneous adsorption process, pure g-C3N4 was successfully coated on

7

CdS nanowires with intimate contact and the morphologies of CdS@g-C3N4 with

8

different g-C3N4 content were depicted in Figure 3(A-C). It can be seen that the

9

core/shell structures can be clearly observed due to the different electron penetrability

10

between CdS and g-C3N4. In addition, the thickness of the g-C3N4 layer increased

11

with the loading amount of g-C3N4 layer increasing, in accordance with previous

12

report.36 The g-C3N4 layer is about 5 nm, 10 nm, 15 nm for CN2, CN3, CN4,

13

respectively. The crystalline phases of the CdS@g-C3N4 nanowires were analyzed by

14

XRD. Figure 3D presents the XRD patterns of CdS@g-C3N4 composite with different

15

ratios of g-C3N4 to CdS, and pure g-C3N4. In XRD pattern, pure CdS (CN0) is

16

crystallized in hexagonal wurtzite structure with the lattice parameters a = 4.132 Å

17

and c = 6.734 Å (JCPDS no. 65-3414). The intensity of the (002) peak of the CdS

18

remarkably declined compared to the standard diffraction data, resulting from its

19

growth preference along the direction of the c axis. Pure g-C3N4 exhibits two distinct

20

diffraction peaks at 13.0° and 27.4° which can be indexed as the (100) and (002)

21

peaks for graphitic materials.36 After loading g-C3N4 on the surface of CdS, the XRD

22

pattern of CdS@g-C3N4 shows no obvious difference compared with pure CdS pattern,

23

owing to the low content (≤ 4%) of g-C3N4.

9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2

Figure 3. (A), (B) and (C) are TEM images of CN2, CN3, and CN4, respectively. (D)

3

XRD patterns of CNX (X = 0, 0.5, 1, 2, 3, and 4) together with g-C3N4.

4

The XPS spectrum depicts that the elements of C, N, Cd, and S are presented in the

5

sample (Figure 4). In detail, the C 1s spectrum presents three peaks at 284.8 eV, 286.1

6

eV and 288.1 eV (Figure 4A). The peaks at 284.8 e V is identified as graphitic carbon

7

(C-C, C=C).41 The peak at 288.1 eV can be ascribed to sp2-boned in N containing

8

aromatic structure (N-C=N), which shows the major environment in g-C3N4.42 The

9

middle peak (286.1 eV) is related to sp3-coordinated carbon species from the defects

10

on g-C3N4 surface.42 Furthermore, three peaks centered at 398.8 eV, 400.1 eV and

11

401.2 eV can be identified from N 1s spectrum (Figure 4B). The main peak at 398.8

12

eV is attributed to the sp2-bonded N in the triazine structure (C-N=C).43 The other two

13

peaks at 400.1 eV and 401.2 eV originate from the N-(C)3 groups and (C-N-H) groups, 10


Page 10 of 23

Page 11 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

respectively.44 On the other hand, the peaks for Cd 3d (Figure 4C) appear at 404.8 eV

2

and 411.7 eV are assigned to the Cd 3d5/2 and Cd3/2 for Cd2+ in CdS nanowries. The S

3

2p peaks at 161.1 eV (S 2p3/2) and 162.3 eV (S 2p1/2) (Figure 4D) are ascribed to be

4

S2- in CdS nanowries. Therefore, the XPS results further verify the successful

5

formation of CdS@g-C3N4 composites.

6

7 8

Figure 4. XPS spectra for CdS nanowires coated with 8 wt% g-C3N4: (a) C1s; (b) N1s;

9

(c) Cd 3d; (d) S 2p.

10

Characterization of Au@Ag NPs

11

To confirm the successful synthesis of Au@Ag NPs, TEM was performed and the

12

micrographs were displayed in Figure 5. As can be seen from Figure 5A, spherical Au

13

NPs are uniformly dispersed with a mean diameter of 40 nm. After Ag-shell was

14

wrapped on the surface of Au seed by in situ growth method, the diameter of the

15

resulted-nanoparticles increased to 50 nm (Figure 5B). Figure 5C depicts the UV-vis

16

absorption spectrum of Au NPs (curve a) and Au@Ag NPs (curve c). Au@Ag NPs

17

show a much broader absorption range compared with the Au NPs. Both the TEM and 11



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

UV-vis data demonstrate that the Au@Ag NPs were prepared successfully.

2

Essentially, the efficient excitation of EPI needs a sufficient spectra overlap

3

between the exciton band of semiconductor and the plasmon band of noble metal

4

nanoparticles. In Figure 5C. Au seeds exhibit an obvious absorption band about 536

5

nm (curve a). After covered with Ag layer, a broad absorption at 350-525 nm appears

6

(curve b). The blue-shifted surface plasmon absorbance indicated the coupling

7

between the Au and Ag layers.39 The PL spectrum of CdS@g-C3N4 (curve c) has a

8

peak at 400 nm, which overlap with the UV-vis absorption of Au@Ag NPs.

9 10

Figure 5. TEM images of (A) Au NPs, (B) Au@Ag NPs. (C) UV-vis absorption

11

spectra of Au NPs (a), Au@Ag NPs (b), and PL spectrum of CdS@g-C3N4 (c).

12

EIS and PEC characterization of the biosensor

13

EIS as an effective tool for describing the interface properties of electrodes was used

14

to monitor the fabrication process of the biosensor. The impedance spectra of the

15

electrodes in each construction step were performed in the presence of 5.0 mM

16

K3[Fe(CN)6]/K4[Fe(CN)6] (1:1) containing 0.1 M KCl (Figure 6A). After

17

CdS@g-C3N4/CS was dropped on the ITO surface, the impedance spectrum of the

18

modified electrode (curve b) displays a high charge-transfer resistance (Ret) compared

19

with the bare ITO electrode (curve a), which is ascribed to the poor electron transfer

20

property of CdS@g-C3N4/CS. When the MB (curve c) and miRNA-21 (curve d) were

21

subsequently assembled on CS/CdS@g-C3N4/ITO electrode, a significant increase of

22

Ret was observed. This increase might be owing to the electrostatic repulsion of

23

MB/miRNA-21 phosphate backbone with negative charges to the [Fe(CN)6]3-/4- ions

24

preventing the electron delivery process. After incubation with pDNA-Au@Ag (curve 12


Page 12 of 23

Page 13 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

e), the electrode gave a higher Ret, implying the successful hybridization of

2

pDNA-Au@Ag with the sheared MB. These results indicate that the designed

3

biosensor was feasible expected.

4

The fabrication process can also be examined by the photocurrent response. The

5

responses of electrodes at the stepwise assembly process was recorded and depicted in

6

Figure 6B. The bare ITO gave no photocurrent response (curve a). The addition of

7

CdS@g-C3N4/CS on the ITO electrode (curve b) produced a sharp increase in

8

photocurrent indicating the efficient photoelectric conversion efficiency of the

9

CdS@g-C3N4. Whereas the photocurrents declined after modified with MB (curve c)

10

and miRNA-21 (curve d), because of the steric hindrance of MB and miRNA-21.

11

When pDNA-Au@Ag was bound on the electrode, the photocurrent intensity

12

decreased noticeably (curve e) owing to the strong EPI between CdS@g-C3N4

13

nanowire and Au@Ag NPs. All of these results suggest the successful fabrication of

14

the PEC biosensor.

15 16

Figure 6. Impedance spectra (A) and photocurrent response (B) of the bare ITO (a),

17

CS/CdS@g-C3N4/ITO

18

MB/GA/CS/CdS@g-C3N4/ITO incubation with 1 nM miRNA-21 and 0.2 U DSN (d),

19

further hybridization with pDNA-Au@Ag (e).

20

Optimization of experimental conditions

21

To achieve excellent performance in PEC assay, some conditions of the detection

22

process were optimized. In Figure S1A, the photocurrent of CdS@g-C3N4/ITO

23

electrode significantly increased with the thickness of g-C3N4 shell increasing,

(b),

MB/GA/CS/CdS@g-C3N4/ITO

13


(c),


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

illustrating that more coated g-C3N4 could provide more photogenerated holes and

2

electrons to join in the PEC process. However, the photocurrent decreased when the

3

weight ratio of g-C3N4 to CdS exceeds 2%. This result may because the excessive

4

amount of weak conductivity g-C3N4 would block the transfer of photogenerated

5

electron. Therefore, CN2 was used for assembly of the PEC sensor.

6

Figure S1B gives the effect of hybridization time between MB and target

7

miRNA-21. The PEC intensity reached the platform at the time of 60 min, indicating

8

the hybridization reaction was saturated. Meanwhile, the incubation time of

9

pDNA-Au@Ag with the sheared MB was also investigated. In Figure S1C, the PEC

10

intensity gradually declined and reached minimum value at 60 min. The results

11

suggested that the amount of pDNA-Au@Ag modified on the electrode increased

12

with the incubation time, and gradually tended to saturation until 60 min. Thus 60 min

13

of hybridization time and incubation time were chosen in the subsequent experiments.

14

Analytical performance

15

The novel PEC biosensor based on the EPI between CdS@g-C3N4 and Au@Ag NPs

16

was used to detect miRNA-21. Under the optimal experimental conditions, the PEC

17

intensity decreased with the increasing concentration of miRNA-21 (Figure 7A) and

18

decrease of photocurrent is proportional to the target concentration logarithmically

19

with the from 0.1 fM to 1.0 nM. The regression equation is I = 1.89 – 6.22 log

20

[CmiRNA-21] (M) with the correlation coefficient of 0.996 (Figure 7B). The limit of

21

detection (LOD) was experimental found as 0.05 fM. Compared with some reported

22

microRNA detection assays, the proposed PEC strategy has a low detection limit

23

(Table S1). This low detection limit could be attributed to the following factors: (i)

24

CdS@g-C3N4 nanowires p-n heterojunction as photoelectrode produce high and stable

25

photocrurrent response; (ii) the high efficiency of the EPI effect between

26

CdS@g-C3N4 nanowire and Au@Ag NPs resulted in the dramatic decrease of

27

photocurrent signal; (iii) DSN-assisted cycle amplification strategy efficiently

28

enhances the signal change in the presence of target. Moreover, the linear range

29

achieved 7 orders of magnitude via the proposed PEC method, which is beneficial to 14


Page 14 of 23

Page 15 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

the practical application in biochemical analysis.

2 3

Figure 7. (A) Photocurrent response of the different concentration of miRNA-21. (B)

4

Calibration curve of the biosensor. Error bars represent standard deviations of

5

measurements (n = 3).

6

Selectivity, reproducibility, and stability of the PEC biosensor

7

The selectivity of the biosensor was evaluated by measuring three miRNAs including

8

completely complementary miRNA-21, the single-base mismatched miRNA-21, and

9

three-base mismatched miRNA-21, respectively. As shown in Figure S2, significant

10

differences in the PEC intensity were obtained between complementary miRNA-21

11

and other RNAs. The single-base mismatched miRNA-21 and three-base mismatched

12

miRNA-21 showed no obvious changes compared to the blank. These results suggest

13

that the sensor owns high sequence specificity and excellent discrimination for similar

14

miRNAs.

15

The reproducibility of the proposed biosensor was tested with intra-assay and

16

inter-assay. The intra-assay precision was acquired by measuring miRNA-21 at three

17

concentrations of 1.0 fM, 10.0 fM, and 100.0 fM with five parallel tests with RSD

18

values of 7.6%, 5.9%, and 6.9%, respectively. While the inter-assay RSD of 8.4%,

19

7.1%, and 8.1% were obtained with five separate biosensors prepared under the same

20

conditions. These results reveal an acceptable reproducibility of the biosensor.

21

The stability of the fabricated biosensor was also estimated. When we stored the

22

biosensor after pDNA-Au@Ag hybridization for three weeks at 4 ℃, no obvious

23

changes of the PEC response was observed, indicating a good stability of the 15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

biosensor.

2 3

MicroRNA detection in complex biological samples

4

MiRNA-21 as a potential biomarker of cancer progression is overexpressed in a wide

5

variety of cancers, whereas the low expression levels of the miRNA-21 in human

6

serum impose great challenges in the analysis of real samples. To evaluate the

7

applicability of the proposed method, the human serum samples from Xinyang

8

Central Hospital (Xinyang, China) containing four breast cancer patients (No. 1-4)

9

and three healthy donors (No. 5-7) were tested using our biosensor and a commercial

10

qRT-PCR as a reference. As shown in Figure S3, the analytical results of the proposed

11

biosensor are well in agreement with the qRT-PCR. Specifically, the contents of

12

miRNA-21 in breast cancer patients are significantly higher than those of in the

13

healthy group, suggesting over-express of miRNA-21 in the blood serum of cancer

14

patients, in accordance with the previous reports.45,46 The RSD values of the

15

commercial qRT-PCR and the proposed method were less than 6.8% and 8.9%,

16

respectively. These results indicate that the proposed biosensor is potential for the

17

miRNA-21 detection in real sample.

18

CONCLUSIONS

19

In summary, we established a novel PEC biosensing platform based on the

20

synergistic effect of EPI between CdS@g-C3N4 heterojunction and Au@AgNPs and

21

DSN-assisted cycle amplification. The ultrasensitive detection of miRNA-21was

22

achieved. Compared with the traditional PEC assay, the merits of this work can be

23

summarized as follows: (i) CdS@g-C3N4 heterojunction as a novel photoactive

24

material which features excellent efficiency of photoelectric conversion as well as

25

good PL intensity was first used in the field of PEC bioanalysis; (ii) the well overlap

26

of the emission spectrum of CdS@g-C3N4 and the wide plasma absorption spectrum

27

of Au@Ag NPs makes the EPI efficiently; and (iii) more generally, coupling such

28

EPI-based signaling mechanism with the DSN-assisted cycle amplification method

29

could serve as sensing basis for other biorecognization events. These characteristics 16


Page 16 of 23

Page 17 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

carried forward the proposed biosensor with high sensitivity and wide linear range.

2

Furthermore, the well-designed PEC biosensor also shows a good promise for

3

potential applications in the detection of disease-related biomarkers with low levels.

4

ASSOCIATED CONTENT

5

Supporting Information

6

Sequence of DNA probes, Table S1. Optimization of experimental conditions, Figure

7

S1. Chemicals and materials, and instrumentation utilized in this work. Photocurrent

8

responses of the biosensor for different miRNA sequences, Figure S2. MiRNA-21

9

detection in complex biological samples, Figure S3. Comparison of the analytical

10

performances of the as-designed PEC biosensor in the determination of miRNA-21

11

with those of other methods, Table S2. The material is available free of charge via the

12

Internet at http://pubs.acs.org.

13 14

NOTES

15

The authors declare no competing financial interest.

16

ACKNOWLEDGEMENTS

17

This work was supported by the National Natural Science Foundation of China

18

(21675136, 21375114, and 21405129,), Plan for Scientific Innovation Talent of Henan

19

Province (2017JR0016), Funding Scheme for the Young Backbone Teachers of

20

Higher Education Institutions in Henan Province (2016GGJS-097), and Nanhu Young

21

Scholar Supporting Program of XYNU.

22 23

REFERENCES

24

(1) Zhao, W.W.; Xu, J.J.; Chen, H.Y. Photoelectrochemical DNA biosensors. Chem.

25

Rev. 2014, 114, 7421-7441.

26

(2) Zhao, W.W.; Xiong, M.; Li, X.R.; Xu, J.J.; Chen, H.Y. Photoelectrochemical 17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 23

1

bioanalysis: A mini review. Electrochem. Commun. 2014, 38, 40-43.

2

(3) Dong, Y.X.; Cao, J.T.; Liu, Y.M.; Ma, S.H. A novel immunosensing platform for

3

highly sensitive prostate specific antigen detection based on dual-quenching of

4

photocurrent from CdSe sensitized TiO2 electrode by gold nanoparticles decorated

5

polydopamine nanospheres. Biosens. Bioelectron. 2017, 91, 246-252.

6

(4) Zhao, W.W.; Xu, J.J.; Chen, H.Y. Photoelectrochemical bioanalysis: the state of

7

the art. Chem. Soc. Rev. 2015, 44, 729-741.

8

(5) Wang, G.L.; Xu, J.J.; Chen, H.Y.; Fu, S.Z. Label-free photoelectrochemical

9

immunoassay for -fetoprotein detection based on TiO2/CdS hybrid. Biosens.

10

Bioelectron. 2009, 25, 791-796.

11

(6) Zhao, W.W.; Yu, P.P.; Xu, J.J.; Chen, H.Y. Ultrasensitive photoelectrochemical

12

biosensing based on biocatalytic deposition. Electrochem. Commun. 2011, 13,

13

495-497.

14

(7) Fan, G. C.; Zhu, H.; Du, D.; Zhang, J. R.; Zhu, J. J.; Lin, Y. H. Enhanced

15

photoelectrochemical immunosensing platform based on CdSeTe@CdS:Mn core-shell

16

quantum dots-sensitized TiO2 amplified by CuS nanocrystals conjugated signal

17

antibodies. Anal. Chem. 2016, 88, 3392-3399.

18

(8) Cao, J.T.; Zhang, J.J.; Gong, Y.; Ruan .X.J.; Liu, Y.M.; Chen, Y.H.; Ren, S.W. A

19

competitive photoelectrochemical aptasensor for thrombin detection based on the use

20

of TiO2 electrode and glucose oxidase label. J. Electroanal. Chem. 2015, 759, 46-50.

21

(9) Tanne, J.; Schafer, D.; Khalid, W.; Park, W.J.; Lisdat, F. Light-controlled

22

bioelectrochemical sensor based on CdSe/ZnS quantum dots. Anal. Chem. 2011, 83,

23

7778-7785.

24

(10) Ma, Z.Y.; Ruan, Y.F.; Xu, F.; Zhao, W.W.; Xu, J.J.; Chen, H.Y. Protein binding

25

bends

26

energy-transfer-based photoelectrochemical protein detection. Anal. Chem. 2016, 88,

27

3864-3871.

28

(11) Shen, Q.M.; Han, L.; Fan, G.C.; Abdel-Halim, E.S.; Jiang, L.P.; Zhu, J.J. Highly

29

sensitive photoelectrochemical assay for DNA methyltransferase activity and inhibitor

the

gold

nanoparticle

capped

DNA

sequence:

18


toward

novel

Page 19 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

screening by exciton energy transfer coupled with enzyme cleavage biosensing

2

strategy. Biosens. Bioelectron. 2015, 64, 449-455.

3

(12) Zang, Y.; Lei, J.P.; Hao, Q.; Ju, H.X. “Signal-on” photoelectrochemical sensing

4

strategy based on target-dependent aptamer conformational conversion for selective

5

detection of lead(II) ion. ACS Appl. Mater. Interfaces 2014, 6, 15991-15997.

6

(13) Zeng, X.X.; Ma, S.S.; Bao, J.C.; Tu, W.W.; Dai, Z.H. Using graphene-based

7

plasmonic nanocomposites to quench energy from quantum dots for signal-On

8

photoelectrochemical aptasensing. Anal. Chem. 2013, 85, 11720-11724.

9

(14) Zhao, W.W.; Wang, J.; Xu, J.J.; Chen, H.Y. Energy transfer between CdS

10

quantum dots and Au nanoparticles in photoelectrochemical detection. Chem.

11

Commun. 2011, 47, 10990-10992.

12

(15) Zhao, W.W.; Yu, P.P.; Shan, Y.; Wang. J.; Xu, J.J.; Chen, H.Y. Exciton-plasmon

13

interactions between CdS quantum dots and Ag nanoparticles in photoelectrochemical

14

system and its biosensing application. Anal. Chem. 2012, 84, 5892-5897.

15

(16) Ma, Z.Y.; Xu, F.; Qin, Y.; Zhao, W.W.; Xu, J.J.; Chen, H.Y. Invoking direct

16

exciton-plasmon interactions by catalytic Ag deposition on Au nanoparticles:

17

photoelectrochemical bioanalysis with high efficiency. Anal. Chem. 2016, 88,

18

4183-4187.

19

(17) Zhu, J.; Huo, X.H.; Liu, X.Q.; Ju, H.X. Gold nanoparticles deposited

20

polyaniline-TiO2

21

photoelectrochemical biosensing. ACS Appl. Mater. Interfaces 2015, 8, 341-349.

22

(18) Fu, J.; Chang, B.B.; Tian, Y.L.; Xi, F.N.; Dong, X.P. Novel C3N4-CdS composite

23

photocatalysts with organic-inorganic heterojunctions: in suit synthesis, exceptional

24

activity, high stability and photocatalytic mechanism. J. Mater. Chem. A 2013, 1,

25

3083-3090.

26

(19) Chen, C.C.; Lin, J.J. Controlled growth of cubic cadmium sulfide nanoparticles

27

using patterned self-assembled monolayers as a template. Adv. Mater. 2001, 13,

28

136-139.

29

(20) Liu, M.M.; Li, F.Y.; Sun, Z.X.; Ma, L.F.; Xu, L.; Wang, Y.H. Noble-metal-free

nanotube

for

surface

plasmon

19


resonance

enhanced


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 23

1

photocatalysts MoS2–graphene/CdS mixed nanoparticles/nanorods morphology with

2

high visible light efficiency for H2 evolution. Chem. Commun. 2014, 50,

3

11004-11007.

4

(21) Zang, Y.; Lei, J.P.; Hao, Q.; Ju, H.X. CdS/MoS2 heterojunction-based

5

photoelectrochemical DNA biosensor via enhanced chemiluminescence excitation.

6

Biosens. Bioelectron. 2016, 77, 557-564.

7

(22) Zhao, W.W.; Shan, S.; Ma, Z.Y.; Wan, L.N.; Xu, J.J.; Chen, H.Y. Acetylcholine

8

esterase antibodies on BiOI nanoflakes/TiO2 nanoparticles electrode: a case of

9

application for general photoelectrochemical enzymatic analysis. Anal. Chem. 2013,

10

85, 11686-11690.

11

(23) Zhang, J.S.; Zhang, M.W.; Yang, C.; Wang, X.C. Nanospherical carbon nitride

12

frameworks with sharp edges accelerating charge collection and separation at a soft

13

photocatalytic interface. Adv. Mater. 2014, 26, 4121-4126.

14

(24) Hou, Y.; Wen, Z.H.; Cui, S.M.; Guo, X.R.; Chen, J.H. Constructing 2D porous

15

graphitic

16

nanojunction with enhanced photoelectrochemical activity. Adv. Mater, 2013, 25,

17

6291-6297.

18

(25) Hou, Y.; Zuo, F.; Dagg, A.P.; Liu, J.K.; Feng, P.Y. Branched WO3 nanosheet array

19

with layered C3N4 heterojunctions and CoOx nanoparticles as a flexible photoanode

20

for efficient photoelectrochemical water oxidation. Adv. Mater. 2014, 26, 5043-5049.

21

(26) Chen, C.F.; Ridzon, D.A.; Broomer, A.J.; Zhou, Z.H.; Lee, D.H.; Nugyen, J.T.;

22

Barbisin, M.; Xu, N.L.; Mahuvakar, V.R.; Andersen, M.R.; Lao, K.Q.; Livak, K.J.;

23

Guegler, K.J. Real-time quantification of microRNAs by stem–loop RT–PCR. Nucleic

24

Acids Res. 2005, 33, e179-e179.

25

(27) Lee, R.C.; Ambros, V. An extensive class of small RNAs in caenorhabditis

26

elegans. Science 2001, 294, 862-864.

27

(28) Thomson, J.M.; Parker, J.; Perou, C.M.; Hammond, S.M. A custom microarray

28

platform for analysis of microRNA gene expression. Nat. methods 2004, 1, 47-53.

29

(29) Feng, Q.M.; Shen, Y.Z.; Li, M.X.; Zhang, Z.L.; Zhao, W.W.; Xu, J.J.; Chen, H.Y.

C3N4

nanosheets/nitrogen-doped

graphene/layered

20


MoS2

ternary

Page 21 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Dual-wavelength electrochemiluminescence ratiometry based on resonance energy

2

transfer between Au nanoparticles functionalized g-C3N4 nanosheet and Ru(bpy)32+

3

for microRNA detection. Anal. Chem. 2015, 88, 937-944.

4

(30) Bai, L.J.; Chai, Y.Q.; Yuan R.; Yuan, Y.L.; Xie, S.B.; Jiang, L.P. Amperometric

5

aptasensor for thrombin detection using enzyme-mediated direct electrochemistry and

6

DNA-based signal amplification strategy. Biosens. Bioelectron. 2013, 50, 325-330.

7

(31) Jiang, X.Y.; Wang, H.J.; Wang H.J.; Yuan, R.; Chai, Y.Q. Signal-switchable

8

electrochemiluminescence system coupled with target recycling amplification strategy

9

for sensitive mercury ion and mucin 1 Assay. Anal. Chem. 2016, 88, 9243-9250.

10

(32) Lin, X.Y.; Zhang, C. Huang, Y.S.; Zhu, Z.; Yang, C.J. Backbone-modified

11

molecular beacons for highly sensitive and selective detection of microRNAs based

12

on duplex specific nuclease signal amplification. Chem. Commun. 2013, 49,

13

7243-7245.

14

(33) Yin, B.C.; Liu, Y.Q.; Ye, B.C. One-Step, multiplexed fluorescence detection of

15

microRNAs based on duplex-specific nuclease signal amplification. J. Am. Chem. Soc.

16

2012, 134, 5064-5067.

17

(34) Hao, N.; Li, X.L.; Zhang, H.R.; Xu, J.J.; Chen, H.Y. A highly sensitive

18

ratiometric electrochemiluminescent biosensor for microRNA detection based on

19

cyclic enzyme amplification and resonance energy transfer. Chem. Commun. 2014, 50,

20

14828-14830.

21

(35) Zhang, X.; Wu, D.Z.; Liu, Z.J.; Cai, S.X.; Zhao, Y.P.; Chen, M.; Xia, Y.K.; Li,

22

C.Y.; Zhang, J.; Chen, J.H. Ultrasensitive label-free electrochemical biosensor for

23

microRNA-21 detection based on 2′-O-methyl modified DNAzyme and duplex

24

specific nuclease assisted target recycling. Chem. Commun. 2014, 50, 12375-12377.

25

(36) Zhang, J.Y.; Wang, Y.H.; Jin, J.; Zhang, J.; Lin, Z.; Huang, F.; Yu, J.G. Efficient

26

visible-light photocatalytic hydrogen evolution and enhanced photostability of

27

core/shell CdS/g-C3N4 nanowires. ACS Appl. Mater. Interfaces 2013, 5, 10317-10324.

28

(37) Liu, Y.; Yan, K.; Zhang, J.D. Graphitic carbon nitride sensitized with CdS

29

quantum dots for visible-light-driven photoelectrochemical aptasensing of tetracycline. 21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

ACS Appl. Mater. Interfaces 2015, 8, 28255-28264.

2

(38) Pan, C.S.; Xu, J.; Wang, Y.J.; Zhu, Y.F. Dramatic activity of C3N4/BiPO4

3

photocatalyst with core/shell structure formed by self-assembly. Adv. Funct. Mater.

4

2012, 22, 1518-1524.

5

(39) Wu, M.S.; He, L.J.; Xu, J.J.; Chen, H.Y. RuSi@Ru(bpy)32+/Au@Ag2S

6

nanoparticles electrochemiluminescence resonance energy transfer system for

7

sensitive DNA detection. Anal. Chem. 2014, 86, 4559-4565.

8

(40) Zhao, M.; Fan, G. C.; Chen, J. J.; Shi, J. J.; Zhu, J. J. Highly sensitive and

9

selective photoelectrochemical biosensor for Hg2+ detection based on dual signal

10

amplification by exciton energy transfer coupled with sensitization effect. Anal. Chem.

11

2015, 87, 12340-12347.

12

(41) Liu, Y.; Liu L.; Shan J.; Zhang, J.D. Electrodeposition of palladium and reduced

13

graphene oxide nanocomposites on foam-nickel electrode for electrocatalytic

14

hydrodechlorination of 4-chlorophenol. J. Hazard. Mater. 2015, 290, 1-8.

15

(42) Cao, S.W.; Yuan, Y.P.; Fang, J.; Shahjamali, M.M.; Boey, F.Y.C.; Barber, J.; Loo,

16

S.C.J.; Xue, C. In-situ growth of CdS quantum dots on g-C3N4 nanosheets for highly

17

efficient photocatalytic hydrogen generation under visible light irradiation. Int. J.

18

Hydrogen Energ. 2013, 38, 1258-1266.

19

(43) Lu, M.L.; Pei, Z.X.; Weng, S.X.; Feng, W.H.; Fang, Z.B.; Zheng, Z.Y.; Huang,

20

M.L.; Liu, P. Constructing atomic layer g-C3N4–CdS nanoheterojunctions with

21

efficiently enhanced visible light photocatalytic activity. Phys. Chem. Chem. Phys.

22

2014, 16, 21280-21288.

23

(44) Jiang, F.; Yan, T.T.; Chen, H.; Sun, A.W.; Xu, C.M.; Wang, X. A g-C3N4–CdS

24

composite catalyst with high visible-light-driven catalytic activity and photostability

25

for methylene blue degradation. Appl. Surf. Sci. 2014, 295, 164-172.

26

(45) Hong, C.Y.; Chen, X.; Li, T.; Li, J.; Yang, H.H.; Chen, J.H.; Chen, G.N.

27

Ultrasensitive electrochemical detection of cancer-associated circulating microRNA in

28

serum samples based on DNA concatamers. Biosens. Bioelectron. 2013, 50, 132-136.

29

(46) Zhuang, J.Y.; Tang, D.P.; Lai, W.Q.; Chen, G.N.; Yang, H.H. Immobilization-free 22


Page 22 of 23

Page 23 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

programmable hairpin probe for ultrasensitive electronic monitoring of nucleic acid

2

based on a biphasic reaction mode. Anal. Chem. 2014, 86, 8400-8407.

3 4 5 6 7 8

For Table of Contents Use Only

9 10

A novel PEC biosensing platform for ultrasensitive detection of microRNA-21 was

11

constructed based on EPI between CdS@g-C3N4 heterojunction and Au@AgNPs

12

coupled with DSN-assisted cycle amplification.

23


ExcitonâPlasmon Interactions between CdS@g-C3N4 Heterojunction

Recommend Documents

ExcitonâPlasmon Interactions between CdS@g-C3N4 Heterojunction