Self-assembled cellulosic superstructures with unanticipated high quantum yields

Domain: physics
Published: 2025-12-10
Editorial outcome: minor_revision

Abstract
Nonconventionalluminophoresdevoidoftraditional,largeπ-conjugatesoften
sufferfromlowsolid-statefluorescencequantumyields(FLQYs).Inparallel,
self-assembledbowl-shapedandhelicalarchitecturesatthemicro-andmac-
roscaleareunusual(mostlyreportedatthenanoscale).Here,wereportthat
surface-stearoylatedcellulosenanocrystalsandcellulosestearoylestersco-
assembleintomacroscalehelices(FLQY:86%)withdiametersof32−104μm.
Meanwhile,surface-lauroylatedcellulosenanocrystalsandcelluloselauroyl
estersco-assembleintoporousbowl-shapedmicroparticles(FLQY:91%)with
diametersof8−19μm.ThehighFLQYsareascribedtothesynergismofthe
denseoxygenclustersandabundantvanderWaalsinteractionsandhydrogen
bondsbetweensidestearoylorlauroylgroups,whichcanpromotethrough-
spaceelectrondelocalization,ultimatelyimprovingfluorescenceperfor-
mance.Theseresultswererationalizedbytheoreticalcalculations.Such
superstructuresexhibitgreatpotentialforstableanti-counterfeitingmaterials
duetotheexcellentregenerationabilityaswellasstructuralstabilityofthe
oxygenclusters.

Introduction
Inrecentyears,nonconventionalluminophoresfreeofcommonlylarge
π-conjugatedstructures,alsocalledclusteroluminogens,haveattracted
great attention because of their biocompatibility, environmental
friendliness,lowcytotoxicity,andflexibilitycomparedtotheconven-
tionalπ-conjugatedfluorophores1–4.Theiremissionisproposedtoarise
from the clustering-triggered emission (CTE) mechanism, wherein
aggregation of heteroatoms (e.g., N, O, S) with electron lone pairs
inducesthrough-spaceinteraction,facilitatinginter-andintramolecular
electron delocalization to form cluster-generated chromophores5–8.
Thesematerialsexhibitfascinatingphotophysicalproperties,including
excitation-dependentluminescence,concentration-enhancedemission,
andaggregation-inducedemission(AIE)9,10.However,theysufferfrom
lowquantumyieldsinthesolidstate,typicallybelow10%,whichsig-
nificantlyrestrictstheirapplications.

Hierarchical architectures constructed via self-assembly pro-
cesses have garnered significant interest due to their broad applic-
ability in fields ranging from semiconductors11, energy storage12,
biomaterials13,sensing14,optics15,16,andelectronics17tocatalysis18.The
self-assembly of these structures is typically driven by weak non-
covalentinteractionssuchashost–guestinteractions19,vanderWaals
interactions20, hydrogen bonding21, electrostatic interactions22,23,
hydrophobicinteractions24,25,andπ–πstacking26,27.Amongthediverse
morphologies achievable through self-assembly, helical super-
structurespredominantlymanifestatthenanoscale—exemplifiedby
nanofibers28andnanoribbons29.Incontrast,helicalarchitectureswith
micro-and macroscaledimensions formed viaself-assemblyremain
scarcelyreported,underscoringthedemandforinnovativeassembly
strategies. Similarly, bowl-shaped superstructures formed via self-
assembly are generallyconfined to the nanoscale and often exhibit
smooth,nonporousmorphologies30.Notably,thefabricationofmicro-
and macroscale, porous bowl-shaped architectures through self-
assemblyrepresentsanunmetchallenge.

Self-assembly-based structural color and luminescent materials
holdsignificantpromiseforanti-counterfeitingapplications31–33.The
formabilityandstabilityofsuchmaterialsarecriticaltotheirpractical
applications.Ontheonehand,theformationofdesiredself-assembled
structuresreliesontheenvironmentalconditions,whichmeansthat
thecorrespondingstructuralorluminescentcolorscanbeaffectedby
theexternalconditionsinpreparationprocess34.Ontheotherhand,
the resulting assemblies may not maintain under harsh conditions,
sincetheyareoftenstabilizedsolelybynon-covalentinteractions.

Herein,wereportthefabricationofhighlyemissivemacroscale
helices(MHs)andhighlyemissive,porousbowl-shapedmicroparticles
(BSMPs) co-assembled from surface-hydrophobized cellulose nano-
crystals(CNCs)andcelluloseesters,achievinghighFLQYvalues(upto
86% and 91%). First, CNCs with surface-attached stearoyl/lauroyl
groupsandpolymericcellulosestearoyl/lauroylesterswereallowedto
construct the MHs and porous BSMPs via solvent casting method.
Then,weinvestigatedtheassembledmorphologiesandfluorescence
behaviorofsixself-andco-assemblysystems.Torationalizethehigh
FLQY values observed, theoretical calculations were performed,
revealingthatthesynergismofdenseoxygenclusterformationand
specific non-covalent interactions are responsible for the highly
emissive behavior. Finally, these superstructures were successfully
employedtofabricaterobustanti-counterfeitingpatterns.

Results
Cellulosestearoylesters(CSEs)andcelluloselauroylesters(CLEs)were
synthesized via esterification with stearoyl chloride and lauroyl
chloride,respectively,atamolarratioof2:1(acylchloridetohydroxyl
groups)(Fig.1,SupplementaryFigs.1and2).Elementalanalysisver-
ified adegree ofsubstitution (DS) of3.0forbothesters,indicating
completefunctionalizationofthecellulosehydroxylgroups.Inaddi-
tion,surface-hydrophobizedCNCs,CNC-C18(surface-attachedstear-
oyl groups) and CNC-C12 (surface-attached lauroyl groups), were
preparedviasurfaceesterificationusingstearoylchlorideandlauroyl
chloride,respectively(Figs.1and2a,SupplementaryFigs.1and2).The
DSswere0.89and0.82fortheCNC-C18andCNC-C12,asdetermined
byelementalanalysis.CNC-C18hasanaveragelengthof75±25nmand
an average diameter of 6.2±2.1nm based on the measurements on
100 individual nanorods in the transmission electron microscopy
(TEM)image(Fig.2c).Incomparison,CNC-C12hasanaveragelength
of80±30nmandanaveragediameterof5.7±2.4nm(Fig.2d).For
CNC-C12 and CNC-C18, the chemical modification of cellulose was
regioselective,occurringprimarilyatC6,followedbyC2andthenC3,
accordingtothepeakareasinthesolid-stateNMRspectra(Supple-
mentaryFig.3,SupplementaryTable1).Thezetapotentialvaluesof
pristineCNC,CNC-C12,andCNC-C18are−22.4±0.4,−22.1±0.7,and
−21.6±0.3mV,respectively,which indicates that the surfacecharge
canberetainedafteresterification(SupplementaryFig.4).

Aftertheself-andco-assemblyofsurface-hydrophobizedCNCs
and polymeric cellulose esters, the distinct solid-state FLQYs were
achieved via oxygen cluster engineering and tailored non-covalent
interactions(Fig.1).Notably,CSE+CNC-C18andCLE+CNC-C12sys-
temsgraduallyco-assembledintotwodistincthighlyemissivearchi-
tectures: MHs (FLQY: 86%) and porous BSMPs (FLQY: 91%),
respectively, during the evaporation of their suspensions in tetra-
hydrofuran (THF) on the surface of silicon wafers in the air
under ambient conditions (Figs. 1 and 2b−e). The two co-assembly
processes are primarily driven by hydrophobic interactions arising
fromthelongaliphaticchainsutilizedinthefunctionalizationofthe
CNCs.Inaddition,asmallnumberofhydrogenbonds,formedbythe
ester groups and residual hydroxyl groups, also contribute to
theassembly.

TheCSE+CNC-C18,CSE,CNC-C18,CLE+CNC-C12,CLE,CNC-C12
systemsunderwentdistinctself-andco-assemblypathways,forming
structurallydivergentsuperstructures(SupplementaryFig.5a,b).The
MHsco-assembledfromCSE+CNC-C18exhibiteddiametersof32−104
μmandconsistedoflayerednanoplateswiththicknessesof44−94nm
(Fig.2c,SupplementaryFig.6).Incontrasttothehelicesco-assembled
byCSEandCNC-C18,CSEaloneonlyself-assembledintoflower-like
microparticles(FLMs)withdiametersof3–7μm,consistingofnano/
mesoflakystructureswiththicknessesof70−120nm(Supplementary
Fig.5a,b).Inaddition,CNC-C18aloneonlyself-assembledintonano/
mesoscopic rod-like superstructures (18RLSs) with diameters of
50–170nm and lengths of 120−950nm. The porous BSMPs co-
assembledfromCLE+CNC-C12exhibiteddiametersof8−19μmand
heightsof3−15μm,andwerecomposedofnanosizedflakystructures
withthicknessesof70−120nm(Fig.2dandSupplementaryFig.5a,b).
IncontrasttotheBSMPsco-assembledbyCLEandCNC-C12,CLEalone
onlyself-assembledintoflakymesostructures(FMs)withthicknesses
of 110−390nm (Supplementary Fig. 5a, b). CNC-C12 alone only self-
assembled into nano/mesoscopic rod-like superstructures (12RLSs)
withdiametersof45−173nmandlengthsof135−880nm.

Moleculardynamics(MD)simulationswereconductedtoanalyze
theself-andco-assemblyprocessesofthesixabove-mentionedsys-
tems(SupplementaryFig.5c,d).Tovisualizetheself-andco-assembly
processes,SupplementaryMovies1−6werederivedfromsimulation
trajectoriesofthelaterstagesapproachingtheequilibriumstates.MD
simulations of the two co-assembly systems (CSE+CNC-C18/CLE+
CNC-C12) revealed anobvious assemblybehavior between the CNC
surfaces and surrounding cellulose esters. The trajectories indicate
thatestermolecules(CSEs/CLEs)areinitiallyattractedtothemodified
CNC surfaces (CNC-C18/CNC-C12), followed by cooperative self-
organization of both components through coupled structural rear-
rangements,ultimatelyformingstableconformations(Supplementary
Movies1and4).Theconformationsofstearoyl/lauroylgroupsonthe
surface-hydrophobizedCNCs(CNC-C18/CNC-C12)andcelluloseesters
(CSEs/CLEs) tend to be stretched and lie parallel in the equilibrium
structuresofthetwoco-assemblysystems(SupplementaryFig.5c,d).
In comparison, there was a tendency towards stacking of the non-
stretchedstearoylandlauroylgroupsfortheself-assemblyofCSEand
CLEsystems(SupplementaryMovies2and5,SupplementaryFig.5c,
d).However,stearoylandlauroylgroupsonadjacentCNCsurfacesfor
self-assembledCNC-C18andCNC-C12systemsareseparatedlikelydue
tosterichindrance(SupplementaryMovies3and6,Supplementary
Fig.5c,d).Therefore,thehydrophobicinteractionsbetweenthepar-
allelstearoylandlauroylgroupsarevitaltotheformationofMHsand
BSMPs(Fig.2b,eandSupplementaryFig.5c,d).Forthesesixself-and
co-assemblysystems,variationsinthelengthandconformationofthe
hydrophobic chains generate distinct driving forces (hydrophobic
interactions),ultimatelyleadingtodifferentmorphologies.

Fluorescence microscopy revealed that the six self- and co-
assembledsuperstructuresexhibitedstrongemissioninthreediffer-
ent channels upon ultraviolet and visible light irradiation (Fig. 3a).
Unlike common dyes, whose emission peak positions remain inde-
pendent of the excitation wavelength, the emission profiles of self-
assembledMHsandporousBSMPsaresignificantlyinfluencedbythe
excitation wavelength (Fig. 3b, c). For MHs, the emission maxima
shiftedfrom412to518nmastheexcitationwavelengthincreasedfrom
350 to 410nm. The corresponding full widths at half maximum
(FWHMs)oftheMHs’spectraatexcitationwavelengthsof350,370,
390, and 410nm are 88, 84, 89, and 95nm, respectively (Fig. 3b).
Similarly,theemissionmaximaofBSMPsshiftedfrom402to506nm
astheexcitationwavelengthincreasedfrom350to410nm.Thecor-
respondingFWHMsoftheBSMPs’spectraatexcitationwavelengthsof
350,370,390,and410nmare98,127,94,and104nm,respectively
(Fig.3c).Theoptimalexcitationwavelengthsoftheexcitationspectra
of MHs and BSMPs also vary depending on the selected emission
wavelength(SupplementaryFig.7).Moreover,FLMsderivedfromCSE,
FMsfromCLE,18RLSsfromCNC-C18,and12RLSsfromCNC-C12also
demonstrate the excitation-dependent behavior (Supplementary
Fig. 8). The coexistence of diverse emissive clusters with varying
degrees of extended electron delocalization is responsible for the
excitation-dependentemission.Thefluorescencelifetimesofthesix
self- and co-assembled superstructures are as follows: MHs (CNC-
C18+CSE), 3.1±0.1ns; FLMs (CSE), 2.4±0.1ns; 18RLSs (CNC-C18),
2.0±0.2ns; BSMPs (CNC-C12+CLE), 2.6±0.1ns; FMs (CLE),
2.5±0.1ns;and12RLSs(CNC-C12),2.1±0.2ns.

Remarkably, MHs and porous BSMPs exhibit high solid-state
fluorescence quantum yields (FLQYs) of 86% (λ =350nm,
λ =412nm) and 91% (λ =350nm, λ =402nm), respectively
(Fig.3d).Amongorganicnonconjugatedluminophores,onlyonesolid,
tri([1,1’-biphenyl]−3-yl)methane (m-TBPM), has been reported to
exhibit a higher efficiency (100%)35. The performance of MHs and
BSMPs starkly contrasts with the majority of such non-conjugated
materials,whichtypicallyachieveFLQYsbelow10%inthesolidstate
(Fig. 3d). In addition, MHs and porous BSMPs exhibit room-
temperaturephosphorescence(SupplementaryFigs.9and10),with
very low quantum efficiencies (in contrast to their high FLQYs): Ф
P
(MHs)=0.7±0.2% (λ =350nm, λ =485nm), Ф (BSMPs)=0.8±
0.2%(λ =350nm,λ =477nm).FLMsderivedfromCSE,FMsfrom
CLE, 18RLSs from CNC-C18,and 12RLSs from CNC-C12 demonstrate
solid-stateFLQYsof54%,59%,31%,and35%,respectively.

Highest occupied molecular orbitals (HOMOs), lowest unoccu-
pied molecular orbitals (LUMOs), excitation energies and oscillator
strengthsofoneandtworepeatingunitsofthecelluloseesterswith
differentDS(i.e.,2-C18-DS1,1-C18-DS1,1-C18-DS3,2-C12-DS1,1-C12-DS1,
1-C12-DS3) were calculated using density functional theory (DFT)
(Fig. 3e−h, Supplementary Figs. 11−14). The average HOMO−LUMO
energygapofstearoyl(C18)-modifiedmoleculesislowerthanthatof
lauroyl (C12)-modified molecules, consistent with the fluorescence
spectra,whichshowlongerexcitationandemissionwavelengthsfor
theself-assembledCSE+CNC-C18systemcomparedtotheCLE+CNC-
C12 system (Fig. 3b, c, h and Supplementary Fig. 7). Furthermore,
significantthrough-spaceelectrondelocalizationwasobservedinthe
HOMOandLUMOofDFT-optimizedconformationsfor2-C18-DS1,
1-C18-DS1,1-C18-DS3,2-C12-DS1,1-C12-DS1,and1-C12-DS3,whichcould
facilitate the excitation and emission processes9,36. As shown in the
DFT-optimized conformations of 1-C18-DS3 and 1-C12-DS3 (Supple-
mentaryFig.15),theO–Odistancesinthecellulosebackboneremain
nearlyconstant,whereasthoseinthesidechains(estergroups)vary
dependingonthesubstituentchainlength.TheaverageO−Odistance
fortheestergroups(ADEGs)of1-C18-DS3(4.32Å)waslargerthanthat
observedin1-C12-DS3(3.98Å).Correspondingly,1-C12-DS3exhibited
enhancedelectroncloudoverlapandmoreextensiveelectrondelo-
calizationregionscomparedto1-C18-DS3(Fig.3e,f),suggestingthat
compact oxygen clusters can promote through-space electron
delocalization.

Since previous studies have shown that increased molecular
rigidity and ordering (e.g., crystallinity) can suppress nonradiative
decayandenhanceCTE6,weexaminedthechangesinthecrystallinity
index(CrI)beforeandaftertheco-assemblyprocesses.Thereweretwo
types of crystalline structures that existed in the MHs and porous
BSMPs:cellulose(polymorphI)andcrystallizedfatty-acylgroups.For
both crystalline structures, the CrI remains essentially unchanged
whencomparingco-assembledCLE+CNC-C12(BSMPs)withpristine
CNC-C12 prior to assembly, as well as co-assembled CSE+CNC-C18
(MHs) with pristine CNC-C18 prior to assembly (Supplementary
Figs. 16 and 17, Supplementary Table 2). Individual CLE/CSE is not
considered,asitisfullydissolvedinTHFbeforeassembly.

As a class of nonconventional luminophores, the fluores-
cenceofcarbohydratesisattributedtoabundantoxygenclusters
and rationalized by the CTE mechanism in the literature9. The
weak interactions within clustered chromophores are critical to
the luminescence process. Therefore, the inter- and intramole-
cularnon-covalentinteractions wereanalyzed usingthe reduced
density gradient (RDG) method37. As shown in Fig. 4a, b, e, f for
C12-modified molecules, strong repulsions dominate within the
sugar rings, while van der Waals interactions primarily exist
betweenthealiphaticchains.Additionally,thedistancesofstrong
attractions, i.e., C−H···O and O−H···O hydrogen bonds, were
measured in the DFT-optimized conformations (Fig. 4c, d). The
abundantvanderWaalsinteractionsandhydrogenbondsinthese
clusteroluminogens can contribute to the conformation rigidifi-
cation, thus diminishing nonradiative decay and favoring fluor-
escenceemission9.

TorationalizethehighFLQYsofMHsandporousBSMPs,radial
distributionfunctions(RDFs)ofoxygenatomswerecalculatedforthe
six self- and co-assembled systems (CNC-C18+CSE, CSE, CNC-C18,
CNC-C12+CLE, CLE, and CNC-C12) based on their MD-simulated
equilibrium structures (Fig. 5a−c). Only oxygen clusters formed by
oxygenatomsinthesidechainswereanalyzedsincetheseclustersare
directlylinked to the self- and co-assembly processes, with vander
Waals interactions and strong attraction between the side chains
(stearoyl/lauroylgroups)servingasthedrivingforces.Thepositionof
thefirstpeakintheRDFscorrespondstotheshortestO−Odistance
withintheoxygenclustersinthesidechains.AccordingtotheRDFs,
theaveragevalueofthefirstpeaksfortheO−Odistancefollowsthe
order: CNC-C18+CSE (2.20Å) <CSE (2.83Å) <CNC-C18 (3.40Å).
Interestingly,theFLQYvaluesareinverselycorrelated:CNC-C18+CSE
(86%) > CSE (54%) > CNC-C18 (31%). Similarly, for the C12-modified
systems, the order of the average value of the first peaks is:
CNC-C12+CLE (2.12Å) <CLE (2.74Å) <CNC-C12 (3.31Å).The
FLQY again follow an opposite trend: CNC-C12+CLE (91%) > CLE (59%) >
CNC-C12(35%).Thisinversecorrelationisfurthersupportedbycom-
parisonsbetween:CNC-C18+CSEvs.CNC-C12+CLE(theshortestO−O
distance:2.20Å>2.12Å;FLQY:86%<91%),CSEvs.CLE(theshortestO
−Odistance:2.83Å>2.74Å;FLQY:54%<59%),andCNC-C18vs.CNC-
C12(theshortestO−Odistance:3.40Å>3.31Å;FLQY:31%<35%),all
consistently demonstrate that shorter O−O distances correlate with
enhanced fluorescence efficiency for these self- and co-assembled
clusteroluminogens.

Anti-counterfeiting patterns were designed using MHs,
leveraging their excitation-dependent fluorescence behavior
(Fig. 6). The patterns fabricated from the as-prepared MHs
appearedwhiteunderdaylightbutdisplayeddistinctfluorescent
colors—purple,blue,andyellow—underUV-Visirradiationat275,
365, and 495nm, respectively (Fig. 6a). Importantly, these emis-
sion colors and FLQY remained highly stable after various post-
treatments (Fig. 6b−g). After dissolution and re-assembly in
dichloromethane(DCM)andtrichloromethane(TCM),bothgood
solvents for CSEs, the fluorescence colors remained unchanged,
indicating that the self-assembled nanoscale oxygen cluster
structures are independent of the fabrication method. Further-
more, the fluorescence was preserved even after exposure to
harshenvironments,includingimmersioninacetone,ethanol,1M
HCl,1MKOH,andsaturatedsolutionofNaClfor5days,aswellas
thermaltreatmentat100°Cfor5hours(Fig.6b−g).Thisstability
is attributed to the robust nanoscale organization of oxygen
clusters formed during self-assembly. Collectively, these results
demonstrate that the oxygen clusters within the superstructures
possess excellent regeneration ability and structural stability,
underscoring their potential for anti-counterfeiting applications
in dynamic orharsh environments.

Methods
Materials
Commercialmicrocrystallinecellulose(MCC)withaparticlesizeof50
μm was purchased from SERVA Electrophoresis GmbH(Heidelberg,
Germany). Pyridine, lauroyl chloride (≥98%), and stearoyl chloride
(≥90%)wereobtainedfromSigma-AldrichChemieGmbH(Steinheim,
Germany). Deionized water (DI water)wasused in all steps, and all
othersolventswereuseddirectlyfromTHGeyer(Hamburg,Germany)
withoutfurthertreatment.

SynthesisofCSEandCLE
CSE and CLE were synthesized under heterogeneous conditions, as
previouslyreportedwithafewmodifications,asindicatedbelow38.
ForsynthesisofCSE,MCC(1g)waspre-driedinavacuumovenat
60°Cfor3htoeliminateresidualmoisturepriortobeingsuspended
in 30mL of pyridine. Then, the cellulose suspension was heated to
100°Cand13.83mLofstearoylchloridewasaddeddropwisetothe
hotMCCsuspension,whilethesystemwaspurgedwithnitrogen.After
1hstirringat100°C,thereactionwasquenchedbypouringthereac-
tionmixtureintoethanol(200mL).Subsequently,theprecipitatewas
obtainedbycentrifugation(7830rpm)at4°Candpurifiedthrough
repeateddissolutionintetrahydrofuranandprecipitationinethanol.
CLE was synthesized analogously to CSE, with modifications in
reagentquantitiesandprecipitationsolvent:8.73mLlauroylchloride
wasusedastheesterifyingagent,andmethanolreplacedethanolas
the antisolvent for precipitation. All other experimental conditions
andpurificationproceduresremainedidenticaltothosedescribedfor
CSEsynthesis.

Preparationofsurface-hydrophobizedCNC(CNC-C18and
CNC-C12)
PristineCNCs:CNCswerepreparedviaHClhydrolysisofMCC.Spe-
cifically,20gofMCCwasdispersedin300mLof4molL-1aqueousHCl
solutionandstirredfor10days.Themixturewasthenheatedto85°C
for4hoursinthepresenceof4gofFeCl₃asacatalyst.Theresulting
CNC suspensions were purified and separated via centrifugation.
Initially,thesuspensionswerecentrifugedat2000rpm,followedby
sedimentationat5000rpmtoobtainuniformCNCs.
CNC-C18: A dispersion of CNCs (30mg/mL, 30mL in anhy-
drous pyridine) was mechanically stirred under nitrogen atmo-
sphere.Stearoylchloridewasaddeddropwiseatamolarratioof
0.75relativetothehydroxylgroupsoncellulose,andthemixture
was heated to 60 °C for 1h to drive esterification. The reaction
mixture was quenched by precipitation into 200mL of 95%
ethanol. The resulting solid was collected via centrifugation
(8000rpm, 10min), extensively washed with ethanol to remove
residualpyridineandunreactedreagents,andfinallyredispersed
in tetrahydrofuran for subsequentuse.
CNC-C12: CNC-C12 was prepared through the same procedure,
withlauroylchloridereplacingstearoylchlorideastheacyldonor.All
other parameters, including molar ratios, reaction conditions, and
post-synthesispurificationsteps,remainedunchanged.

Self-assemblyexperiment
SuspensionsofCNC-C18andCNC-C12(1mg/mLeach)wereindividu-
allyblendedwithCSEandCLEsolutions(1mg/mLeach)ata1:1volume
ratio.Subsequently,theresultingmixtures(10μL)werepipettedonto
siliconwafers.Superstructureswereformeduponsolvent(THF)eva-
porationunderambientconditions.Theself-assemblyexperimentsfor
pristinesuspensionsofCNC-C18andCNC-C12,solutionsofCSEand
CLE(1mg/mLeach)beforeblending,werecarriedoutusingthesame
procedures.

Elementalanalysis
ElementalanalysiswasperformedonanelementalanalyzerVarioELIII
CHNinstrumentfromElementar(Hanau).Thedegreeofsubstitution
(DS)wascalculatedaccordingtothepublishedmethod(Supplemen-
taryNote1)39.

Zetapotential
Zeta potentialof CNCaqueous suspensions (0.2mg/mL) weremea-
suredbyaNano-ZS(MalvernInstrumentsLtd.,UK).Allthesamples
weretestedintriplicate.

Differentialscanningcalorimetry(DSC)
DSCmeasurementswererecordedonaNETZSCH/DSC/200/F3/Maia
(NETZSCH,Germany)between20and80°Cwithaheatingrateof
5K/min. Approximately 10mg of each sample was used for the
measurements,withanemptycrucibleservingasthereference.

Attenuatedtotalreflectance(ATR)Fourier-transforminfrared
(FTIR)spectroscopy
FTIRspectroscopywasconductedonBRUKERALPHASpectrometer
(Bruker,Germany)atroomtemperature.Allsamplesweremeasured
between 4000 and 400cm−1 with resolution of 4cm−1 using
PlatinumATR.

Scanningelectronmicroscopy(SEM)
SEMimageswerecapturedusingaLEOSupra-35high-resolutionfield
emissionscanningelectronmicroscope(CarlZeissAG,Germany).A
layer of Au/Pd nanoparticles was vacuum-coated on the samples
beforeobservation.

Transmissionelectronmicroscopy(TEM)
Thesurface-hydrophobizedCNCswerepreparedfromtheirsuspen-
sionsinTHFofabout0.01wt%.TheTEMobservationwasperformed
onaCM12TransmissionElectronMicroscope(Philips,Netherland).

Fluorescencemicroscopyandspectroscopy
FluorescenceimageswereacquiredwithaKeyenceBZ-X810fluores-
cencemicroscopeatthreedifferentexcitation/emissionwavelengths:
blue (ex/em) 360/460nm, green (ex/em) 470/525nm, red (ex/em)
545/605nm.Thesolid-stateexcitationandemissionspectra,lifetimes,
absolute quantum yields were measured on a FLS1000 steady/tran-
sient state fluorescence spectrometer equipped with an integrating
sphere.

Solid-stateNMRspectroscopy
AllexperimentswereconductedonaBrukerAvanceIIIHDspectro-
meteroperatingat14.1T(600MHz1Hfrequency)usingDVT600W2
BL1.3mmHXY(forsamplesCNC-C18andCNC-C12)and4mmHXY(for
samplesCSE,CLEandMCC)probes.Thetemperatureofthenitrogen
coolinggaswassetto289K,withaflowrateof300–500litersper
hour.Forcrosspolarizationtransferfrom1Hto13C,alinearrampof
80%→100%wasapplied40.SupplementaryTable3summarizesaddi-
tional experimental parameters for all five samples, including the
magicanglespinning(MAS)rates,recycledelay(D1),totaltime,cross
polarization(CP)conditions,decouplingparametersandacquisition
time(AQ).

Densityfunctionaltheory(DFT)calculations
All-electron DFT calculations have been carried out by the ORCA
quantumchemistrysoftware(Version6.0.0)41.
Forgeometryoptimizationcalculations,B3LYPfunctionalandthe
def2-SVP basis set42 were used, and the optimal geometry for each
compound was determined (Supplementary Data 1−6). The DFT-D3
dispersioncorrectionwithBJ-damping43,44wasappliedtocorrectthe
weak interaction to improve the calculation accuracy. The excited
states calculations were performed with B3LYP functional and the
def2-SVP basis set. Orbital energy level analysis was performed by
Multiwfnsoftware45,46.
ThenatureofnoncovalentinteractionwasstudiedbyusingRDG
(reduced density gradient) method37 through Multiwfn software45,46.
ThevisualizationofRDGwasrenderedbyVMD47.

Moleculardynamics(MD)simulations
Equilibriummoleculardynamicssimulationwascarriedouttoinves-
tigate the self-assembly at molecular level using LAMMPS48 under
periodicboundaryconditions.Thesurface-hydrophobizedCNC(CNC-
C18/CNC-C12)wascomposedofaCNCcoreandasurfaceofhydro-
phobicalkylchain(stearoyl(C18)andlauroyl(C12)groups),asshown
inSupplementaryFigs.19and20.TheCNCcorewasmodeledusing
thecellulose-builderdevelopedbyGomesandSkafatUnicamp49.The
CNC core is fixed as a rigid body under subsequent simulations,
absenceofrelativemovementsofatomicpositions.Thehydrophobic
chainswereuniformlygraftedontothesurfaceoftheCNC,showing
parallel arrangement in equilibrium,similarto polymer comb. Note
thatsuchconformationisnotintentionalbymodeling,butisaresultof
denselygrafting.
Sixgroupsofsimulationswereconducted:
(1) Co-assembly of C18-hydrophobized CNC and CSEs: CNC-
C18+CSE.
(2) Self-assemblyofCSE.
(3) Self-assemblyofCNC-C18.
(4) Co-assembly of C12-hydrophobized CNC and CLEs: CNC-
C12+CLE.
(5) Self-assemblyofCLE.
(6) Self-assemblyofCNC-C12.
GAFF2 force fieldand RESP charge wereused to model all the
macromolecules.
All the systems were relaxed to the equilibrium state at room
temperature for at least 1ns under the NPT ensemble. For better
visualization,thevolumeofthesimulatedboxeswasallsetbiggerthan
180×180×180Å3.Theself-assemblywassimulatedunderNVTensem-
bleforatleast2ns.Theinitialandfinalconfigurationswereprovidedin
SupplementaryData7−12.Radialdistributionfunctions(RDFs)were
calculatedunderequilibriumstate.

Dataavailability
ThedatageneratedinthisstudyareprovidedintheSupplementary
Information/SourceDatafile.Alldatasupportingthefindingsofthis
study are available from the corresponding authors upon
request.Sourcedataareprovidedwiththispaper.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This is a very good paper that can be accepted with some minor revisions. The work is well-presented and has been carried out in a thorough way. There are a few issues with it that could help improve it in terms of couching the work in the wider context of cellulosic superstructures. For instance, the work discusses supramolecular interactions, which have recently been reviewed https://www.nature.com/articles/s41578-025-00810-5. At some points during the discussion it is not clear which supramolecular interactions are key in the formation of the superstructures. I would have thought that with such a large C-chain attached to the sample that this would be hydrophobic, but the authors could be more precise.\nWhich carbons do the carbon chains during modification attach to? Is it primarily C6, or is it less regioselective? Have the authors carried out any SS NMR to check this? Moreover, are the CNCs that they use charged? If so do the CNCs retain charge or is the modification to high for this to take place? There are examples in the literature of the charge being retained, as well as having hydrophobic groups attached e.g. Nigmatullin et al.\nThe authors talk about a 'flaky' microstructure, but it is not clear what they mean by this. Is the material brittle, or are they referring to the bowl shaped materials in Figure 2?\nWhat might be the wider applications of these materials, beyond counterfitting? Are there any other possibilities?", "reviewer_2": "The manuscript reports a novel co-assembly of surface-hydrophobized cellulose nanocrystals (CNCs) with cellulose esters to form macroscale helices (MHs) and porous bowl-shaped microparticles (BSMPs) that exhibit exceptionally high solid-state fluorescence (FL) with quantum yields (FLQY) of 86% and 91%. This is compared to typical nonconjugated luminophores, which usually show very low FLQYs (often <10%, e.g. carboxylated CNC gave only 7.8% in solid). The authors attribute the bright luminescence to dense “oxygen clusters” and extensive van der Waals and hydrogen-bond interactions among the stearoyl/lauroyl side chains, promoting through-space electron delocalization (consistent with the clusteroluminescence concept). They also demonstrate broad, excitation-dependent emission colors and suggest potential use in durable anti-counterfeiting materials due to good structural stability. The study combines experimental characterization (morphology, spectroscopy, FLQY measurements) with DFT/MD simulations to elucidate the emission mechanism. Overall, this paper could be accepted once the following issues are addressed.\n1) While the manuscript attributes high FLQY to dense oxygen clusters and noncovalent interactions, it remains unclear how crystalline order or amorphous character evolves during the self-assembly process and whether this contributes to fluorescence enhancement. Since previous studies have shown that increased molecular rigidity and ordering (e.g., crystallinity) can suppress nonradiative decay and enhance clusterization-triggered emission (CTE), it is important to evaluate the crystallinity before and after self-assembly.\n2) Perform X-ray diffraction (XRD) measurements on the individual components (e.g., CNC-C18, CSE) and the co-assembled MHs and BSMPs. Compare the degree of crystallinity to determine whether assembly induces increased structural order or localized amorphous regions that could facilitate oxygen clustering.\n3) If possible, complement with DSC or Raman spectroscopy to support conclusions about molecular packing and rigidity.\n4) The authors claim these QYs are “the highest among reported organic nonconjugated luminophores”, However, a very recent work (Wang et al., Nat. Commun. 2024, 15, 6426) reported a nonconjugated organic solid (m-TBPM) with 100% QY. The authors should acknowledge this and either clarify their claim (e.g. highest for cellulose‐based systems or for macroscale assemblies) or explain how their results differ (e.g. broader emission, structural features). In any case, citing would update readers and strengthen the discussion. Meanwhile, the authors are strongly encouraged to review these three references (Progress in Polymer Science, 2019, 90, 35-117; Nat. Commun. 2025, 16, 3910; Mater. Today 2020, 32, 275-292) to gain a more comprehensive understanding of this field. It should be noted that the reviewer is not requesting the authors to cite any of these works, but rather offering them as recommended reading to better acquaint themselves with the historical context and current perspectives in this area. I believe the authors have the potential to produce even more interesting and impactful work in the future with these backgrounds.\n5) When reporting FLQY, specify the measurement method (integrating sphere, relative method, etc.) and standard used, as these high values require careful calibration.", "reviewer_3": "This study describes the fabrication of highly emissive macroscale helices (MHs) and porous block-selective microparticles (BSMPs) via co-assembly of surface-hydrophobized cellulose nanocrystals (CNCs) and cellulose esters. This method yields materials with unprecedented quantum yields (up to 86% and 91%) among nonconventional luminophores. The authors present an impressive approach to achieving these superstructures with exceptional efficiencies. I recommend publication with minor revisions to address the points listed below.\n1. The first paragraph, for the introduction of the clustering-triggered emission mechanism, other than ref. 4, the following review is highly suitable: Acc. Chem. Res. 2025, 85, 612.\n2. The authors attribute the excitation-dependent emission to the “red-edge effect,” but for CTE systems, this behavior typically arises from the coexistence of diverse emissive clusters.\n3. MHs and porous BSMPs exhibit exceptional solid-state luminescence quantum yields. Similar high quantum yields were reported for other materials in this work. To ensure accuracy, were these data cross-validated using a different instrument?\n4. Normally, nonconventional luminophores like CNCs are phosphorescent. Do these solids exhibit room-temperature or cryotemperature phosphorescence?", "reviewer_4": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Dear Reviewers,\nWe very much appreciate your valuable and insightful comments and suggestions.\nAccordingly, we have conducted supplementary experiments per the recommendations\nof the reviewers. As well, we revised our manuscript (all changes are shown in red).\nIncluded below are the original comments by the Reviewers in black text and our\nresponses in blue.\nReviewer #1 (Remarks to the Author):\nThis is a very good paper that can be accepted with some minor revisions. The work is\nwell-presented and has been carried out in a thorough way. There are a few issues with\nit that could help improve it in terms of couching the work in the wider context of\ncellulosic superstructures. For instance, the work discusses supramolecular interactions,\nwhich have recently been reviewed https://www.nature.com/articles/s41578-025-\n00810-5. At some points during the discussion it is not clear which supramolecular\ninteractions are key in the formation of the superstructures. I would have thought that\nwith such a large C-chain attached to the sample that this would be hydrophobic, but\nthe authors could be more precise.\nReply: Thank you for your positive comments and valuable suggestions to improve the\nquality of our manuscript. We do agree that the hydrophobic interactions are the key\ndriven force for the formation of the superstructures, because of the functionalization\nwith long aliphatic chains. In addition to hydrophobic interactions, we suppose that the\nsmall amount of hydrogen bonds, formed by the ester groups as well as the unmodified\nhydroxyl groups, can also drive the assembly process. Accordingly, we have revised the\ndescriptions in our Revised Manuscript to make this clear. (As we described in our\nRevised Manuscript, “the two co-assembly processes are primarily driven by\nhydrophobic interactions arising from the long aliphatic chains utilized in the\nfunctionalization of the CNCs. In addition, a small number of hydrogen bonds, formed\nby the ester groups and residual hydroxyl groups, also contribute to the assembly.”)\nIn addition, we have cited this paper (https://doi.org/10.1038/s41578-025-00810-5)\nmentioned by you in our Revised Manuscript (ref. 19) since it is highly relevant to our\nstudy, in terms of self-assembled cellulosic superstructures.\n1) Which carbons do the carbon chains during modification attach to? Is it primarily\nC6, or is it less regioselective? Have the authors carried out any SS NMR to check this?\nMoreover, are the CNCs that they use charged? If so do the CNCs retain charge or is\nthe modification to high for this to take place? There are examples in the literature of\nthe charge being retained, as well as having hydrophobic groups attached e.g.\nNigmatullin et al.\nReply: We thank the Reviewer for the questions.\nFor both CSE and CLE, the hydroxyl groups are fully substituted with long aliphatic\nchains (DS = 3). For CNC-C12 (DS = 0.82) and CNC-C18 (DS = 0.89), the chemical\nmodification of cellulose is regioselective, occurring primarily at C6, followed by C2\nand then C3, as indicated by the solid-state NMR spectra (Figure R1 and Table R1).\nThe degree of substitution (DS) for C2 (DS ) and C3 (DS ) was determined from the\n2 3\npeak splitting (upfield shift) of the adjacent carbons (C1 and C4), whereas the DS for\nC6 (DS ) was calculated from the ratio of peaks corresponding to unsubstituted and\n6\nsubstituted hydroxyl groups (J. Polym. Sci. A Polym. Chem., 1986, 24, 2981–2993).\nWe have added these results to the Revised Supplementary Information.\nFigure R1. Solid-state 13C NMR spectra of CNC-C12 showing the peak regions of a)\nC1, b) C4, c) C6. Solid-state 13C NMR spectra of CNC-C18 showing the peak regions\nof d) C1, e) C4, f) C6. DS = Area 2 / (Area 1 + Area 2), DS = Area 5 / (Area 3 + Area\n2 3\n4 + Area 5), DS = Area 7 / (Area 6 + Area 7 + Area 8).\n2 3 6\nthe solid-state NMR spectra.\nSample DS DS DS\n2 3 6\nCNC-C12 0.26 0.15 0.39\nCNC-C18 0.33 0.10 0.43\nThe pristine CNCs prior to modification show a zeta potential of −22.4 ± 0.4 mV\n(Figure R2). They were prepared by hydrochloric acid hydrolysis of MCC and possess\nonly surface hydroxyl groups, which are poorly ionizable, with no readily ionizable\ngroups such as sulfate or carboxyl groups. After esterification with stearoyl chloride or\nlauroyl chloride, the introduced ester groups also exhibit a low degree of ionization. As\nshown in Figure R2, the surface charge is retained after esterification, with values of\n−22.1 ± 0.7 mV for CNC-C12 and −21.6 ± 0.3 mV for CNC-C18. We have added these\nresults to the Revised Supplementary Information.\nFigure R2. Zeta potential results of a) CNC, b) CNC-C12, and c) CNC-C18.\n2) The authors talk about a 'flaky' microstructure, but it is not clear what they mean by\nthis. Is the material brittle, or are they referring to the bowl shaped materials in Figure\n2?\nReply: We thank the Reviewer for this question. In addition to the co-assembly system\n(CNC-C12+CLE), we further analyzed the corresponding self-assembly systems\n(CNC-C12, CLE), as control experiments, to investigate the effect of initial assembling\nunits on the oxygen clusters. As we mentioned in our manuscript, ‘in contrast to the\nBSMPs co-assembled by CLE and CNC-C12, CLE alone only self-assembled into flaky\nmesostructures (FMs) with thicknesses of 110−390 nm (Figure S7a,b).’ Figure R3\nbelow is a copy of Figure S7 for better review. The ‘flaky’ microstructure refers to the\nmorphology in the fifth column of Figure R3 (Figure S7a,b).\nFigure R3. Morphologies of the superstructures and conformations of the hydrophobic\nchains for the six self- and co-assembly systems (labeled above).\n3) What might be the wider applications of these materials, beyond counterfitting?\nAre there any other possibilities?\nReply: We thank the Reviewer for this comment. Other potential applications include\nbut are not limited to encryption/decryption, molecular imaging, CPL (circularly\npolarized luminescence) materials, UV absorbers, UV-vis light detection owing to the\nλ -dependent emission.\nex\nReviewer #2 (Remarks to the Author):\nThe manuscript reports a novel co-assembly of surface-hydrophobized cellulose\nnanocrystals (CNCs) with cellulose esters to form macroscale helices (MHs) and\nporous bowl-shaped microparticles (BSMPs) that exhibit exceptionally high solid-state\nfluorescence (FL) with quantum yields (FLQY) of 86% and 91%. This is compared to\ntypical nonconjugated luminophores, which usually show very low FLQYs (often\n<10%, e.g. carboxylated CNC gave only 7.8% in solid). The authors attribute the bright\nluminescence to dense “oxygen clusters” and extensive van der Waals and hydrogen-\nbond interactions among the stearoyl/lauroyl side chains, promoting through-space\nelectron delocalization (consistent with the clusteroluminescence concept). They also\ndemonstrate broad, excitation-dependent emission colors and suggest potential\nuse in durable anti-counterfeiting materials due to good structural stability. The study\ncombines experimental characterization (morphology, spectroscopy, FLQY\nmeasurements) with DFT/MD simulations to elucidate the emission mechanism.\nOverall, this paper could be accepted once the following issues are addressed.\nReply: We sincerely thank the Reviewer for the constructive input and valuable\nsuggestions, which have been very helpful in improving both the scientific merit and\nclarity of the discussion of the manuscript.\n1) While the manuscript attributes high FLQY to dense oxygen clusters and\nnoncovalent interactions, it remains unclear how crystalline order or amorphous\ncharacter evolves during the self-assembly process and whether this contributes to\nfluorescence enhancement. Since previous studies have shown that increased molecular\nrigidity and ordering (e.g., crystallinity) can suppress nonradiative decay and enhance\nclusterization-triggered emission (CTE), it is important to evaluate the crystallinity\nbefore and after self-assembly.\nReply: We thank the Reviewer for pointing this out and we do agree that it is important\nto evaluate the crystallinity before and after assembly. The crystallinity changes were\nevaluated via solid-state NMR, Raman and DSC before and after self-assembly, please\nfind the results of this investigation in the response to Comments 2) and 3) below.\n2) Perform X-ray diffraction (XRD) measurements on the individual components (e.g.,\nCNC-C18, CSE) and the co-assembled MHs and BSMPs. Compare the degree of\ncrystallinity to determine whether assembly induces increased structural order or\nlocalized amorphous regions that could facilitate oxygen clustering.\nReply: We thank the Reviewer for this suggestion. For our co-assembly systems, there\nare two types of crystalline structures: cellulose (polymorph I) and crystallized fatty-\nacyl groups. We did perform XRD measurements and concluded that this technique is\nnot an appropriate method to determine the crystallinity index (CrI) for either of these\ncrystalline structures (Figure R4). For cellulose (polymorph I), the stacking of long\naliphatic chains (stearoyl/lauroyl groups) produces a broad amorphous peak (2θ =\n16.5−26.5°). This peak has also been reported in similar self-assembled systems in the\nliterature (Aggregate 2025, 6, e695; Small 2021, 17, 2102938). As shown in Figure R4,\nthis amorphous peak (2θ = 16.5−26.5°) overlaps with the characteristic peaks of\ncellulose. For crystallized fatty-acyl groups, it is particularly challenging to distinguish\ncrystalline and amorphous contributions. On the one hand, their diffraction regions\noverlap with the characteristic peaks of cellulose (Figure R4). On the other hand,\nobtaining a single crystal—which would be necessary to resolve the intrinsic crystalline\npeaks—is difficult. Instead, we employed solid-state NMR and Raman spectroscopy to\ndetermine the CrI of cellulose (polymorph I), and DSC measurements to determine the\nCrI of crystallized fatty-acyl groups (Figures R5–R7, Table R2).\nFigure R4. XRD results of the co-assembled BSMPs and MHs.\nFor cellulose (polymorph I), the CrI determined by solid-state NMR spectroscopy was\ncalculated as the ratio of the crystalline peak area to the total area of the C4 peaks (Chem.\nSoc. Rev., 2023, 52, 6417–6446; Angew. Chem. Int. Ed. 2020, 59, 3218–3225;\nBiotechnol Biofuels 3, 10 (2010)) (Figure R5). The results indicate that the CrI remains\nessentially unchanged when comparing co-assembled CLE+CNC-C12 (BSMPs) with\npristine CNC-C12 prior to assembly, as well as co-assembled CSE+CNC-C18 (MHs)\nwith pristine CNC-C18 prior to assembly. Individual CLE/CSE is not considered, as it\nis fully dissolved in THF before assembly. We have added the above results to the\nRevised Manuscript.\nFigure R5. Solid-state 13C NMR spectra of a,b) BSMPs co-assembled from CLE+CNC-\nC12, c) pristine CNC-C12 prior to assembly (partial enlargement of Figure S4b), d,e)\nMHs co-assembled from CSE+CNC-C18, f) pristine CNC-C18 prior to assembly\n(partial enlargement of Figure S4a). The stars label the spinning sidebands.\nFor crystallized fatty-acyl groups, we employed DSC to determine the CrI values (see\nthe response to Comment 3) below).\n3) If possible, complement with DSC or Raman spectroscopy to support conclusions\nabout molecular packing and rigidity.\nReply: We thank the Reviewer for this suggestion.\nRegarding the CrI for cellulose (polymorph I), we also performed Raman spectroscopy\nmeasurements to further support the conclusion (Figure R6). The CrI values were\ncalculated according to the Raman band intensity ratio of the 380 and 1096 cm-1\n(Cellulose (2010) 17:721–733). Similarly, the CrI remains essentially unchanged when\ncomparing co-assembled CLE+CNC-C12 (BSMPs) with pristine CNC-C12 prior to\nassembly, as well as co-assembled CSE+CNC-C18 (MHs) with pristine CNC-C18 prior\nto assembly. To avoid potential concerns regarding discrepancies in CrI values obtained\nby different methods, we did not include the Raman spectroscopy results in the Revised\nManuscript. Such differences are common, as reported in the literature (e.g., Table 2 in\nCarbohydrate Polymers 190 (2018) 262–270; Table 2 in Cellulose (2010) 17:721–733).\nFigure R6. Raman spectra of a) MHs co-assembled from CSE+CNC-C18, b) pristine\nCNC-C18 prior to assembly, c) BSMPs co-assembled from CLE+CNC-C12, d) pristine\nCNC-C12 prior to assembly.\nFor crystallized fatty-acyl groups, we employed DSC measurements to determine the\nCrI values (Figure R7 and Table R2). Again, the CrI remains essentially unchanged\nwhen comparing co-assembled CSE+CNC-C18 (MHs) with pristine CNC-C18 prior to\nassembly, as well as co-assembled CLE+CNC-C12 (BSMPs) with pristine CNC-C12\nprior to assembly (Figure R7 and Table R2). We have added the above results to the\nRevised Manuscript.\nFigure R7. DSC results of a) MHs co-assembled from CSE+CNC-C18, b) pristine\nCNC-C18 prior to assembly, c) BSMPs co-assembled from CLE+CNC-C12, d) pristine\nCNC-C12 prior to assembly.\nTable R2. CrI values for crystallized fatty-acyl groups, calculated from the DSC results.\nSample m (mg) ΔH (J/g) m (mg) DS m (mg) CrI\nsamp f crys acyl\nMHs 8.9 29.9 1.204 1.51 6.368 18.9%\nCNC-C18 9.9 25.1 1.124 0.89 5.902 19.1%\nBSMPs 8.7 29.4 1.157 1.49 5.478 21.1%\nCNC-C12 9.5 23.2 0.997 0.82 4.582 21.8%\nm : mass of the sample used for DSC measurement, ΔH: enthalpy of heat fusion, m : mass of\nsamp f crys\nthe crystallized fatty-acyl groups, DS: degree of substitution, m : mass of all fatty-acyl groups,\nacyl\nCrI: calculated crystallinity index. For sample MHs, mixing equal masses of CNC-C18 and CSE\nyields an equivalent DS of 1.51, while for sample BSMPs, mixing equal masses of CNC-C12 and\nCLE yields an equivalent DS of 1.49. CrI = (m /m ) × 100%.\ncrys acyl\nTherefore, in response to the three Comments 1-3), we still attribute the high FLQY to\ndense oxygen clusters and noncovalent interactions, as originally described. The\nassembly process induces oxygen cluster formation without enhancing the crystallinity\nof either cellulose (polymorph I) or crystallized fatty-acyl groups.\n4) The authors claim these QYs are “the highest among reported organic nonconjugated\nluminophores”, However, a very recent work (Wang et al., Nat. Commun. 2024, 15,\n6426) reported a nonconjugated organic solid (m-TBPM) with 100% QY. The authors\nshould acknowledge this and either clarify their claim (e.g. highest for cellulose‐based\nsystems or for macroscale assemblies) or explain how their results differ (e.g. broader\nemission, structural features). In any case, citing would update readers and strengthen\nthe discussion. Meanwhile, the authors are strongly encouraged to review these three\nreferences (Progress in Polymer Science, 2019, 90, 35-117; Nat. Commun. 2025, 16,\n3910; Mater. Today 2020, 32, 275-292) to gain a more comprehensive understanding\nof this field. It should be noted that the reviewer is not requesting the authors to cite\nany of these works, but rather offering them as recommended reading to better acquaint\nthemselves with the historical context and current perspectives in this area. I believe\nthe authors have the potential to produce even more interesting and impactful work in\nthe future with these backgrounds.\nReply: We thank the Reviewer for pointing out the imprecise description of the high\nQYs. Accordingly, we have revised our wording from “the highest among reported\norganic nonconjugated luminophores” to “the highest among reported biomass-based\nsystems”. In the Revised Manuscript, the following statement was added, “… the\nhighest values reported among biomass-based systems. Within the broader class of\norganic nonconjugated luminophores, only one solid, m-TBPM, has been reported with\na higher efficiency (100%).” We have now included a citation to Wang et al. (Nat.\nCommun. 2024, 15, 6426), who reported this 100% QY material (ref. 45).\nIn addition, the three references (Progress in Polymer Science, 2019, 90, 35-117; Nat.\nCommun. 2025, 16, 3910; Mater. Today 2020, 32, 275-292) comprehensively and\nsystematically discussed the nonconjugated luminophores. These three references,\ntogether with the report by Wang et al. (Nat. Commun. 2024, 15, 6426) describing a\nnonconjugated organic solid (m-TBPM) with 100% QY, are highly relevant to our study\nand can provide inspiration for readers in this area. Therefore, we have cited all of these\nreferences in the Revised Manuscript (ref. 4, 7, 8, 45). We thank the Reviewer again\nfor recommending these papers, which have helped us better understand both the\nhistorical context and current perspectives in this field.\n5) When reporting FLQY, specify the measurement method (integrating sphere, relative\nmethod, etc.) and standard used, as these high values require careful calibration.\nReply: We thank the Reviewer for this comment. Absolute quantum yields were\nmeasured on a FLS1000 steady/transient state fluorescence spectrometer equipped with\nan integrating sphere. We have added this information to the Revised Supplementary\nInformation.\nReviewer #3 (Remarks to the Author):\nThis study describes the fabrication of highly emissive macroscale helices (MHs) and\nporous block-selective microparticles (BSMPs) via co-assembly of surface-\nhydrophobized cellulose nanocrystals (CNCs) and cellulose esters. This method yields\nmaterials with unprecedented quantum yields (up to 86% and 91%) among\nnonconventional luminophores. The authors present an impressive approach to\nachieving these superstructures with exceptional efficiencies. I recommend publication\nwith minor revisions to address the points listed below.\nReply: We thank the Reviewer very much for evaluating our manuscript, for the\npositive feedback and for the constructive input. The Reviewer’s comments were very\nvaluable to improve the study and its presentation. We have addressed all the\nReviewer’s suggestions as outlined below.\n1. The first paragraph, for the introduction of the clustering-triggered emission\nmechanism, other than ref. 4, the following review is highly suitable: Acc. Chem. Res.\n2025, 85, 612.\nReply: We thank the Reviewer for this suggestion. We were unable to find the reference\nstated above and have assumed that the Reviewer was referring to Acc. Chem. Res.\n2025, 58, 4, 612–624, which has now been added to our Revised Manuscript (ref. 6).\n2. The authors attribute the excitation-dependent emission to the “red-edge effect,” but\nfor CTE systems, this behavior typically arises from the coexistence of diverse emissive\nclusters.\nReply: We thank the Reviewer for pointing this out. We do agree that excitation-\ndependent behavior typically arises from the coexistence of diverse emissive clusters.\nAccordingly, we have revised the description in our Revised Manuscript, to attribute\nthe excitation-dependent emission to the coexistence of diverse emissive clusters as\nwell. The following sentence was added to our Revised Manuscript to address this\ncomment, “the coexistence of diverse emissive clusters with varying degrees of\nextended electron delocalization is responsible for the excitation-dependent emission”.\n3. MHs and porous BSMPs exhibit exceptional solid-state luminescence quantum\nyields. Similar high quantum yields were reported for other materials in this work. To\nensure accuracy, were these data cross-validated using a different instrument?\nReply: We thank the Reviewer for this comment. Yes, these data were cross-validated\nusing two FLS1000 spectrometers, with errors of less than 2%. As stated in our\nmanuscript, the FLQYs are 86 ± 2% and 91 ± 2%, and these values were consistently\nobtained from both instruments.\n4. Normally, nonconventional luminophores like CNCs are phosphorescent. Do these\nsolids exhibit room-temperature or cryotemperature phosphorescence?\nReply: We thank the Reviewer for this question. Yes, these solids exhibit room-\ntemperature phosphorescence (Figures R8 and R9), with very low quantum efficiencies\n(in contrast to their high FLQYs): Ф (MHs) = 0.7 ± 0.2% (λ = 350 nm, λ = 485\nP ex em\nnm), Ф (BSMPs) = 0.8 ± 0.2% (λ = 350 nm, λ = 477 nm). We have added these\nP ex em\nphosphorescence results including delayed spectra, lifetimes and quantum efficiencies\nto our Revised Manuscript.\nFigure R8. a) Prompt and b) delayed (t = 0.1 ms) emission spectra of MHs at different\nd\nλ values at room temperature. c) Prompt and d) delayed (t = 0.1 ms) emission spectra\nex d\nof BSMPs at different λ values at room temperature (λ listed in legend, λ labelled\nex ex max\nabove the peak).\nFigure R9. Solid-state phosphorescence lifetimes of a) MHs (λ = 350 nm, λ = 485\nex em\nnm) and b) BSMPs (λ = 350 nm, λ = 477 nm) at room temperature.\nex em\nReviewer #4 (Remarks to the Author):\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nReply: We greatly appreciate the time and effort you dedicated to providing feedback\non our manuscript. The combined reviewer comments are presented and addressed by\nus in the above text."}, {"round": 2, "reviewer_comments": {"reviewer_1": "I am happy with the revisions and the responses to my queries. The paper can now be published.", "reviewer_2": "I have carefully reviewed the revised manuscript. The authors have thoroughly addressed the issues raised by the reviewers, and I believe the manuscript is suitable for publication in Nature Communications.", "reviewer_3": "The authors have carefully revised their manuscript to address all the concerns of the reviewers. The current version is acceptable for publication.", "reviewer_4": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": ""}]

Decision letter